Restore views in a fragment added programmatically

Restore views in a fragment added programmatically - java

I have a single activity with a navigation drawer (the basic one provided by Eclipse new app wizard). I have a FrameLayout as a container for the different fragments of the app, which are replaced when selecting an item in the navigation drawer. They are also added to the BackStack.
These fragments contain a LinearLayout, which has some EditTexts and a Button. If the button is pressed, a new LinearLayout is created and a couple TextViews are added to it with the content of the EditTexts. The user can repeat this option more than once, so I cannot tell how many LinearLayouts I'll need, therefore I need to add them programmatically.
One of these fragments xml:
<LinearLayout
android:id="#+id/pen_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<LinearLayout
android:id="#+id/new_pen_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/activity_vertical_margin"
android:background="#drawable/border"
android:orientation="vertical"
android:paddingBottom="#dimen/home_section_margin_bottom"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/home_section_margin_top" >
<EditText
android:id="#+id/new_pen_round"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="number"
android:hint="#string/new_pen_round_hint"
android:textSize="#dimen/normal_text_size" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="2" >
<Button
android:id="#+id/new_pen_cancel_button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginRight="#dimen/new_item_button_margin_right"
android:layout_weight="1"
android:background="#drawable/button_bg"
android:paddingBottom="#dimen/new_item_button_padding_bottom"
android:paddingTop="#dimen/new_item_button_padding_top"
android:text="#string/new_item_cancel_button"
android:textSize="#dimen/normal_text_size" />
<Button
android:id="#+id/new_pen_insert_button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginLeft="#dimen/new_item_button_margin_left"
android:layout_weight="1"
android:background="#drawable/button_bg"
android:paddingBottom="#dimen/new_item_button_padding_bottom"
android:paddingTop="#dimen/new_item_button_padding_top"
android:text="#string/new_pen_insert_button"
android:textSize="#dimen/normal_text_size" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
There are actually many other EditTexts but I removed them here to keep it short, the result is the same. It's java file:
public class PenaltiesFragment extends Fragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_penalties, container, false);
Button insertNewPen = (Button) view.findViewById(R.id.new_pen_insert_button);
insertNewPen.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
TextView round = (TextView) getActivity().findViewById(R.id.new_pen_round);
LinearLayout layout = (LinearLayout) getActivity().findViewById(R.id.pen_layout);
int numChilds = layout.getChildCount();
CustomPenaltyLayout penalty = new CustomPenaltyLayout(getActivity(), round.getText());
layout.addView(penalty, numChilds - 1);
}
});
return view;
}
}
I removed some useless methods, which are just the default ones. CustomPenaltyLayoutis a subclass of LinearLayout which I created, it just creates some TextViews and adds them to itself.
Everything works fine here. The user inserts data in the EditText, presses the Insert button and a new layout is created and added in the fragment.
What I want to achieve is: say that I open the navigation drawer and select another page, the fragment gets replaced and if I go back to this fragment (via navigation drawer or via Back button) I want the text, that the user added, to be still there.
I do not call PenaltiesFragment.newInstance() everytime I switch back to this fragment, I instead create the PenaltiesFragment object once and keep using that one. This is what I do:
Fragment fragment;
switch (newContent) {
// various cases
case PEN:
if(penFragment == null) // penFragment is a private field of the Main Activity
penFragment = PenaltiesFragment.newInstance();
fragment = penFragment;
break;
}
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.container, fragment)
.addToBackStack("fragment back")
.commit();
I understand that onCreateView() is called again when the fragment is reloaded, right? So that is probably why a new, blank fragment is what I see. But how do I get the inserted CustomPenaltyLayout back? I cannot create it in the onCreateView() method.

I found a solution to my problem. I replaced the default FrameLayout that Android automatically created as a container for my fragments, with a ViewPager, then created a FragmentPagerAdapter like this:
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
Fragment fragment;
switch (position) {
// ...other cases
case PEN:
fragment = PenaltiesFragment.newInstance();
break;
// ...other cases
}
return fragment;
}
#Override
public int getCount() {
return 6;
}
}
Then the only thing left to do to keep all the views at all times has been to add this line to my activity onCreate method.
mPager.setOffscreenPageLimit(5);
See the documentation for details on how this method works.
This way, though, I had to reimplement all the back button logic, but it's still simple, and this is how I did it: I create a java.util.Stack<Integer> object, add fragment numbers to it (except when you use the back button, see below), and override onBackPressed() to make it pop the last viewed fragment instead of using the back stack, when my history stack is not empty.
You want to avoid pushing elements on the Stack when you press the back button, otherwise you will get stuck between two fragments if you keep using the back button, instead of eventually exiting.
My code:
MyAdapter mAdapter;
ViewPager mPager;
Stack<Integer> pageHistory;
int currentPage;
boolean saveToHistory;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.container);
mPager.setAdapter(mAdapter);
mPager.setOffscreenPageLimit(5);
pageHistory = new Stack<Integer>();
mPager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageSelected(int arg0) {
if(saveToHistory)
pageHistory.push(Integer.valueOf(currentPage));
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
saveToHistory = true;
}
#Override
public void onBackPressed() {
if(pageHistory.empty())
super.onBackPressed();
else {
saveToHistory = false;
mPager.setCurrentItem(pageHistory.pop().intValue());
saveToHistory = true;
}
};

