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EditTextPreference doesn't work with Strings

I created a Settings Activity with the Android Template.
First, everything worked fine, but now I wanted to get the String from the EditTextPreference. But when I started to run it, it crashed because of this error:
java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
I used the right Key and the getString Method.
Since that happened every time I want to open the Settings my app crashes and I get that Error:
2020-02-01 17:22:55.260 24468-24468/de.fabipfolix.vertretungsplan E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.fabipfolix.vertretungsplan, PID: 24468
java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:288)
at androidx.preference.Preference.getPersistedString(Preference.java:1686)
at androidx.preference.EditTextPreference.onSetInitialValue(EditTextPreference.java:106)
at androidx.preference.Preference.onSetInitialValue(Preference.java:1614)
at androidx.preference.Preference.dispatchSetInitialValue(Preference.java:1587)
at androidx.preference.Preference.onAttachedToHierarchy(Preference.java:1311)
at androidx.preference.Preference.onAttachedToHierarchy(Preference.java:1326)
at androidx.preference.PreferenceGroup.addPreference(PreferenceGroup.java:249)
at androidx.preference.PreferenceGroup.addItemFromInflater(PreferenceGroup.java:170)
at androidx.preference.PreferenceInflater.rInflate(PreferenceInflater.java:345)
at androidx.preference.PreferenceInflater.rInflate(PreferenceInflater.java:346)
at androidx.preference.PreferenceInflater.inflate(PreferenceInflater.java:157)
at androidx.preference.PreferenceInflater.inflate(PreferenceInflater.java:109)
at androidx.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:216)
at androidx.preference.PreferenceFragmentCompat.setPreferencesFromResource(PreferenceFragmentCompat.java:377)
at de.fabipfolix.vertretungsplan.SettingsActivity$SettingsFragment.onCreatePreferences(SettingsActivity.java:42)
at androidx.preference.PreferenceFragmentCompat.onCreate(PreferenceFragmentCompat.java:160)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2586)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:838)
at androidx.fragment.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1197)
at androidx.fragment.app.FragmentTransition.calculateFragments(FragmentTransition.java:1080)
at androidx.fragment.app.FragmentTransition.startTransitions(FragmentTransition.java:119)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1866)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2663)
at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:246)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425)
at android.app.Activity.performStart(Activity.java:7825)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
I already commented on everything I've done today and I have no idea what the problem is.
The Design Window of the XML file says that I have to put a boolean.
Does anyone know how to solve this?
Here are my files:
root_preferences.xml:
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<PreferenceCategory app:title="Login Daten">
<EditTextPreference
android:ems="10"
android:inputType="text"
android:key="pref_username"
android:title="BenutzernameEditText"
app:title="Benutzername"
app:useSimpleSummaryProvider="true" />
<EditTextPreference
android:dialogTitle="Passwort"
android:inputType="text"
android:key="pref_password"
android:title="Passwort" />
</PreferenceCategory>
<PreferenceCategory app:title="Benachrichtigungen">
<SwitchPreference
android:defaultValue="true"
android:key="switchNotifications"
android:summary="#string/summarySwitchNotifications"
android:title="NotificationSwitch" />
</PreferenceCategory>
<PreferenceCategory app:title="Hintergrundaktivität">
</PreferenceCategory>
<PreferenceCategory app:title="Oberstufe">
<SwitchPreference
android:contentDescription="Kursbezeichnungen mit Komma trennen"
android:defaultValue="false"
android:key="switchKurse"
android:title="Kurse filtern" />
<EditTextPreference
android:dialogMessage="Kursnamen mit Komma trennen "
android:key="pref_kurse"
android:summary="Kursnamen mit Komma trennen "
android:title="Kursbezeichnungen"
android:inputType="text"
app:dialogTitle="Kursbezeichnungen" />
</PreferenceCategory>
MainActivity:
public class MainActivity extends AppCompatActivity {
FloatingActionButton fabRefresh;
RecyclerView recyclerView;
RecyclerView.Adapter adapter;
RecyclerView.LayoutManager layoutManager;
ArrayList<Vertretungsstunde> vertretungen;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SharedPreferences sharedPref =PreferenceManager.getDefaultSharedPreferences(this);
Boolean notifications = sharedPref.getBoolean(SettingsActivity.KEY_PREF_NOTIFICATIONS_SWITCH, false);
String username = sharedPref.getString(SettingsActivity.KEY_PREF_USERNAME_TEXT, "");
ArrayList<Vertretungsstunde> list = ...;
//RECYCLERVIEW
recyclerView = findViewById(R.id.rv_VertretungenHeute);
recyclerView.setHasFixedSize(false);
layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(layoutManager);
((SimpleItemAnimator) recyclerView.getItemAnimator()).setSupportsChangeAnimations(false);
adapter = new VertretungsAdapter(this, list);
recyclerView.setAdapter(adapter);
//TOOLBAR
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//REFRESH BUTTON
fabRefresh = findViewById(R.id.fabRefresh);
fabRefresh.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) { //FABRefresh OnClickListener
Toast.makeText(MainActivity.this, "Refreshing...", Toast.LENGTH_SHORT).show();
//...
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
Intent intent = new Intent(MainActivity.this, de.fabipfolix.vertretungsplan.SettingsActivity.class);
startActivity(intent);
return true;
}
return super.onOptionsItemSelected(item);
}
}
SettingsActivity:
public class SettingsActivity extends AppCompatActivity {
public static final String KEY_PREF_NOTIFICATIONS_SWITCH = "switchNotifications";
public static final String KEY_PREF_FILTER_SWITCH = "switchKurse";
public static final String KEY_PREF_KURSE_TEXT ="pref_kurse";
public static final String KEY_PREF_PASSWORD_TEXT = "pref_password";
public static final String KEY_PREF_USERNAME_TEXT = "pref_username";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.settings_activity);
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.settings, new SettingsFragment())
.commit();
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.setDisplayHomeAsUpEnabled(true);
}
}
public static class SettingsFragment extends PreferenceFragmentCompat {
#Override
public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
setPreferencesFromResource(R.xml.root_preferences, rootKey);
}
}
}

