一起学Android之音频视频

Posted 2022-04-10 hsiang

概述

android多媒体框架支持各种常见的媒体类型，可以很容易地将音频、视频和图像集成到App中。通过MediaPlayer Api，可以从应用程序资源（RAW）、文件系统或网络上数据流资源来播放音频或视频。本文演示了如何通过Api播放音频和视频文件，来获得良好性能和愉快的用户体验，仅供学习分享使用，如有不足之处，还请指正。

涉及知识点

1.  MediaPlayer 可以用来控制audio/video文件或流播放的类。通过此类，可以方便的控制音频/视频文件的播放，暂停和停止等操作。
2. Uri 统一资源标识符(Uniform Resource Identifier，或URI)是一个用于标识某一互联网资源名称的字符串。
3. VideoView 自带的一种播放视频的组件。
4. SurfaceView 可以通过后台绘制显示的视图组件。 

Activity中播放音频

 页面上播放音频文件，步骤如下：

1. 准备资源文件，并播放

 1 private MediaPlayer mMediaPlayer;
 2 
 3     /**
 4      * 开始
 5      * @param v
 6      */
 7     public void bn_start(View v)
 8         if(mMediaPlayer==null) 
 9             ready();
10         
11         mMediaPlayer.start();
12     
13 
14  /**
15      * 创建MediaPlayer并到prepare状态
16      */
17     private void ready()
18         if(mMediaPlayer==null)
19             mMediaPlayer=new MediaPlayer();//Idle
20             //Log.i("TAG", "ready: "+filePath);
21             File file=new File(Environment.getExternalStorageDirectory(),"goldfallen.mp3");
22             Log.i("TAG", "ready: "+file.getPath());
23             Log.i("TAG", "ready: "+file.exists());
24             Uri uri= Uri.fromFile(file);
25             try 
26                 mMediaPlayer.setDataSource(AudioActivity.this,uri);
27                 mMediaPlayer.prepare();//Prepared
28              catch (IOException e) 
29                 Log.i("TAG", "ready: "+ e.getMessage());
30                 e.printStackTrace();
31             
32         
33     

2. 暂停播放

1 /**
2      * 暂停
3      * @param v
4      */
5     public void bn_pause(View v)
6         if(mMediaPlayer!=null && mMediaPlayer.isPlaying())
7             mMediaPlayer.pause();
8         
9     

3. 停止

 1   /**
 2      * 停止
 3      * @param v
 4      */
 5     public void bn_stop(View v)
 6         if(mMediaPlayer!=null && mMediaPlayer.isPlaying())
 7             mMediaPlayer.stop();
 8             mMediaPlayer.release();
 9             mMediaPlayer=null;
10         
11     

4. 释放资源（当页面销毁时，播放资源也要同时释放）

1  @Override
2     protected void onDestroy() 
3         if(mMediaPlayer!=null && mMediaPlayer.isPlaying())
4             mMediaPlayer.stop();
5             mMediaPlayer.release();
6             mMediaPlayer=null;
7         
8         super.onDestroy();
9     

5. 通过静态函数创建对象

 1 /**
 2      * D:\Android\Project\DemoMedia\app\src\main\res\raw\A2012.mp3:
 3      * Error: ‘A‘ is not a valid file-based resource name character:
 4      * File-based resource names must contain only lowercase a-z, 0-9, or underscore
 5      */
 6     private void ready2()
 7         if(mMediaPlayer==null)
 8             mMediaPlayer= MediaPlayer.create(this,R.raw.ab2012);
 9         
10     

通过服务来播放音频

当页面关闭时，音频文件还可以在后台播放。步骤如下：

1. 定义后台服务，当服务启动时，创建MediaPlayer对象，并注册服务接收对象。

 1 public class Audioservice extends Service 
 2 
 3     private MediaPlayer mMediaPlayer;
 4 
 5     private OperatorReceiver mReceiver;
 6 
 7     public AudioService() 
 8     
 9 
10     @Override
11     public void onCreate() 
12         super.onCreate();
13         mMediaPlayer=new MediaPlayer();
14         mReceiver=new OperatorReceiver();
15         IntentFilter filter=new IntentFilter("operator.receiver");
16         registerReceiver(mReceiver,filter);
17     
18 
19     @Override
20     public IBinder onBind(Intent intent) 
21         return null;
22     
23 
24     @Override
25     public int onStartCommand(Intent intent, int flags, int startId) 
26         Log.i("TAG", "onStartCommand: ----ready ");
27         ready();
28         return super.onStartCommand(intent, flags, startId);
29     
30 
31     @Override
32     public void onDestroy() 
33         if(mMediaPlayer!=null && mMediaPlayer.isPlaying())
34             mMediaPlayer.stop();
35         
36         if(mMediaPlayer!=null)
37             mMediaPlayer.release();
38             mMediaPlayer=null;
39         
40         unregisterReceiver(mReceiver);
41         super.onDestroy();
42     
43 
44     private void start()
45         mMediaPlayer.start();
46     
47 
48     private  void pause()
49         mMediaPlayer.pause();
50     
51 
52     private void stop()
53         mMediaPlayer.stop();
54         ready();
55     
56 
57     private void ready()
58         mMediaPlayer.reset();
59         try 
60             String filePath= Environment.getExternalStorageDirectory()+"/ab2012.mp3";
61             Log.i("TAG", "ready: "+filePath);
62             File file=new File(filePath);
63             if(file.exists()) 
64                 mMediaPlayer.setDataSource(filePath);
65                 mMediaPlayer.prepare();
66             else
67                 Log.i("TAG", "ready: 文件不存在 ");
68             
69          catch (IOException e) 
70             Log.i("TAG", "ready: "+e.getMessage());
71             e.printStackTrace();
72         
73     
74 