Related

Android getListView() in fragment error

I keep having an issue with my android app where it is crashing with the following error when swiping between tabs:
09-16 16:19:27.142 4750-4750/com.khackett.runmate E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.khackett.runmate, PID: 4750
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:167)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:135)
at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:115)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
This is the MyRunsFragment:
public class MyRunsFragment extends ListFragment {
protected SwipeRefreshLayout mSwipeRefreshLayout;
// member variable to store the list of routes the user has accepted
protected List<ParseObject> mAcceptedRoutes;
private int MY_STATUS_CODE = 1111;
// Default constructor for MyRunsFragment
public MyRunsFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_my_runs, container, false);
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}
#Override
public void onResume() {
super.onResume();
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
// create the message object which is set to the message at the current position
ParseObject route = mAcceptedRoutes.get(position);
// String messageType = message.getString(ParseConstants.KEY_FILE_TYPE);
JSONArray parseList = route.getJSONArray(ParseConstants.KEY_LATLNG_POINTS);
JSONArray parseListBounds = route.getJSONArray(ParseConstants.KEY_LATLNG_BOUNDARY_POINTS);
String objectId = route.getObjectId();
String routeName = route.getString(ParseConstants.KEY_ROUTE_NAME);
// JSONArray ids = route.getJSONArray(ParseConstants.KEY_RECIPIENT_IDS);
// Start a map activity to display the route
Intent intent = new Intent(getActivity(), MapsActivityTrackRun.class);
intent.putExtra("parseLatLngList", parseList.toString());
intent.putExtra("parseLatLngBoundsList", parseListBounds.toString());
intent.putExtra("myRunsObjectId", objectId);
intent.putExtra("myRunsRouteName", routeName);
// Start the MapsActivityDisplayRoute activity
startActivityForResult(intent, MY_STATUS_CODE);
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
}
private void retrieveAcceptedRoutes() {
// query the routes class/table in parse
// get messages where the logged in user ID is in the list of the recipient ID's (we only want to retrieve the messages sent to us)
// querying the message class is similar to how we have been querying users
ParseQuery<ParseObject> queryRoute = new ParseQuery<ParseObject>(ParseConstants.CLASS_ROUTES);
// use the 'where' clause to search through the messages to find where our user ID is one of the recipients
queryRoute.whereEqualTo(ParseConstants.KEY_ACCEPTED_RECIPIENT_IDS, ParseUser.getCurrentUser().getObjectId());
// order results so that most recent message are at the top of the inbox
queryRoute.addDescendingOrder(ParseConstants.KEY_CREATED_AT);
// query is ready - run it
queryRoute.findInBackground(new FindCallback<ParseObject>() {
// When the retrieval is done from the Parse query, the done() callback method is called
#Override
public void done(List<ParseObject> routes, ParseException e) {
// dismiss the progress indicator here
// getActivity().setProgressBarIndeterminateVisibility(false);
// End refreshing once routes are retrieved
// done() is called from onResume() and the OnRefreshListener
// Need to check that its called from the the OnRefreshListener before ending it
if (mSwipeRefreshLayout.isRefreshing()) {
mSwipeRefreshLayout.setRefreshing(false);
}
// the list being returned is a list of routes
if (e == null) {
// successful - routes found. They are stored as a list in messages
mAcceptedRoutes = routes;
// adapt this data for the list view, showing the senders name
// create an array of strings to store the usernames and set the size equal to that of the list returned
String[] usernames = new String[mAcceptedRoutes.size()];
// enhanced for loop to go through the list of users and create an array of usernames
int i = 0;
for (ParseObject message : mAcceptedRoutes) {
// get the specific key
usernames[i] = message.getString(ParseConstants.KEY_SENDER_NAME);
i++;
}
// Create the adapter once and update its state on each refresh
if (getListView().getAdapter() == null) {
// the above adapter code is now replaced with the following line
RouteMessageAdapter adapter = new RouteMessageAdapter(getListView().getContext(), mAcceptedRoutes);
// Force a refresh of the list once data has changed
adapter.notifyDataSetChanged();
// need to call setListAdapter for this activity. This method is specifically from the ListActivity class
setListAdapter(adapter);
} else {
// refill the adapter
// cast it to RouteMessageAdapter
((RouteMessageAdapter) getListView().getAdapter()).refill(mAcceptedRoutes);
}
}
}
});
}
protected SwipeRefreshLayout.OnRefreshListener mOnRefreshListener = new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
// When list is swiped down to refresh, retrieve the users runs from the Parse backend
retrieveAcceptedRoutes();
}
};
}
And the fragment_my_runs layout file:
<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"
tools:context=".MainActivity$PlaceholderFragment">
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/swipeRefreshLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true">
<ListView
android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:clipToPadding="false"
android:paddingBottom="#dimen/inbox_vertical_margin"/>
</android.support.v4.widget.SwipeRefreshLayout>
<TextView
android:id="#android:id/empty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/empty_inbox_label"
android:textSize="#dimen/default_text_size"/>
</RelativeLayout>
The TabFragmentContainer
public class TabFragmentContainer extends Fragment {
// Create the FragmentPagerAdapter that will provide and manage tabs for each section.
public static MyFragmentPagerAdapter myFragmentPagerAdapter;
public static TabLayout tabLayout;
// The ViewPager is a layout widget in which each child view is a separate tab in the layout.
// It will host the section contents.
public static ViewPager viewPager;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate tab_layout_fragment_container view and setup views for the TabLayout and ViewPager items.
View view = inflater.inflate(R.layout.tab_layout_fragment_container, null);
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
// Runnable() method required to implement setupWithViewPager() method
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;
}
}
The FragmentPagerAdapter:
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
// The context to be passed in when the adapter is created.
private Context mContext;
// The number of tabs in the layout.
public static int numberOfTabs = 3;
/**
* Default constructor that accepts a FragmentManager parameter to add or remove fragments.
*
* #param context the context from the activity using the adapter.
* #param fragmentManager the FragmentManager for managing Fragments inside of the TabFragmentContainer.
*/
public MyFragmentPagerAdapter(Context context, FragmentManager fragmentManager) {
super(fragmentManager);
mContext = context;
}
/**
* Method to return the relevant fragment for the selected tab.
*/
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new MyRunsFragment();
case 1:
return new InboxRouteFragment();
case 2:
return new FriendsFragment();
}
return null;
}
/**
* Method that gets the number of tabs in the layout.
*
* #return the number of tabs in the layout.
*/
#Override
public int getCount() {
return numberOfTabs;
}
/**
* Method that returns the title of each tab in the layout.
*/
#Override
public CharSequence getPageTitle(int position) {
Locale locale = Locale.getDefault();
switch (position) {
case 0:
return mContext.getString(R.string.title_section1).toUpperCase(locale);
case 1:
return mContext.getString(R.string.title_section2).toUpperCase(locale);
case 2:
return mContext.getString(R.string.title_section3).toUpperCase(locale);
}
return null;
}
}
The tab_layout_fragment_container file that contains the ViewPager widget:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/ColorPrimaryPurple"
app:tabGravity="fill"
app:tabIndicatorColor="#color/ColorPrimaryPurple"
app:tabMode="fixed"
app:tabSelectedTextColor="#color/textColorPrimary"
app:tabTextColor="#color/pressedPurpleButton">
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
</LinearLayout>
The onCreate() method in my MainActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialise the DrawerLayout and NavigationView views.
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mNavigationView = (NavigationView) findViewById(R.id.navigationDrawerMenu);
// Inflate the first fragment to be displayed when logged into the app.
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView, new TabFragmentContainer()).commit();
// Setup click events on the NavigationView items.
// When an item is selected, replace the tab fragment container with the requested fragment.
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.navItemHome) {
FragmentTransaction tabFragmentContainer = mFragmentManager.beginTransaction();
tabFragmentContainer.replace(R.id.containerView, new TabFragmentContainer()).commit();
}
if (menuItem.getItemId() == R.id.navItemRunHistory) {
FragmentTransaction runHistoryFragment = mFragmentManager.beginTransaction();
runHistoryFragment.replace(R.id.containerView, new RunHistoryFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemSettings) {
FragmentTransaction settingsFragment = mFragmentManager.beginTransaction();
settingsFragment.replace(R.id.containerView, new SettingsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemHelp) {
FragmentTransaction instructionsFragment = mFragmentManager.beginTransaction();
instructionsFragment.replace(R.id.containerView, new InstructionsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemMyProfile) {
FragmentTransaction myProfileFragment = mFragmentManager.beginTransaction();
myProfileFragment.replace(R.id.containerView, new MyProfileFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemLogOut) {
// User has selected log out option. Log user out and return to login screen.
ParseUser.logOut();
navigateToLogin();
}
return false;
}
});
// Set up the Toolbar.
setupToolbar();
}
I have followed other answers here and added the getListView() functionality to the onViewCreated() method but the problem still persists... Can anyone point out where I might be going wrong?

