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Night mode to SharedPreferences is only causing errors

I theoretically have 2 related questions.
1) I tried to make a night mode for my app. That works so far pretty good. Then I wanted to put the setting the User chooses to SharedPreferences. In my first try, It just didn't work. All I did was getting red and causing errors. After a lot of research on the Internet, I found another idea. Now the app is starting but crashing immediately again. The error has to be in the SharedPreferences because as soon as I delete this part it is working again. I just can't find the error and it doesn't show me a red area or so either.
2) Just to check if my research are right. Is it true that it is not possible anymore to make a time-related Night mode? Means dark at night, light at day? I found out that MODE_NIGHT_AUTO_TIME was supposed to do that but is deprecated and they suggest to use MODE_NIGHT_AUTO_BATTERY which is kinda something really different.
btw. here is my code if it helps from the Setting:
public class Settings extends AppCompatActivity {
private static final String TAG = "SettingsActivity";
private RelativeLayout layout;
private SharedPreferences preferences;
private Bundle savedInstanceState;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
assert getSupportActionBar() != null;
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Spinner spinner = findViewById(DarkMode);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
Log.e(TAG, "onItemSelected: " + position);
handleNightMode(position);
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
Log.e(TAG, "onNothingSelected: ");
}
});
}
private void handleNightMode(int position) {
switch (position) {
case 0:
Log.e(TAG, "Nothing Selected");
break;
case 1:
Log.e(TAG, "FOLLLOW_SYSTEM");
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM);
getDelegate().applyDayNight();
break;
case 2:
Log.e(TAG, "YES");
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
getDelegate().applyDayNight();
break;
case 3:
Log.e(TAG, "NO");
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
getDelegate().applyDayNight();
break;
case 4:
Log.e(TAG, "AUTO");
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
getDelegate().applyDayNight();
break;
default:
Log.e(TAG, "FOLLLOW_SYSTEM");
break;
}
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
String NightMode = preferences.getString("prefTheme", "NO");
if (NightMode.equals("YES"))
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
if (NightMode.equals("NO"))
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
else if (NightMode.equals("AUTO"))
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
the MainActivity:
public class MainActivity extends AppCompatActivity {
int currentDayNight;
private Button settings;
private RelativeLayout layout;
private SharedPreferences preferences;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
layout = findViewById(R.id.layout);
settings = findViewById(R.id.btn_settings);
currentDayNight = AppCompatDelegate.getDefaultNightMode();
settings.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openSettings();
}
});
}
private void openSettings() {
Intent intent = new Intent(this, Settings.class);
startActivity(intent);
}
}
logcat:
04-16 21:31:59.861 11136-11136/? I/art: Not late-enabling -Xcheck:jni (already on)
04-16 21:32:00.033 11136-11136/com.goldenegg.darkmode W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter androidx.vectordrawable.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
04-16 21:32:00.086 11136-11136/com.goldenegg.darkmode I/art: Rejecting re-init on previously-failed class java.lang.Class<androidx.core.view.ViewCompat$2>
04-16 21:32:00.087 11136-11136/com.goldenegg.darkmode I/art: Rejecting re-init on previously-failed class java.lang.Class<androidx.core.view.ViewCompat$2>
04-16 21:32:00.168 11136-11149/com.goldenegg.darkmode I/art: Background partial concurrent mark sweep GC freed 523(79KB) AllocSpace objects, 0(0B) LOS objects, 50% free, 1007KB/2031KB, paused 6.320ms total 27.683ms
04-16 21:32:00.204 11136-11136/com.goldenegg.darkmode D/AndroidRuntime: Shutting down VM
--------- beginning of crash
04-16 21:32:00.205 11136-11136/com.goldenegg.darkmode E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.goldenegg.darkmode, PID: 11136
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.goldenegg.darkmode/com.goldenegg.darkmode.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' 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$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.goldenegg.darkmode.MainActivity.onCreate(MainActivity.java:34)
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) 
Thanks for your Help.
have a great day

