利用 Android handler機制實現ProgressDialog

布局文件比較簡單，只有一個按鈕：

<?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) {

 //設置進度條當前值，并將線程對象放入線程隊列
 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("正在登陸，請稍后...");
 progressDialog.setTitle("登陸系統");
 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();    //得到一個消息對象
 //將msg對象的參數設置為i,Message類共有兩個參數arg1和arg2，用這兩個成員變量傳遞消息的優點是系統性能消耗最少
 msg.arg1 = i;               
 try {
     Thread.sleep(100);
 } catch (InterruptedException e) {
     e.printStackTrace();
 }
 //將msg壓入消息隊列,sendMessage方法是異步的，不等消息被處理，該方法就返回，繼續往下執行
 handler.sendMessage(msg);
 if(i == progressDialog.getMax()){
     //當i達到最大值時，從消息隊列中刪除msg
     handler.removeCallbacks(updateThread, msg);
     progressDialog.dismiss();
 }

}
};
}</pre>運行效果圖如下：