使用Service、AsyncTask和Thread制作智能Android媒体播放器应用程序

Question

首先： 如果我有拼写错误，很抱歉。我来自巴拉圭，正在使用谷歌翻译。

这可能看起来有点傻，但我是一个完美主义者，像任何优秀的开发人员和设计师一样，不想在我的项目中出现错误。我正在学习过程中，并希望能从您那里学到更多。

我见过媒体播放器应用程序，允许用户快速并反复按下播放/停止按钮而不会关闭应用程序，并且仍然可以正常运行，因此我阅读了有关服务、异步任务和线程的内容。不仅要在后台播放声音，还要避免UI错误导致应用程序关闭。我还有很多问题。

我想知道是否使用以下资源（在线找到：found online）是正确的方法，但我已经尝试过了，当我多次按下播放/停止按钮时，应用程序会崩溃，有时甚至无法播放歌曲。

package com.myaudioservice.app;

import android.app.Service;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.AsyncTask;
import android.os.Binder;
import android.os.IBinder;

/**
 * Service to serv MediaPlayer in background
 *
 * @author Eugeny Pozharsky
 */
public class PlayerService extends Service {
    private final IBinder mBinder = new LocalBinder();
    private MediaPlayer mediaPlayer;
    private PlayerCallback callback;

    public class LocalBinder extends Binder {
        PlayerService getService() {
            return PlayerService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    /**
     * Kill MediaPlayer to release resources
     */
    @Override
    public void onDestroy() {
        super.onDestroy();
        if (mediaPlayer != null) {
            stop();
            mediaPlayer.release();
        }
    }

    /**
     * Starts playing stream.
     * Note that we just start media player and do not obtain real URL of the stream.
     * So, URL that will be redirected by server will not work. To make such URLs works, adding
     * algorithm to obtain the real URL (f.e., create HttpConnection, connect to the server and
     * get real URL from connection).
     *
     * @param url String with URL of a server to connect
     */
    public void start(String url) {
        if (mediaPlayer == null) {
            mediaPlayer = new MediaPlayer();
        }
        if (isPlaying()) {
            mediaPlayer.stop();
            mediaPlayer.reset();
        }
        new Player().execute(url);
        Log.e("PlayerService", "start()");
    }

    /**
     * Stops playing of the stream.
     */
    public void stop() {
        // stopping MediaPlayer in separate thread because it can take a time
        new Thread(new Runnable() {
            @Override
            public void run() {
                if (mediaPlayer != null) {
                    if (mediaPlayer.isPlaying()) {
                        mediaPlayer.stop();
                    }
                    //mediaPlayer.release();
                    //mediaPlayer = null;
                }
            }
        }).start();
        if (callback != null) {
            callback.onStopped();
        }
        Log.e("PlayerService", "stop()");
    }

    /**
     * Is stream playing?
     *
     * @return true or false
     */
    public Boolean isPlaying() {
        return mediaPlayer != null && mediaPlayer.isPlaying();
    }

    public void setCallback(PlayerCallback callback) {
        this.callback = callback;
    }

    /**
     * Background task to start MediaPlayer. It is used because starting playing of remote stream may
     * take long time and we must not block UI thread.
     * Also, this approach allows to cancel starting process (not implemented in current version)
     */
    private class Player extends AsyncTask<String, Void, Void> {

        /**
         * This function called in UI thread and we callback to activity to update UI elements
         */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            if (callback != null) {
                callback.onPreStart();
            }
        }

        /**
         * This function called in UI thread and we callback to activity to update UI elements
         */
        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            if (mediaPlayer == null || !mediaPlayer.isPlaying()) {
                // Start MediaPlayer fail.
                if (callback != null) {
                    callback.onStartFailed();
                }
            } else {
                if (callback != null) {
                    callback.onStarted();
                }
            }
        }

