Android构建音频播放器课程(三)

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.javapublicclassAndroidBuildingMusicPlayerActivityextendsActivity       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.javapublicclassAndroidBuildingMusicPlayerActivityextendsActivity       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）  AndroidBuildingMusicPlayerActivity.java/**         * 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HandlerAndroidBuildingMusicPlayerActivity.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;            }        }    }