这个问题在这里已有答案：
我创建了一个音乐流应用，可以从Firebase中获取数据。但问题是，当我播放一首歌并转到主要活动时，应用已停止消息显示并且应用程序关闭。当我从列表视图播放歌曲并返回时，应用程序停止。我能做什么请告诉我。我的代码
public class ViewUploadsActivity extends AppCompatActivity implements MediaPlayer.OnBufferingUpdateListener,View.OnTouchListener
,MediaPlayer.OnCompletionListener{
//the listview
ListView listView;
private SeekBar seekBarProgress;
private int mediaFileLengthInMilliseconds;
private final Handler handler = new Handler();
CustomArrayAdapter adapter;
//database reference to get uploads data
DatabaseReference mDatabaseReference;
//list to store uploads data
List<Upload> uploadList = new ArrayList<>();
private TextView mSelectedTrackTitle,selected_track_ar;
private ImageView mSelectedTrackImage;
private MediaPlayer mMediaPlayer =new MediaPlayer();
private ImageView mPlayerControl;
TextView length;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_upload);
listView = (ListView) findViewById(R.id.listView);
//status = (TextView) findViewById(R.id.status);
seekBarProgress = (SeekBar)findViewById(R.id.length);
listView.setStackFromBottom(true);
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
togglePlayPause();
}
});
mSelectedTrackTitle(TextView)findViewById(R.id.selected_track_title);
mSelectedTrackImage =
(ImageView)findViewById(R.id.selected_track_image);
mPlayerControl = (ImageView)findViewById(R.id.player_control);
selected_track_ar=(TextView)findViewById(R.id.selected_track_ar);
mPlayerControl.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
togglePlayPause();
}
});
get();
//getting the database reference
mDatabaseReference = FirebaseDatabase.getInstance().
getReference(Constants.DATABASE_PATH_UPLOADS);
//retrieving upload data from firebase database
mDatabaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
Upload upload = postSnapshot.getValue(Upload.class);
uploadList.add(upload);
}
adapter = new CustomArrayAdapter(getApplicationContext(),
(ArrayList<Upload>) uploadList);
listView.setAdapter(adapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mMediaPlayer != null) {
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.stop();
}
mMediaPlayer.release();
mMediaPlayer = null;
}
}
private void togglePlayPause() {
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.pause();
mPlayerControl.setImageResource(R.drawable.ic_play);
} else if(!mMediaPlayer.isPlaying()){
mMediaPlayer.start();
mPlayerControl.setImageResource(R.drawable.ic_pause);
mediaFileLengthInMilliseconds = mMediaPlayer.getDuration();
primarySeekBarProgressUpdater();
mSelectedTrackImage.setImageResource(R.drawable.images);
}
}
public void get()
{
seekBarProgress.setMax(99); // It means 100% .0-99
seekBarProgress.setOnTouchListener(this);
mMediaPlayer.setOnBufferingUpdateListener(this);
mMediaPlayer.setOnCompletionListener(this);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int
i, long l) {
//getting the upload
Upload upload = uploadList.get(i);
mSelectedTrackTitle.setText(upload.getName());
selected_track_ar.setText(upload.getAr());
if (mMediaPlayer.isPlaying()) {
mMediaPlayer.stop();
mMediaPlayer.reset();
seekBarProgress.setProgress(0);
}
try {
mMediaPlayer.setDataSource(upload.getUrl());
mMediaPlayer.prepare();
} catch (IOException e) {
e.printStackTrace();
}
}
});
}
private void primarySeekBarProgressUpdater() {
seekBarProgress.setProgress((int
(((float)mMediaPlayer.getCurrentPosition()
/mediaFileLengthInMilliseconds)*100));
// This math construction give a percentage of "was playing"/"song
length"
if (mMediaPlayer.isPlaying()) {
Runnable notification = new Runnable() {
public void run() {
primarySeekBarProgressUpdater();
}
};
handler.postDelayed(notification,1000);
}
}
@Override
public boolean onTouch(View v, MotionEvent event) {
if(v.getId() == R.id.length){
/** Seekbar onTouch event handler. Method which seeks MediaPlayer to
seekBar primary progress position*/
if(mMediaPlayer.isPlaying()){
SeekBar sb = (SeekBar)v;
int playPositionInMillisecconds = (mediaFileLengthInMilliseconds
/ 100) * sb.getProgress();
mMediaPlayer.seekTo(playPositionInMillisecconds);
}
}
return false;
}
@Override
public void onBufferingUpdate(MediaPlayer mp, int percent) {
seekBarProgress.setSecondaryProgress(percent);
}
@Override
public void onCompletion(MediaPlayer mp) {
mPlayerControl.setImageResource(R.drawable.ic_play);
}
}
logcat的
Unrecognized GLES max version string in extensions:
ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_dma_v1
12-19 12:28:13.753 1377-3347/? E/OMXNodeInstance:
setConfig(5610023:google.mp3.decoder,
ConfigPriority(0x6f800002)) ERROR: Undefined(0x80001001)
12-19 12:28:31.338 5777-5777/com.example.admin.firebsaseuploadd
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.admin.firebsaseuploadd, PID: 5777
java.lang.NullPointerException: Attempt to invoke virtual method 'int
android.media.MediaPlayer.getCurrentPosition()' on a null object
reference
at
com.example.admin.firebsaseuploadd.ViewUploadsActivity.