Android: Unable to pause activity : java.lang.NullPointerException: null object reference [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 3 years ago.
Everything works fine in my app but when I press the back button (I mean exit app) the app is crashing. And I don't know why? I tried a couple of solutions but nothing works. It's a sounds/ringtones application.
I am a newbie at Android and I need some advice like "delete this" / "add this"
Here my code
package com.app.trying;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Environment;
import android.support.design.widget.NavigationView;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.MenuItem;
import android.widget.Toast;
import com.app.trying.tabs.Tab3;
import com.app.trying.tabs.Tab1;
import com.app.trying.tabs.Tab2;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import java.io.File;
public class MainActivity extends AppCompatActivity {
public MediaPlayer mp;
DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Banner Ad
AdView mAdView = (AdView) findViewById(R.id.adView);
AdRequest adRequest = new AdRequest.Builder().build();
mAdView.loadAd(adRequest);
toolbarTabs();
sidebar();
externalStorageAccess();
}
// Creates sidebar and sets onClickListeners
public void sidebar(){
mNavigationView = (NavigationView) findViewById(R.id.navigationView);
mNavigationView.setItemIconTintList(null);
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
switch (menuItem.getItemId()){
case R.id.sounds:
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();
break;
case R.id.share:
Intent shareIntent = new Intent(Intent.ACTION_SEND);
shareIntent.setType("text/plain");
shareIntent.putExtra(Intent.EXTRA_SUBJECT, getText(R.string.app_name));
shareIntent.putExtra(Intent.EXTRA_TEXT, getText(R.string.share_text) + " " + getText(R.string.app_name) + "\n\n" + getText(R.string.playstore_link));
startActivity(Intent.createChooser(shareIntent, getText(R.string.share_via)));
break;
}
return false;
}
});
}
// Is listening which sound on Tab1 has been clicked
public void TabOneItemClicked(int position) {
cleanUpMediaPlayer();
mp=MediaPlayer.create(MainActivity.this, Tab1.soundfiles[position]);
mp.start();
}
// Is listening which sound on Tab2 has been clicked
public void TabTwoItemClicked(int position) {
cleanUpMediaPlayer();
mp=MediaPlayer.create(MainActivity.this, Tab2.soundfiles[position]);
mp.start();
}
// Is listening which sound on Tab3 has been clicked
public void TabThreeItemClicked ( int position){
cleanUpMediaPlayer();
mp=MediaPlayer.create(MainActivity.this, Tab3.soundfiles[position]);
mp.start();
}
// Cleans MediaPlayer
public void cleanUpMediaPlayer() {
if (mp != null) {
try {
mp.stop();
mp.release();
mp = null;
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(MainActivity.this, "Error", Toast.LENGTH_LONG).show();
}
}
}
// Access external storage
public void externalStorageAccess(){
final File FILES_PATH = new File(Environment.getExternalStorageDirectory(), "Android/data/"+ getText(R.string.package_name) +"/files");
if (Environment.MEDIA_MOUNTED.equals(
Environment.getExternalStorageState())) {
if (!FILES_PATH.mkdirs()) {
Log.w("error", "Could not create " + FILES_PATH);
}
} else {
Toast.makeText(MainActivity.this, "Error", Toast.LENGTH_LONG).show();
finish();
}
}
// Creates toolbar Tabs
public void toolbarTabs(){
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView, new TabFragment()).commit();
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.app_name,
R.string.app_name);
mDrawerLayout.setDrawerListener(mDrawerToggle);
mDrawerToggle.syncState();
}
#Override
protected void onPause() {
super.onPause();
stopMediaPlayer();
}
public void stopMediaPlayer()
{
mp.stop();
}
}
And this is my error logs.
2019-05-09 19:13:22.296 704-704/? E/cnss-daemon: Invalid mac address: 0x555555f110M
2019-05-09 19:13:32.682 704-704/? E/cnss-daemon: Stale or unreachable neighbors, ndm state: 4
2019-05-09 19:13:39.537 443-2253/? E/ANDR-PERF-MPCTL: Invalid profile no. 0, total profiles 0 only
2019-05-09 19:13:40.333 24095-24175/? E/libEGL: validate_display:99 error 3008 (EGL_BAD_DISPLAY)
2019-05-09 19:13:43.035 443-2253/? E/ANDR-PERF-MPCTL: Invalid profile no. 0, total profiles 0 only
2019-05-09 19:13:43.116 24095-24095/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.app.trying, PID: 24095
java.lang.RuntimeException: Unable to pause activity {com.app.trying/com.app.trying.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
at android.app.ActivityThread.performPauseActivityIfNeeded(ActivityThread.java:3735)
at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3701)
at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3675)
at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3649)
at android.app.ActivityThread.-wrap16(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1487)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6111)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
at com.app.trying.MainActivity.stopMediaPlayer(MainActivity.java:155)
at com.app.trying.MainActivity.onPause(MainActivity.java:150)
at android.app.Activity.performPause(Activity.java:6917)
at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1323)
at android.app.ActivityThread.performPauseActivityIfNeeded(ActivityThread.java:3724)
at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3701) 
at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3675) 
at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3649) 
at android.app.ActivityThread.-wrap16(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1487) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6111) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
2019-05-09 19:13:43.736 2484-2484/? E/Launcher3: Meminfo, NativeHeapAllocatedSize18887424
2019-05-09 19:13:43.736 2484-2484/? E/Launcher3: Meminfo, NativeHeapSize35651584
2019-05-09 19:13:43.736 2484-2484/? E/Launcher3: Meminfo, getNativeHeapFreeSize16764160
2019-05-09 19:13:51.682 704-704/? E/cnss-daemon: Stale or unreachable neighbors, ndm state: 4
How should I resolve this error? Any help would be great. Thanks.

