Handler小例子（非常简单的handler例子，适合初学者，高手勿喷）

例子一：


使用Handler循环打印

package djx.android;
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;
public class HandlerTest extends Activity {
private Button button_begin=null;
private Button button_end=null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

button_begin=(Button)findViewById(R.id.button_begin);
button_begin.setOnClickListener(new beginOnClickListener());

button_end=(Button)findViewById(R.id.button_end);
button_end.setOnClickListener(new endOnClickListener());
}
class beginOnClickListener implements OnClickListener{
@Override
public void onClick(View arg0) {
handler.post(runnable);
}

}
class endOnClickListener implements OnClickListener{
@Override
public void onClick(View arg0) {
handler.removeCallbacks(runnable);
}

}
Handler handler=new Handler();
Runnable runnable=new Runnable(){
@Override
public void run() {
System.out.println("thread Update......");
handler.postDelayed(runnable, 3000);
}

};
}

例子二：


handler更新progressBar

执行过程分析：

点击按钮->progressBar变为可见->handler将runnable对象放入队列等待执行，由于当前队列中仅有这一个对象，故而立即得到执行->执行Runnable，控制台打印Thread is Beging!->i自增10，并赋值给msg的变量arg1->当前线程休眠1s->handler.sendMessage(msg)即handler向消息队列发送msg，在handler的 handleMessage(Message msg)方法中会得到msg对象，progressBar设置当前值。->如果i还未达到最大值100的话继续handler将runnab对象放入队列，否则移出队列结束。

package djx.handler;
import android.app.Activity;
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.ProgressBar;
public class ProgressBarHandler extends Activity {
private Button button_begin=null;
private ProgressBar pb=null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

button_begin=(Button)findViewById(R.id.button_begin);
button_begin.setOnClickListener(new beginOnClickListener());

pb=(ProgressBar)findViewById(R.id.progressBar);
pb.setMax(100);
}
class beginOnClickListener implements OnClickListener{
@Override
public void onClick(View v) {
pb.setVisibility(View.VISIBLE);
handler.post(runnable);
}

}
Handler handler=new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
pb.setProgress(msg.arg1);
if(msg.arg1==100){
handler.removeCallbacks(runnable);
}
else
handler.post(runnable);

}

};
Runnable runnable=new Runnable(){
int i=0;
@Override
public void run() {
System.out.println("Thread is Beging!");
i=i+10;
Message msg=handler.obtainMessage();
msg.arg1=i;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendMessage(msg);
System.out.println("**********："+i);

}

};
}