Based on these facts:
The exception is thrown because there is no root view yet when done() calls getListView().
done() is called when the query made by retrieveAcceptedRoutes() gets a response.
retrieveAcceptedRoutes is called in multiple places, including the OnRefreshListener mOnRefreshListener, which is registered as the refresh listener in onCreateView() before there is a root view (that is, before onCreateView() returns).
...it is possible for getListView() to be called before there is a root view.
Try moving these 3 statements from onCreateView() to onViewCreated(), so that way the refresh listener can only be called when there is a root view.
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);

onViewCreated is called immediately after onCreateView, but the super.onViewCreated call is missing, perhaps this is root cause of your issue.
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState); // add this line back in
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}

I read your question again then I guess that:
Your ListFragment is destroyed while your background task keeps running. So when it's done, your callback would like to update the ListView which is no longer alive.
Actually, viewPager.setOffscreenPageLimit(3); may do the trick, but it's not a good practice. It forces your ViewPager to create and store more Fragments in memory which is not necessary. You can solve this without doing so.
What you should do: one of the following two practice should be fine, or both:
Destroy your task in your onPause or whatever lifecycle method, before your onDestroyView.
Exclude the code where you update your ListView inside your done() method. Make it a local method where you will check your ListView carefully, and there, you should ask your update process to run on UI thread to avoid any threading problem. Make sure to check if your getView() is not null (but not your getListView(), since it throws Exception if getView() returns null).
I recommend you to use both of them to make sure: your view is still useable and you don't waste your resource when running task in invisible fragment. Don't forget that by default, once your fragment is invisible, it is considered to be destroyed (not always, for example ViewPager keep reference of 2 fragments, but keep in mind that case).