Your MediaPlayer instance is null as shown in the stacktrace, so:
public void stopMediaPlayer()
{
if (mp != null) {
mp.stop();
}
}

It can happen that your MediaPlayer instance is never initialization. So you have to handle it.

Error when inflating class Fragment

I have bug I don't know how to fix.
I need to add a Fragment, but it won't work.
Everything happens in void firstTime() and the error shows that it's on line setContentView(R.layout.activity_main);.
I really don't know how to fix this.
I tried a lot of things, but it just does not work.
Please, help me.
MainActivity class:
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
private MapFragment mapsFragment;
static MainActivity can;
static FloatingActionButton fab;
static FloatingActionButton show;
private String encoded_string;
private Bitmap bitmap;
private String picturePath;
View rootView;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
private void initializeMapsFragment() {
FragmentTransaction mTransaction = getSupportFragmentManager().beginTransaction();
mapsFragment = new MapFragment();
SupportMapFragment supportMapFragment = mapsFragment;
mTransaction.add(R.id.map, supportMapFragment);
mTransaction.commitNow();
}
#RequiresApi(api = Build.VERSION_CODES.GINGERBREAD)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
can = this;
Log.d("--***** MAP ", "::Loading Map");
setContentView(R.layout.activity_main);
initializeMapsFragment();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fab = (FloatingActionButton) findViewById(R.id.fab);
show = (FloatingActionButton) findViewById(R.id.show);
show.hide();
fab.hide();
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
callPopup();
}
});
show.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
stats();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
can, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(can);
Button searchButton = (Button) findViewById(R.id.searchButton);
searchButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
EditText searchView = (EditText) findViewById(R.id.searchView1);
String text = searchView.getText().toString();
Geocoder geocoder = new Geocoder(getBaseContext());
List<Address> addresses = null;
try {
// Getting a maximum of 3 Address that matches the input
// text
addresses = geocoder.getFromLocationName(text, 3);
if (addresses != null && !addresses.equals(""))
search(addresses);
} catch (Exception e) {
}
}
});
client = new GoogleApiClient.Builder(can).addApi(AppIndex.API).build();
}
public void start(){
setContentView(R.layout.activity_main);
initializeMapsFragment();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fab = (FloatingActionButton) findViewById(R.id.fab);
show = (FloatingActionButton) findViewById(R.id.show);
show.hide();
fab.hide();
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
callPopup();
}
});
show.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
stats();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
can, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(can);
Button searchButton = (Button) findViewById(R.id.searchButton);
searchButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
EditText searchView = (EditText) findViewById(R.id.searchView1);
String text = searchView.getText().toString();
Geocoder geocoder = new Geocoder(getBaseContext());
List<Address> addresses = null;
try {
// Getting a maximum of 3 Address that matches the input
// text
addresses = geocoder.getFromLocationName(text, 3);
if (addresses != null && !addresses.equals(""))
search(addresses);
} catch (Exception e) {
}
}
});
client = new GoogleApiClient.Builder(can).addApi(AppIndex.API).build();
}
protected void search(List<Address> addresses) {
Address address = (Address) addresses.get(0);
LatLng latLng = new LatLng(address.getLatitude(), address.getLongitude());
MapFragment.mapView.moveCamera(CameraUpdateFactory.newLatLng(latLng));
MapFragment.mapView.animateCamera(CameraUpdateFactory.zoomTo(15));
}
#RequiresApi(api = Build.VERSION_CODES.GINGERBREAD)
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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) {
return true;
}
return super.onOptionsItemSelected(item);
}
#RequiresApi(api = Build.VERSION_CODES.HONEYCOMB)
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
FragmentManager fm = getFragmentManager();
android.support.v4.app.FragmentManager sFm = getSupportFragmentManager();
int id = item.getItemId();
if (id == R.id.nav_camera) {
if (!mapsFragment.isAdded())
sFm.beginTransaction().add(R.id.map, mapsFragment).commit();
else
sFm.beginTransaction().show(mapsFragment).commit();
} else if (id == R.id.nav_share) {
Intent sharingIntent = new Intent(Intent.ACTION_SEND);
sharingIntent.setType("text/plain");
String shareBody = "Check this app out --> link.kys";
sharingIntent.putExtra(Intent.EXTRA_SUBJECT, "Best Free Parking app");
sharingIntent.putExtra(Intent.EXTRA_TEXT, shareBody);
startActivity(Intent.createChooser(sharingIntent, "Share via"));