        /**
         * This function called from separate thread and we do long-time operation in it
         *
         * @param strings params
         * @return null
         */
        @Override
        protected Void doInBackground(String... strings) {
            //mediaPlayer = new MediaPlayer();
            try {
                mediaPlayer.setDataSource(strings[0]);
                mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
                mediaPlayer.prepare();
                mediaPlayer.start();
            } catch (Exception e) {
                if (mediaPlayer != null) {
                    mediaPlayer.release();
                }
                mediaPlayer = null;
            }
            return null;
        }
    }
}

我想知道我是否应该随时取消我的 AsyncTask 进程，或者是否应该添加/修改一些内容，以便我的应用程序不会崩溃。我应该如何做？有人能指导我吗？

通常，如果出现错误，我会在日志中看到以下信息：

java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once)

对于播放/停止按钮：

btn_control.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                control((!ON_PLAY) ? 1 : 0);
            }
        });

private void control(int est) {

        if(est==1){
            if (!hayConexion()) {
                Toast.makeText(Principal.this, getString(R.string.error_conexion_txt), Toast.LENGTH_SHORT).show();
            } else {
                if (mBound) {
                    mService.start();
                    ON_PLAY = true;
                }
            }
        }else if(est==0) {

            if (mBound) {
                mService.stop();
                ON_PLAY = false;
            }
        }

    }

编辑：

日志记录：

09-08 03:13:08.333  32438-32474/com.myaudioservice.app V/MediaPlayer-JNI﹕ native_setup
09-08 03:13:08.333  32438-32474/com.myaudioservice.app V/MediaPlayer﹕ constructor
09-08 03:13:08.343  32438-32474/com.myaudioservice.app V/MediaPlayer﹕ setListener
09-08 03:13:08.343  32438-32474/com.myaudioservice.app I/MediaPlayer﹕ path is null
09-08 03:13:08.343  32438-32474/com.myaudioservice.app D/MediaPlayer﹕ setDataSource IOException happend :
    java.io.FileNotFoundException: No content provider: rtsp://ip/folder/file.stream
            at android.content.ContentResolver.openTypedAssetFileDescriptor(ContentResolver.java:1053)
            at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:907)
            at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:834)
            at android.media.MediaPlayer.setDataSource(MediaPlayer.java:988)
            at android.media.MediaPlayer.setDataSource(MediaPlayer.java:942)
            at com.myaudioservice.app.PlayerService$Player.doInBackground(PlayerService.java:156)
            at com.myaudioservice.app.PlayerService$Player.doInBackground(PlayerService.java:130)
            at android.os.AsyncTask$2.call(AsyncTask.java:288)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)
09-08 03:13:08.343  32438-32474/com.myaudioservice.app D/MediaPlayer﹕ Couldn't open file on client side, trying server side
09-08 03:13:08.353  32438-32474/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 03:13:08.353  32438-32474/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 03:13:08.353  32438-32474/com.myaudioservice.app D/com.myaudioservice.app.PlayerService﹕ Preparing: rtsp://ip/folder/file.stream
09-08 03:13:08.353  32438-32474/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 03:13:08.353  32438-32474/com.myaudioservice.app V/MediaPlayer﹕ prepare
09-08 03:13:09.384  32438-32438/com.myaudioservice.app E/PlayerService﹕ stop()
09-08 03:13:09.394  32438-32495/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 03:13:09.394  32438-32495/com.myaudioservice.app V/MediaPlayer-JNI﹕ release
09-08 03:13:09.394  32438-32495/com.myaudioservice.app V/MediaPlayer﹕ setListener
09-08 03:13:09.394  32438-32495/com.myaudioservice.app V/MediaPlayer﹕ disconnect
09-08 03:13:09.544  32438-32438/com.myaudioservice.app D/AndroidRuntime﹕ Shutting down VM
09-08 03:13:09.544  32438-32438/com.myaudioservice.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4193eda0)
09-08 03:13:09.544  32438-32438/com.myaudioservice.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.myaudioservice.app, PID: 32438
    java.lang.IllegalStateException
            at android.media.MediaPlayer.isPlaying(Native Method)
            at com.myaudioservice.app.PlayerService.reproduciendo(PlayerService.java:118)
            at com.myaudioservice.app.PlayerService.start(PlayerService.java:84)
            at com.myaudioservice.app.MainActivity.control(MainActivity.java:298)
            at com.myaudioservice.app.MainActivity.access$100(MainActivity.java:38)
            at com.myaudioservice.app.MainActivity$1.onClick(MainActivity.java:173)
            at android.view.View.performClick(View.java:4640)
            at android.view.View$PerformClick.run(View.java:19425)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5593)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