remove all these imports:
import com.yourName.runmate.R;
Then resync your gradle and rebuild your project.
Also see here:
"cannot resolve symbol R" in Android Studio
edit
Your first obvious mistake in your Main is
mFragmentManager = getSupportFragmentManager();
should be:
mFragmentManager = getFragmentManager();
or change your Main activity to:
MainActivity extends FragmentActivity to make use of the support fragment manager.
You have a lot of unnecessary code in your question, majority of comments can be removed and imports for the purpose of this question.
What I have come up with is there is no activity, being used. The ListFragment needs to be attached to an Activity or you are trying to call that activity view before it is created.
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
If you are using Main, then you are not pulling them together well, from what I can see.
Firstly:
Take everything out of your onCreate and onCreateView (for all fragments) except the view inflater.
Place all the extra code into either onViewCreated or onActivityCreated. That way no methods can be called on a null view, as these are called after it is created.
Secondly, you need to sort out your activities and with what you're exactly trying to achieve.
You want a page viewer and a fragmentlist. The pageviewer needs to be associated with an activity, or activity fragment, not a fragment. Otherwise there is no view to attach the pageviewer pages to.
Use a FragmentActivity not a Fragment. To be the activity you run your ListFragment from.
public class TabFragmentContainer extends FragmentActivity {
MyPageAdapter pageAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_layout_fragment_container); // change to view layout.
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getFragmentManager(), getFragments());
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
}
}
I would suggest putting this into your ListFragment, to ensure your activity is created. You will need to move most of your code from your onCreate methods and put them in onViewCreated or onActivityCreated
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ArrayAdapter adapter = ArrayAdapter.createFromResource(getActivity(), R.layout.my_listview)layout, android.R.layout.simple_list_item_1);
setListAdapter(adapter);
getListView().setOnItemClickListener(this);
}
This code is just a guide, you'll need to tweak it.
Let me know if this helps.
These Q&As are excellent.
Content view not yet created
android Illegal state exception content view not yet create?
Fragment same principles applies to viewpager fragments ViewPager

Try to declare:
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
viewPager.setAdapter(myFragmentPagerAdapter);
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
before:
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;

Null pointer when setting text/background on android app [duplicate]

This is a canonical question for a problem frequently posted on StackOverflow.
I'm following a tutorial. I've created a new activity using a wizard. I get NullPointerException when attempting to call a method on Views obtained with findViewById() in my activity onCreate().
Activity onCreate():
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View something = findViewById(R.id.something);
something.setOnClickListener(new View.OnClickListener() { ... }); // NPE HERE
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
Layout XML (fragment_main.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="packagename.MainActivity$PlaceholderFragment" >
<View
android:layout_width="100dp"
android:layout_height="100dp"
android:id="#+id/something" />
</RelativeLayout>

The tutorial is probably outdated, attempting to create an activity-based UI instead of the fragment-based UI preferred by wizard-generated code.
The view is in the fragment layout (fragment_main.xml) and not in the activity layout (activity_main.xml). onCreate() is too early in the lifecycle to find it in the activity view hierarchy, and a null is returned. Invoking a method on null causes the NPE.
The preferred solution is to move the code to the fragment onCreateView(), calling findViewById() on the inflated fragment layout rootView:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
View something = rootView.findViewById(R.id.something); // not activity findViewById()
something.setOnClickListener(new View.OnClickListener() { ... });
return rootView;
}
As a side note, the fragment layout will eventually be a part of the activity view hierarchy and discoverable with activity findViewById() but only after the fragment transaction has been run. Pending fragment transactions get executed in super.onStart() after onCreate().

Try OnStart() method and just use
View view = getView().findViewById(R.id.something);
or Declare any View using getView().findViewById method in onStart()
Declare click listener on view by anyView.setOnClickListener(this);

Try to shift your accessing views to the onViewCreated method of fragment because sometimes when you try to access the views in onCreate method they are not rendered at the time resulting null pointer exception.
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
View something = findViewById(R.id.something);
something.setOnClickListener(new View.OnClickListener() { ... }); // NPE HERE
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}

