在Hold模式打开/关闭后，我的Android应用程序无法再次播放音乐。
我的代码一开始运行良好（歌曲听起来）。但是当用户按下保持按钮时，应用程序无法继续播放（保持后再次返回屏幕时）。
通过调试，我检查了当你按下保持按钮（重新启动手机）时，你进入了onResume内部（很明显），但mediaPlayer.prepare()抛出了java.lang.IllegalStateException（捕获在捕获块中），并显示消息：prepareSynccalled in state 0
在onResume()之后，我调用了方法play（），它抛出了以下错误：
尝试在错误的状态下执行seekTo
错误（-38，0）
尝试在没有有效媒体播放器的情况下调用getDuration
错误（-38，0）
有什么想法吗？：S
这是我的代码：Fragment.java
public class FragmentMediaPlayer extends Fragment implements OnSeekBarChangeListener {
private MediaPlayer mediaPlayer;
public TextView duration;
private double timeElapsed = 0, finalTime = 0;
private int forwardTime = 5000, backwardTime = 5000;
private Handler durationHandler = new Handler();
private SeekBar seekBar;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
View rootView = inflater.inflate(R.layout.media_player, container,
false);
// initialize views
initializeViews(rootView);
return rootView;
}
public void initializeViews(View rootView) {
mediaPlayer = MediaPlayer.create(getActivity(), R.raw.song);
try {
mediaPlayer.prepare();
} catch (IllegalStateException | IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finalTime = mediaPlayer.getDuration();
duration = (TextView) rootView.findViewById(R.id.songDuration);
duration.setText(String.format(
"%d min, %d sec",
0,0));
seekBar = (SeekBar) rootView.findViewById(R.id.seekBar);
seekBar.setMax((int) finalTime);
seekBar.setOnSeekBarChangeListener(this);
ImageButton playButton = (ImageButton) rootView.findViewById(R.id.media_play);
playButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
play();
}
});
ImageButton media_pause = (ImageButton) rootView.findViewById(R.id.media_pause);
media_pause.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
pause(v);
}
});
ImageButton media_ff = (ImageButton) rootView.findViewById(R.id.media_ff);
media_ff.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
forward(v);
}
});
ImageButton media_rew = (ImageButton) rootView.findViewById(R.id.media_rew);
media_rew.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
rewind(v);
}
});
}
// play mp3 song
public void play() {
timeElapsed = mediaPlayer.getCurrentPosition();
seekBar.setProgress((int) timeElapsed);
mediaPlayer.seekTo((int) timeElapsed) ;
mediaPlayer.start();
durationHandler.postDelayed(updateSeekBarTime, 100);
}
// handler to change seekBarTime
private Runnable updateSeekBarTime = new Runnable() {
public void run() {
// get current position
timeElapsed = mediaPlayer.getCurrentPosition();
// set seekbar progress
seekBar.setProgress((int) timeElapsed);
// set time remaing
//double timeRemaining = finalTime - timeElapsed;
duration.setText(String.format(
"%d min, %d sec",
TimeUnit.MILLISECONDS.toMinutes((long) timeElapsed),
TimeUnit.MILLISECONDS.toSeconds((long) timeElapsed)
- TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS
.toMinutes((long) timeElapsed))));
// repeat yourself that again in 100 miliseconds
durationHandler.postDelayed(this, 100);
}
};
// pause mp3 song
public void pause(View view) {
mediaPlayer.pause();
timeElapsed = mediaPlayer.getCurrentPosition();
}
// go forward at forwardTime seconds
public void forward(View view) {
// check if we can go forward at forwardTime seconds before song endes
if ((timeElapsed + forwardTime) <= finalTime) {
timeElapsed = timeElapsed + forwardTime;
// seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
// go backwards at backwardTime seconds
public void rewind(View view) {
// check if we can go back at backwardTime seconds after song starts
if ((timeElapsed - backwardTime) > 0) {
timeElapsed = timeElapsed - backwardTime;
// seek to the exact second of the track
mediaPlayer.seekTo((int) timeElapsed);
}
}
@Override
public void onResume() {
super.onResume();
try {
mediaPlayer.prepare();
} catch (IllegalStateException | IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
play();
}
@Override
public void onPause() {
super.onPause();
mediaPlayer.pause();
}
@Override
public void onStop() {
// Stop updates and Disconnect from LocationServices
mediaPlayer.stop();
durationHandler.removeCallbacks(updateSeekBarTime);
super.onStop();
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if(fromUser) {
mediaPlayer.seekTo(progress);
seekBar.setProgress(progress);
}
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
这是我的布局.xml：
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fillViewport="true"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:orientation="vertical">
<TextView
android:id="@+id/songName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/play_text" />
<TextView
android:id="@+id/songDuration"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center" />
<SeekBar
android:id="@+id/seekBar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="30dp"
android:layout_marginBottom="30dp"
android:gravity="center_horizontal"
android:orientation="horizontal" >
<ImageButton
android:id="@+id/media_rew"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="14dp"