新的日志记录：

 09-08 14:49:24.360    9651-9651/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:24.360    9651-9651/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:24.390    9651-9651/com.myaudioservice.app E/PlayerService﹕ start()
    09-08 14:49:24.480   9651-10534/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:24.480   9651-10534/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:24.480   9651-10534/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
    09-08 14:49:24.480   9651-10534/com.myaudioservice.app V/MediaPlayer﹕ reset
    09-08 14:49:24.490    9651-9651/com.myaudioservice.app E/PlayerService﹕ stop()
    09-08 14:49:24.620    9651-9651/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:24.620    9651-9651/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:24.650    9651-9651/com.myaudioservice.app E/PlayerService﹕ start()
    09-08 14:49:24.770   9651-10535/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:24.770   9651-10535/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:24.770   9651-10535/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
    09-08 14:49:24.770   9651-10535/com.myaudioservice.app V/MediaPlayer﹕ reset
    09-08 14:49:24.780    9651-9651/com.myaudioservice.app E/PlayerService﹕ stop()
    09-08 14:49:24.890    9651-9651/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:24.890    9651-9651/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:24.910    9651-9651/com.myaudioservice.app E/PlayerService﹕ start()
    09-08 14:49:25.021   9651-10540/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:25.031   9651-10540/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:25.031   9651-10540/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
    09-08 14:49:25.031   9651-10540/com.myaudioservice.app V/MediaPlayer﹕ reset
    09-08 14:49:25.041    9651-9651/com.myaudioservice.app E/PlayerService﹕ stop()
    09-08 14:49:25.151    9651-9651/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
    09-08 14:49:25.151    9651-9651/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
    09-08 14:49:25.181    9651-9651/com.myaudioservice.app E/PlayerService﹕ start()

编辑2： -----------------------------------------------------------------------

我认为我已经完成了，直到我遇到一个bug（就在我的服务最后）:(

编辑的PlayerService类

package com.myaudioservice.app;

import android.app.Service;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;


public class PlayerService extends Service implements MediaPlayer.OnPreparedListener, MediaPlayer.OnInfoListener, MediaPlayer.OnCompletionListener {

    private static final String LOG_TAG = PlayerService.class.getName();
    private String URL_STREAM = "rtsp://domain/folder/file.stream";

    private MediaPlayer mMediaPlayer = null;
    private PlayerCallback callback;
    private final IBinder mBinder = new LocalBinder();

    public class LocalBinder extends Binder {
        PlayerService getService() {
            return PlayerService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }


    @Override
    public void onDestroy(){
        if (mMediaPlayer != null) {
            stop();
            mMediaPlayer.release();
            mMediaPlayer = null;
        }
    }

    /**
     * Starts playing stream.
     * Note that we just start media player and do not obtain real URL of the stream.
     * So, URL that will be redirected by server will not work. To make such URLs works, adding
     * algorithm to obtain the real URL (f.e., create HttpConnection, connect to the server and
     * get real URL from connection).
     *
     * //@param url String with URL of a server to connect
     */
    public void start() {
        if (mMediaPlayer == null) mMediaPlayer = new MediaPlayer();
        if (isPlaying()) {
            mMediaPlayer.stop();
            mMediaPlayer.reset();
        }

        try {
            mMediaPlayer.setDataSource(URL_STREAM);
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            if (callback != null) callback.onPreStart();
            Log.e(LOG_TAG, "Preparando: " + URL_STREAM);
            mMediaPlayer.prepareAsync();