Based on the comments:
You probably had previous saved data that could be breaking the current implementation. Cleaning storage should do it if that´s the case

Fragment's view placed inside a FrameLayout throws a NullPointerException

I'm trying to use a FrameLayout on one of my activities. I want this FrameLayout to be a placeholder in an activity and I want to add/replace/remove fragments inside it.
I have a simple cafe app used for studying android. For simplicity I will post the code for the Cake and Breads category.
Problem: NullPointerException. I don't know the reason WHY my fragment's view is null. I'm guessing maybe the fragment lifecycle didn't run so the view was not inflated thus accessing the view throws a nullpointer? Please help me understand WHY a nullpointer is thrown.
Flow of the App
User selects a specific cake or bread in a ListFragment > CakeAndBreadActivity is called > Display Cake or Bread specific detail
I'm looking for: the explanation and reason behind the NullPointerException in the view and How can I display the Cakes and Bread details into the fragment when using FrameLayout.
NullPointerException
--------- beginning of crash
10-25 01:41:21.550 2374-2374/com.cafe E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.cafe, PID: 2374
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cafe/com.cafe.CakeAndBreadActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
at com.cafe.CakeAndBreadDetailFragment.displayCakeAndBreadDetails(CakeAndBreadDetailFragment.java:97)
at com.cafe.CakeAndBreadActivity.displayCakeAndBreadDetails(CakeAndBreadActivity.java:30)
at com.cafe.CakeAndBreadActivity.onCreate(CakeAndBreadActivity.java:19)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
CakeAndBreadActivity
public class CakeAndBreadActivity extends Activity implements CakeAndBreadDetailFragment.onCakeAndBreadDetailFragmentListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cake_and_bread);
displayCakeAndBreadDetails();
}
public void displayCakeAndBreadDetails(){
Intent cakeAndBreadIntent = getIntent();
int cakeAndBreadId = Integer.valueOf(cakeAndBreadIntent.getIntExtra("cakeAndBreadNumber", 0));
CakeAndBreadDetailFragment cakeAndBreadDetail = new CakeAndBreadDetailFragment();
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
cakeAndBreadDetail.displayCakeAndBreadDetails(cakeAndBreadId);
fragmentTransaction.replace(R.id.cake_and_bread_detail_frame_layout_id, cakeAndBreadDetail);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
#Override
public void onCakeAndBreadDetail(int id) {
}
}
activity_cake_and_bread.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.cafe.CakeAndBreadActivity">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:id="#+id/cake_and_bread_detail_frame_layout_id"/>
</LinearLayout>
CakeAndBreadDetailFragment
public class CakeAndBreadDetailFragment extends Fragment {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
private onCakeAndBreadDetailFragmentListener mListener;
public CakeAndBreadDetailFragment() {
}
public static CakeAndBreadDetailFragment newInstance(String param1, String param2) {
CakeAndBreadDetailFragment fragment = new CakeAndBreadDetailFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_cake_and_bread_detail, container, false);
}
public void onButtonPressed(int id) {
if (mListener != null) {
mListener.onCakeAndBreadDetail(id);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof onCakeAndBreadDetailFragmentListener) {
mListener = (onCakeAndBreadDetailFragmentListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement onCakeAndBreadDetailFragmentListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface onCakeAndBreadDetailFragmentListener {
// TODO: Update argument type and name
void onCakeAndBreadDetail(int id);
}
public void displayCakeAndBreadDetails(int id){
CakeAndBread cakeAndBread = (CakeAndBread)CakeAndBread.getCakeAndBreadList().get(id);
View cakeAndBreadView = getView();
TextView cakeAndBreadTextView = (TextView)cakeAndBreadView.findViewById(R.id.cake_and_bread_detail_fragment_id);
cakeAndBreadTextView.setText(cakeAndBread.getCakeAndBreadName() + " " + cakeAndBread.getCakeAndBreadNutritionFacts());
}
}
fragment_cake_and_bread_detail.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.cafe.CakeAndBreadDetailFragment">
<!-- TODO: Update blank fragment layout -->
<TextView
android:id="#+id/cake_and_bread_detail_fragment_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
EDIT: as suggested, the fragment was not completely loaded when I'm trying to access the view, thus the nullpointerexception is thrown. Now my problem is the framelayout or the fragment doesn't show the textview that I placed in the fragment, how do I solve this? I'm passing cake and bread id and then setting the text in the setText(...) method of the TextView.