primarySeekBarProgressUp
dater(ViewUploadsActivity.java:245)
at
com.example.admin.firebsaseuploadd.ViewUploadsActivity.
access$500(ViewUploadsActivity.java:62)
at com.example.admin.firebsaseuploadd.ViewUploadsActivity$5.
run(ViewUploadsActivity.java:249)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.
run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
12-19 12:28:31.974 1311-1311/? E/EGL_emulation: tid 1311: egl
CreateSyncKHR(1881): error 0x3004 (EGL_BAD_ATTRIBUTE)
12-19 12:28:32.533 1372-3348/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:32.533 1372-3348/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:32.534 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:32.564 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:28:32.564 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:28:32.595 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:28:37.712 1372-1794/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:37.714 1372-1794/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:37.715 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:37.728 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed
with status -12.
12-19 12:28:37.728 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:28:37.729 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:28:42.882 1372-1443/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:42.883 1372-1443/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:42.883 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:42.916 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:28:42.917 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:28:42.929 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:28:48.085 1372-1793/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:48.136 1372-1793/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:48.151 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:48.248 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:28:48.249 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:28:48.251 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:28:53.439 1372-1793/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:53.439 1372-1793/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:53.443 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:53.455 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:28:53.456 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:28:53.457 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:28:58.551 1372-1793/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:28:58.552 1372-1793/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:28:58.552 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status: -12
12-19 12:28:58.573 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:28:58.574 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord
object.
12-19 12:28:58.577 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:29:03.652 1372-1794/? E/AudioFlinger: not enough memory for
AudioTrack size=131296
12-19 12:29:03.652 1372-1794/? E/AudioFlinger: createRecordTrack_l()
initCheck failed -12; no control block?
12-19 12:29:03.652 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord:
AudioFlinger could not create record track, status:-12
12-19 12:29:03.678 2522-
5797/com.google.android.googlequicksearchbox:search E/AudioRecord-JNI:
Error creating AudioRecord instance: initialization check failed with
status -12.
12-19 12:29:03.678 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:29:03.679 2522-
5797/com.google.android.googlequicksearchbox:search E/ActivityThread:
Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.recorded
12-19 12:29:08.775 1372-1443/? E/AudioFlinger: not enough memory for
AudioTrack
size=131296
12-19 12:29:08.775 1372-1443/? E/AudioFlinger: createRecordTrack_l()
initCheck
failed -12; no control block?
12-19 12:29:08.778 2522-5
797/com.google.android.googlequicksearchbox:search
E/AudioRecord: AudioFlinger could not create record track, status: -12
12-19 12:29:08.804 2522-5797/com.google.android.googlequicksearchbox:search
E/AudioRecord-JNI: Error creating AudioRecord instance: initialization
check failed with status -12.
12-19 12:29:08.805 2522-
5797/com.google.android.googlequicksearchbox:search
E/android.media.AudioRecord: Error code -20 when initializing native
AudioRecord object.
12-19 12:29:08.809 2522-
5797/com.google.android.googlequicksearchbox:search
E/ActivityThread: Failed to find provider info for
com.google.android.apps.gsa.testing.ui.audio.record ed
当我读你的logcat时，你的问题是'int android.media.MediaPlayer.getCurrentPosition（）'中的NullPointerException。当你回到MainActivity时，将会召唤ViewUploadsActivity#onDestroy()。这个方法清除你的mMediaPlayer并将其设置为null。但是，您有一个通知处理程序，它总是随时间运行。最后一次跑，这个跑者叫iewUploadsActivity#primarySeekBarProgressUpdater()，也叫seekBarProgress.setProgress((int (((float)mMediaPlayer.getCurrentPosition()))。
解：
mMediaPlayer.getCurrentPosition()之前检查null
if (mMediaPlayer != null) {
int position = mMediaPlayer.getCurrentPosition();
seekBarProgress.setProgress(position);
}
onDestroy()停止你的经纪人