        } catch (Exception e) {
            if (mMediaPlayer != null) {
                mMediaPlayer.reset();
            }
            Log.e(LOG_TAG, e.toString());
            //mMediaPlayer = null;
        }

        mMediaPlayer.setOnPreparedListener(this);
        mMediaPlayer.setOnInfoListener(this);
        mMediaPlayer.setOnCompletionListener(this);
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        mp.start();
        Log.e(LOG_TAG, "start()");
    }


    @Override
    public boolean onInfo(MediaPlayer mp, int what, int extra) {
        switch (what) {
            case MediaPlayer.MEDIA_ERROR_IO:
            case MediaPlayer.MEDIA_ERROR_MALFORMED:
            case MediaPlayer.MEDIA_ERROR_NOT_VALID_FOR_PROGRESSIVE_PLAYBACK:
            case MediaPlayer.MEDIA_ERROR_SERVER_DIED:
            case MediaPlayer.MEDIA_ERROR_TIMED_OUT:
            case MediaPlayer.MEDIA_ERROR_UNSUPPORTED:
                if (mMediaPlayer == null || !mMediaPlayer.isPlaying()) {
                    // Start MediaPlayer fail.
                    if (callback != null) callback.onStartFailed();
                }
                Log.e(LOG_TAG, "Error");
                break;
            case MediaPlayer.MEDIA_INFO_BUFFERING_START:
                if (callback != null) callback.onStarted();
                Log.e(LOG_TAG, "Almacenando en búfer");
                break;
            case MediaPlayer.MEDIA_INFO_BUFFERING_END:
                if (callback != null) callback.onPlaying();
                Log.e(LOG_TAG, "Reproduciendo");
                break;
        }
        return false;
    }

    @Override
    public void onCompletion(MediaPlayer mp) {
        Log.e(LOG_TAG, "Reproducción finalizada");
        stop();
    }

    /**
     * Stops playing of the stream.
     */
    public void stop() {
        // stopping MediaPlayer in separate thread because it can take a time
        new Thread(new Runnable() {
            @Override
            public void run() {
                if (mMediaPlayer != null) {
                    if (mMediaPlayer.isPlaying()) mMediaPlayer.stop(); // I get the error here when I destroy the Service quickly
                    mMediaPlayer.reset();
                }
            }
        }).start();
        if (callback != null) callback.onStopped();
        Log.e(LOG_TAG, "stop()");
    }

    /**
     * Is stream playing?
     *
     * @return true or false
     */
    public Boolean isPlaying() {
        return mMediaPlayer != null && mMediaPlayer.isPlaying();
    }

    public void setCallback(PlayerCallback callback) {
        this.callback = callback;
    }

