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My AsyncTask in another class is causing NullPointerException when it is called in this class

I am quite new to android development and I am facing a NullPointerException when I am trying to call an AsyncTask which is an inner class in another class.
I believe it is the way I am instantiating it but this is what I have:
// This onClick is in my adapter class - which is a separate Java File and class
#Override
public void onClick(View v) {
UploadRes uploadRes = new UploadRes();
UploadRes.UploadResConfirm uploadResConfirm = uploadRes.new UploadResConfirm(v.getContext());
uploadResConfirm.execute(fileName, filePath);
}
public class UploadResConfirm extends AsyncTask<String, String, String> {
Dialog dialog;
Context context;
public UploadResConfirm(Context context){
this.context = context;
}
#Override
protected void onPreExecute(){
dialog = new Dialog(UploadRes.this);
dialog.setTitle("Currently uploading");
dialog.show();
}
I believe it has got something to do with the dialog box itself being instantiated in the AsyncTask class.
The error stack trace on Logcat - its the Dialog, I think its in the wrong place...
java.lang.NullPointerException
at codeman.androapp.UploadRes$UploadResConfirm.onPreExecute(UploadRes.java:246)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at android.view.View.performClick(View.java:4240)
at android.view.View$PerformClick.run(View.java:17721)
at android.os.Handler.handleCallback(Handler.java:730)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Some help if any would be much obliged.

Instead of dialog = new Dialog(UploadRes.this);
Try
dialog = new Dialog(context);
your are passing a wrong context to create dialog.

AsyncTask with progressbar

The following code is a part of my app and it isn't working and I don't know why.
I don't know at which place I can put the "new MormaKaugummi().execute();". At any place the App crashed and gave me the error "Unfortunately, Criminal Life has stopped."
The "counter textview" is in an another activity in the same app.
(The name of the App is Criminal Life).
I need a unique solution because I'm new in Android programming.
public class Morma extends AppCompatActivity {
class MormaKaugummi extends AsyncTask<String, String, String> {
private int count = 0;
private void count() {
count++;
}
private void update() {
TextView counter = (TextView) findViewById(R.id.counter);
String Kcounter = Integer.toString(count);
counter.setText(Kcounter);
}
#Override
protected String doInBackground(String... params) {
count();
update();
return null;
}
}
private ProgressBar progressBarKaugummi;
private int progressStatusKaugummi = 0;
private Handler handlerKaugummi = new Handler();
#Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_morma);
Button buttonMormaKaugummiKlauen = (Button) findViewById(R.id.buttonMormaKaugummiKlauen);
buttonMormaKaugummiKlauen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
progressBarKaugummi = (ProgressBar) findViewById(R.id.progressBarMormaKaugummi);
new Thread(new Runnable() {
public void run() {
while (progressStatusKaugummi < 100) {
progressStatusKaugummi += 1;
handlerKaugummi.post(new Runnable() {
public void run() {
progressBarKaugummi.setProgress(progressStatusKaugummi);
}
});
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
if (progressStatusKaugummi == 100) {
progressBarKaugummi.setProgress(0);
recreate();
new MormaKaugummi().execute();
}
}
});
That's the logcat
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: java.lang.RuntimeException: An error occured while executing doInBackground()
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.lang.Thread.run(Thread.java:856)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: Caused by: java.lang.NullPointerException
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at peppermine_studios.criminallife.Morma$MormaKaugummi.update(Morma.java:26)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at peppermine_studios.criminallife.Morma$MormaKaugummi.doInBackground(Morma.java:32)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at peppermine_studios.criminallife.Morma$MormaKaugummi.doInBackground(Morma.java:15)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at java.lang.Thread.run(Thread.java:856)
11-07 13:48:35.514 622-622/peppermine_studios.criminallife W/EGL_emulation: eglSurfaceAttrib not implemented
11-07 13:48:35.674 622-622/peppermine_studios.criminallife W/EGL_emulation: eglSurfaceAttrib not implemented
11-07 13:48:37.364 622-1376/? I/Process: Sending signal. PID: 622 SIG: 9