cakeAndBreadDetail.displayCakeAndBreadDetails(cakeAndBreadId);
fragmentTransaction.replace(R.id.cake_and_bread_detail_frame_layout_id, cakeAndBreadDetail);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
You are calling displayCakeAndBreadDetails(..) which calls displayCakeAndBreadDetails(..) which calls getView().
At that point you haven't inserted the fragment yet (happens after fragmentTransaction.commit();) so there is no view associated with the fragment. Hence getView() returns null.

#Kiskae is correct. You're calling cakeAndBreadDetail.displayCakeAndBreadDetails(cakeAndBreadId), when the fragment isn't ready which will result in a NullPointerException. Try:
public class CakeAndBreadActivity extends Activity implements CakeAndBreadDetailFragment.onCakeAndBreadDetailFragmentListener {
public void displayCakeAndBreadDetails(){
Intent cakeAndBreadIntent = getIntent();
int cakeAndBreadId = Integer.valueOf(cakeAndBreadIntent.getIntExtra("cakeAndBreadNumber", 0));
CakeAndBreadDetailFragment cakeAndBreadDetail = CakeAndBreadDetailFragment.newInstance(cakeAndBreadId);
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.cake_and_bread_detail_frame_layout_id, cakeAndBreadDetail);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
}
public class CakeAndBreadDetailFragment extends Fragment {
private static final String ARG_CAKE_AND_BREAD_ID = "ARG_CAKE_AND_BREAD_ID";
public CakeAndBreadDetailFragment() {
}
public static CakeAndBreadDetailFragment newInstance(int cakeAndBreadId) {
CakeAndBreadDetailFragment fragment = new CakeAndBreadDetailFragment();
Bundle args = new Bundle();
args.putInt(ARG_CAKE_AND_BREAD_ID, cakeAndBreadId);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_cake_and_bread_detail, container, false);
if (getArguments != null) {
int cakeAndBreadId = getArguments.getInt(ARG_CAKE_AND_BREAD_ID, -1);
if (cakeAndBreadId != -1) {
displayCakeAndBreadDetails(cakeAndBreadId);
}
}
return view;
}
public void displayCakeAndBreadDetails(int id){
...
}
}

