Android开发---MediaPlayer简单音乐播放器

功能介绍

• 实现一个简单的播放器，类似网易云音乐形式，功能包括：

  1. 播放、暂停，停止，退出功能；
  2. 后台播放功能；
  3. 进度条显示播放进度、拖动进度条改变进度功能；
  4. 播放时图片旋转，显示当前播放时间功能；

• 界面样式 
  

功能实现

1. MediaPlayer的实现

• MediaPlayer常用方法介绍
•  
  MediaPlayer的实现包括初始化MediaPlayer，MediaPlayer的功能实现，包括播放、暂停、停止、离开等，具体细节如下： 
  MediaPlayer的初始化包括读取一个MP3格式的音乐文件并设置其为循环播放：

public void initMediaPlayer() {        try {            //String file_path = "/storage/0123-4567/K.Will-Melt.mp3";            String file_path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/K.Will-Melt.mp3";            //String file_path = "/data/K.Will-Melt.mp3";            mediaPlayer.setDataSource(file_path);            mediaPlayer.prepare();            mediaPlayer.setLooping(true);  // 设置循环播放        } catch (Exception e) {            e.printStackTrace();        }    }
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播放/暂停功能的实现放在Play/Pause按钮中，所以需要二选一判断MediaPlayer的状态来设置音乐的播放与暂停：

public void playOrPause() {        flag++;        if (flag >= 1000) flag = 2;        which = "pause";        if(mediaPlayer.isPlaying()){            mediaPlayer.pause();            animator.pause();        } else {            mediaPlayer.start();
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类似的，停止功能的实现放在Stop按钮中，用于停止音乐并将其置于初始态即“00:00”：

public void stop() {        which = "stop";        animator.pause();        if(mediaPlayer != null) {            mediaPlayer.pause();            mediaPlayer.stop();            try {                mediaPlayer.prepare();                mediaPlayer.seekTo(0);            } catch (Exception e) {                e.printStackTrace();            }        }    }
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说明：由于调用stop()后，有时音乐并没有马上停止，所以我额外加了一个pause()来确保音乐停止播放。

同样，离开功能实现放在了Quit按钮中，主要实现整个应用的退出，具体应包括解绑Service，结束Activity等等：

private void quit() {        musicService.animator.end();        handler.removeCallbacks(runnable);        unbindService(sc);        try {            finish();            System.exit(0);        } catch (Exception e) {            e.printStackTrace();        }    }
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2. Service的应用

• Service即“服务” ，它与Activity属于同一等级的应用程序组件，都代表可执行的程序。不同的是Activity拥有前台运行的用户界面，而Service不能自己运行，需要通过某个Activity或者其他Context对象来调用。Service在后台运行，它不能与用户直接进行交互。在默认情况下，Service运行在应用程序进程的主线程之中。可以通过Context.startService()和Context.bindService()两种方式来启动Service。
• 通过Service可以使程序在退出之后仍然能够对事件或用户操作做出反应，或者在后台继续运行某些程序功能。
• Android赋予Services比处于不活动（inactivity）的Activities更高的优先级，所以它们的进程不会轻易被系统杀掉。
• Activity与Service的交互示意图为： 
   
  有了以上知识的积累，基本可以实现Service的必要部分,如下： 
  1.新建一个继承于Service的MusicService类

public class MusicService extends Service {    public final IBinder binder = new MyBinder();    public class MyBinder extends Binder {        MusicService getService() {            return MusicService.this;        }    }
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/**     * onBind 是 Service 的虚方法，因此我们不得不实现它。     * 返回 null，表示客服端不能建立到此服务的连接。     */    @Override    public IBinder onBind(Intent intent) {        return binder;    }
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2.并在Activity中绑定MusicService：

 @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        getOverflowMenu();        setContentView(R.layout.activity_main);        bindServiceConnection();        musicService = new MusicService();
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private ServiceConnection sc = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {            musicService = ((MusicService.MyBinder) iBinder).getService();        }        @Override        public void onServiceDisconnected(ComponentName componentName) {            musicService = null;        }    };    private void bindServiceConnection() {        Intent intent = new Intent(this, MusicService.class);        startService(intent);        bindService(intent, sc, this.BIND_AUTO_CREATE);    }
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3. Handler更新UI界面