android:contentDescription="@string/rewind"
android:src="@android:drawable/ic_media_rew" />
<ImageButton
android:id="@+id/media_pause"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="14dp"
android:contentDescription="@string/pause"
android:src="@android:drawable/ic_media_pause" />
<ImageButton
android:id="@+id/media_play"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="14dp"
android:contentDescription="@string/play"
android:src="@android:drawable/ic_media_play" />
<ImageButton
android:id="@+id/media_ff"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="14dp"
android:contentDescription="@string/forward"
android:src="@android:drawable/ic_media_ff" />
</LinearLayout>
</LinearLayout>
</ScrollView>
我认为这段代码应该可以解决您的问题。
public class FragmentMediaPlayer extends Fragment implements OnSeekBarChangeListener {
private MediaPlayer mediaPlayer;
public TextView duration;
private int timeElapsed = 0, finalTime = 0;
private int forwardTime = 5000, backwardTime = 5000;
private Handler durationHandler = new Handler();
private SeekBar seekBar;
private boolean pausedFromButton = false;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
View rootView = inflater.inflate(R.layout.media_player, container,
false);
// Initialize different views from the layout
duration = (TextView) rootView.findViewById(R.id.songDuration);
duration.setText(String.format(
"%d min, %d sec",
0,0));
seekBar = (SeekBar) rootView.findViewById(R.id.seekBar);
seekBar.setOnSeekBarChangeListener(this);
ImageButton playButton = (ImageButton) rootView.findViewById(R.id.media_play);
playButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
play();
}
});
ImageButton media_pause = (ImageButton) rootView.findViewById(R.id.media_pause);
media_pause.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
pause();
}
});
ImageButton media_ff = (ImageButton) rootView.findViewById(R.id.media_ff);
media_ff.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
forward();
}
});
ImageButton media_rew = (ImageButton) rootView.findViewById(R.id.media_rew);
media_rew.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
rewind();
}
});
return rootView;
}
@Override
public void onResume() {
super.onResume();
prepareMediaPlayer();
play();
}
@Override
public void onPause() {
super.onPause();
//Not call pause because it's necessaty to distinguish between onPause() and when the user press the pause buttonn
mediaPlayer.pause();
}
@Override
public void onStop() {
// Stop updates and Disconnect from Services
mediaPlayer.stop();
durationHandler.removeCallbacks(updateSeekBarTime);
super.onStop();
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if(fromUser) {
mediaPlayer.seekTo(progress);
seekBar.setProgress(progress);
}
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
// TODO Auto-generated method stub
}
/**
* Prepare MediaPlayer and recover from bad status
*/
private void prepareMediaPlayer() {
mediaPlayer = MediaPlayer.create(getActivity(), R.raw.song);
finalTime = mediaPlayer.getDuration();
seekBar.setMax(finalTime);
mediaPlayer.seekTo(timeElapsed);
mediaPlayer.setOnPreparedListener(new OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
mp.start();
}
});
mediaPlayer.setOnCompletionListener(new
OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer arg0) {
pausedFromButton = true;
}
});
}
/**
* play mp3 song
*/
public void play() {
if(pausedFromButton) {
prepareMediaPlayer();
pausedFromButton = false;
}
seekBar.setProgress(timeElapsed);
durationHandler.postDelayed(updateSeekBarTime, 100);
}
/**
* handler to change seekBarTime
*/
private Runnable updateSeekBarTime = new Runnable() {
public void run() {
// get current position
timeElapsed = mediaPlayer.getCurrentPosition();
// set seekbar progress
seekBar.setProgress(timeElapsed);
// set time remaing
//double timeRemaining = finalTime - timeElapsed;
duration.setText(String.format(
"%d min, %d sec",
TimeUnit.MILLISECONDS.toMinutes((long) timeElapsed),
TimeUnit.MILLISECONDS.toSeconds((long) timeElapsed)
- TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS
.toMinutes((long) timeElapsed))));
// repeat yourself that again in 100 miliseconds
durationHandler.postDelayed(this, 100);
}
};
/**
* pause mp3 song
*/
public void pause() {
mediaPlayer.pause();
timeElapsed = mediaPlayer.getCurrentPosition();
pausedFromButton = true;
}
/**
* go forward at forwardTime seconds
*/
public void forward() {
// check if we can go forward at forwardTime seconds before song endes
if ((timeElapsed + forwardTime) <= finalTime) {
timeElapsed = timeElapsed + forwardTime;
// seek to the exact second of the track
mediaPlayer.seekTo(timeElapsed);
}
}
/**
* go backwards at backwardTime seconds
*/
public void rewind() {
// check if we can go back at backwardTime seconds after song starts
if ((timeElapsed - backwardTime) > 0) {
timeElapsed = timeElapsed - backwardTime;
// seek to the exact second of the track
mediaPlayer.seekTo(timeElapsed);
}
}
}