java - 还有一个 mediaPlayer IllegalStateException : screen timeout

Question

我已经为 Android 制作/下载了一个运行良好的 Java 媒体播放器类，除了在屏幕超时或手动关闭它时，在恢复时，我在尝试 mediaPlayer.isPlaying() 时得到 IllegalStateException 。

谷歌搜索我发现这可能是媒体播放器处于错误状态。然后我尝试了 try {...} catch(IllegalStateException... 东西，但是我添加了太多东西，而且事情变得一团糟失去了控制(而且没有成功)。

然后我尝试了类似的东西:

mediaPlayer.setOnErrorListener(new OnErrorListener() {
            public boolean onError(MediaPlayer mp, int what, int extra) {
                mp.release();
                return false;
            }

但它不起作用，仍然出现 IllegalStateException 错误。 (编辑:顺便说一句，here 它说“IllegalStateExceptions 不会触发 OnErrorListener 调用”。这是正确的吗？？)

所以，我的问题:

1) 屏幕超时时发生了什么使媒体播放器进入错误状态？ 2)我怎样才能防止这种情况发生？ 3) 我需要在 mediaPlayer.setOnErrorListener 里面放什么？ 4) 我是否错过了错误监听器的某些内容，需要以某种方式处理它？<​​/p>

抱歉...这里是新手。

编辑:我需要添加调用，所以这里是整个类:

package com.floritfoto.apps.ave;

import java.io.FileDescriptor;
import java.io.IOException;

import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.media.MediaPlayer.OnErrorListener;

public class Music implements OnCompletionListener{
    MediaPlayer mediaPlayer;
    boolean isPrepared = false;

    public Music(FileDescriptor fileDescriptor){
        mediaPlayer = new MediaPlayer();
        try{
            mediaPlayer.setDataSource(fileDescriptor);
            mediaPlayer.prepare();
            isPrepared = true;
            mediaPlayer.setOnCompletionListener(this);
            mediaPlayer.setOnErrorListener(new OnErrorListener() {
                public boolean onError(MediaPlayer mp, int what, int extra) {
                    mp.release();
                    return false;
                }
            });
        } catch(Exception ex){
            throw new RuntimeException("Couldn't load music, uh oh!");
        }
    }

    public void onCompletion(MediaPlayer mediaPlayer) {
        synchronized(this){
            isPrepared = false;
        }       
    }               

    public void play() {
        if(mediaPlayer.isPlaying()){
            return;
        }   
        try{
            synchronized(this){
                if(!isPrepared){
                    mediaPlayer.prepare();
                }
                mediaPlayer.seekTo(0);
                mediaPlayer.start();
            }
        } catch(IllegalStateException ex){
            ex.printStackTrace();
        } catch(IOException ex){
            ex.printStackTrace();
        }   
    }   

    public void stop() {
        mediaPlayer.stop();
        synchronized(this){
            isPrepared = false;
        }       
    }       

    public void switchTracks(){
        mediaPlayer.seekTo(0);
        mediaPlayer.pause();
    }   

    public void pause() {
        mediaPlayer.pause();
    }

    public boolean isPlaying() {
        return mediaPlayer.isPlaying();
    }

    public boolean isLooping() {
        return mediaPlayer.isLooping();
    }

    public void setLooping(boolean isLooping) {
        mediaPlayer.setLooping(isLooping);
    }

    public void setVolume(float volumeLeft, float volumeRight) {
        mediaPlayer.setVolume(volumeLeft, volumeRight);
    }

    public String getDuration() {
        return String.valueOf((int)(mediaPlayer.getDuration()/1000));
    }
    public void dispose() {
        if(mediaPlayer.isPlaying()){
            stop();
        }
        mediaPlayer.release();
    }
}

这是错误:

E/AndroidRuntime(21110): FATAL EXCEPTION: main
E/AndroidRuntime(21110): java.lang.RuntimeException: Unable to pause activity {com.floritfoto.apps.ave/com.floritfoto.apps.ave.OpenBird}: java.lang.IllegalStateException
E/AndroidRuntime(21110):        at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2718)
E/AndroidRuntime(21110):        at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2674)
E/AndroidRuntime(21110):        at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:2652)
E/AndroidRuntime(21110):        at android.app.ActivityThread.access$800(ActivityThread.java:127)
E/AndroidRuntime(21110):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1170)
E/AndroidRuntime(21110):        at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(21110):        at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(21110):        at android.app.ActivityThread.main(ActivityThread.java:4507)
E/AndroidRuntime(21110):        at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(21110):        at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(21110):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
E/AndroidRuntime(21110):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
E/AndroidRuntime(21110):        at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(21110): Caused by: java.lang.IllegalStateException
E/AndroidRuntime(21110):        at android.media.MediaPlayer.isPlaying(Native Method)
E/AndroidRuntime(21110):        at com.floritfoto.apps.ave.Music.dispose(Music.java:101)
E/AndroidRuntime(21110):        at com.floritfoto.apps.ave.OpenBird.onPause(OpenBird.java:211)
E/AndroidRuntime(21110):        at android.app.Activity.performPause(Activity.java:4563)
E/AndroidRuntime(21110):        at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1198)
E/AndroidRuntime(21110):        at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2705)
E/AndroidRuntime(21110):        ... 12 more
W/ActivityManager( 1864):   Force finishing activity r.intent.getComponent().flattenToShortString()

Answer 1

在调用 isPlaying() 之前尝试检查 mediaPlayer 是否为 null 将 isPlaying() 方法替换为:

@Override
public boolean isPlaying()
{
    super.isPlaying();
if ( mediaPlayer != null && mediaPlayer.isPlaying() )
    return true;
else
    return false;   
}