通过Handler来管理UI，最要需要用到post和postDelayed两个函数： 
1. post(Runnable r) 
将r加入到消息队列中（其实就是利用UI主线程执行一段代码，这样可以随时在其他线程中调整控件） 
2. postDelayed(Runnabled r,long delayMillis) 
将r加入到消息队列中，并在指定时间之后触发（单位为毫秒） 
所以，为了实现音乐的播放显示等功能，需要重写Runnable的run函数，具体实现如下：

public Handler handler = new Handler();    public Runnable runnable = new Runnable() {        @Override        public void run() {            isPlay.setOnClickListener(new myOnClickListener());            stop.setOnClickListener(new myOnClickListener());            quit.setOnClickListener(new myOnClickListener());            if(musicService.mediaPlayer.isPlaying()) {                stateText.setText("Playing");            } else {                if (musicService.which.equals("stop"))  {                    stateText.setText("Stop");                } else if (musicService.which.equals("pause")){                    stateText.setText("Pause");                }            }            playingTime.setText(time.format(musicService.mediaPlayer.getCurrentPosition()));            totalTime.setText(time.format(musicService.mediaPlayer.getDuration()));            seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());            seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {                @Override                public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {                    if (fromUser) {                        musicService.mediaPlayer.seekTo(seekBar.getProgress());                    }                }                @Override                public void onStartTrackingTouch(SeekBar seekBar) {                }                @Override                public void onStopTrackingTouch(SeekBar seekBar) {                }            });            handler.postDelayed(runnable, 100);        }    };
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4. 实现图片的旋转

图片的动画效果实现需要用到ObjectAnimator类，ObjectAnimator类可用于图片的平移、旋转、缩放等动画，此处我们只需要用到其旋转功能，具体实现如下：

public  void AnimatorAction() {        if (mediaPlayer.isPlaying()) {            animator.setDuration(5000);            animator.setInterpolator(new LinearInterpolator()); // 均速旋转            animator.setRepeatCount(ValueAnimator.INFINITE); // 无限循环            animator.setRepeatMode(ValueAnimator.INFINITE);            animator.start();        }    }
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说明：animator是ObjectAnimator的一个实例对象，setDuration为5000表示旋转一周需要的时间为5000，所以可用来设置旋转的速度；同时设置为无线循环模式，并且添加一个插值器达到匀速旋转的目的，最后调用pause()等函数动态控制动画状态，如下： 

5. 进度条SeekBar功能实现

SeekBar的功能包括显示歌曲播放进度以及拖动SeekBar至任意位置来改变播放进度，由于Android已经封装好了这些函数，所以直接调用就好了，也比较好理解，具体实现如下：

seekBar = (SeekBar) findViewById(R.id.seekBar);        seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());        seekBar.setMax(musicService.mediaPlayer.getDuration());
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seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());            seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {                @Override                public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {                    if (fromUser) {                        musicService.mediaPlayer.seekTo(seekBar.getProgress());                    }                }                @Override                public void onStartTrackingTouch(SeekBar seekBar) {                }                @Override                public void onStopTrackingTouch(SeekBar seekBar) {                }            });
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6. 动态权限申请

参见Android动态权限申请

7. 判断程序是否处于后台

由于音乐需要支持后台播放，再次由后台进入前台会对前台的事件功能等产生影响，所以可以添加一个后台判断函数，并添加一个标志来记录应用是否进入后台。

private boolean isApplicationBroughtToBackground() {        ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);        List<ActivityManager.RunningTaskInfo> tasks = am.getRunningTasks(1);        if (!tasks.isEmpty()) {            ComponentName topActivity = tasks.get(0).topActivity;            if (!topActivity.getPackageName().equals(getPackageName())) {                return true;            }        }        return false;    }
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附上MainActivity和Service部分的完整代码