2. 操作接收者定义如下：

 1  /**
 2      * 操作接收器
 3      */
 4     class OperatorReceiver extends BroadcastReceiver
 5     
 6         @Override
 7         public void onReceive(Context context, Intent intent) 
 8             int cmd=intent.getIntExtra("cmd",-1);
 9             Log.i("TAG", "onReceive: "+cmd);
10             switch (cmd)
11                 case Tools.PLAY:
12                     start();
13                     break;
14                 case Tools.PAUSE:
15                     pause();
16                     break;
17                 case Tools.STOP:
18                     stop();
19                     break;
20                 default:
21                     start();
22                     break;
23 
24             
25         
26     

3. 启动服务

1   Intent intent =new Intent(this,AudioService.class);
2   startService(intent);

4. 前台Activity通过发送广播命令进行控制音频的播放与暂停

 1 /**
 2      * 开始
 3      * @param v
 4      */
 5     public void bn_start(View v)
 6         Intent intent=new Intent("operator.receiver");
 7         intent.putExtra("cmd",Tools.PLAY);
 8         sendBroadcast(intent);
 9         Log.i("TAG", "bn_start: "+"service");
10     
11 
12     /**
13      * 暂停
14      * @param v
15      */
16     public void bn_pause(View v)
17         Intent intent=new Intent("operator.receiver");
18         intent.putExtra("cmd",Tools.PAUSE);
19         sendBroadcast(intent);
20     
21 
22     /**
23      * 停止
24      * @param v
25      */
26     public void bn_stop(View v)
27         Intent intent=new Intent("operator.receiver");
28         intent.putExtra("cmd",Tools.STOP);
29         sendBroadcast(intent);
30     

5.通过后台服务的方式，需要在AndroidManifest.xml文件中进行注册

1  <service
2             android:name=".AudioService"
3             android:enabled="true"
4             android:exported="true">
5         </service>

通过VideoView来播放视频

 通过VideoView进行播放视频文件，只需要设置资源URI即可，具体如下：

 1  private VideoView mVideoView;
 2     @Override
 3     protected void onCreate(Bundle savedInstanceState) 
 4         super.onCreate(savedInstanceState);
 5         setContentView(R.layout.activity_video);
 6         mVideoView= (VideoView) this.findViewById(R.id.vv_info);
 7         //设置路径
 8         File file=new File(Environment.getExternalStorageDirectory(),"DCIM/Camera/VID20190629142614.mp4");
 9         Log.i("TAG", "onCreate: "+file.getPath());
10         if(!file.exists())
11             Log.i("TAG", "onCreate: 文件不存在");
12         
13         Uri uri=Uri.fromFile(file);
14         mVideoView.setVideoURI(uri);
15         //设置Media Controller
16         MediaController controller=new MediaController(this);
17         mVideoView.setMediaController(controller);
18         //获取焦点
19         mVideoView.requestFocus();
20         mVideoView.start();
21         //设置播放完成事件
22         mVideoView.setOnCompletionListener(new MediaPlayer.OnCompletionListener() 
23             @Override
24             public void onCompletion(MediaPlayer mp) 
25                 Toast.makeText(VideoActivity.this, "播放完毕", Toast.LENGTH_SHORT).show();
26             
27         );
28     

通过MediaPlayer来播放视频

通过MediaPlayer来播放视频文件，然后通过SurfaceView来显示视频内容，具体步骤如下：

1.启动，通过setDisplay来设置显示内容

 1 public  void bn_start(View view)  
 2         mMediaPlayer.reset();//到Idle状态
 3         //设置路径
 4         File file=new File(Environment.getExternalStorageDirectory(),"DCIM/Camera/VID20190629142614.mp4");
 5         Log.i("TAG", "onCreate: "+file.getPath());
 6         if(!file.exists())
 7             Log.i("TAG", "onCreate: 文件不存在");
 8          else 
 9             Log.i("TAG", "onCreate: 文件存在 ");
10         
11         Uri uri=Uri.fromFile(file);
12         try 
13             mMediaPlayer.setDataSource(this,uri);
14             mMediaPlayer.setDisplay(mSurfaceView.getHolder());
15             mMediaPlayer.prepare();
16             mMediaPlayer.start();
17          catch (IOException e) 
18             e.printStackTrace();
19         
20     

2. 暂停与停止

 1  public  void bn_pause(View view)
 2         if(mMediaPlayer.isPlaying())
 3             mMediaPlayer.pause();
 4         
 5     
 6 
 7     public  void bn_stop(View view)
 8         if(mMediaPlayer.isPlaying())
 9             mMediaPlayer.stop();
10         
11     

3. 资源释放

 1  @Override
 2     protected void onDestroy() 
 3         if(mMediaPlayer!=null && mMediaPlayer.isPlaying())
 4             mMediaPlayer.stop();
 5         
 6         if(mMediaPlayer!=null)
 7             mMediaPlayer.release();
 8             mMediaPlayer=null;
 9         
10         super.onDestroy();
11     

权限设置

如果要播放视频，需要相应的权限设置，并在安装时获取请求权限

1     <uses-permission android:name="android.permission.INTERNET"/>
2     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
3     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
4     <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

备注

合抱之木，生于毫末；九层之台，起于垒土；千里之行，始于足下。