Android构建音频播放器课程(三)_Android

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 String songTitle = songsList.get(songIndex).get("songTitle"); songTitleLabel.setText(songTitle); // Changing Button Image to pause image btnPlay.setImageResource(R.drawable.btn_pause); // set Progress bar values songProgressBar.setProgress(0); songProgressBar.setMax(100); // Updating progress bar updateProgressBar(); }catch(IllegalArgumentException e) { e.printStackTrace(); }catch(IllegalStateException e) { e.printStackTrace(); }catch(IOException e) { e.printStackTrace(); } }

3.Forward / Backward button click events（向前向后事件监听）

添加按钮事件侦听器，歌指定秒前和向后

1.前进按钮单击事件-移动歌曲以指定数量的秒向前，

AndroidBuildingMusicPlayerActivity.java
/** * Forward button click event * Forwards song specified seconds * */ btnForward.setOnClickListener(newView.OnClickListener() { @Override publicvoidonClick(View arg0) { // get current song position intcurrentPosition = mp.getCurrentPosition(); // check if seekForward time is lesser than song duration if(currentPosition + seekForwardTime <= mp.getDuration()){ // forward song mp.seekTo(currentPosition + seekForwardTime); }else{ // forward to end position mp.seekTo(mp.getDuration()); } } });

2.向后按钮单击事件-移动歌曲以指定秒数落后，

AndroidBuildingMusicPlayerActivity.java
/** * Backward button click event * Backward song to specified seconds * */ btnBackward.setOnClickListener(newView.OnClickListener() { @Override publicvoidonClick(View arg0) { // get current song position intcurrentPosition = mp.getCurrentPosition(); // check if seekBackward time is greater than 0 sec if(currentPosition - seekBackwardTime >= 0){ // forward song mp.seekTo(currentPosition - seekBackwardTime); }else{ // backward to starting position mp.seekTo(0); } } });

4.Next / Back button click events（上一首下一首事件监听）

点击添加按钮侦听器的下一个和上一个。

1.Next按钮单击事件-从播放列表播放下一首歌曲（不是最后一首）

AndroidBuildingMusicPlayerActivity.java
/** * Next button click event * Plays next song by taking currentSongIndex + 1 * */ btnNext.setOnClickListener(newView.OnClickListener() { @Override publicvoidonClick(View arg0) { // check if next song is there or not if(currentSongIndex < (songsList.size() - 1)){ playSong(currentSongIndex +1); currentSongIndex = currentSongIndex +1; }else{ // play first song playSong(0); currentSongIndex =0; } } });

2.后退按钮单击事件——播放前一首歌曲（不是第一首）

/**

         * Back button click event

         * Plays previous song by currentSongIndex - 1

         * */

        btnPrevious.setOnClickListener(newView.OnClickListener() {

            @Override

            publicvoidonClick(View arg0) {

                if(currentSongIndex > 0){

                    playSong(currentSongIndex - 1);

                    currentSongIndex = currentSongIndex - 1;

                }else{

                    // play last song

                    playSong(songsList.size() - 1);

                    currentSongIndex = songsList.size() - 1;

}

}

});

5.更新SeekBar的进度和时间

  要更新进度条计时器，我实现了在后台运行一个后台线程，使用一个Handler
AndroidBuildingMusicPlayerActivity.java/**
     * Update timer on seekbar
     * */
    publicvoidupdateProgressBar() {
        mHandler.postDelayed(mUpdateTimeTask,100);
    }  
 
    /**
     * Background Runnable thread
     * */
    privateRunnable mUpdateTimeTask = new Runnable() {
           publicvoidrun() {
               longtotalDuration = mp.getDuration();
               longcurrentDuration = mp.getCurrentPosition();
 
               // Displaying Total Duration time
               songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration));
               // Displaying time completed playing
               songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration));
 
               // Updating progress bar
               intprogress = (int)(utils.getProgressPercentage(currentDuration, totalDuration));
               //Log.d("Progress", ""+progress);
               songProgressBar.setProgress(progress);
 
               // Running this thread after 100 milliseconds
               mHandler.postDelayed(this,100);
           }
        };
 
