handler机制实现ProgressDialog

布局文件比较简单，只有一个按钮：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <Button android:text="Login"
    	android:id="@+id/loginBtn"
    	android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
    	/>
</LinearLayout>

本程序参照mars老师的视频写的，下面是主程序代码：

package com.cloay;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
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;

/**
 * Myhandler.java
 * @author Cloay
 * 2011-9-6
 */
public class Myhandler extends Activity{
	private Button button;
	private ProgressDialog progressDialog;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.handler);
		button = (Button)findViewById(R.id.loginBtn);
		button.setOnClickListener(new loginBtnListener());
	}
	/*
	 * 使用Handler更新UI
	 */
	Handler handler = new Handler(){

		@Override
		public void handleMessage(Message msg) {
			//设置进度条当前值，并将线程对象放入线程队列
			progressDialog.setProgress(msg.arg1);
			handler.post(updateThread);
		}
		
	};
	class loginBtnListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			handler.post(updateThread);
			progressDialog = new ProgressDialog(Myhandler.this);
			progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
			progressDialog.setMessage("正在登陆，请稍后...");
			progressDialog.setTitle("登陆系统");
			progressDialog.setIcon(R.drawable.ask);
			progressDialog.setMax(100);
			progressDialog.setProgress(0);
			progressDialog.setCancelable(true);
			progressDialog.setButton("取消", new DialogInterface.OnClickListener() {
				
				@Override
				public void onClick(DialogInterface dialog, int which) {
					// TODO Auto-generated method stub
					dialog.dismiss();
				}
			});
			progressDialog.show();
		}
		
	}
	Runnable updateThread = new Runnable() {
		int i = 0;
		@Override
		public void run() {
			i += 5;
			Message msg = handler.obtainMessage();    //得到一个消息对象
			//将msg对象的参数设置为i,Message类共有两个参数arg1和arg2，用这两个成员变量传递消息的优点是系统性能消耗最少
			msg.arg1 = i;               
			try {
				Thread.sleep(100);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			//将msg压入消息队列,sendMessage方法是异步的，不等消息被处理，该方法就返回，继续往下执行
			handler.sendMessage(msg);
			if(i == progressDialog.getMax()){
				//当i达到最大值时，从消息队列中删除msg
				handler.removeCallbacks(updateThread, msg);
				progressDialog.dismiss();
			}
		}
		
	};
}

运行效果图如下：

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