利用 Android 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>

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();     }    }       };  }