使用計時訊息來控制LED

上篇提到如何利用計時器來更新UI內容，本篇將介紹它來控制LED，平台使用長高科技的6410XP，為了使模擬器能順利開啟執行畫面，我們把觸發硬體的控制命令放在按鈕的事件處理函式內。在此程式需要建立三個按鈕分別來控制閃爍、開啟驅動、關閉閃爍。其完整程式列表如下：
1. UpdateUIActivity.java

package tw.com.dmatek.dma6410xp.led;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class UpdateUIActivity extends Activity {
    protected static final int led_on = 1;
 private long mStartTime;
    TextView mTimeLabel;
    private int flag=0;
 private int fd;
 Button start,open,stop;
    /** Called when the activity is first created. */ 
    @Override    
    public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);
     mTimeLabel = (TextView) findViewById(R.id.timer);
     mStartTime = System.currentTimeMillis();
        mHandler.removeCallbacks(mUpdateTimeTask);
        stop=(Button) findViewById(R.id.stop);
        stop.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
          mHandler.removeCallbacks(mUpdateTimeTask);
   }
         
        });
     start=(Button) findViewById(R.id.start);
     start.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    // TODO Auto-generated method stub
          mStartTime = System.currentTimeMillis();

          mHandler.postDelayed(mUpdateTimeTask, 100);
   }
      
     });
     start.setEnabled(false);
   open=(Button) findViewById(R.id.open);
    open.setOnClickListener(new OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
        fd = Linuxc.openled();
          
        if (fd < 0){
         setTitle("open device false!");
           
         finish(); 
        }
        else {
          setTitle("open device success!");
          start.setEnabled(true);
          open.setEnabled(false);
        }
  }
     
    });

     }    
    private Handler mHandler = new Handler();
    private Runnable mUpdateTimeTask = new Runnable() {
     public void run() {
      final long start = mStartTime;
      long millis = System.currentTimeMillis() - start; 
      int seconds = (int) (millis / 1000);
      int minutes = seconds / 60;
      seconds     = seconds % 60; 
      if (seconds < 10) { 
       mTimeLabel.setText("" + minutes + ":0" + seconds); 
       } else { 
        mTimeLabel.setText("" + minutes + ":" + seconds);
        } 
      flag=1-flag;
      Linuxc.send(2, flag+1);
      mHandler.postDelayed(mUpdateTimeTask, 100); 
      }  
     };
}

2. Linuxc.java

package tw.com.dmatek.dma6410xp.led;

import android.util.Log;

public class Linuxc {
 static {
        try {
            Log.i("JNI", "Trying to load libled.so");
            
            System.loadLibrary("led"); 
        }
        catch (UnsatisfiedLinkError ule) {
            Log.e("JNI", "WARNING: Could not load libled.so");
        }}
  
 public static native int openled();
 
 public static native int closeled();
   
 public static native int send(int led_num, int on_off);
}