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
public void firstTime() {
setContentView(R.layout.firsttime);
(findViewById(R.id.cancelBut))
.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
//View view = can.findViewById(android.R.id.content);
//Log.d("a", "" + ((ViewGroup)view).getChildCount() );
//((ViewGroup) view).removeView(view);
android.support.v4.app.FragmentManager sFm = getSupportFragmentManager();
sFm.beginTransaction().remove(mapsFragment).commitNow();
if(mapsFragment.isAdded()){
Log.d("--***** FRAGMENT ", "::Still On");
}
start();
}
});
}
public static void load(){
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(can);
if (!prefs.getBoolean("firstTime", false)) {
can.firstTime();
//SharedPreferences.Editor editor = prefs.edit();
//editor.putBoolean("firstTime", true);
//editor.commit();
}
}
private void stats() {
setContentView(R.layout.stats);
RatingBar ratingbar = (RatingBar) findViewById(R.id.ratingBar);
ratingbar.setRating((float) 2.0);
ratingbar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
public void onRatingChanged(RatingBar ratingBar, float rating,
boolean fromUser) {
ratingBar.setRating((float) 2.0);
}
});
((Button) findViewById(R.id.cancBut)).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
setContentView(R.layout.content_main);
}
});
}
}
Xml file:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.robertas.parking.bestfreeparking.MainActivity"
tools:showIn="#layout/app_bar_main">
<fragment
android:id="#+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.robertas.parking.test.MapsActivity"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_weight="0.68" />
<EditText
android:id="#+id/searchView1"
android:inputType="textPersonName"
android:layout_width="250dp"
android:layout_height="34dp"
android:layout_marginTop="14dp"
android:hint="Search Location"
android:ems="10"
android:textColor="#android:color/black"
android:background="#android:color/white"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true">
</EditText>
<Button
android:id="#+id/searchButton"
android:layout_width="wrap_content"
android:layout_height="25dp"
android:background="#drawable/places_ic_search"
android:layout_alignBottom="#+id/searchView1"
android:layout_alignRight="#+id/searchView1"
android:layout_alignEnd="#+id/searchView1"
android:layout_alignTop="#+id/searchView1"
android:layout_marginLeft="216dp"
android:layout_marginStart="216dp"
android:layout_alignLeft="#+id/searchView1"
android:layout_alignStart="#+id/searchView1" />
</RelativeLayout>
Error:
android.view.InflateException: Binary XML file line #12: Error inflating class fragment
Log:
03-10 20:21:45.036 31937-31937/com.robertas.parking.bestfreeparking D/AndroidRuntime: Shutting down VM
03-10 20:21:45.036 31937-31937/com.robertas.parking.bestfreeparking E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.robertas.parking.bestfreeparking, PID: 31937
android.view.InflateException: Binary XML file line #12: Error inflating class fragment
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:916)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:802)
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:916)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:802)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143)
at com.robertas.parking.bestfreeparking.MainActivity.start(MainActivity.java:161)
at com.robertas.parking.bestfreeparking.MainActivity$8.onClick(MainActivity.java:356)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
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)
Caused by: java.lang.IllegalArgumentException: Binary XML file line #12: Duplicate id 0x7f0f00e8, tag null, or parent id 0x7f0f00e7 with another fragment for com.google.android.gms.maps.SupportMapFragment
at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2427)
at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:120)
at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:378)
at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:33)
at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:77)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806) 
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:916) 
at android.view.LayoutInflater.rInflate(LayoutInflater.java:802) 
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:916) 
at android.view.LayoutInflater.rInflate(LayoutInflater.java:802) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:504) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:414) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:365) 
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:284) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143) 
at com.robertas.parking.bestfreeparking.MainActivity.start(MainActivity.java:161) 
at com.robertas.parking.bestfreeparking.MainActivity$8.onClick(MainActivity.java:356) 
at android.view.View.performClick(View.java:4780) 
at android.view.View$PerformClick.run(View.java:19866) 