InflateException when creating Navigation Drawer

I created an android application using ButterKnife. I wanted to add an activity with Navigation bar . So I used , Navigation Drawer Activityin android studio.
Then I tried to launch it using another activity .Like this ,
Intent intent = new Intent(this, AddInfoActivity.class);
startActivity(intent);
Then I got following error message.
FATAL EXCEPTION: main
Process: xxx.com.au.abcd, PID: 13408
java.lang.RuntimeException: Unable to start activity ComponentInfo{xxx.com.au.abcd/xxx.com.au.abcd.activities.AddInfoActivity}: android.view.InflateException: Binary XML file line #18: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2436)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498)
at android.app.ActivityThread.access$900(ActivityThread.java:179)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1324)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5641)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.view.InflateException: Binary XML file line #18: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:719)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:761)
at android.view.LayoutInflater.inflate(LayoutInflater.java:498)
at android.view.LayoutInflater.inflate(LayoutInflater.java:398)
at android.view.LayoutInflater.inflate(LayoutInflater.java:354)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
at xxx.com.au.abcd.activities.AddInfoActivity.onCreate(AddInfoActivity.java:33)
at android.app.Activity.performCreate(Activity.java:5484)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2400)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498) 
at android.app.ActivityThread.access$900(ActivityThread.java:179) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1324) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:146) 
at android.app.ActivityThread.main(ActivityThread.java:5641) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException
at xxx.com.au.abcd.activities.NavigationDrawerFragment.onCreateView(NavigationDrawerFragment.java:103)
at android.app.Fragment.performCreateView(Fragment.java:1700)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:866)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1040)
at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1142)
at android.app.Activity.onCreateView(Activity.java:5020)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:36)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:75)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:695)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:761) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:498) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:398) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:354) 
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140) 
at xxx.com.au.abcd.activities.AddInfoActivity.onCreate(AddInfoActivity.java:33) 
at android.app.Activity.performCreate(Activity.java:5484) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2400) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498) 
at android.app.ActivityThread.access$900(ActivityThread.java:179) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1324) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:146) 
at android.app.ActivityThread.main(ActivityThread.java:5641) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515)
And this is my activity with navigation bar,
AddInfoActivity.java
import android.app.Activity;
import butterknife.ButterKnife;
import tekhinno.com.au.mygulukose.R;
public class AddInfoActivity extends BaseActivity
implements NavigationDrawerFragment.NavigationDrawerCallbacks {
/**
* Fragment managing the behaviors, interactions and presentation of the navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in {#link #restoreActionBar()}.
*/
private CharSequence mTitle;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_info_activity);
ButterKnife.inject(this);
mNavigationDrawerFragment = (NavigationDrawerFragment)
getFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
#Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
.commit();
}
public void onSectionAttached(int number) {
switch (number) {
case 1:
mTitle = getString(R.string.title_section1);
break;
case 2:
mTitle = getString(R.string.title_section2);
break;
case 3:
mTitle = getString(R.string.title_section3);
break;
}
}
public void restoreActionBar() {
ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setTitle(mTitle);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_add_info, container, false);
return rootView;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((AddInfoActivity) activity).onSectionAttached(
getArguments().getInt(ARG_SECTION_NUMBER));
}
}
}
NavigationDrawerFragment.java
import butterknife.ButterKnife;
import tekhinno.com.au.mygulukose.R;
/**
* Fragment used for managing interactions for and presentation of a navigation drawer.
* See the <a href="https://developer.android.com/design/patterns/navigation-drawer.html#Interaction">
* design guidelines</a> for a complete explanation of the behaviors implemented here.
*/
public class NavigationDrawerFragment extends Fragment {
/**
* Remember the position of the selected item.
*/
private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";
/**
* Per the design guidelines, you should show the drawer on launch until the user manually
* expands it. This shared preference tracks this.
*/
private static final String PREF_USER_LEARNED_DRAWER = "navigation_drawer_learned";
/**
* A pointer to the current callbacks instance (the Activity).
*/
private NavigationDrawerCallbacks mCallbacks;
/**
* Helper component that ties the action bar to the navigation drawer.
*/
private ActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;
private ListView mDrawerListView;
private View mFragmentContainerView;
private int mCurrentSelectedPosition = 0;
private boolean mFromSavedInstanceState;
private boolean mUserLearnedDrawer;
public NavigationDrawerFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Read in the flag indicating whether or not the user has demonstrated awareness of the
// drawer. See PREF_USER_LEARNED_DRAWER for details.
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
mUserLearnedDrawer = sp.getBoolean(PREF_USER_LEARNED_DRAWER, false);
if (savedInstanceState != null) {
mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
mFromSavedInstanceState = true;
}
// Select either the default item (0) or the last selected item.
