Android 多媒体之播放音乐

界面如下

布局文件如下

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.thinkpad.music.MainActivity">
<Button
    android:id="@+id/PLAY"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="PLAY"
 />
    <Button
        android:id="@+id/PAUSE"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="PAUSE"
/>
    <Button
        android:id="@+id/STOP"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="STOP"
    />
<ProgressBar
    android:id="@+id/pro"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    style="?android:attr/progressBarStyleHorizontal"
    />
</LinearLayout>

package com.example.thinkpad.music;

        import android.Manifest;
        import android.content.pm.PackageManager;
        import android.media.MediaPlayer;
        import android.os.Environment;
        import android.os.Handler;
        import android.os.Message;
        import android.provider.MediaStore;
        import android.support.v4.app.ActivityCompat;
        import android.support.v4.app.NotificationCompat;
        import android.support.v4.content.ContextCompat;
        import android.support.v7.app.AppCompatActivity;
        import android.os.Bundle;
        import android.util.Log;
        import android.view.View;
        import android.widget.Button;
        import android.widget.ProgressBar;
        import android.widget.Toast;

        import java.io.File;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private MediaPlayer mediaPlayer=new MediaPlayer();
    private ProgressBar progressBar;
    private double percent;
    private  int count=0;
    private  Thread thread;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button play=(Button) findViewById(R.id.PLAY);
        Button pause=(Button) findViewById(R.id.PAUSE);
        Button stop=(Button) findViewById(R.id.STOP);
        play.setOnClickListener(this);
        pause.setOnClickListener(this);
        stop.setOnClickListener(this);
       progressBar=(ProgressBar)findViewById(R.id.pro);
        if(ContextCompat.checkSelfPermission(MainActivity.this,Manifest.permission.WRITE_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(MainActivity.this,new String[]{
                    Manifest.permission.WRITE_EXTERNAL_STORAGE
            },1);
        }else{
            initMediaPlayer();//初始化MediaPlayer
          //  mediaPlayer.start();
        }

    }
    private void initMediaPlayer(){
        try{
            File file=new File(Environment.getExternalStorageDirectory(),"music.mp3");
          mediaPlayer.setDataSource(file.getPath());//指定音频文件路径
int time=-mediaPlayer.getDuration();
            Toast.makeText(this,"time"+time,Toast.LENGTH_LONG).show();
           progressBar.setMax(time/1000000);
            File file1=new File(Environment.getExternalStorageDirectory(),"music.mp3");
            mediaPlayer.setDataSource(file1.getPath());//指定音频文件路径
            mediaPlayer.prepare();//让MediaPlayer进入准备状态
        }catch(Exception e){
            e.printStackTrace();
        }
    }
    @Override
    public  void onRequestPermissionsResult(int requestCode,String[] permissions,int[] grantResults){
        switch (requestCode){
            case 1:
                if(grantResults.length>0&&grantResults[0]==PackageManager.PERMISSION_GRANTED){
                    initMediaPlayer();
                }else{
                    Toast.makeText(this,"拒绝权限将无法使用程序",Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }
    @Override
    public void onClick(View v){
        switch (v.getId()){
            case R.id.PLAY:
                if (!mediaPlayer.isPlaying()){
                    mediaPlayer.start();//开始播放
                thread  =  new Thread(mRunnable);
                    thread.start();
                }
                break;
            case R.id.PAUSE:

                if(mediaPlayer.isPlaying()){
                    mediaPlayer.pause();//暂停播放
                }
                break;
            case R.id.STOP:
                if(mediaPlayer.isPlaying()){
                    mediaPlayer.reset();//停止播放
                    initMediaPlayer();
                }
                break;
            default:
                break;
        }
    }

    @Override
    protected void onDestroy(){
        super.onDestroy();
        if(mediaPlayer!=null){
            mediaPlayer.stop();
            mediaPlayer.release();
        }
    }
 private Runnable mRunnable = new Runnable() {//在此线程下使进度条增加。
        public void run() {
                      while(true) {
                           try {
                                      Thread.sleep(1000);
                                      mHandler.sendMessage(mHandler.obtainMessage());
                                 } catch (InterruptedException e) {
                                 }
                          }
                   }
    };
    private Handler mHandler = new Handler() {
       public void handleMessage(Message msg) {
                     super.handleMessage(msg);

          // Log.d("test","3wdwdwdwdddddddddddddddddddddddddddddddddddddddd");

          int progress=progressBar.getProgress();
           progress+=1;
              progressBar.setProgress(progress);
                  }
     };
}