Agreed, this is a typical error because people often don't really understand how Fragments work when they begin working on Android development. To alleviate confusion, I created a simple example code that I originally posted on Application is stopped in android emulator , but I posted it here as well.
An example is the following:
public class ContainerActivity extends FragmentActivity implements ExampleFragment.Callback
{
#Override
public void onCreate(Bundle saveInstanceState)
{
super.onCreate(saveInstanceState);
this.setContentView(R.layout.activity_container);
if (saveInstanceState == null)
{
getSupportFragmentManager().beginTransaction()
.add(R.id.activity_container_container, new ExampleFragment())
.addToBackStack(null)
.commit();
}
getSupportFragmentManager().addOnBackStackChangedListener(new OnBackStackChangedListener()
{
public void onBackStackChanged()
{
int backCount = getSupportFragmentManager().getBackStackEntryCount();
if (backCount == 0)
{
finish();
}
}
});
}
#Override
public void exampleFragmentCallback()
{
Toast.makeText(this, "Hello!", Toast.LENGTH_LONG).show();
}
}
activity_container.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<FrameLayout
android:id="#+id/activity_container_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
ExampleFragment:
public class ExampleFragment extends Fragment implements View.OnClickListener
{
public static interface Callback
{
void exampleFragmentCallback();
}
private Button btnOne;
private Button btnTwo;
private Button btnThree;
private Callback callback;
#Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
try
{
this.callback = (Callback) activity;
}
catch (ClassCastException e)
{
Log.e(this.getClass().getSimpleName(), "Activity must implement Callback interface.", e);
throw e;
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View rootView = inflater.inflate(R.layout.fragment_example, container, false);
btnOne = (Button) rootView.findViewById(R.id.example_button_one);
btnTwo = (Button) rootView.findViewById(R.id.example_button_two);
btnThree = (Button) rootView.findViewById(R.id.example_button_three);
btnOne.setOnClickListener(this);
btnTwo.setOnClickListener(this);
btnThree.setOnClickListener(this);
return rootView;
}
#Override
public void onClick(View v)
{
if (btnOne == v)
{
Toast.makeText(getActivity(), "One.", Toast.LENGTH_LONG).show();
}
else if (btnTwo == v)
{
Toast.makeText(getActivity(), "Two.", Toast.LENGTH_LONG).show();
}
else if (btnThree == v)
{
callback.exampleFragmentCallback();
}
}
}
fragment_example.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button
android:id="#+id/example_button_one"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="30dp"
android:text="#string/hello"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"/>
<Button
android:id="#+id/example_button_two"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/example_button_one"
android:layout_alignRight="#+id/example_button_one"
android:layout_below="#+id/example_button_one"
android:layout_marginTop="30dp"
android:text="#string/hello" />
<Button
android:id="#+id/example_button_three"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/example_button_two"
android:layout_alignRight="#+id/example_button_two"
android:layout_below="#+id/example_button_two"
android:layout_marginTop="30dp"
android:text="#string/hello" />
</RelativeLayout>
And that should be a valid example, it shows how you can use an Activity to display a Fragment, and handle events in that Fragment. And also how to communicate with the containing Activity.

The view "something" is in fragment and not in activity, so instead of accessing it in activity you must access it in the fragment class like
In PlaceholderFragment.class
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_main, container,
false);
View something = root .findViewById(R.id.something);
something.setOnClickListener(new View.OnClickListener() { ... });
return root;
}

You are trying to access UI elements in the onCreate() but , it is too early to access them , since in fragment views can be created in onCreateView() method.
And onActivityCreated() method is reliable to handle any actions on them, since activity is fully loaded in this state.

Add the following in your activity_main.xml
<fragment
android:id="#+id/myFragment"
android:name="packagename.MainActivity$PlaceholderFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
</fragment>

Since you have declared your View in the fragment_main.xml,move that piece of code where you get the NPE in the onCreateView() method of the fragment.
This should solve the issue.

in the posted code above in the question there is a problem :
you are using R.layout.activity_main in oncreate method, but the xml files name is "fragment_main.xml" , means you are trying to get the view of fragment_main.xml file which is not being shown so it gives null pointer exception. change the code like :
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_main);// your xml layout ,where the views are
View something = findViewById(R.id.something);
something.setOnClickListener(new View.OnClickListener() { ... }); // NPE HERE
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}

You have to remember important thing is :
NullPointerException occurs when you have declared your variable and trying to retreive its value before assigning value to it.

Use onViewCreated() Method whenever using or calling views from fragments.
override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
View v = view.findViewById(R.id.whatever)
}

I've got the same NullPointerException initializing a listener after calling findViewById() onCreate() and onCreateView() methods.
But when I've used the onActivityCreated(Bundle savedInstanceState) {...} it works. So, I could access the GroupView and set my listener.
I hope it be helpful.

Most popular library for finding views which is used by almost every developer.
ButterKnife
As I can their are enough answers explaining finding views with proper methodology. But if you are android developer and code frequently on daily basis then you can use butter-knife which saves a lot time in finding views and you don't have write code for it, With in 2-3 steps you can find views in milliseconds.
Add dependency in app level gradle:
implementation 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'
Add plugin for butter knife:
File -> Settings -> plugins->
Then search for Android ButterKnife Zelezny and install plugin and restart your studio and you are done with it.
Now just go to Oncreate method of your activity and right click on your layout_name and tap on generate button and select butterknife injection option and your views references will be automatically created like mention below:
#BindView(R.id.rv_featured_artist)
ViewPager rvFeaturedArtist;
#BindView(R.id.indicator)
PageIndicator indicator;
#BindView(R.id.rv_artist)
RecyclerView rvArtist;
#BindView(R.id.nsv)
NestedScrollingView nsv;
#BindView(R.id.btn_filter)
Button btnFilter;

Do I need fragments and how to access them?

