019_01播放视频之SurfaceView

　　MediaPlayer主要用于播放音频，因此它没有提供图像输出界面，所以要借助于SurfaceView来显示MediaPalyer播放的图像输出。

　　SurfaceHolder是一个接口，其作用就像一个关于Surface的监听器。提供访问和控制SurfaceView背后的Surface 相关的方法 （providingaccess and control over this SurfaceView's underlying surface），它通过三个回调方法，让我们可以感知到Surface的创建、销毁或者改变。在SurfaceView中有一个方法getHolder，可以很方便地获得SurfaceView所对应的Surface所对应的SurfaceHolder

package com.example.day19_01videoplayer;

import java.io.IOException;
import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Environment;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;

public class MainActivity extends Activity {

    private SurfaceHolder holder;
    private MediaPlayer mediaPlayer;
    private final int STATE_IDLE = 0;
    private final int STATE_PLAYING = 1;
    private final int STATE_PAUSED = 2;
    private final int STATE_STOP =3;

    private int current_state = STATE_IDLE;
    private String path;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        SurfaceView surfaceView = (SurfaceView) findViewById(R.id.sf_video);
        holder = surfaceView.getHolder();
        path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/sirendingzhi.mp4";

    }

     public void play(View v){
         
         if (mediaPlayer==null) {
             mediaPlayer = new MediaPlayer();             
         }
         
        if (current_state==STATE_PAUSED) {
            mediaPlayer.start();    
        } 
         
        if (current_state==STATE_IDLE||current_state==STATE_STOP) {
            mediaPlayer.reset();
             try {
                mediaplay();    
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } 
        
        current_state=STATE_PLAYING;

         
     }

    private void mediaplay() throws IOException {
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mediaPlayer.setDisplay(holder); 
        mediaPlayer.setDataSource(path);        
        mediaPlayer.prepare();
        mediaPlayer.start();

    }
     
     public void pause(View v){ 
         if (current_state==STATE_PLAYING) {
                mediaPlayer.pause();
                current_state=STATE_PAUSED;
            }
     }
     
     public void stop(View v){
         if (mediaPlayer!=null) {
               if (current_state==STATE_PLAYING||current_state==STATE_PAUSED) {
                    mediaPlayer.stop();
                     mediaPlayer.reset();
                     current_state=STATE_STOP;
               }    
        }
         
     }
     
     public void replay(View v){
         
          if (current_state!=STATE_IDLE) {
              if (current_state==STATE_STOP) {
                    
               }
             
               if (current_state==STATE_PLAYING||current_state==STATE_PAUSED) {
                    mediaPlayer.stop();
                    mediaPlayer.reset();    
               }    
                 try {
                    mediaplay();    
               } catch ( Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }        
                  current_state=STATE_PLAYING;
        }          
     }
     
     @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        
        if (mediaPlayer!=null) {
            mediaPlayer.stop();
            mediaPlayer.reset();
            mediaPlayer.release();
        }    
    }     
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.day19_01videoplayer.MainActivity" 
    android:orientation="vertical">

    <LinearLayout 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="播放"
            android:onClick="play" />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="暂停"
            android:onClick="pause" />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="停止"
            android:onClick="stop" />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="重播"
            android:onClick="replay" />
    </LinearLayout>
    
    <SurfaceView 
        android:id="@+id/sf_video"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />
 
</LinearLayout >