一起学Android之音频视频

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。