}

日志输出：

09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 19:15:39.578  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ Preparando: rtsp://domain/folder/file.stream
09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 19:15:39.578  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ prepareAsync
09-08 19:15:39.678  27582-31945/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:39.678  27582-31945/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
09-08 19:15:39.678  27582-31945/com.myaudioservice.app V/MediaPlayer﹕ reset
09-08 19:15:39.678  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=1, ext1=0, ext2=0
09-08 19:15:39.688  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(1, 0, 0) callback on disconnected mediaplayer
09-08 19:15:39.688  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=8, ext1=0, ext2=0
09-08 19:15:39.688  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(8, 0, 0) callback on disconnected mediaplayer
09-08 19:15:39.688  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:15:39.798  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
09-08 19:15:39.798  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:39.808  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 19:15:39.808  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 19:15:39.808  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ Preparando: rtsp://domain/folder/file.stream
09-08 19:15:39.808  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 19:15:39.808  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ prepareAsync
09-08 19:15:39.938  27582-31952/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:39.938  27582-31952/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
09-08 19:15:39.938  27582-31952/com.myaudioservice.app V/MediaPlayer﹕ reset
09-08 19:15:39.938  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=1, ext1=0, ext2=0
09-08 19:15:39.938  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(1, 0, 0) callback on disconnected mediaplayer
09-08 19:15:39.938  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=8, ext1=0, ext2=0
09-08 19:15:39.938  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(8, 0, 0) callback on disconnected mediaplayer
09-08 19:15:39.948  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:15:40.069  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
09-08 19:15:40.069  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.079  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 19:15:40.079  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 19:15:40.079  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ Preparando: rtsp://domain/folder/file.stream
09-08 19:15:40.079  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 19:15:40.079  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ prepareAsync
09-08 19:15:40.179  27582-31957/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.179  27582-31957/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
09-08 19:15:40.179  27582-31957/com.myaudioservice.app V/MediaPlayer﹕ reset
09-08 19:15:40.179  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=1, ext1=0, ext2=0
09-08 19:15:40.189  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(1, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.189  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=8, ext1=0, ext2=0
09-08 19:15:40.189  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(8, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.189  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:15:40.289  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
09-08 19:15:40.289  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.299  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 19:15:40.299  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 19:15:40.299  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ Preparando: rtsp://domain/folder/file.stream
09-08 19:15:40.299  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 19:15:40.299  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ prepareAsync
09-08 19:15:40.429  27582-31966/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.429  27582-31966/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
09-08 19:15:40.429  27582-31966/com.myaudioservice.app V/MediaPlayer﹕ reset
09-08 19:15:40.429  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=1, ext1=0, ext2=0
09-08 19:15:40.429  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(1, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.429  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:15:40.429  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=8, ext1=0, ext2=0
09-08 19:15:40.429  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(8, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.549  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ isPlaying: no active player
09-08 19:15:40.549  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.559  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ setAudioStreamType: 3
09-08 19:15:40.559  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ MediaPlayer::setAudioStreamType
09-08 19:15:40.559  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ Preparando: rtsp://domain/folder/file.stream
09-08 19:15:40.559  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setVideoSurfaceTexture
09-08 19:15:40.559  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ prepareAsync
09-08 19:15:40.659  27582-31972/com.myaudioservice.app V/MediaPlayer-JNI﹕ isPlaying: 0
09-08 19:15:40.659  27582-31972/com.myaudioservice.app V/MediaPlayer-JNI﹕ reset
09-08 19:15:40.659  27582-31972/com.myaudioservice.app V/MediaPlayer﹕ reset
09-08 19:15:40.659  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=1, ext1=0, ext2=0
09-08 19:15:40.659  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(1, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.659  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ message received msg=8, ext1=0, ext2=0
09-08 19:15:40.659  27582-27596/com.myaudioservice.app V/MediaPlayer﹕ notify(8, 0, 0) callback on disconnected mediaplayer
09-08 19:15:40.669  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:16:01.281  27582-27582/com.myaudioservice.app D/AbsListView﹕ onDetachedFromWindow
09-08 19:16:01.311  27582-27582/com.myaudioservice.app E/com.myaudioservice.app.PlayerService﹕ stop()
09-08 19:16:01.311  27582-27582/com.myaudioservice.app V/MediaPlayer-JNI﹕ release
09-08 19:16:01.311  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ setListener
09-08 19:16:01.311  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ disconnect
09-08 19:16:01.311  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ destructor
09-08 19:16:01.311  27582-32148/com.myaudioservice.app W/dalvikvm﹕ threadid=14: thread exiting with uncaught exception (group=0x4193eda0)
09-08 19:16:01.311  27582-27582/com.myaudioservice.app V/MediaPlayer﹕ disconnect
09-08 19:16:01.321  27582-32148/com.myaudioservice.app E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-15992
    Process: com.myaudioservice.app, PID: 27582
    java.lang.IllegalStateException
            at android.media.MediaPlayer.isPlaying(Native Method)
            at com.myaudioservice.app.PlayerService$1.run(PlayerService.java:129)
            at java.lang.Thread.run(Thread.java:841)