• MainActivity.java

package com.example.kx.temp;import android.Manifest;import android.animation.ObjectAnimator;import android.animation.ValueAnimator;import android.app.Activity;import android.app.ActivityManager;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.ServiceConnection;import android.content.pm.PackageManager;import android.media.MediaPlayer;import android.net.Uri;import android.os.Environment;import android.os.Handler;import android.os.IBinder;import android.support.v4.app.ActivityCompat;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.Menu;import android.view.View;import android.view.ViewConfiguration;import android.view.animation.LinearInterpolator;import android.widget.Button;import android.widget.ImageView;import android.widget.SeekBar;import android.widget.TextView;import com.google.android.gms.appindexing.Action;import com.google.android.gms.appindexing.AppIndex;import com.google.android.gms.common.api.GoogleApiClient;import java.lang.reflect.Field;import java.text.SimpleDateFormat;import java.util.List;public class MainActivity extends AppCompatActivity {    private Button isPlay;    private Button stop;    private Button quit;    private ImageView coverImage;    // private ObjectAnimator animator;    private int flag = 0;    private TextView totalTime;    private TextView playingTime;    private TextView stateText;    private SeekBar seekBar;    private TextView pathText;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        getOverflowMenu();        setContentView(R.layout.activity_main);        bindServiceConnection();        musicService = new MusicService();        coverImage = (ImageView) findViewById(R.id.coverImage);        musicService.animator = ObjectAnimator.ofFloat(coverImage, "rotation", 0, 359);        isPlay = (Button) findViewById(R.id.isPlayButton);        isPlay.setOnClickListener(new myOnClickListener());        stop = (Button) findViewById(R.id.stopButton);        stop.setOnClickListener(new myOnClickListener());        quit = (Button) findViewById(R.id.quitButton);        quit.setOnClickListener(new myOnClickListener());        seekBar = (SeekBar) findViewById(R.id.seekBar);        seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());        seekBar.setMax(musicService.mediaPlayer.getDuration());        totalTime = (TextView) findViewById(R.id.totalTime);        playingTime = (TextView) findViewById(R.id.playingTime);        stateText = (TextView) findViewById(R.id.stateText);        pathText = (TextView) findViewById(R.id.pathText);        String sdcard = "音乐文件的路径为：" + Environment.getExternalStorageDirectory().getAbsolutePath().toString()+"/K.Will-Melt.mp3";        pathText.setText(sdcard);    }    private MusicService musicService;    private SimpleDateFormat time = new SimpleDateFormat("mm:ss");    private ServiceConnection sc = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {            musicService = ((MusicService.MyBinder) iBinder).getService();        }        @Override        public void onServiceDisconnected(ComponentName componentName) {            musicService = null;        }    };    private void bindServiceConnection() {        Intent intent = new Intent(this, MusicService.class);        startService(intent);        bindService(intent, sc, this.BIND_AUTO_CREATE);    }    public Handler handler = new Handler();    public Runnable runnable = new Runnable() {        @Override        public void run() {            isPlay.setOnClickListener(new myOnClickListener());            stop.setOnClickListener(new myOnClickListener());            quit.setOnClickListener(new myOnClickListener());            if(musicService.mediaPlayer.isPlaying()) {                stateText.setText("Playing");            } else {                if (musicService.which.equals("stop"))  {                    stateText.setText("Stop");                } else if (musicService.which.equals("pause")){                    stateText.setText("Pause");                }            }            playingTime.setText(time.format(musicService.mediaPlayer.getCurrentPosition()));            totalTime.setText(time.format(musicService.mediaPlayer.getDuration()));            seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());            seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {                @Override                public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {                    if (fromUser) {                        musicService.mediaPlayer.seekTo(seekBar.getProgress());                    }                }                @Override                public void onStartTrackingTouch(SeekBar seekBar) {                }                @Override                public void onStopTrackingTouch(SeekBar seekBar) {                }            });            handler.postDelayed(runnable, 100);        }    };    @Override    public void onPause(){        super.onPause();        if(isApplicationBroughtToBackground()) {            musicService.isReturnTo = 1;            Log.e("b","后台中");        }    }    @Override    public void onRestart() {        super.onRestart();        musicService.isReturnTo = 1;    }    @Override    protected void onResume() {        musicService.AnimatorAction();        verifyStoragePermissions(this);        if(musicService.mediaPlayer.isPlaying()) {            stateText.setText("Playing");        } else {            if (musicService.which.equals("stop"))  {                stateText.setText("Stop");            } else if (musicService.which.equals("pause")){                stateText.setText("Pause");            }        }        seekBar.setProgress(musicService.mediaPlayer.getCurrentPosition());        seekBar.setMax(musicService.mediaPlayer.getDuration());        handler.post(runnable);        super.onResume();        Log.d("hint", "handler post runnable");    }    private class myOnClickListener implements View.OnClickListener {        @Override        public void onClick(View view) {            switch (view.getId()) {                case R.id.isPlayButton:                    changePlay();                    musicService.playOrPause();                    break;                case R.id.stopButton:                    musicService.stop();                    changeStop();                    break;                case R.id.quitButton:                    quit();                    break;                default:                    break;            }        }    }    private void changePlay() {        if(musicService.mediaPlayer.isPlaying()){            stateText.setText("Pause");            isPlay.setText("PLAY");            //animator.pause();        } else {            stateText.setText("Playing");            isPlay.setText("PAUSE");        }    }    private void changeStop() {        stateText.setText("Stop");        seekBar.setProgress(0);        //animator.pause();    }    private void quit() {        musicService.animator.end();        handler.removeCallbacks(runnable);        unbindService(sc);        try {            finish();            System.exit(0);        } catch (Exception e) {            e.printStackTrace();        }    }    @Override    public void onStop() {        super.onStop();    }    @Override    public void onDestroy() {        unbindService(sc);        super.onDestroy();    }    //这里是在登录界面label上右上角添加三个点，里面可添加其他功能    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.settings, menu);        return true;    }    private void getOverflowMenu() {        try {            ViewConfiguration config = ViewConfiguration.get(this);            Field menuKeyField = ViewConfiguration.class.getDeclaredField("sHasPermanentMenuKey");            if (menuKeyField != null) {                menuKeyField.setAccessible(true);                menuKeyField.setBoolean(config, false);            }        } catch (Exception e) {            e.printStackTrace();        }    }    private boolean isApplicationBroughtToBackground() {        ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);        List<ActivityManager.RunningTaskInfo> tasks = am.getRunningTasks(1);        if (!tasks.isEmpty()) {            ComponentName topActivity = tasks.get(0).topActivity;            if (!topActivity.getPackageName().equals(getPackageName())) {                return true;            }        }        return false;    }    // Storage Permissions    private static final int REQUEST_EXTERNAL_STORAGE = 1;    private static String[] PERMISSIONS_STORAGE = {            Manifest.permission.READ_EXTERNAL_STORAGE,            Manifest.permission.WRITE_EXTERNAL_STORAGE    };    /**     * Checks if the app has permission to write to device storage     *     * If the app does not has permission then the user will be prompted to grant permissions     *     * @param activity     */    public static void verifyStoragePermissions(Activity activity) {        // Check if we have write permission        int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);        if (permission != PackageManager.PERMISSION_GRANTED) {            // We don't have permission so prompt the user            ActivityCompat.requestPermissions(                    activity,                    PERMISSIONS_STORAGE,                    REQUEST_EXTERNAL_STORAGE            );        }    }}
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• Service

