Android

Question

我在 Stack-overflow 上搜索了很多答案，但 none 对我有用，必须使用这个，我用过但也不起作用...

private void releaseMediaPlayer() {
    if (mediaPlayer != null) {
        if(mediaPlayer.isPlaying()) {
            mediaPlayer.stop();
        }
        mediaPlayer.release();
        mediaPlayer = null;
        }
    }

声明为：MediaPlayer mediaPlayer=new MediaPlayer();

准备媒体播放器方法是这样的：

public void playMp3(String _link){
        setVolumeControlStream(AudioManager.STREAM_MUSIC);
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);

    try {
        mediaPlayer.setDataSource(_link);
        mediaPlayer.prepareAsync();
        mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                btnDegjo.setVisibility(View.VISIBLE);
            }
        });
    } catch (IOException e) {
        e.printStackTrace();
    }
}

当用户点击按钮时，mp3 正在播放或暂停或停止.. 我的需求：当用户点击后退按钮或onDestroy mediaPlayer被释放时，方法playMp3(link);被调用onCreate..我不知道用户是立即返回还是播放音乐然后返回..

@Override
    public void onBackPressed() {
    super.onBackPressed();
    releaseMediaPlayer();
}

@Override
    protected void onDestroy() {
    super.onDestroy();  
    releaseMediaPlayer();
}

当用户点击后退按钮或 onDestroy 应用程序停止工作时使用此代码.. 为什么？

编辑：

10-13 15:45:09.886: E/AndroidRuntime(10589): FATAL EXCEPTION: main 10-13 15:45:09.886: E/AndroidRuntime(10589): Process: com.FS.myapp, PID: 10589 10-13 15:45:09.886: E/AndroidRuntime(10589): java.lang.RuntimeException: Unable to pause activity {com.FS.myapp/com.FS.myapp.SS}: java.lang.NullPointerException 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3242) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3193) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:3171) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.access00(ActivityThread.java:151) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1338) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.os.Handler.dispatchMessage(Handler.java:110) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.os.Looper.loop(Looper.java:193) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.main(ActivityThread.java:5292) 10-13 15:45:09.886: E/AndroidRuntime(10589): at java.lang.reflect.Method.invokeNative(Native Method) 10-13 15:45:09.886: E/AndroidRuntime(10589): at java.lang.reflect.Method.invoke(Method.java:515) 10-13 15:45:09.886: E/AndroidRuntime(10589): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824) 10-13 15:45:09.886: E/AndroidRuntime(10589): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640) 10-13 15:45:09.886: E/AndroidRuntime(10589): at dalvik.system.NativeStart.main(Native Method) 10-13 15:45:09.886: E/AndroidRuntime(10589): Caused by: java.lang.NullPointerException 10-13 15:45:09.886: E/AndroidRuntime(10589): at com.FS.myapp.SS.onPause(SS.java:62) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.Activity.performPause(Activity.java:5368) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1239) 10-13 15:45:09.886: E/AndroidRuntime(10589): at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3224) 10-13 15:45:09.886: E/AndroidRuntime(10589): ... 12 more

Answer 1

您的堆栈跟踪和 onPause 方法表明您的变量之一为空。

快速修复可以是：

@Override 
protected void onPause() { 
    if (mediaPlayer != null && mediaPlayer.isPlaying()){
        mediaPlayer.pause();
    }

    if (btnPlay != null)
        btnPlay.setText("Play"); 

    super.onPause();
}

Android - MediaPlayer.release 销毁无效

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