一個簡易的音頻播放器實作

XML代碼塊

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:layout_height="match_parent">

    <SeekBar
        android:id="@+id/seek_bar"
        android:max="100"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"/>
    <LinearLayout
        android:layout_marginTop="5dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center">
        <Button
            android:id="@+id/play_or_pause"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="播放"/>
         <Button
             android:id="@+id/stop"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
             android:text="停止"/>

    </LinearLayout>

</LinearLayout>

界面圖片
在這里插入圖片描述

實作功能

可以通過拖動進度條來播放音樂，音樂播放時進度條也會跟著移動，當播放完畢時進度條走滿
點擊播放鍵進入播放狀態，同時按鍵文字變為“暫停”，點擊“暫停”時暫停播放，文字變為“播放”，下次再點擊“播放”將繼續從上次播放位置播放
在任意狀態點擊“停止”將會停止播放，下次播放從頭開始

定義好功能介面，能控制播放功能以及UI界面改變功能，

public interface IPlayControl {
    //播放狀態
    int PLAYER_STATE_PLAY=1;
    int PLAYER_STATE_PAUSE=2;
    int PLAYER_STATE_STOP=3;
    /**
     * 把UI的控制權介面設定給邏輯層
     * @param iPlayViewControl
     */
    void registerViewController(IPlayViewControl iPlayViewControl);

    /**
     * 取消介面的注冊
     */
    void unregisterViewController();
    /**
     * 播放音樂
     */
    void playOrPause();
    /**
     * 停止播放
     */
    void stop();
    /**
     * 設定播放進度
     * @param seek 這個是播放進度
     */
    void seekTo(float seek);
}
/**
*這是用來控制UI的
*/
public interface IPlayViewControl {
    /**
     * 播放狀態改變通知
     */
    void onPlayerStateChange(int state);
    /**
     * 進度條狀態改變通知
     */
    void onSeekChange(float seek);
}

在Activity中

@RequiresApi(api = Build.VERSION_CODES.M)
public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private static final int PERMISSION_CODE = 1;
    private SeekBar mSeekBar;
    private Button mPlayOrPause;
    private Button mStop;
    private boolean mIsBind;
    private IPlayControl mIPlayControl;
    private boolean isUserTouchProgress;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化控制元件
        initView();
        //設定事件監聽
        initListener();
        //開啟服務（因為系結服務不能長期運行，所以采用二者結合的方式）
        startService(new Intent(this, PlayService.class));
		//因為要要在記憶體卡中讀取音樂，需要獲得運行時權限（模擬器api27,大于等于29的需要在
        //AndroidManifest.xml中添加android:requestLegacyExternalStorage="true")
        if ((checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)!= PackageManager.PERMISSION_GRANTED)) {
            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},PERMISSION_CODE);
        }else {
            //系結服務
            initBindService();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode==PERMISSION_CODE){
            if(grantResults[0]==PackageManager.PERMISSION_GRANTED){
                //系結服務
                initBindService();
            }
        }
    }

    /**
     * 系結服務（不能長時期運行）
     */
    private void initBindService() {
        Intent intent = new Intent(MainActivity.this, PlayService.class);
        mIsBind = bindService(intent, mConnection, BIND_AUTO_CREATE);
        Log.d(TAG, "bindService..");
    }

    private ServiceConnection mConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mIPlayControl = (IPlayControl) service;
            mIPlayControl.registerViewController(mIPlayViewControl);
            Log.d(TAG,"mConnection..");
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            //如果斷開連接就把它置空
            mIPlayControl = null;
        }
    };

    private void initListener() {
        mSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                //進度條發生改變

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                //用戶用手拖動進度條
                isUserTouchProgress=true;

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                //進度條停止拖動，獲得當前進度
                int touchProgress = seekBar.getProgress();
                Log.d(TAG, "touchProgress==" + touchProgress);
                if (mIPlayControl != null) {
                    //呼叫這個方法可以用進度條控制音頻播放，傳入的是一個百分比
                    mIPlayControl.seekTo(touchProgress);
                }
                isUserTouchProgress=false;
            }
        });
        mPlayOrPause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //播放或暫停
                if (mIPlayControl != null) {
                    mIPlayControl.playOrPause();
                }
            }
        });
        mStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //關閉按鈕被點擊了
                if (mIPlayControl != null) {
                    mIPlayControl.stop();
                }
            }
        });

    }

    private void initView() {
        mSeekBar = this.findViewById(R.id.seek_bar);
        mPlayOrPause = this.findViewById(R.id.play_or_pause);
        mStop = this.findViewById(R.id.stop);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        if (mIsBind && mConnection != null) {
            Log.d(TAG, "onDestroy...");
            //釋放資源
            mIPlayControl.unregisterViewController();
            unbindService(mConnection);
            mIsBind = false;
        }
    }

    /**
     * UI控制介面應該實作在Activity中
     */
    private IPlayViewControl mIPlayViewControl = new IPlayViewControl() {
        @Override
        public void onPlayerStateChange(int state) {
            //跟據播放狀態來更新UI
            switch (state){
                case PLAYER_STATE_PLAY:
                    //播放狀態的話要修改按鈕顯示成暫停
                    mPlayOrPause.setText("暫停");
                    break;
                case PLAYER_STATE_PAUSE:
                case PLAYER_STATE_STOP:
                    //暫停狀態的話要修改按鈕顯示成播放
                    mPlayOrPause.setText("播放");
                    break;

