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
);
    }
}