- Arnaldo

---

在Android中处理视频和图像可能会导致内存不足错误，这是由于您的应用程序没有足够的内存而引起的。请分享您的logcat以便我们更好地识别问题。 - Murtaza Khursheed Hussain

感谢 @MurtazaKhursheedHussain，我知道这不是内存问题。已添加 Logcat。 - Arnaldo

正如您所看到的，有两个错误：1. 文件未找到和2. 非法状态。 - Murtaza Khursheed Hussain

不，文件已存在。当我使用setDataSource(context, url)而不是setDataSource(url))时会出现这个信息。我只是编辑了流媒体的URL以进行分享。 - Arnaldo

Answer 1

文档中指出，MediaPlayer.isPlaying()如果内部播放器引擎未初始化或已释放，则会抛出IllegalStateException异常。

该代码不是线程安全的，这可能是异常的原因（线程调用release（）并在mediaPlayer设置为null之前，在已发布的mediaPlayer上调用isPlaying（））。 您需要添加一些同步以使其正常工作（或使用MediaPlayer的异步方法）。

- Kamil W

---

你真的在帮我吗，@KamilW，我谢谢你！我修改了代码按照你的建议进行处理 **(EDIT 2)**，结果几乎完美。我认为我更接近我的目标了，但是在多次按下按钮后关闭应用程序时，它仍然会失败并出现 isPlaying() 方法的问题，这次是在线程中出现的。): - Arnaldo

如果我没有调用release()方法，而且mMediaPlayer不为null，为什么会发生这种情况？也许在if(mMediaPlayer.isPlaying()) mMediaPlayer.stop();之前我应该重新初始化？还是我只需要删除那行代码，只留下reset()？这是一个好的实践吗？ - Arnaldo

错误可能是因为您仍然有一个使用mediaPlayer的线程没有同步。为了确保应用程序不会因此崩溃，您需要向mediaPlayer对象添加同步，但在文档中我没有找到任何提到stop()和reset()函数需要很长时间才能完成（无论如何，您在主线程中使用这些函数），所以我认为您不需要在那里使用这个线程。 - Kamil W

所以最终，如果我使用prepareAsync()，我就不需要使用 AsyncTask 和 Thread 了，是这样理解吗？并且，如果我在我的主活动（我在其中使用按钮控制音频）中使用此代码： `@ Override public boolean onKeyDown(int keyCode，KeyEvent event){     如果（keyCode == KeyEvent.KEYCODE_BACK）{          如果（ON_PLAY） moveTaskToBack（true）;      }}我就不需要在我的服务的onDestroy()中调用我的stop()` 方法，对吗？ - Arnaldo

谢谢@KamilW，你能看一下我的答案并检查一下代码，告诉我是否一切正常吗？ - Arnaldo

Answer 2

好了，我想我终于得到了我想要的。 我不知道是否应该将 @KamilW 的回答标记为正确，因为它是完全正确的，但我将用正确的代码来回答我的问题（或者至少认为是正确的），这可能对其他人有用。

我的最终代码：

package com.myaudioservice.app;

import android.app.Service;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;


public class PlayerService extends Service implements MediaPlayer.OnPreparedListener, MediaPlayer.OnInfoListener, MediaPlayer.OnErrorListener, MediaPlayer.OnCompletionListener {

    private static final String LOG_TAG = PlayerService.class.getName();
    private String URL_STREAM = "rtsp://domain/folder/file.stream";

    private MediaPlayer mMediaPlayer = null;
    private PlayerCallback callback;
    private final IBinder mBinder = new LocalBinder();

    public class LocalBinder extends Binder {
        PlayerService getService() {
            return PlayerService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }


    @Override
        public void onDestroy(){
            if (mMediaPlayer != null) {
                mMediaPlayer.release();
                mMediaPlayer = null;
            }
        }

    /**
     * Starts playing stream.
     * Note that we just start media player and do not obtain real URL of the stream.
     * So, URL that will be redirected by server will not work. To make such URLs works, adding
     * algorithm to obtain the real URL (f.e., create HttpConnection, connect to the server and
     * get real URL from connection).
     *
     * //@param url String with URL of a server to connect
     */
    public void start() {
        if (mMediaPlayer == null) mMediaPlayer = new MediaPlayer();
        if (isPlaying()) {
            mMediaPlayer.stop();
            mMediaPlayer.reset();
        }

        try {
            mMediaPlayer.setDataSource(URL_STREAM);
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            if (callback != null) callback.onPreStart();
            Log.e(LOG_TAG, "Preparando: " + URL_STREAM);
            mMediaPlayer.prepareAsync();

        } catch (Exception e) {
            if (mMediaPlayer != null) {
                mMediaPlayer.reset();
            }
            if (callback != null) callback.onStartFailed();
            Log.e(LOG_TAG, e.toString());
            //mMediaPlayer = null;
        }

        mMediaPlayer.setOnPreparedListener(this);
        mMediaPlayer.setOnInfoListener(this);
        mMediaPlayer.setOnErrorListener(this);
        mMediaPlayer.setOnCompletionListener(this);
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        mp.start();
        Log.e(LOG_TAG, "start()");
    }


    @Override
    public boolean onInfo(MediaPlayer mp, int what, int extra) {
        switch (what) {
            case MediaPlayer.MEDIA_INFO_BUFFERING_START:
                if (callback != null) callback.onStarted();
                Log.e(LOG_TAG, "Almacenando en búfer");
                break;
            case MediaPlayer.MEDIA_INFO_BUFFERING_END:
                if (callback != null) callback.onPlaying();
                Log.e(LOG_TAG, "Reproduciendo");
                break;
        }
        return false;
    }

    @Override
    public void onCompletion(MediaPlayer mp) {
        Log.e(LOG_TAG, "Reproducción finalizada");
        stop();
    }

    /**
     * Stops playing of the stream.
     */
    public void stop() {
        // stopping MediaPlayer in separate thread because it can take a time
        new Thread(new Runnable() {
            @Override
            public void run() {
                if (mMediaPlayer != null) {
                    if (mMediaPlayer.isPlaying()) mMediaPlayer.stop();
                    mMediaPlayer.reset();
                }
            }
        }).start();
        if (callback != null) callback.onStopped();
        Log.e(LOG_TAG, "stop()");
    }

    /**
     * Is stream playing?
     *
     * @return true or false
     */
    public Boolean isPlaying() {
        return mMediaPlayer != null && mMediaPlayer.isPlaying();
    }

    public void setCallback(PlayerCallback callback) {
        this.callback = callback;
    }

@Override
public boolean onError(MediaPlayer mp, int what, int extra){

    if(what == MediaPlayer.MEDIA_ERROR_UNKNOWN ||
            what == MediaPlayer.MEDIA_ERROR_SERVER_DIED ||
            extra == MediaPlayer.MEDIA_ERROR_IO ||
            extra == MediaPlayer.MEDIA_ERROR_MALFORMED ||
            extra == MediaPlayer.MEDIA_ERROR_UNSUPPORTED ||
            extra == MediaPlayer.MEDIA_ERROR_TIMED_OUT ||
            extra == MediaPlayer.MEDIA_ERROR_NOT_VALID_FOR_PROGRESSIVE_PLAYBACK){

        stop();
        if (callback != null) callback.onStartFailed();
    }
    return true;// Si hay error, no es necesario llamar a onCompletionListener, por eso: true
}


}

我也希望能够得到专家的检查，告诉我代码需要改进的地方（如果可以的话）。谢谢。

- Arnaldo