selectItem(mCurrentSelectedPosition);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Indicate that this fragment would like to influence the set of actions in the action bar.
setHasOptionsMenu(true);
}
**#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mDrawerListView = (ListView) inflater.inflate(
R.layout.drawer_add_info, container, false);
mDrawerListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
});
mDrawerListView.setAdapter(new ArrayAdapter<String>(
getActionBar().getThemedContext(),
android.R.layout.simple_list_item_activated_1,
android.R.id.text1,
new String[]{
getString(R.string.title_section1),
getString(R.string.title_section2),
getString(R.string.title_section3),
}));
mDrawerListView.setItemChecked(mCurrentSelectedPosition, true);
return mDrawerListView;
}**
public boolean isDrawerOpen() {
return mDrawerLayout != null && mDrawerLayout.isDrawerOpen(mFragmentContainerView);
}
/**
* Users of this fragment must call this method to set up the navigation drawer interactions.
*
* #param fragmentId The android:id of this fragment in its activity's layout.
* #param drawerLayout The DrawerLayout containing this fragment's UI.
*/
public void setUp(int fragmentId, DrawerLayout drawerLayout) {
mFragmentContainerView = getActivity().findViewById(fragmentId);
mDrawerLayout = drawerLayout;
// set a custom shadow that overlays the main content when the drawer opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the navigation drawer and the action bar app icon.
mDrawerToggle = new ActionBarDrawerToggle(
getActivity(), /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.navigation_drawer_open, /* "open drawer" description for accessibility */
R.string.navigation_drawer_close /* "close drawer" description for accessibility */
) {
#Override
public void onDrawerClosed(View drawerView) {
super.onDrawerClosed(drawerView);
if (!isAdded()) {
return;
}
getActivity().invalidateOptionsMenu(); // calls onPrepareOptionsMenu()
}
#Override
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
if (!isAdded()) {
return;
}
if (!mUserLearnedDrawer) {
// The user manually opened the drawer; store this flag to prevent auto-showing
// the navigation drawer automatically in the future.
mUserLearnedDrawer = true;
SharedPreferences sp = PreferenceManager
.getDefaultSharedPreferences(getActivity());
sp.edit().putBoolean(PREF_USER_LEARNED_DRAWER, true).apply();
}
getActivity().invalidateOptionsMenu(); // calls onPrepareOptionsMenu()
}
};
// If the user hasn't 'learned' about the drawer, open it to introduce them to the drawer,
// per the navigation drawer design guidelines.
if (!mUserLearnedDrawer && !mFromSavedInstanceState) {
mDrawerLayout.openDrawer(mFragmentContainerView);
}
// Defer code dependent on restoration of previous instance state.
mDrawerLayout.post(new Runnable() {
#Override
public void run() {
mDrawerToggle.syncState();
}
});
mDrawerLayout.setDrawerListener(mDrawerToggle);
}
private void selectItem(int position) {
mCurrentSelectedPosition = position;
if (mDrawerListView != null) {
mDrawerListView.setItemChecked(position, true);
}
if (mDrawerLayout != null) {
mDrawerLayout.closeDrawer(mFragmentContainerView);
}
if (mCallbacks != null) {
mCallbacks.onNavigationDrawerItemSelected(position);
}
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mCallbacks = (NavigationDrawerCallbacks) activity;
} catch (ClassCastException e) {
throw new ClassCastException("Activity must implement NavigationDrawerCallbacks.");
}
}
#Override
public void onDetach() {
super.onDetach();
mCallbacks = null;
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(STATE_SELECTED_POSITION, mCurrentSelectedPosition);
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Forward the new configuration the drawer toggle component.
mDrawerToggle.onConfigurationChanged(newConfig);
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
// If the drawer is open, show the global app actions in the action bar. See also
// showGlobalContextActionBar, which controls the top-left area of the action bar.
if (mDrawerLayout != null && isDrawerOpen()) {
inflater.inflate(R.menu.global, menu);
showGlobalContextActionBar();
}
super.onCreateOptionsMenu(menu, inflater);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
if (item.getItemId() == R.id.action_example) {
Toast.makeText(getActivity(), "Example action.", Toast.LENGTH_SHORT).show();
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* Per the navigation drawer design guidelines, updates the action bar to show the global app
* 'context', rather than just what's in the current screen.
*/
private void showGlobalContextActionBar() {
ActionBar actionBar = getActionBar();
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setTitle(R.string.app_name);
}
private ActionBar getActionBar() {
return getActivity().getActionBar();
}
/**
* Callbacks interface that all activities using this fragment must implement.
*/
public static interface NavigationDrawerCallbacks {
/**
* Called when an item in the navigation drawer is selected.
*/
void onNavigationDrawerItemSelected(int position);
}
}
And these are my layout files,
fragment_add_info.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="tekhinno.com.au.mygulukose.activities.AddInfoActivity$PlaceholderFragment">
<TextView
android:id="#+id/section_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
drawer_add_info.xml
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#cccc"
android:choiceMode="singleChoice"
android:divider="#android:color/transparent"
android:dividerHeight="0dp"
tools:context="tekhinno.com.au.mygulukose.activities.NavigationDrawerFragment" />
add_info_activity.xml
<!-- A DrawerLayout is intended to be used as the top-level content view using match_parent for both width and height to consume the full space available. -->
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="tekhinno.com.au.mygulukose.activities.AddInfoActivity">
<!-- As the main content view, the view below consumes the entire
space available using match_parent in both dimensions. -->
<FrameLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- The drawer is given a fixed width in dp and extends the full height of
the container. -->
<fragment
android:id="#+id/navigation_drawer"
android:name="tekhinno.com.au.mygulukose.activities.NavigationDrawerFragment"
android:layout_width="#dimen/navigation_drawer_width"
android:layout_height="match_parent"
android:layout_gravity="start"
tools:layout="#layout/drawer_add_info" />
</android.support.v4.widget.DrawerLayout>
NOTE :- These layout files and NavigationDrawerFragment.java were generated by Android Studio.
Have any idea about this problem ?