package com.example.kx.temp;import android.Manifest;import android.animation.ObjectAnimator;import android.animation.ValueAnimator;import android.app.Activity;import android.app.ActivityManager;import android.app.Service;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.pm.PackageManager;import android.media.MediaPlayer;import android.os.Binder;import android.os.Environment;import android.os.IBinder;import android.support.v4.app.ActivityCompat;import android.util.Log;import android.view.animation.LinearInterpolator;import java.io.File;import java.util.List;/** * Created by kx on 2016/11/3. */public class MusicService extends Service {    public final IBinder binder = new MyBinder();    public class MyBinder extends Binder {        MusicService getService() {            return MusicService.this;        }    }    public static int isReturnTo = 0;    public static MediaPlayer mediaPlayer = new MediaPlayer();    public static ObjectAnimator animator;    public MusicService() {        initMediaPlayer();    }    public void initMediaPlayer() {        try {            //String file_path = "/storage/0123-4567/K.Will-Melt.mp3";            String file_path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/K.Will-Melt.mp3";            //String file_path = "/data/K.Will-Melt.mp3";            mediaPlayer.setDataSource(file_path);            mediaPlayer.prepare();            mediaPlayer.setLooping(true);  // 设置循环播放        } catch (Exception e) {            e.printStackTrace();        }    }    public  void AnimatorAction() {        if (mediaPlayer.isPlaying()) {            animator.setDuration(5000);            animator.setInterpolator(new LinearInterpolator()); // 均速旋转            animator.setRepeatCount(ValueAnimator.INFINITE); // 无限循环            animator.setRepeatMode(ValueAnimator.INFINITE);            animator.start();        }    }    private int flag = 0;    public static String which = "";    public void playOrPause() {        flag++;        if (flag >= 1000) flag = 2;        which = "pause";        if(mediaPlayer.isPlaying()){            mediaPlayer.pause();            animator.pause();        } else {            mediaPlayer.start();            if ((flag == 1) || (isReturnTo == 1)) {                animator.setDuration(5000);                animator.setInterpolator(new LinearInterpolator()); // 均速旋转                animator.setRepeatCount(ValueAnimator.INFINITE); // 无限循环                animator.setRepeatMode(ValueAnimator.INFINITE);                animator.start();            } else {                animator.resume();            }        }    }    public void stop() {        which = "stop";        animator.pause();        if(mediaPlayer != null) {            mediaPlayer.pause();            mediaPlayer.stop();            try {                mediaPlayer.prepare();                mediaPlayer.seekTo(0);            } catch (Exception e) {                e.printStackTrace();            }        }    }    @Override    public void onDestroy() {        mediaPlayer.stop();        mediaPlayer.release();        super.onDestroy();    }    /**     * onBind 是 Service 的虚方法，因此我们不得不实现它。     * 返回 null，表示客服端不能建立到此服务的连接。     */    @Override    public IBinder onBind(Intent intent) {        return binder;    }}
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至此，基于MediaPlayer的简单音乐播放器基本可以实现，如需要完整项目代码，可留下邮箱。