一塊兒學Android之音頻視頻

概述

Android多媒體框架支持各類常見的媒體類型，能夠很容易地將音頻、視頻和圖像集成到App中。經過MediaPlayer Api，能夠從應用程序資源（RAW）、文件系統或網絡上數據流資源來播放音頻或視頻。本文演示瞭如何經過Api播放音頻和視頻文件，來得到良好性能和愉快的用戶體驗，僅供學習分享使用，若有不足之處，還請指正。

涉及知識點

1.  MediaPlayer 能夠用來控制audio/video文件或流播放的類。經過此類，能夠方便的控制音頻/視頻文件的播放，暫停和中止等操做。
2. Uri 統一資源標識符(Uniform Resource Identifier，或URI)是一個用於標識某一互聯網資源名稱的字符串。
3. VideoView 自帶的一種播放視頻的組件。
4. SurfaceView 能夠經過後臺繪製顯示的視圖組件。 

Activity中播放音頻

 頁面上播放音頻文件，步驟以下：

1. 準備資源文件，並播放

 1 private MediaPlayer mMediaPlayer;
 2 
 3     /**
 4      * 開始
 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      * 建立MediaPlayer併到prepare狀態
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. 暫停播放

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

3. 中止

 1   /**
 2      * 中止
 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. 釋放資源（當頁面銷燬時，播放資源也要同時釋放）

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. 經過靜態函數建立對象

 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     }

經過服務來播放音頻

當頁面關閉時，音頻文件還能夠在後臺播放。步驟以下：

1. 定義後臺服務，當服務啓動時，建立MediaPlayer對象，並註冊服務接收對象。

 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. 操做接收者定義以下：

 1  /**
 2      * 操做接收器
 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. 啓動服務

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

4. 前臺Activity經過發送廣播命令進行控制音頻的播放與暫停

 1 /**
 2      * 開始
 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      * 暫停
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      * 中止
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.經過後臺服務的方式，須要在AndroidManifest.xml文件中進行註冊

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

經過VideoView來播放視頻

 經過VideoView進行播放視頻文件，只須要設置資源URI便可，具體以下：

 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         //設置路徑
 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         //設置Media Controller
16         MediaController controller=new MediaController(this);
17         mVideoView.setMediaController(controller);
18         //獲取焦點
19         mVideoView.requestFocus();
20         mVideoView.start();
21         //設置播放完成事件
22         mVideoView.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
23             @Override
24             public void onCompletion(MediaPlayer mp) {
25                 Toast.makeText(VideoActivity.this, "播放完畢", Toast.LENGTH_SHORT).show();
26             }
27         });
28     }

經過MediaPlayer來播放視頻

經過MediaPlayer來播放視頻文件，而後經過SurfaceView來顯示視頻內容，具體步驟以下：

1.啓動，經過setDisplay來設置顯示內容

 1 public  void bn_start(View view)  {
 2         mMediaPlayer.reset();//到Idle狀態
 3         //設置路徑
 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. 暫停與中止

 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. 資源釋放

 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     }

權限設置

若是要播放視頻，須要相應的權限設置，並在安裝時獲取請求權限

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"/>

備註

合抱之木，生於毫末；九層之臺，起於壘土；千里之行，始於足下。