I am new to Android so my question may seem ridiculous but I cant figure it out.
I started creating an app some time ago and using 'Create new Android Activity' usually created a .java and .xml file for it, and everything worked. Now, after update when I use 'Create new Android Activity' it creates .java with class (which now extends ActionBarActivity and not Activity as before) and it adds a fragment_nameofactivity.xml + all things to make it work like internal class extending Fragment...
Now I used to do some ListView display on the page and without a fragment it all works great, but when fragment got introduced I can no longer findViewById(R.id.list_view) if its inside a fragment...
My question is do I need to place my whole functionality inside the class extending Fragment? I tried but it didn't work... Or do I still write all my functionality in the original class and then somehow access the listView in the fragment...
Here is the code:
public class PlayersActivity extends ActionBarActivity {
PlayerDataDatabaseAdapter playerDataHelper;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_players);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
playerDataHelper = new PlayerDataDatabaseAdapter(this);
playerDataHelper.open();
displayPlayersList();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.players, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_players,
container, false);
return rootView;
}
}
private void displayPlayersList() {
Cursor cursor = playerDataHelper.getAllPlayers();
String [] columns = playerDataHelper.columnsToBind();
int [] to = new int[] {
R.id.player_name,
};
SimpleCursorAdapter dataAdapter = new SimpleCursorAdapter(this, R.layout.fragment_player_details, cursor, columns, to, 0);
ListView listView = (ListView) findViewById(R.id.players_list);
listView.setAdapter(dataAdapter);
listView.setOnItemClickListener(new OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> listView, View view, int position, long id) {
Cursor cursor = (Cursor) listView.getItemAtPosition(position);
int player_id = cursor.getInt(cursor.getColumnIndexOrThrow("_id"));
Intent intent = new Intent(PlayersActivity.this, EditPlayerActivity.class);
intent.putExtra("PlayerId", player_id);
startActivity(intent);
}
});
}
public void addNewPlayer(View view) {
Intent intent = new Intent(this, AddPlayerActivity.class);
startActivity(intent);
}
}
Fragment_players.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="uk.co.eximage.soccermum.PlayersActivity$PlaceholderFragment" >
<TextView
android:id="#+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_alignParentTop="true"
android:text="#string/players"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Button
android:id="#+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal = "true"
android:layout_below="#+id/textView1"
android:onClick="addNewPlayer"
android:text="#string/add_player" />
<ListView
android:id="#+id/players_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button1"
>
</ListView>
</RelativeLayout>
activity_players.xml:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="uk.co.eximage.soccermum.PlayersActivity"
tools:ignore="MergeRootFrame" />
Running this returns NullPointerException on the line that tries to get players_list:
ListView listView = (ListView) findViewById(R.id.players_list);
after this listView is null.
What am I doing wrong?
And finally do I need fragments? Maybe I should just remove them and do it the 'old' way with one view per page?

You need to iniaitlize ListView in Fragment
ListView listView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_players,
container, false);
listView = (ListView)rootView. findViewById(R.id.players_list);
playerDataHelper = new PlayerDataDatabaseAdapter(getActivity());
playerDataHelper.open();
displayPlayersList();
The ListView belongs to fragment_players.xml. Move all your code related to fragment in onCreateView.
Edit:
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
ListView listView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_players,
container, false);
listView = (ListView)rootView. findViewById(R.id.players_list);
playerDataHelper = new PlayerDataDatabaseAdapter(getActivity());
playerDataHelper.open();
displayPlayersList();
return rootView;
}
private void displayPlayersList() {
Cursor cursor = playerDataHelper.getAllPlayers();
String [] columns = playerDataHelper.columnsToBind();
int [] to = new int[] {
R.id.player_name,
};
SimpleCursorAdapter dataAdapter = new SimpleCursorAdapter(getActivity(), R.layout.fragment_player_details, cursor, columns, to, 0);
listView.setAdapter(dataAdapter);
listView.setOnItemClickListener(new OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> listView, View view, int position, long id) {
Cursor cursor = (Cursor) listView.getItemAtPosition(position);
int player_id = cursor.getInt(cursor.getColumnIndexOrThrow("_id"));
Intent intent = new Intent(getActivity(), EditPlayerActivity.class);
intent.putExtra("PlayerId", player_id);
startActivity(intent);
}
});
}
}

Fragments were introduced to better support the tablet form factor. If you don't plan to rearrange your display (ie. show list and detail view together), you don't need fragments and can go the old way.

You should have to initialize Listview from fragment rootView
Either you have to Declare ListView globally and intialize inside onCreateView of Fragment or have to declare View rootView globally and initialize listview by
ListView listView = (ListView) rootView .findViewById(R.id.players_list);

Change fragment visibility in runtime when the fragment was created using FragmentPagerAdapter