You are using getFragmentManager() to get the fragment manager. You need to get SupportFragmentManager if you are extending AppCompatActivity by your BaseActivity.
#Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
.commit();
}
Note: While using support packages you need to use SupportFragmentManager.

Cannot Set Up Android Nav Drawer in Action Bar

I am trying to set up the Android Nav Drawer with an action bar. I am having difficulty setting the icon for the Nav Drawer and generating all of the list items as well. Below is my code, I am currently generating a NullPointer Exception:
Crash:
--------- beginning of crash
04-20 18:02:03.690 13170-13170/com.sourcey.materialloginexample E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.sourcey.materialloginexample, PID: 13170
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sourcey.materialloginexample/com.troychuinard.fanpolls.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
at com.troychuinard.fanpolls.MainActivity.onCreate(MainActivity.java:71)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
at android.app.ActivityThread.access$800(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5254) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
 
MainActivity:
public class MainActivity extends AppCompatActivity implements HomePollsFragment.OnFragmentInteractionListener {
private Toolbar toolbar;
private Firebase mPollsRef;
private ViewPager mPager;
private ScreenSlidePagerAdapter mPagerAdapter;
private DateFormat mDateFormat;
private Date mDate;
private String mCurrentDateString;
private ValueEventListener v;
private String[] mPlanetTitles;
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.action_tool_bar);
setSupportActionBar(toolbar);
Firebase.setAndroidContext(this);
mPollsRef = FirebaseUtil.FIREBASE.child("Polls");
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
toolbar, /* nav drawer icon to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description */
R.string.drawer_close /* "close drawer" description */) {
};
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
ArrayList<String> drawerTitleArray = new ArrayList<>();
drawerTitleArray.add(0, "TEST");
drawerTitleArray.add(1, "TEST 1");
// Set the adapter for the list view
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, drawerTitleArray));
// TODO: Add Fragment Code to check if savedInstanceState == null; add at Activity Level?
// Check that the activity is using the layout version with
// the fragment_container FrameLayout
//set up viewpager for current day
mPager = (ViewPager) findViewById(R.id.home_polls_viewpager_fragment_container);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
//get current date to apply to Viewpager
mDateFormat = new SimpleDateFormat("MM-dd-yyyy");
mDate = new Date();
mCurrentDateString = mDateFormat.format(mDate);
// TODO: Checkn if AuthStateListenerNecessary
//Determine whether necessary to use an AuthStateListener here
// mUserRef.addAuthStateListener(new Firebase.AuthStateListener() {
// #Override
// public void onAuthStateChanged(AuthData authData) {
// if (authData == null) {
// Intent backToSignIn = new Intent(getApplication(), SignupActivity.class);
// startActivity(backToSignIn);
// finish();
// }
// }
// })
}
#Override
protected void onStart() {
super.onStart();
v = new ValueEventListener() {
//testing methodology of adding children
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int pollsAvailable = (int) dataSnapshot.child(mCurrentDateString).getChildrenCount();
mPagerAdapter.setPollsAvailable(pollsAvailable);
Log.i("TAG", "There are " + String.valueOf(pollsAvailable) + " children in today's poll count.");
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
};
mPollsRef.addValueEventListener(v);
}
#Override
protected void onStop() {
super.onStop();
mPollsRef.removeEventListener(v);
}
#Override
public void onFragmentInteraction(Uri uri) {
}
class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
private int pollsAvailable = 0;
//fragment adapter constructor
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return HomePollsFragment.newInstance(position);
}
#Override
public int getCount() {
return pollsAvailable;
}
public void setPollsAvailable(int pollsAvailable) {
this.pollsAvailable = pollsAvailable;
this.notifyDataSetChanged();
}
}
#Override
public void onBackPressed() {
super.onBackPressed();
if (mPager.getCurrentItem() == 0) {
// If the user is currently looking at the first step, allow the system to handle the
// Back button. This calls finish() on this activity and pops the back stack.
super.onBackPressed();
} else {
// Otherwise, select the previous step.
mPager.setCurrentItem(mPager.getCurrentItem() - 1);
}
}
}
XML:
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.Toolbar
android:id="#+id/action_tool_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/actionRed">
</android.support.v7.widget.Toolbar>
<android.support.v4.view.ViewPager
android:id="#+id/home_polls_viewpager_fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
</LinearLayout>
<!-- The navigation drawer -->
<ListView
android:id="#+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="#android:color/transparent"
android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>

I do it like this:
android.support.v7.app.ActionBar actionBar = getSupportActionBar();
if(actionBar != null){
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);
}
This should solve the java.lang.NullPointerException.
"and generating all of the list items as well"
I cant see whats the problem here. Could you explain it a little bit?
The icon - Three horizontal lines in closed mode, a back arrow in opened mode with a nice smoot animation:
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
drawerLayout, /* DrawerLayout object */
toolbar, /* nav drawer icon to replace 'Up' caret */
R.string.nav, /* "open drawer" description */
R.string.nav /* "close drawer" description */
) {
/** Called when a drawer has settled in a completely closed state. */
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
if(extra == null){
toolbar.setTitle(title);
}else{
toolbar.setTitle(title + " - " + extra);
}
isOpen = false;
}
/** Called when a drawer has settled in a completely open state. */
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
actionBar.setTitle(R.string.nav);
isNavReady = true;
isOpen = true;
}
};
drawerLayout.addDrawerListener(drawerToggle);
#Override
public boolean onOptionsItemSelected(MenuItem item){
return drawerToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);
}
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
drawerToggle.syncState();
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
drawerToggle.onConfigurationChanged(newConfig);
}