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) 
03-10 20:21:45.039 1499-1878/system_process W/ActivityManager: Force finishing activity 1 com.robertas.parking.bestfreeparking/.MainActivity
[ 03-10 20:21:45.046 1499: 1878 D/ ]
HostConnection::get() New Host Connection established 0x7ffc98084ec0, tid 1878
03-10 20:21:45.051 1123-1123/? E/EGL_emulation: tid 1123: eglCreateSyncKHR(1299): error 0x3004 (EGL_BAD_ATTRIBUTE)
03-10 20:21:45.152 1499-1558/system_process I/OpenGLRenderer: Initialized EGL, version 1.4
03-10 20:21:45.194 1499-1558/system_process W/EGL_emulation: eglSurfaceAttrib not implemented
03-10 20:21:45.194 1499-1558/system_process W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0x7ffca953fb40, error=EGL_SUCCESS
03-10 20:21:45.612 1499-1518/system_process W/ActivityManager: Activity pause timeout for ActivityRecord{38e88b4d u0 com.robertas.parking.bestfreeparking/.MainActivity t155 f}
03-10 20:21:45.645 1756-2040/com.google.android.googlequicksearchbox W/EGL_emulation: eglSurfaceAttrib not implemented
03-10 20:21:45.645 1756-2040/com.google.android.googlequicksearchbox W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xe1c93620, error=EGL_SUCCESS
03-10 20:21:46.616 1622-1622/com.android.systemui W/ResourceType: No package identifier when getting value for resource number 0x00000000
03-10 20:21:46.616 1622-1622/com.android.systemui W/PackageManager: Failure retrieving resources for com.robertas.parking.bestfreeparking: Resource ID #0x0
03-10 20:21:46.832 1756-1756/com.google.android.googlequicksearchbox I/Choreographer: Skipped 69 frames! The application may be doing too much work on its main thread.
03-10 20:21:47.332 1756-2040/com.google.android.googlequicksearchbox W/OpenGLRenderer: Incorrectly called buildLayer on View: aep, destroying layer...
03-10 20:21:47.448 1499-1577/system_process W/AudioTrack: AUDIO_OUTPUT_FLAG_FAST denied by client
03-10 20:21:47.465 31937-31937/? I/Process: Sending signal. PID: 31937 SIG: 9
03-10 20:21:47.474 1499-14634/system_process I/WindowState: WIN DEATH: Window{394fad98 u0 com.robertas.parking.bestfreeparking/com.robertas.parking.bestfreeparking.MainActivity}
03-10 20:21:47.474 1499-1874/system_process I/ActivityManager: Process com.robertas.parking.bestfreeparking (pid 31937) has died
03-10 20:21:47.475 1499-1874/system_process W/ActivityManager: Scheduling restart of crashed service com.robertas.parking.bestfreeparking/com.android.tools.fd.runtime.InstantRunService in 1000ms
03-10 20:21:47.480 1123-1123/? W/SurfaceFlinger: couldn't log to binary event log: overflow.
03-10 20:21:47.521 1499-1558/system_process D/OpenGLRenderer: endAllStagingAnimators on 0x7ffc9dfec000 (RippleDrawable) with handle 0x7ffca9734500
03-10 20:21:47.525 1499-1753/system_process W/InputMethodManagerService: Got RemoteException sending setActive(false) notification to pid 31937 uid 10058
03-10 20:21:47.537 1956-32415/com.google.android.googlequicksearchbox:search I/HotwordRecognitionRnr: Starting hotword detection.
03-10 20:21:47.537 1956-32414/com.google.android.googlequicksearchbox:search I/MicrophoneInputStream: mic_starting gzi#c6aa4d0
03-10 20:21:47.568 1135-1912/? E/audio_hw_generic: Error opening input stream format 1, channel_mask 0010, sample_rate 16000
03-10 20:21:47.569 1135-32418/? I/AudioFlinger: AudioFlinger's thread 0xf59c4000 ready to run
03-10 20:21:47.581 2146-32417/com.google.android.gms W/IcingInternalCorpora: getNumBytesRead when not calculated.
03-10 20:21:47.584 1956-32414/com.google.android.googlequicksearchbox:search I/MicrophoneInputStream: mic_started gzi#c6aa4d0
03-10 20:21:47.602 1956-1956/com.google.android.googlequicksearchbox:search I/HotwordWorker: onReady
03-10 20:21:47.629 2146-2248/com.google.android.gms W/Settings: Setting adb_enabled has moved from android.provider.Settings.Secure to android.provider.Settings.Global.
03-10 20:21:47.629 2146-2248/com.google.android.gms I/Icing: Usage reports 1 indexed 1 rejected 0 imm upload true
03-10 20:21:47.634 2146-2248/com.google.android.gms W/Icing: App history upload skipped 1 0 0
03-10 20:21:48.101 1135-1535/? W/AudioFlinger: write blocked for 469 msecs, 16 delayed writes, thread 0xf58ac000
03-10 20:21:48.503 32429-32429/? I/art: Not late-enabling -Xcheck:jni (already on)
03-10 20:21:48.507 1499-1518/system_process I/ActivityManager: Start proc 32429:com.robertas.parking.bestfreeparking/u0a58 for service com.robertas.parking.bestfreeparking/com.android.tools.fd.runtime.InstantRunService
03-10 20:21:48.775 32429-32429/com.robertas.parking.bestfreeparking I/FirebaseInitProvider: FirebaseApp initialization unsuccessful
03-10 20:21:48.777 32429-32429/com.robertas.parking.bestfreeparking I/InstantRun: Starting Instant Run Server for com.robertas.parking.bestfreeparking
03-10 20:21:48.777 1499-14635/system_process W/ActivityManager: getRunningAppProcesses: caller 10058 does not hold REAL_GET_TASKS; limiting output