I'm trying to create my first Android app that looks like following: there is main activity with multiple fragments initialized by FragmentPagerAdapter. There is another activity (SettingsActivity) where I want to list all the fragment names and allow hiding some of them. To hide them I want to use the following:
FragmentManager fm=getFragmentManager();
Fragment myFragment=fm.findFragmentByTag("tag");
fm.beginTransaction().hide(myFragment).commit();
The problem is that I don't know fragment id or tag, not sure if they exist. How I can get them? Should I switch to XML definition to make it possible?
Adapter:
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
switch (index){
case 0:
return new CoverFragment();
case 1:
return new NumbersConverterFragment();
case 2:
return new TempConverterFragment();
case 3:
return new LengthConverterFragment();
case 4:
return new AreaConverterFragment();
case 5:
return new VolumeConverterFragment();
case 6:
return new WeightConverterFragment();
case 7:
return new SpeedConverterFragment();
}
return null;
}
#Override
public int getCount() {
return 8;
}
Main activity:
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
private ViewPager viewPager;
private TabsPagerAdapter tabsPagerAdapter;
private ActionBar actionBar;
#Override
protected void onCreate(Bundle savedInstanceState) {
String[] tabs={getString(R.string.title_section0), getString(R.string.title_section1),getString(R.string.title_section2)};
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager=(ViewPager) findViewById(R.id.pager);
actionBar=getActionBar();
tabsPagerAdapter=new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(tabsPagerAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for(String tab : tabs){
actionBar.addTab(actionBar.newTab().setText(tab).setTabListener(this));
}
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
...
});
}
Fragment layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#fbfdfb"
>
<TextView android:text="#string/celsius_" android:id="#+id/textView1"
android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>
<EditText android:text="" android:id="#+id/txtCelsius" android:layout_width="match_parent"
android:layout_height="wrap_content"></EditText>
<TextView android:text="#string/fahrenheit_" android:id="#+id/textView1"
android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>
<EditText android:text="" android:id="#+id/txtFahrenheit" android:layout_width="match_parent"
android:layout_height="wrap_content"></EditText>
<TextView android:text="#string/kelvin_" android:id="#+id/textView1"
android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>
<EditText android:text="" android:id="#+id/txtKelvin" android:layout_width="match_parent"
android:layout_height="wrap_content"></EditText>
</LinearLayout>
Fragment class:
public class TempConverterFragment extends Fragment {
EditText txtCelsius, txtFahrenheit, txtKelvin;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.temp_converter_fragment, container, false);
txtCelsius = (EditText) rootView.findViewById(R.id.txtCelsius);
txtFahrenheit = (EditText) rootView.findViewById(R.id.txtFahrenheit);
txtKelvin = (EditText) rootView.findViewById(R.id.txtKelvin);
...
}
...
}
Thanks in advance.

If SettingsActivity is not the Activity holding the FragmentPagerAdapter, then you would have to re-create all the fragments. The nature of a fragment is to be closely tied to it's activity.
If SettingsActivity is the Activity holding the FragmentPagerAdapter, then As I recall, FragmentPagerAdapter will initialize all the 8 fragments as soon as possible to have them ready when you swipe, unlike FragmentStatePagerAdapter. This means that you should (I think) be able to create each fragment in the constructor TabsPagerAdapter and keeping a reference to them, which you could access using getter methods on the TabsPagerAdapter.
Here is an example of how to get easy access to your pageradapter fragments:
public class DisplayPagerAdapter extends FragmentStatePagerAdapter {
private static final String TAG = "DisplayPagerAdapter";
SparseArray<DisplayFragment> registeredFragments = new SparseArray<DisplayFragment>();
#Inject DisplayCoreModule display;
public DisplayPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public int getCount() {
return (display != null && display.getPagesCount() > 0) ? display.getPagesCount() : 1;
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
#Override
public Fragment getItem(int position) {
Log.d(TAG, "getItem " + position);
return DisplayFragment.newInstance(position);
}
#Override
public CharSequence getPageTitle(int position) {
if (display != null && display.getPagesCount() > 0) {
return "Side " + (position+1);
} else {
return super.getPageTitle(position);
}
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Log.d(TAG, "instantiateItem " + position);
DisplayFragment fragment = (DisplayFragment) super.instantiateItem(container, position);
registeredFragments.put(position, fragment);
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
Log.d(TAG, "destroyItem " + position);
registeredFragments.remove(position);
super.destroyItem(container, position, object);
}
public Fragment getRegisteredFragment(int position) {
return registeredFragments.get(position);
}
public SparseArray<DisplayFragment> getRegisteredFragments() {
return registeredFragments;
}
}
Now if you implement this usage of registeredFragments , you can call tabsPagerAdapter.getRegisteredFragment(2) to get your TempConverterFragment.
SparseArray<DisplayFragment> should be SparseArray<Fragment> in your case
Now this does not solve the your SettingsActivity problem. But if I understand you correctly, then adding the fragments your want directly in the layout XML of SettingsActivity would make sense. Then it would be easy to temporarily hide the fragments or whatever using:
FragmentManager fm=getFragmentManager();
Fragment myFragment=fm.findFragmentById(R.id.frag_tempconverter)
fm.beginTransaction().hide(myFragment).commit();
Notice the use of findFragmentById. The tag is usually used for dynamically added fragments (atleast in my mind). The findFragmentById will surely return a fragment if it is defined in the XML layout but just to be clear, it will be a new instance of the fragment.
To address your questions:
What if I move the fragments to the main activity XML? Won't it make things simpler
Do not think so, the updated answer shows how to easily access the fragments (from within your main activity).
Though not sure I can use FragmentManager in SettingsActivity
Sure you can. You can add new fragments, access available fragments (from predefined XML using findById or dynamically added using findByTag). You cannot, however, access the same instance of the fragment as was kept by your main activity.
To share information between the fragments and the two activities, you need to persist the state of your fragments somehow (which is a different topic).
All in all I think you are on the right path, you just need to combine the right pieces of the puzzle :)