You are trying to do findviewbyId and update the text view in your doInBackground method via the update function, which you cannot do.
As for the crash its happening because of a null pointer exception as you can read for yourself in the logcat's caused by clause it tells you the exact line number where the null pointer exception is thrown
Caused by: java.lang.NullPointerException
11-07 13:48:34.964 622-1376/peppermine_studios.criminallife E/AndroidRuntime: at peppermine_studios.criminallife.Morma$MormaKaugummi.update(Morma.java:26)
as you can see here, its caused by null pointer at line 26 in Morma.java and I am guessing that your TextView counter is null since you are trying to initialize a variable to reference a UI element from a non-UI thread, the counter variable will be initialized as null obviously.
Now for the solution:
What you need to do is put the update function in the onPostExecute method for the async task class. Reason: onPostExceute runs on whatever thread the asyntcTask.execute method was called from so you are supposed to do your UI update in the onPostExecute method
#Override
protected String doInBackground(String... params) {
count();
return null;
}
#Override
protect void onPostExecute(String result) {
update();
}
Also since you are returning null from doInBackground anyway you should Extend AsyncTask<String,String,Void> ideally.
EDIT 1:
Added code
public class Morma extends AppCompatActivity {
// make the text view class variable if you want to update it outside of onCreate.
private TextView mCounterTextView;
class MormaKaugummi extends AsyncTask<Void, Void, Void> {
private int count = 0;
private void count() {
count++;
}
private void update() {
String Kcounter = Integer.toString(count);
mCounterTextView.setText(Kcounter);
}
#Override
protected void doInBackground(Void... aVoid) {
count();
}
#Override
protected void onPostExecute(Void aVoid) {
update();
}
}
private ProgressBar progressBarKaugummi;
private int progressStatusKaugummi = 0;
private Handler handlerKaugummi = new Handler();
#Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_morma);
Button buttonMormaKaugummiKlauen = (Button) findViewById(R.id.buttonMormaKaugummiKlauen);
// initiate all your view items in onCreate.
mCounterTextView = (TextView) findViewById(R.id.counter);
buttonMormaKaugummiKlauen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
progressBarKaugummi = (ProgressBar) findViewById(R.id.progressBarMormaKaugummi);
new Thread(new Runnable() {
public void run() {
while (progressStatusKaugummi < 100) {
progressStatusKaugummi += 1;
handlerKaugummi.post(new Runnable() {
public void run() {
progressBarKaugummi.setProgress(progressStatusKaugummi);
}
});
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}).start();
if (progressStatusKaugummi == 100) {
progressBarKaugummi.setProgress(0);
recreate();
new MormaKaugummi().execute();
}
}
});
You need to initialize all your view elements like the textview in onCreate itself and keep the reference as a class variable if you are going to use that view outside of onCreate.

Create Dialog Box For Checking Internet Connection in Android

I'm implementing to show dialog box when Internet is offline, when i run my app i got "FATAL Exception main" and ClassCastException when when i click on button and application is crash . Can someone tell me what i am doing wrong ? Thanks to you in Advanced.
here is code how i check is internet enabled or not:
public class AndroidDetectInternetConnectionActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btnStatus = (Button) findViewById(R.id.btn_check);
btnStatus.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (!isOnline())
{
showNoConnectionDialog(this);
}
}
});
}
public static void showNoConnectionDialog(OnClickListener onClickListener)
{
final Context ctx = (Context) onClickListener;
AlertDialog.Builder builder = new AlertDialog.Builder(ctx);
builder.setCancelable(true);
builder.setMessage(R.string.no_connection);
builder.setTitle(R.string.no_connection_title);
builder.setPositiveButton(R.string.settings_button_text, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which)
{
ctx.startActivity(new Intent(Settings.ACTION_WIRELESS_SETTINGS));
}
});
builder.setNegativeButton(R.string.cancel_button_text, new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
return;
}
});
builder.setOnCancelListener(new DialogInterface.OnCancelListener()
{
public void onCancel(DialogInterface dialog) {
return;
}
});
builder.show();
}
public boolean isOnline()
{
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnectedOrConnecting())
{
return true;
}
return false;
}
}
// This is my Log Cat stack trace
11-15 11:57:19.115: D/AndroidRuntime(453): Shutting down VM
11-15 11:57:19.115: W/dalvikvm(453): threadid=1: thread exiting with uncaught exception (group=0x40015560)
11-15 11:57:19.122: E/AndroidRuntime(453): FATAL EXCEPTION: main
11-15 11:57:19.122: E/AndroidRuntime(453): java.lang.ClassCastException: com.example.detectinternetconnection.AndroidDetectInternetConnectionActivity$1
11-15 11:57:19.122: E/AndroidRuntime(453): at com.example.detectinternetconnection.AndroidDetectInternetConnectionActivity.showNoConnectionDialog(AndroidDetectInternetConnectionActivity.java:99)
11-15 11:57:19.122: E/AndroidRuntime(453): at com.example.detectinternetconnection.AndroidDetectInternetConnectionActivity$1.onClick(AndroidDetectInternetConnectionActivity.java:64)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.view.View.performClick(View.java:2485)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.view.View$PerformClick.run(View.java:9080)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.os.Handler.handleCallback(Handler.java:587)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.os.Handler.dispatchMessage(Handler.java:92)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.os.Looper.loop(Looper.java:123)
11-15 11:57:19.122: E/AndroidRuntime(453): at android.app.ActivityThread.main(ActivityThread.java:3683)
11-15 11:57:19.122: E/AndroidRuntime(453): at java.lang.reflect.Method.invokeNative(Native Method)
11-15 11:57:19.122: E/AndroidRuntime(453): at java.lang.reflect.Method.invoke(Method.java:507)
11-15 11:57:19.122: E/AndroidRuntime(453): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-15 11:57:19.122: E/AndroidRuntime(453): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-15 11:57:19.122: E/AndroidRuntime(453): at dalvik.system.NativeStart.main(Native Method)
11-15 11:57:24.892: I/Process(453): Sending signal. PID: 453 SIG: 9