    /**
     *
     * */
    @Override
    publicvoidonProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) {
 
    }
 
    /**
     * When user starts moving the progress handler
     * */
    @Override
    publicvoidonStartTrackingTouch(SeekBar seekBar) {
        // remove message Handler from updating progress bar
        mHandler.removeCallbacks(mUpdateTimeTask);
    }
 
    /**
     * When user stops moving the progress hanlder
     * */
    @Override
    publicvoidonStopTrackingTouch(SeekBar seekBar) {
        mHandler.removeCallbacks(mUpdateTimeTask);
        inttotalDuration = mp.getDuration();
        intcurrentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration);
 
        // forward or backward to certain seconds
        mp.seekTo(currentPosition);
 
        // update timer progress again
        updateProgressBar();
    }

6.Repeat button click event（事件监听）  在单击按钮重复isRepeat我们需要设置为true,反之亦然。我们也需要改变图像源重复按钮来集中状态
AndroidBuildingMusicPlayerActivity.java/**
         * Button Click event for Repeat button
         * Enables repeat flag to true
         * */
        btnRepeat.setOnClickListener(newView.OnClickListener() {
 
            @Override
            publicvoidonClick(View arg0) {
                if(isRepeat){
                    isRepeat = false;
                    Toast.makeText(getApplicationContext(),"Repeat is OFF", Toast.LENGTH_SHORT).show();
                    btnRepeat.setImageResource(R.drawable.btn_repeat);
                }else{
                    // make repeat to true
                    isRepeat = true;
                    Toast.makeText(getApplicationContext(),"Repeat is ON", Toast.LENGTH_SHORT).show();
                    // make shuffle to false
                    isShuffle = false;
                    btnRepeat.setImageResource(R.drawable.btn_repeat_focused);
                    btnShuffle.setImageResource(R.drawable.btn_shuffle);
                }
            }
        });

7.Shuffle button click event（事件监听）“洗牌”按钮上，我们需要设置isShuffle为true，反之亦然。此外，我们需要改变图像源洗牌按钮集中状态。
AndroidBuildingMusicPlayerActivity.java/**
         * Button Click event for Shuffle button
         * Enables shuffle flag to true
         * */
        btnShuffle.setOnClickListener(newView.OnClickListener() {
 
            @Override
            publicvoidonClick(View arg0) {
                if(isShuffle){
                    isShuffle = false;
                    Toast.makeText(getApplicationContext(),"Shuffle is OFF", Toast.LENGTH_SHORT).show();
                    btnShuffle.setImageResource(R.drawable.btn_shuffle);
                }else{
                    // make repeat to true
                    isShuffle=true;
                    Toast.makeText(getApplicationContext(),"Shuffle is ON", Toast.LENGTH_SHORT).show();
                    // make shuffle to false
                    isRepeat = false;
                    btnShuffle.setImageResource(R.drawable.btn_shuffle_focused);
                    btnRepeat.setImageResource(R.drawable.btn_repeat);
                }
            }
        });

8.继承 song onCompletion Listener接口   实现这个监听器很重要，当歌曲播放完毕后他会通知你，在这个方法中,我们需要自动播放下一首歌曲根据重复和shuffle条件。
  
AndroidBuildingMusicPlayerActivity.java/**
     * On Song Playing completed
     * if repeat is ON play same song again
     * if shuffle is ON play random song
     * */
    @Override
    publicvoidonCompletion(MediaPlayer arg0) {
 
        // check for repeat is ON or OFF
        if(isRepeat){
            // repeat is on play same song again
            playSong(currentSongIndex);
        }elseif(isShuffle){
            // shuffle is on - play a random song
            Random rand = new Random();
            currentSongIndex = rand.nextInt((songsList.size() - 1) - 0 + 1) + 0;
            playSong(currentSongIndex);
        }else{
            // no repeat or shuffle ON - play next song
            if(currentSongIndex < (songsList.size() - 1)){
                playSong(currentSongIndex + 1);
                currentSongIndex = currentSongIndex + 1;
            }else{
                // play first song
                playSong(0);
                currentSongIndex = 0;
            }
        }
    }