Custom ListView click issue on items in Android

So I have a custom ListView object. The list items have two textviews stacked on top of each other, plus a horizontal progress bar that I want to remain hidden until I actually do something. To the far right is a checkbox that I only want to display when the user needs to download updates to their database(s). When I disable the checkbox by setting the visibility to Visibility.GONE, I am able to click on the list items. When the checkbox is visible, I am unable to click on anything in the list except the checkboxes. I've done some searching but haven't found anything relevant to my current situation. I found this question but I'm using an overridden ArrayAdapter since I'm using ArrayLists to contain the list of databases internally. Do I just need to get the LinearLayout view and add an onClickListener like Tom did? I'm not sure.
Here's the listview row layout XML:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="?android:attr/listPreferredItemHeight"
android:padding="6dip">
<LinearLayout
android:orientation="vertical"
android:layout_width="0dip"
android:layout_weight="1"
android:layout_height="fill_parent">
<TextView
android:id="#+id/UpdateNameText"
android:layout_width="wrap_content"
android:layout_height="0dip"
android:layout_weight="1"
android:textSize="18sp"
android:gravity="center_vertical"
/>
<TextView
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:id="#+id/UpdateStatusText"
android:singleLine="true"
android:ellipsize="marquee"
/>
<ProgressBar android:id="#+id/UpdateProgress"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:indeterminateOnly="false"
android:progressDrawable="#android:drawable/progress_horizontal"
android:indeterminateDrawable="#android:drawable/progress_indeterminate_horizontal"
android:minHeight="10dip"
android:maxHeight="10dip"
/>
</LinearLayout>
<CheckBox android:text=""
android:id="#+id/UpdateCheckBox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
And here's the class that extends the ListActivity. Obviously it's still in development so forgive the things that are missing or might be left laying around:
public class UpdateActivity extends ListActivity {
AccountManager lookupDb;
boolean allSelected;
UpdateListAdapter list;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
lookupDb = new AccountManager(this);
lookupDb.loadUpdates();
setContentView(R.layout.update);
allSelected = false;
list = new UpdateListAdapter(this, R.layout.update_row, lookupDb.getUpdateItems());
setListAdapter(list);
Button btnEnterRegCode = (Button)findViewById(R.id.btnUpdateRegister);
btnEnterRegCode.setVisibility(View.GONE);
Button btnSelectAll = (Button)findViewById(R.id.btnSelectAll);
btnSelectAll.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
allSelected = !allSelected;
for(int i=0; i < lookupDb.getUpdateItems().size(); i++) {
lookupDb.getUpdateItem(i).setSelected(!lookupDb.getUpdateItem(i).isSelected());
}
list.notifyDataSetChanged();
// loop through each UpdateItem and set the selected attribute to the inverse
} // end onClick
}); // end setOnClickListener
Button btnUpdate = (Button)findViewById(R.id.btnUpdate);
btnUpdate.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
} // end onClick
}); // end setOnClickListener
lookupDb.close();
} // end onCreate
#Override
protected void onDestroy() {
super.onDestroy();
for (UpdateItem item : lookupDb.getUpdateItems()) {
item.getDatabase().close();
}
}
#Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
UpdateItem item = lookupDb.getUpdateItem(position);
if (item != null) {
item.setSelected(!item.isSelected());
list.notifyDataSetChanged();
}
}
private class UpdateListAdapter extends ArrayAdapter<UpdateItem> {
private List<UpdateItem> items;
public UpdateListAdapter(Context context, int textViewResourceId, List<UpdateItem> items) {
super(context, textViewResourceId, items);
this.items = items;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = null;
if (convertView == null) {
LayoutInflater li = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = li.inflate(R.layout.update_row, null);
} else {
row = convertView;
}
UpdateItem item = items.get(position);
if (item != null) {
TextView upper = (TextView)row.findViewById(R.id.UpdateNameText);
TextView lower = (TextView)row.findViewById(R.id.UpdateStatusText);
CheckBox cb = (CheckBox)row.findViewById(R.id.UpdateCheckBox);
upper.setText(item.getName());
lower.setText(item.getStatusText());
if (item.getStatusCode() == UpdateItem.UP_TO_DATE) {
cb.setVisibility(View.GONE);
} else {
cb.setVisibility(View.VISIBLE);
cb.setChecked(item.isSelected());
}
ProgressBar pb = (ProgressBar)row.findViewById(R.id.UpdateProgress);
pb.setVisibility(View.GONE);
}
return row;
}
} // end inner class UpdateListAdapter
}
edit: I'm still having this problem. I'm cheating and adding onClick handlers to the textviews but it seems extremely stupid that my onListItemClick() function is not being called at all when I am not clicking on my checkbox.

The issue is that Android doesn't allow you to select list items that have elements on them that are focusable. I modified the checkbox on the list item to have an attribute like so:
android:focusable="false"
Now my list items that contain checkboxes (works for buttons too) are "selectable" in the traditional sense (they light up, you can click anywhere in the list item and the "onListItemClick" handler will fire, etc).
EDIT: As an update, a commenter mentioned "Just a note, after changing the visibility of the button I had to programmatically disable the focus again."

In case you have ImageButton inside the list item you should set the descendantFocusability value to 'blocksDescendants' in the root list item element.
android:descendantFocusability="blocksDescendants"
And the focusableInTouchMode flag to true in the ImageButton view.
android:focusableInTouchMode="true"

I've had a similar issue occur and found that the CheckBox is rather finicky in a ListView. What happens is it imposes it's will on the entire ListItem, and sort of overrides the onListItemClick. You may want to implement a click handler for that, and set the text property for the CheckBox as well, instead of using the TextViews.
I'd say look into this View object as well, it may work better than the CheckBox
Checked Text View

use this line in the root view of the list item
android:descendantFocusability="blocksDescendants"

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