change this line
final Context ctx = (Context) onClickListener;
to below one
final Context ctx = AndroidDetectInternetConnectionActivity.this;
basically you are trying to conver onClickListener to Contex which is incorrect and can not be casted.
Either you directly use ActivityName.this wherever you need context instance, or define static Context ctx as a class variable and intialize it in onCreate()by just adding this line ctx =this also remember to intialize it before using it.
Enjoy

There are two ways to solve this problem.
1) showNoConnectionDialog(this); and later on:
public static void showNoConnectionDialog(Context ctx) ...
2) showNoConnectionDialog(); and later on: public void showNoConnectionDialog() { Context ctx = AndroidDetectInternetConnectionActivity.this

You basic problem is generated by the line:
final Context ctx = (Context) onClickListener;
This is simply not a context so trying to force it to be one doesn't work.
I believe that you wanted to do was pass a context (or activity) to this function (as opposed to the local unnamed OnClickListener class that you are now passing)
The easiest solution would be to simple not pass anything to the constructor and use AndroidDetectInternetConnectionActivity.this to access your valid context.

BadTokenException even after referring to Activity and not the application context

android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy#406a6678 is not valid; is your activity running?
at android.view.ViewRoot.setView(ViewRoot.java:528)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:177)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
at android.view.Window$LocalWindowManager.addView(Window.java:424)
at android.app.Dialog.show(Dialog.java:241)
at android.app.Activity.showDialog(Activity.java:2569)
at android.app.Activity.showDialog(Activity.java:2527)
at MyCode$8$4.run(MyCode.java:557)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
at dalvik.system.NativeStart.main(Native Method)
I am getting above exception when following code is executed. This file dialog will shown once the processing is done and progressbar reaches 100%. FileSaveDialog extends Dialog and implements OnCompletionListener
runOnUiThread(new Runnable() {
#Override
public void run() {
showDialog(error.Code());//Line 557
}
});
#Override
protected Dialog onCreateDialog(int id) {
Dialog dialog;
AlertDialog.Builder builder;
final ScrollView scrollView = new ScrollView(this);
final TextView textView = new TextView(this);
switch (id) {
// Other cases are here
case 4:
File playFile = new File(mediaPath, TEMP_WAV_FILE_NAME);
dialog = new FileSaveDialog(this, getResources(),
playFile.getAbsolutePath(), saveDiscardHandler);
dialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
#Override
public void onCancel(DialogInterface dialog) {
// do whatever you want the back key to do
cleanUp();
}
});
break;
// Other cases are here
default:
dialog = null;
}
return dialog;
}

You must check activity isFinishing() If the activity is finishing, returns true; else returns false.

MediaController - Error when Show() called

I have this code for show the MediaController, but it give me a fatal error when I'm calling to Show() method.
The MediaPlayer itself working on Service and get Intent from the MediaPlayerControl interface.
My code:
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mediaController = new MediaController(this, false);
mediaController.setMediaPlayer(mediaPlayerControl);
mediaController.setAnchorView(findViewById(R.id.mediaController));
mediaController.setEnabled(true);
mediaController.show(0);
}
//implements MediaPlayerControl interface
private MediaPlayerControl mediaPlayerControl = new MediaPlayerControl()
{
//Override the methods to send Intent to the MediaPlayer Service
....
....
};
my logcat:
07-27 11:03:07.365: E/AndroidRuntime(328): FATAL EXCEPTION: main
07-27 11:03:07.365: E/AndroidRuntime(328): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.radius100fm/com.example.radius100fm.MainActivity}: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.os.Handler.dispatchMessage(Handler.java:99)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.os.Looper.loop(Looper.java:123)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread.main(ActivityThread.java:3683)
07-27 11:03:07.365: E/AndroidRuntime(328): at java.lang.reflect.Method.invokeNative(Native Method)
07-27 11:03:07.365: E/AndroidRuntime(328): at java.lang.reflect.Method.invoke(Method.java:507)
07-27 11:03:07.365: E/AndroidRuntime(328): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-27 11:03:07.365: E/AndroidRuntime(328): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-27 11:03:07.365: E/AndroidRuntime(328): at dalvik.system.NativeStart.main(Native Method)
07-27 11:03:07.365: E/AndroidRuntime(328): Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?
07-27 11:03:07.365: E/AndroidRuntime(328): at android.view.ViewRoot.setView(ViewRoot.java:527)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:177)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.view.Window$LocalWindowManager.addView(Window.java:424)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.widget.MediaController.show(MediaController.java:304)
07-27 11:03:07.365: E/AndroidRuntime(328): at com.example.radius100fm.MainActivity.onCreate(MainActivity.java:100)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-27 11:03:07.365: E/AndroidRuntime(328): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
07-27 11:03:07.365: E/AndroidRuntime(328): ... 11 more
What is the problem with my code?

