Android节拍器

写完Java节拍器，本以为能够很容易的过渡到Android节拍器。后来发现不对。在网上查询了之后，才知道，Android考虑到线程安全问 题，不允许在线程中执行UI线程。这里我们要学到一个Android中重要的类：android.os.Handler,这个可以实现各处线程间的消息传 递。

      我们可以在原先的TimerTask子类MyTimerTask的方法run()中，只是给Handler发送一个Message。我们让Handler进行UI线程上的操作（在节拍器的例子中，指的是更新那个显示节拍的控件的数值）。

      最终节拍器打节拍的同时发生。（由于时间原因，音量控制尚未实现）实现截图如下：

 
    

 

 package  com.Android.Jiapaiqi;

 import  android.app.Activity;
 import  android.content.Context;
 import  android.media.AudioManager;
 import  android.media.SoundPool;
 import  android.os.Bundle;
 import  android.os.Handler;
 import  android.os.Message;
 import  android.view.View;
 import  android.view.View.OnClickListener;
 import  android.widget.Button;
 import  android.widget.EditText;
 import  android.widget.SeekBar;
 import  android.widget.TextView;
 import  android.widget.SeekBar.OnSeekBarChangeListener;

 import  java.util.Timer;
 import  java.util.TimerTask;

 public   class  ActivityMain  extends  Activity {

     Button button_start;
     Button button_stop;
     EditText edit_sudu;
     EditText edit_paishu;
     TextView result;
     SeekBar seekbar;
     public   float  tempo;
     public   int  section;
     public   int  pp;
     Handler handler;
     Timer mytimer;

     private  SoundPool sndHigh;
     private  SoundPool sndLow;
     private   int  hitOfHigh;
     private   int  hitOfLow;

     //声音控制
     private  AudioManager audioManager;
     //声音变量
     private   int  volume= 0 ;
     //声音模式
     //private int mode;
     //是否有声音
     private   int  flag= 1 ;

     //内部类
     class  MyTimerTask  extends  TimerTask{

         @Override
         public   void  run() {
             Message message=new  Message();
             message.what=1 ;
             handler.sendMessage(message);
         }
     };

     /** Called when the activity is first created. */
     @Override
     public   void  onCreate(Bundle savedInstanceState) {
         super .onCreate(savedInstanceState);

         pp=1 ;
         setContentView(R.layout.main);

         final  EditText edit_sudu = (EditText) this .findViewById(R.id.edit_sudu);
         final  EditText edit_paishu = (EditText) this .findViewById(R.id.edit_paishu);
         final  TextView result = (TextView)findViewById(R.id.result);

         handler = new  Handler()
         {
             public   void  handleMessage(Message msg)
             {
                 switch (msg.what)
                 {
                 case   1 :
                     result.setText(String.valueOf(pp));
                         if (pp== 1 )
                             // play (int soundID, float leftVolume, float rightVolume, int priority, int loop, float rate)
                             //播放音频，可以对左右音量分别设置，还可以设置优先级，循环次数以及速率
                             sndHigh.play(hitOfHigh, 1 ,  1 ,  0 ,  0 ,  1 );
                         else
                             sndLow.play(hitOfLow, 1 ,  1 ,  0 ,  0 ,  1 );
                     if (pp!=section)
                     {
                         pp++;
                     }
                     else
                     {
                         pp=1 ;
                     }
                         break ;
                 }
                 super .handleMessage(msg);
             }
         };

         button_start = (Button) findViewById(R.id.button_start);
         button_start.setOnClickListener(new  OnClickListener() {
             public   void  onClick(View v) {
                 tempo=Float.parseFloat(edit_sudu.getText().toString());
                 section=Integer.parseInt(edit_paishu.getText().toString());
                 mytimer=new  Timer();
                 float  tempFloat= 60 /tempo* 1000 ;
                 mytimer.schedule(new  MyTimerTask(), 0 , ( long )tempFloat);
             }
         });

         button_stop = (Button) findViewById(R.id.button_stop);
         button_stop.setOnClickListener(new  OnClickListener() {
             public   void  onClick(View v) {
                 mytimer.cancel();
                 sndHigh.pause(hitOfHigh);
                 sndLow.pause(hitOfLow);
             }
         });

         final  SeekBar seekbar = (SeekBar) findViewById(R.id.seekbar);
         //设置拖动条的初始值和文本框的初始值
         seekbar.setMax(7 );
         seekbar.setProgress(5 );
         seekbar.setOnSeekBarChangeListener(new  OnSeekBarChangeListener()
         {
             @Override
             public   void  onProgressChanged(SeekBar seekBar,  int  progress,
                     boolean  fromUser) {
                 // TODO Auto-generated method stub
             }
             @Override
             public   void  onStartTrackingTouch(SeekBar seekBar) {
                 // TODO Auto-generated method stub

             }
             @Override
             public   void  onStopTrackingTouch(SeekBar seekBar) {
                 // TODO Auto-generated method stub
             }
         });
         audioManager = (AudioManager) getBaseContext().getSystemService(Context.AUDIO_SERVICE);
         //通过getStreamVolume获得当前音量大小
         volume=audioManager.getStreamVolume(AudioManager.STREAM_RING);
         //把当前音量的值 设置给进度条
         //seekbar.setProgress(volume);

         sndHigh = new  SoundPool( 10 , AudioManager.STREAM_SYSTEM, 5 );
         //载入音频流
         hitOfHigh = sndHigh.load(getBaseContext(), R.drawable.high, 0 );

         sndLow = new  SoundPool( 10 , AudioManager.STREAM_SYSTEM, 5 );
         //载入音频流
         hitOfLow = sndLow.load(getBaseContext(), R.drawable.low, 0 );
     }
 }