Everything happens in firstTime() void and error shows that it's on line setContentView(R.layout.activity_main);.
You can't do this.
start() and firstTime() are not the entrypoints to your activity/application.
onCreate() is and that is where you can only call setContentView(R.layout.activity_main).
Even so, static methods that "load" any Activity aren't going to work.
public static void load(){
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(can);
if (!prefs.getBoolean("firstTime", false)) {
can.firstTime(); // This doesn't work like this
}
}
Especially if you did MainActivity.load() somewhere else in your other classes.
Reading your error, see that start() -> setContentView() is causing the problem...
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:143)
at com.robertas.parking.bestfreeparking.MainActivity.start(MainActivity.java:161)
at com.robertas.parking.bestfreeparking.MainActivity$8.onClick(MainActivity.java:356)
at android.view.View.performClick(View.java:4780)
And the real error message
Duplicate id 0x7f0f00e8, tag null, or parent id 0x7f0f00e7 with another fragment for com.google.android.gms.maps.SupportMapFragment
Meaning that the Fragment "#+id/maps" has already been added into the FragmentManger of the Activity class, so it has been duplicated.
Activities should ideally not call setContentView outside of onCreate.
Reason being = You call setContentView, therefore removing the MapFragment (and other Views) entirely from the root view, so 1) the FragmentManger cannot find anything previously added, 2) Any view you had used findViewById before (probably) no longer exists.
If you are wanting to "replace" the content of some Activity, then you should use Fragments + a FrameLayout + a FragmentTransaction.replace() method call.

