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Android构建音频播放器课程(三)

热度:108   发布时间:2016-05-01 17:57:49.0
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 OnCompletionListenerSeekBar.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)
  
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;
            }
        }
    }


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