            }

        }

        @Override
        public void onSeekChange(final float seek) {
            //改變進度條更新，有一個條件，當用戶手碰在進度條上就不更新,不然會抖動
            Log.d(TAG, "onSeekChange: -->"+seek);
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    if (!isUserTouchProgress) {
                        mSeekBar.setProgress((int)seek);
                    }
                }
            });

        }
    };
}

在Service中

/**
* 在相應的方法中設定好邏輯
*/
public class PlayService extends Service {
    private PlayerPresenter mPlayerPresenter;
    @Override
    public void onCreate() {
        super.onCreate();
        if(mPlayerPresenter==null){
            //當mPlayerPresenter為空時創建，這是繼承的Binder類
            mPlayerPresenter=new PlayerPresenter();
        }
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        //系結之后回傳一個IBinder型別
        return mPlayerPresenter;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        //服務銷毀時將其置空
        mPlayerPresenter=null;
    }
}

在PlayerPresenter中

繼承了Binder類同時實作了IPlayContol介面，因為這個唯一能夠使Service跟Activity進行資料交換的橋梁，

首先實作方法

public class PlayerPresenter extends Binder implements IPlayControl {
    private static final String TAG = "PlayerPresenter";
    //設定成成員變數控制UI
    private IPlayViewControl mIPlayViewControl;
    //設定初始播放狀態為停止播放
    private int currentState = PLAYER_STATE_STOP;
    //定義一個播放器
    public MediaPlayer mMediaPlayer;
    //開啟一個計時器
    private Timer mTimer;
    //開啟一個任務
    private SeekTimeTask mSeekTimeTaskask;

    @Override
    public void registerViewController(IPlayViewControl iPlayViewControl) {
        //獲得UI控制權
        this.mIPlayViewControl = iPlayViewControl;
    }

    @Override
    public void unregisterViewController() {
        mIPlayViewControl=null;
    }

    @Override
    public void playOrPause() {
        Log.d(TAG,"playOrPause");
        if(currentState==PLAYER_STATE_STOP){
            //創建播放器
            initPlayer();
            //設定資料源
            try {
                //按照流程，具體可以參考Android.cn搜索MediaPlayer
                mMediaPlayer.setDataSource("/mnt/sdcard/jay.mp3");
                mMediaPlayer.prepare();
                mMediaPlayer.start();
                //改變當前狀態
                currentState=PLAYER_STATE_PLAY;
                startTimer();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }else if(currentState==PLAYER_STATE_PLAY){
            //如果當前狀態是播放的我們就暫停
            if (mMediaPlayer != null) {
                mMediaPlayer.pause();
                currentState=PLAYER_STATE_PAUSE;
                stopTimer();
            }
        }else if(currentState==PLAYER_STATE_PAUSE){
            //如果當前是暫停的我們就繼續播放音樂
            if (mMediaPlayer != null) {
                mMediaPlayer.start();
                currentState=PLAYER_STATE_PLAY;
                startTimer();
            }
        }
        //通知UI界面
        if (mIPlayViewControl != null) {
            mIPlayViewControl.onPlayerStateChange(currentState);
        }

    }

    /**
     * 初始化播放器
     */
    private void initPlayer() {
        if (mMediaPlayer==null) {
            mMediaPlayer = new MediaPlayer();
            //設定播放型別
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        }
    }

    @Override
    public void stop() {
        Log.d(TAG,"stop");
        //stop的時候要判斷是否有在播放
        if (mMediaPlayer != null ) {
            mMediaPlayer.stop();
            //更新播放狀態和UI
            currentState=PLAYER_STATE_STOP;
            stopTimer();
            if (mIPlayViewControl != null) {
                mIPlayViewControl.onPlayerStateChange(currentState);
            }
            //釋放資源
            mMediaPlayer.release();
            mMediaPlayer=null;
        }
    }

    @Override
    public void seekTo(float seek) {
        Log.d(TAG,"seekTo.."+seek);
        //0~100之間，需要做一個轉換，得到的seek是一個百分比
        if (mMediaPlayer != null) {
            int tarSeek = (int) (seek*1.0f/100 * mMediaPlayer.getDuration());
            mMediaPlayer.seekTo(tarSeek);
        }
    }

    /**
     * 開啟一個TimerTask
     */
    private void startTimer(){
        if (mTimer == null) {
            mTimer = new Timer();
        }
        if (mSeekTimeTaskask == null) {
            mSeekTimeTaskask = new SeekTimeTask();
        }
        //把任務扔到計時器里面，在特定的延遲時間每500ms更新一次
        mTimer.schedule(mSeekTimeTaskask,0,500);
    }
    private void stopTimer(){
        if (mTimer != null) {
            mTimer.cancel();
            mTimer=null;
        }
        if (mSeekTimeTaskask != null) {
            mSeekTimeTaskask.cancel();
            mSeekTimeTaskask=null;
        }
    }
    //設定一個task放進Timer中，每隔一段時間進行一次
    private class SeekTimeTask extends TimerTask {
        @Override
        public void run() {
            if (mMediaPlayer != null && mIPlayViewControl!=null) {
                //獲取當前的播放進度
                int currentPosition = mMediaPlayer.getCurrentPosition();
                //Log.d(TAG, "current play position --->"+ currentPosition);
                //換算成占100里面的多少了（因為設定的進度條數值為100）
                float curPosition = currentPosition*1.0f / mMediaPlayer.getDuration()*100;
                Log.d(TAG,"curPosition--->"+curPosition);
               //設定進度條顯示 
              mIPlayViewControl.onSeekChange(curPosition);
            }
        }
    }
}

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