Make sure you compile com.google.android.gms.maps in your build.gradle file. Add this to your dependencies if it's not there:
dependencies {
<other dependencies>
compile 'com.google.android.gms:play-services-maps:10.2.0'
}
And remember to import it in your java file:
import com.google.android.gms.maps.SupportMapFragment;
And on the tools:context, it should be .MainActivity

Android Drawer items not working

I have created a drawer menu in android studio and changed items of drawer. I want to start another activity or view another layout on item click. but i get the following error and application is stopped.
03-24 21:38:28.202 2227-10289/? D/GassUtils: Found app info for package com.example.imran.myapp:1. Hash: 6b9333e031907d7a6a6c12cd9fdfa0d23bd13ee0f40c9617ddd005dc358321b0
03-24 21:38:28.202 2227-10289/? D/k: Found info for package com.example.imran.myapp in db.
03-24 21:38:38.722 1035-1167/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp
03-24 21:38:38.782 9789-9789/? I/Timeline: Timeline: Activity_launch_request id:com.example.imran.myapp time:121627337
03-24 21:38:38.802 1035-1853/? W/ActivityManager: NORMAL SET : srcAppInfo.processName = com.example.imran.myapp, destAppInfo.processName = com.example.imran.myapp
03-24 21:38:38.802 1035-1853/? W/ActivityManager: startActivity called from finishing ActivityRecord{28b176ac u0 com.example.imran.myapp/.MainActivity t2394 f}; forcing Intent.FLAG_ACTIVITY_NEW_TASK for: Intent { cmp=com.example.imran.myapp/.Home (has extras) }
03-24 21:38:38.802 1035-1853/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp
03-24 21:38:39.402 1035-1532/? I/WindowManager: Switching to real app window: Window{11c67d3b u0 com.example.imran.myapp/com.example.imran.myapp.Home}
03-24 21:38:39.622 1035-1069/? I/Timeline: Timeline: Activity_windows_visible id: ActivityRecord{dca1b0 u0 com.example.imran.myapp/.Home t2396} time:121628177
03-24 21:38:58.462 9789-9789/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.imran.myapp, PID: 9789
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.closeDrawer(int)' on a null object reference
at com.example.imran.myapp.Home.onNavigationItemSelected(Home.java:120)
at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:146)
at android.support.v7.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811)
at android.support.v7.internal.view.menu.SubMenuBuilder.dispatchMenuItemSelected(SubMenuBuilder.java:84)
at android.support.v7.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:153)
at android.support.v7.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958)
at android.support.design.internal.NavigationMenuPresenter.onItemClick(NavigationMenuPresenter.java:196)
at android.widget.AdapterView.performItemClick(AdapterView.java:334)
at android.widget.AbsListView.performItemClick(AbsListView.java:1536)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3683)
at android.widget.AbsListView$3.run(AbsListView.java:5604)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6145)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
03-24 21:38:58.462 1035-1514/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp
03-24 21:38:58.462 1035-1514/? W/ActivityManager: Force finishing activity com.example.imran.myapp/.Home
03-24 21:38:58.462 1035-1514/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp
03-24 21:38:58.542 1035-1035/? D/CrashAnrDetector: processName: com.example.imran.myapp
03-24 21:38:58.542 1035-1035/? D/CrashAnrDetector: broadcastEvent : com.example.imran.myapp data_app_crash
03-24 21:38:58.992 1035-1062/? W/ActivityManager: Activity pause timeout for ActivityRecord{dca1b0 u0 com.example.imran.myapp/.Home t2396 f}
Java files:
Home.java
package com.example.imran.myapp;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
public class Home extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Button logout = (Button) findViewById(R.id.logout_button);
TextView text1 = (TextView) findViewById(R.id.result_sms);
final UserLocalStore loginuser = new UserLocalStore(getApplicationContext());
SharedPreferences mPrefs = getSharedPreferences("userDetails",0);
String str1=(mPrefs.getString("fullname","Default_Value"));
String email = loginuser.getLoggedInUser().email;
text1.setText("Welcome "+str1+"- Your email: "+email);
logout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
loginuser.clearUserData();
//startActivity(new Intent(getApplicationContext(), MainActivity.class));
finish();
startActivity(new Intent(getApplicationContext(), MainActivity.class));
//setContentView(R.layout.activity_main);
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, 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) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_photos) {
// Handle the camera action
//setContentView(R.layout.myaccount);
} else if (id == R.id.nav_myaccount) {
setContentView(R.layout.activity_myaccount2);
//
} else if (id == R.id.nav_logout) {
UserLocalStore loginuser = new UserLocalStore(this);
loginuser.clearUserData();
finish();
startActivity(new Intent(getApplicationContext(), MainActivity.class));
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
In the last part of home.java when i add setContentView(R.layout.activity_myaccount2);
then the app crashes.