FragmentTabHost - No tab known for tag null

Few days ago I implemented TabHostFramgent in a Fragment with a NavigationDrawer, and I faced with a problem that is the following error :
java.lang.IllegalStateException: No tab known for tag null
The thing is that all works perfectly since my first item list of my NavigationDrawer is my TabHostFragment, so it works perfect, but the problem is when I go in example to the second item and then I want to go back to the first item, every time that I try so it crashes.
I was searching everywhere, here in SO, code.google.com, etc... and I still don't get the proper answer.
My tab_host_test_2.xmllooks like :
<android.support.v4.app.FragmentTabHost xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TabWidget
android:id="#android:id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" />
<FrameLayout
android:id="#android:id/tabcontent"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_weight="0" />
<FrameLayout
android:id="#+id/realtabcontent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1" />
</LinearLayout>
</android.support.v4.app.FragmentTabHost>
My activity_main.xml where I've got my NavigationDrawer looks like :
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- Framelayout to display Fragments -->
<FrameLayout
android:id="#+id/frame_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- Listview to display slider menu -->
<ListView
android:id="#+id/list_slidermenu"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="#color/list_divider"
android:dividerHeight="1dp"
android:listSelector="#drawable/list_selector"
android:background="#color/list_background"/>
</android.support.v4.widget.DrawerLayout>
My TabHostFragment.java:
public class TabHostFragment extends Fragment {
public TabHostFragment(){
}
private FragmentTabHost mTabHost;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.tab_host_test2, container, false);
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
mTabHost = (FragmentTabHost)view.findViewById(android.R.id.tabhost);
mTabHost.setup(getActivity(), getChildFragmentManager(), R.id.realtabcontent);
mTabHost.addTab(mTabHost.newTabSpec("tab1").setIndicator("Tab1"),
MisOfertasFragment.class, null);
mTabHost.addTab(mTabHost.newTabSpec("tab2").setIndicator("Tab2"),
RecomendacionesFragment.class, null);
}
}
My ActivityMain.java:
public class MainActivity extends FragmentActivity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
// saber si esta abierto
public boolean mDrawerOpened;
// nav drawer title
private CharSequence mDrawerTitle;
private FragmentTabHost mTabHost;
// used to store app title
private CharSequence mTitle;
//para ponerlo visible
public MenuItem mi;
// slide menu items
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private ArrayList<NavDrawerItem> navDrawerItems;
private NavDrawerListAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
// load slide menu items
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
// nav drawer icons from resources
navMenuIcons = getResources()
.obtainTypedArray(R.array.nav_drawer_icons);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.list_slidermenu);
navDrawerItems = new ArrayList<NavDrawerItem>();
// adding nav drawer items to array
// Home
navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
// Find People
navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
// Photos
navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
// Communities, Will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1)));
// Pages
navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
// What's hot, We will add a counter here
navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1)));
//AyudaSugerencias
navDrawerItems.add(new NavDrawerItem(navMenuTitles[6], navMenuIcons.getResourceId(6, -1)));
navDrawerItems.add(new NavDrawerItem(navMenuTitles[7], navMenuIcons.getResourceId(7, -1)));
// Recycle the typed array
navMenuIcons.recycle();
mDrawerList.setOnItemClickListener(new SlideMenuClickListener());
// setting the nav drawer list adapter
adapter = new NavDrawerListAdapter(getApplicationContext(),
navDrawerItems);
mDrawerList.setAdapter(adapter);
// enabling action bar app icon and behaving it as toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setBackgroundDrawable(new ColorDrawable(0xff1d97dd));
getActionBar().setHomeButtonEnabled(true);
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, //nav menu toggle icon
R.string.app_name, // nav drawer open - description for accessibility
R.string.app_name // nav drawer close - description for accessibility
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(
Html.fromHtml("<font color='ffffff'>"
+ mTitle + "</font>"));
// calling onPrepareOptionsMenu() to show action bar icons
invalidateOptionsMenu();
mDrawerOpened = false;
syncState();
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(
Html.fromHtml("<font color='ffffff'>"
+ mDrawerTitle + "</font>"));
// calling onPrepareOptionsMenu() to hide action bar icons
invalidateOptionsMenu();
mDrawerOpened = true;
syncState();
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
// on first time display view for first nav item
displayView(0);
}
}
/**
* Slide menu item click listener
*/
private class SlideMenuClickListener implements
ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// display view for selected nav drawer item
displayView(position);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
Fragment fragment = null;
// toggle nav drawer on selecting action bar app icon/title
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action bar actions click
switch (item.getItemId()) {
case R.id.action_settings:
return true;
case R.id.ofertasRefresh:
return true;
case R.id.menu_search:
return true;
case R.id.newOffer:
getFragmentManager().beginTransaction().replace(R.id.frame_container, new TipusNouProducte()).commit();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* *
* Called when invalidateOptionsMenu() is triggered
*/
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// if nav drawer is opened, hide the action items
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
if (mDrawerOpened) {
menu.removeItem(R.id.ofertasRefresh);
menu.removeItem(R.id.menu_search);
menu.removeItem(R.id.newOffer);
}
if (!mDrawerOpened) {
menu.add(Menu.NONE, R.id.ofertasRefresh, Menu.NONE, mTitle);
}
return super.onPrepareOptionsMenu(menu);
}
/**
* Diplaying fragment view for selected nav drawer list item
*/
private void displayView(int position) {
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
Fragment fragment = null;
switch (position) {
case 0:
fragment = new TabHostFragment();
break;
case 1:
fragment = new RecomendacionesFragment();
break;
case 2:
fragment = new LocalizacionFragment();
break;
case 3:
fragment = new ListaProductosFragment();
break;
case 4:
fragment = new ConfiguracionFragment();
break;
case 5:
fragment = new AyudaSugerenciasFragment();
break;
case 6:
fragment = new AyudaSugerencias();
break;
default:
break;
}
if (fragment != null) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.frame_container, fragment).commit(); /// here says that replace android.app.Fragment in FragmentTransaction cannot be applied...
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(navMenuTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
} else {
// error in creating fragment
Log.e("MainActivity", "Error in creating fragment");
}
}
#Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
}
The full LogCat error is :
03-04 16:53:05.708 2232-2232/info.androidhive.slidingmenu E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: info.androidhive.slidingmenu, PID: 2232
java.lang.IllegalStateException: No tab known for tag null
at android.support.v4.app.FragmentTabHost.doTabChanged(FragmentTabHost.java:330)
at android.support.v4.app.FragmentTabHost.onAttachedToWindow(FragmentTabHost.java:280)
at android.view.View.dispatchAttachedToWindow(View.java:13406)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2707)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2714)
at android.view.ViewGroup.addViewInner(ViewGroup.java:3919)
at android.view.ViewGroup.addView(ViewGroup.java:3733)
at android.view.ViewGroup.addView(ViewGroup.java:3678)
at android.view.ViewGroup.addView(ViewGroup.java:3654)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:958)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
EDIT
The answer of #Y.S., was kinda different about what I was asking for, but it could be a solution, but it didn't worked fine at all, and the NavigationDrawer is under the TabHostFragment, etc... I don't want to change anything of my layout.

