Android构建音频播放器教程(三)

10. 为Audio Player写相关类文件
打开你的主要活动类（MainActivity）处理主要player界面，并且继承 OnCompletionListener, SeekBar.OnSeekBarChangeListener.在这种情况下，我的主要活动名称是AndroidBuildingMusicPlayerActivity。
AndroidBuildingMusicPlayerActivity.java publicclassAndroidBuildingMusicPlayerActivityextendsActivity
implementsOnCompletionListener, SeekBar.OnSeekBarChangeListener {

现在声明所有变量需要为此音频播放器类。（audio player class）

AndroidBuildingMusicPlayerActivity.java
publicclassAndroidBuildingMusicPlayerActivityextendsActivity
       implementsOnCompletionListener, SeekBar.OnSeekBarChangeListener {
    privateImageButton btnPlay;
    privateImageButton btnForward;
    privateImageButton btnBackward;
    privateImageButton btnNext;
    privateImageButton btnPrevious;
    privateImageButton btnPlaylist;
    privateImageButton btnRepeat;
    privateImageButton btnShuffle;
    privateSeekBar songProgressBar;
    privateTextView songTitleLabel;
    privateTextView songCurrentDurationLabel;
    privateTextView songTotalDurationLabel;
    // Media Player
    private MediaPlayer mp;
    // Handler to update UI timer, progress bar etc,.
    privateHandler mHandler =newHandler();;
    privateSongsManager songManager;
    privateUtilities utils;
    privateintseekForwardTime =5000;// 5000 milliseconds
    privateintseekBackwardTime =5000;// 5000 milliseconds
    privateintcurrentSongIndex =0;
    privatebooleanisShuffle =false;
    privatebooleanisRepeat =false;
    privateArrayList<HashMap<String, String>> songsList =newArrayList<HashMap<String, String>>();

现在引用XML布局的所有按钮，图像类

AndroidBuildingMusicPlayerActivity.java
// All player buttons
        btnPlay = (ImageButton) findViewById(R.id.btnPlay);
        btnForward = (ImageButton) findViewById(R.id.btnForward);
        btnBackward = (ImageButton) findViewById(R.id.btnBackward);
        btnNext = (ImageButton) findViewById(R.id.btnNext);
        btnPrevious = (ImageButton) findViewById(R.id.btnPrevious);
        btnPlaylist = (ImageButton) findViewById(R.id.btnPlaylist);
        btnRepeat = (ImageButton) findViewById(R.id.btnRepeat);
        btnShuffle = (ImageButton) findViewById(R.id.btnShuffle);
        songProgressBar = (SeekBar) findViewById(R.id.songProgressBar);
        songTitleLabel = (TextView) findViewById(R.id.songTitle);
        songCurrentDurationLabel = (TextView) findViewById(R.id.songCurrentDurationLabel);
        songTotalDurationLabel = (TextView) findViewById(R.id.songTotalDurationLabel);
        // Mediaplayer
        mp =newMediaPlayer();
        songManager =newSongsManager();
        utils =newUtilities();
        // Listeners
        songProgressBar.setOnSeekBarChangeListener(this);// Important
        mp.setOnCompletionListener(this);// Important
        // Getting all songs list
        songsList = songManager.getPlayList();

1.加载播放列表（PlayList）
为playlist button写单击事件侦听器，在点击播放按钮时我们需要加载PlayListAcitivity.java ，从列表中选择一个特定的歌曲上我们需要得到songIndex。
AndroidBuildingMusicPlayerActivity.java /**
         * Button Click event for Play list click event
         * Launches list activity which displays list of songs
         * */
        btnPlaylist.setOnClickListener(newView.OnClickListener() {
            @Override
            publicvoidonClick(View arg0) {
                Intent i =newIntent(getApplicationContext(), PlayListActivity.class);
                startActivityForResult(i,100);
            }
        });

接收选定的歌曲索引增加以下功能（请确保您添加此功能以外的onCreate方法）

AndroidBuildingMusicPlayerActivity.java /**
     * Receiving song index from playlist view
     * and play the song
     * */
    @Override
    protectedvoidonActivityResult(intrequestCode,
                                     intresultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(resultCode == 100){
             currentSongIndex = data.getExtras().getInt("songIndex");
             // play selected song
             playSong(currentSongIndex);
        }
    }

2.Playing Song（播放歌曲）
添加以下功能添加到你的类，这个函数接受songIndex作为参数并播放。当开始播放一首歌切换播放按钮暂停按钮状态。
AndroidBuildingMusicPlayerActivity.java /**
     * Function to play a song
     * @param songIndex - index of song
     * */
    publicvoid playSong(intsongIndex){
        // Play song
        try{
            mp.reset();
            mp.setDataSource(songsList.get(songIndex).get("songPath"));
            mp.prepare();
            mp.start();
            // Displaying Song title
&nbs

补充：移动开发 , Android ,