The problem here is a Null Pointer Exception when calling drawer.closeDrawer(); and as you've stated this happens after setContentView(R.layout.activity_myaccount2); is called.
By using setContentView, you're replacing your whole layout with another one, and it seems in this case like you're replacing your layout that contains R.id.drawer_layout with another one that doesn't contain it. The null pointer exception then happens when you try to use findViewById and closeDrawer, when the layout containing the drawer isn't there anymore, it's been replaced with another using setContentView.
To fix this you may need to rethink how you are structuring your app and displaying different content. As a starting point, I'd suggest looking up examples using an Activity which contains your drawer and Fragments to show the different pieces of content. The Activity and drawer are always there, only the fragments change, like this tutorial.

Android - IllegalStateException: could not execute method of the activity

I know that this is question had been asked several time, but I saw that the answer always change in relation to the code.
So, I have GameActivity that retrieve informations from a database in the global "info" variable, that is a String[].
Next I need to replace the current fragment with another fragment in relation to the button pressed (see methods "trueAnswer" and "falseAnswer"), and set two TextViews of that new fragment with the informations retrieved in the "info" string array.
The problem is that I'm able to set the informations the first time, in the first fragment in the method onStart() when the activity is created, but then seems like the "info" array is empty, because the "if" in the methods "trueAnswer" and "falseAnswer" doesn't works, and when I try to set the TextViews in the new fragment with the method "changeText(String, String)", the app crashes and return a NullPointerExeption.
I can't really see where is the error in the code, so I post here my methods and the logCat, hoping that may help you too.
GameActivity:
import java.io.IOException;
import android.content.SharedPreferences;
import android.database.SQLException;
import android.graphics.Color;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.TextView;
import android.widget.Toast;
public class GameActivity extends ActionBarActivity {
public long n = 0;
public String[] info = new String[3];
DataBase myDbHelper = new DataBase(this);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.replace(R.id.container, new PlaceholderFragment()).commit();
}
}
public void randomize(){
n = Math.round((Math.random()*3)+1);
}
public String[] getDatabaseInfo(){
myDbHelper.refresh();
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("NON HO CARICATO IL DATABASE TI PREGO SCUSAMI");
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
return info = myDbHelper.getQuestion(n);
}
#Override
public void onStart(){
super.onStart();
randomize();
getDatabaseInfo();
TextView d = (TextView)findViewById(R.id.question);
d.setText(info[1]);
}
#Override
public void onResume(){
super.onResume();
// Controlla qual e il colore di sfondo nei settings e lo applica
FrameLayout ll = (FrameLayout)findViewById(R.id.container);
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
int bgc = Color.parseColor(sharedPref.getString("background_color", "#000000"));
if(bgc == Color.BLACK){
TextView myTextView = (TextView)findViewById(R.id.question);
TextView r = (TextView)findViewById(R.id.answer);
myTextView.setTextColor(Color.WHITE);
r.setTextColor(Color.GRAY);
}
ll.setBackgroundColor(bgc);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.game, 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);
}
public void trueAnswer(View view){
if(info[2] == "1"){
// Create new fragment and transaction
FragmentCorrect newFragment = new FragmentCorrect();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.container, newFragment);
// Commit the transaction
transaction.commit();
newFragment.changeText(info[1], info[0]);
}else{
// Create new fragment and transaction
FragmentWrong newFragment = new FragmentWrong();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.container, newFragment);
// Commit the transaction
transaction.commit();
newFragment.changeText(info[1], info[0]);
}
}
public void falseAnswer(View view){
if(info[2] == "1"){
// Create new fragment and transaction
FragmentCorrect newFragment = new FragmentCorrect();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.container, newFragment);
// Commit the transaction
transaction.commit();
newFragment.changeText(info[1], info[0]);
}else{
// Create new fragment and transaction
FragmentWrong newFragment = new FragmentWrong();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack
transaction.replace(R.id.container, newFragment);
// Commit the transaction
transaction.commit();
newFragment.changeText(info[1], info[0]);
}
}
/**
* 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_game, container,
false);
return rootView;
}
}
}
FragmentCorrect:
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class FragmentCorrect extends Fragment {
TextView questionTv, answerTv;
public FragmentCorrect() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_corretto, container,
false);
questionTv = (TextView)rootView.findViewById(R.id.question);
answerTv = (TextView)rootView.findViewById(R.id.answer);
return rootView;
}
public void changeText(String question, String answer){
questionTv.setText(question);
answerTv.setText(answer);
}
}
FragmentWrong:(same code as FragmentCorrect, but with a different fragment layout).
LogCat:
05-19 12:13:04.278: E/AndroidRuntime(16694): FATAL EXCEPTION: main
05-19 12:13:04.278: E/AndroidRuntime(16694): java.lang.IllegalStateException: Could not execute method of the activity
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.view.View$1.onClick(View.java:3704)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.view.View.performClick(View.java:4232)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.view.View$PerformClick.run(View.java:17298)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.os.Handler.handleCallback(Handler.java:615)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.os.Handler.dispatchMessage(Handler.java:92)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.os.Looper.loop(Looper.java:137)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.app.ActivityThread.main(ActivityThread.java:4921)
05-19 12:13:04.278: E/AndroidRuntime(16694): at java.lang.reflect.Method.invokeNative(Native Method)
05-19 12:13:04.278: E/AndroidRuntime(16694): at java.lang.reflect.Method.invoke(Method.java:511)
05-19 12:13:04.278: E/AndroidRuntime(16694): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
05-19 12:13:04.278: E/AndroidRuntime(16694): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
05-19 12:13:04.278: E/AndroidRuntime(16694): at dalvik.system.NativeStart.main(Native Method)
05-19 12:13:04.278: E/AndroidRuntime(16694): Caused by: java.lang.reflect.InvocationTargetException
05-19 12:13:04.278: E/AndroidRuntime(16694): at java.lang.reflect.Method.invokeNative(Native Method)
05-19 12:13:04.278: E/AndroidRuntime(16694): at java.lang.reflect.Method.invoke(Method.java:511)
05-19 12:13:04.278: E/AndroidRuntime(16694): at android.view.View$1.onClick(View.java:3699)
05-19 12:13:04.278: E/AndroidRuntime(16694): ... 11 more
05-19 12:13:04.278: E/AndroidRuntime(16694): Caused by: java.lang.NullPointerException
05-19 12:13:04.278: E/AndroidRuntime(16694): at com.example.quizone_2.FragmentWrong.changeText(FragmentWrong.java:29)
05-19 12:13:04.278: E/AndroidRuntime(16694): at com.example.quizone_2.GameActivity.trueAnswer(GameActivity.java:151)
05-19 12:13:04.278: E/AndroidRuntime(16694): ... 14 more
05-19 12:13:06.403: I/Process(16694): Sending signal. PID: 16694 SIG: 9
Thank you very much in advance

You're creating a new fragment and immediately calling changeText() on it. The fragment transaction that creates the fragment view, calling the lifecycle callbacks such as onCreateView(), has not yet been run.
Consider passing arguments to your fragmens using a bundle and not call fragment methods directly outside fragment lifecycle.

You are calling
newFragment.changeText(info[1], info[0]);
too soon. You need to wait till the Fragment is attached to the Activity. Your views are null.
Also use .equalsto compare strings instead of == .
if(info[2].equals("1"))
Get to know Fragment lifecycle
http://developer.android.com/guide/components/fragments.html
Adding further to what laalto posted
Send data from activity to fragment in android