As the error suggests
Java : illegal state exception : no tab known for tag null
you tried to initialise TabHost but TabHost was null.
Try the code that I have used to initialise the TabHost and it works fine. Keep you code in onCreateView(). This problem occurs when you try to setup your FragmentTabHost in onViewCreated(), which is called too late. Try to set it up in onCreateView(), and add at least one tab before returning the view Object.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
// Create FragmentTabHost
mTabHost = new FragmentTabHost(getActivity());
// Locate fragment1.xml to create FragmentTabHost
mTabHost.setup(getActivity(), getChildFragmentManager(), R.layout.fragment1);
mTabHost.addTab(mTabHost.newTabSpec("groups").setIndicator("",getResources().getDrawable(R.drawable.tab_group_icon)),FragmentTab1.class, null);
mTabHost.addTab(mTabHost.newTabSpec("contacts").setIndicator("",getResources().getDrawable(R.drawable.tab_user_icon)),FragmentTab2.class, null);
MainActivity.fabButton.setVisibility(View.VISIBLE);
return mTabHost;
}
change Layout to:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<FrameLayout
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1" />
<android.support.v4.app.FragmentTabHost
android:id="#android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<FrameLayout
android:id="#android:id/tabcontent"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_weight="0" />
</android.support.v4.app.FragmentTabHost>
</LinearLayout>
Hope it helps.

There is another way to display tabs which can be used here.
Define TabHostFragment like this:
public class TabHostFragment extends Fragment implements ActionBar.TabListener{
public TabHostFragment(){
}
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
ViewPager mViewPager;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.tab_host_test2, container, false);
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState){
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getChildFragmentManager());
final ActionBar actionBar = ((FragmentActivity)getActivity()).getSupportActionBar();
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mViewPager = (ViewPager) view.findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
actionBar.addTab(
actionBar.newTab()
.setText(mAppSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
#Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
mViewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int i) {
Fragment f = null;
switch (i) {
case 0:
f = new MisOfertasFragment();
break;
case 1:
f = new RecomendacionesFragment();
break;
}
return f;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
return getFragmentTitle(position);
}
private String getFragmentTitle(int position){
if(position == 0)
return "Tab 1";
else if(position == 1)
return "Tab 2";
else
return "";
}
}
}
Define tab_host_test2.xml like this:
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Rest of the code remains the same.
Try this. This should work.
EDIT:
Add this to the displayView() method:
if(position != 0)
getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);

specify in .xml file where you are using this TabHostFragment(complete path like com.my.TabHostFragment). like
<com.my.TabHostFragment
android:id="#+id/fragmentId"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>