Use this method.
#Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if(mediaController != null)
mediaController.show(0);
}

I got the same problem and after several hours got the solution. I did the following:
Summary:
The Activity class implements the interfaces: MediaPlayer.OnPreparedListener and MediaController.MediaPlayerControl
OnCreate. setContentView.
onStart. Create MediaPlayer and MediaController, start the listener with setOnPreparedListener and call prepare() method of MediaPlayer.
Implement method onPrepared. Link the mediaController with the mediaPlayer, start mediaPlayer and here is where the method show() is called using a handler, only when we know that mediaPlayer is ready.
My code:
public class MainActivity extends Activity implements MediaPlayer.OnPreparedListener, MediaController.MediaPlayerControl {
private static final String TAG = "AudioPlayer";
private MediaPlayer mediaPlayer;
private MediaController mediaController;
private Handler handler = new Handler();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
protected void onStart() {
Log.d(TAG, "Play - onStart");
super.onStart();
mediaPlayer = new MediaPlayer();
mediaController = new MediaController(this);
mediaPlayer.setOnPreparedListener(this);
try {
AssetFileDescriptor afd = getApplicationContext().getResources().openRawResourceFd(R.raw.audio_example);
mediaPlayer.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(), afd.getDeclaredLength());
mediaPlayer.prepare();
afd.close();
} catch (IOException e) {
Log.e(TAG, "Error opening audio: " + e.getCause());
}
}
// override this method because of the OnPreparedListener interface
#Override
public void onPrepared(MediaPlayer mediaPlayer) {
Log.d(TAG, "Play - onPrepared");
mediaController.setMediaPlayer(this);
mediaController.setAnchorView(findViewById(R.id.mediaController1));
mediaPlayer.start();
handler.post(new Runnable() {
#Override
public void run() {
mediaController.setEnabled(true);
mediaController.show(0);
}
});
}
// override these methods because of the MediaController.MediaPlayerControl interface
#Override
public boolean canPause() {
return true;
}
#Override
public boolean canSeekBackward() {
return true;
}
#Override
public boolean canSeekForward() {
return true;
}
#Override
public int getAudioSessionId() {
// TODO Auto-generated method stub
return 0;
}
#Override
public int getBufferPercentage() {
// TODO Auto-generated method stub
return 0;
}
#Override
public int getCurrentPosition() {
return mediaPlayer.getCurrentPosition();
}
#Override
public int getDuration() {
return mediaPlayer.getDuration();
}
#Override
public boolean isPlaying() {
return mediaPlayer.isPlaying();
}
#Override
public void pause() {
mediaPlayer.pause();
}
#Override
public void seekTo(int pos) {
mediaPlayer.seekTo(pos);
}
#Override
public void start() {
mediaPlayer.start();
}
// release resources before kill the Activity
#Override
protected void onStop() {
Log.d(TAG, "Play - onStop");
super.onStop();
if (mediaPlayer != null) {
mediaController.hide();
mediaPlayer.stop();
mediaPlayer.release();
mediaPlayer = null;
}
} }

Ok, so finely I found the answer.
The problem is in the line:
mediaController.show(0);
Because it called in onCreate() and the app still not activated.
Simple tried, add bottom that callingmediaController.show(0); when it clicked, and the app work perfect.
So now I have to call this line after the app get activate.
I'm tried onStart() and onResume() and it not working. The same error logCat.
How can I fix that??

I needed to show the MediaController to a already running MediaPlayer, so I couldn't set the OnPreparedListener like e_v_e said.
With the answer to this question: Can't fix MediaController.show() exception I discovered that the show method is been called before all the activity lifecycle methods were called. The solution proposed there(setting a delay to show) works, but to avoid the delay, you can place the show inside the onAttachedToWindow method, that is called after all the activity lifecycle methods.

Just put the mediaPlayer.prepare() and mediaPlayer.start() in a thread like handler or AsyncTask and done.
If you are using kotlin and anko lib, you can put it in doAsync {}.