Android基礎教程：handler機制實現ProgressDialog

布局文件比較簡單，只有一個按鈕：

1. <?xml version="1.0" encoding="utf-8"?>
2. <LinearLayout xmlns:Android="http://schemas.android.com/apk/res/android"
3. android:orientation="vertical"
4. android:layout_width="fill_parent"
5. android:layout_height="fill_parent"
6. >
7. <Button android:text="Login"
8. android:id="@+id/loginBtn"
9. android:layout_width="wrap_content"
10. android:layout_height="wrap_content"
11. />
12. </LinearLayout>

1. package com.cloay;
3. import android.app.Activity;
4. import android.app.ProgressDialog;
5. import android.content.DialogInterface;
6. import android.os.Bundle;
7. import android.os.Handler;
8. import android.os.Message;
9. import android.view.View;
10. import android.view.View.OnClickListener;
11. import android.widget.Button;
13. /**
14. * Myhandler.java
15. * @author Cloay
16. * 2011-9-6
17. */
18. public class Myhandler extends Activity{
19. private Button button;
20. private ProgressDialog progressDialog;
21. @Override
22. protected void onCreate(Bundle savedInstanceState) {
23. // TODO Auto-generated method stub
24. super.onCreate(savedInstanceState);
25. setContentView(R.layout.handler);
26. button = (Button)findViewById(R.id.loginBtn);
27. button.setOnClickListener(new loginBtnListener());
28. }
29. /*
30. * 使用Handler更新UI
31. */
32. Handler handler = new Handler(){
34. @Override
35. public void handleMessage(Message msg) {
36. //設置進度條當前值，並將線程對象放入線程隊列
37. progressDialog.setProgress(msg.arg1);
38. handler.post(updateThread);
39. }
41. };
42. class loginBtnListener implements OnClickListener{
44. @Override
45. public void onClick(View v) {
46. handler.post(updateThread);
47. progressDialog = new ProgressDialog(Myhandler.this);
48. progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
49. progressDialog.setMessage("正在登陸，請稍後...");
50. progressDialog.setTitle("登陸系統");
51. progressDialog.setIcon(R.drawable.ask);
52. progressDialog.setMax(100);
53. progressDialog.setProgress(0);
54. progressDialog.setCancelable(true);
55. progressDialog.setButton("取消", new DialogInterface.OnClickListener() {
57. @Override
58. public void onClick(DialogInterface dialog, int which) {
59. // TODO Auto-generated method stub
60. dialog.dismiss();
61. }
62. });
63. progressDialog.show();
64. }
66. }
67. Runnable updateThread = new Runnable() {
68. int i = 0;
69. @Override
70. public void run() {
71. i += 5;
72. Message msg = handler.obtainMessage(); //得到一個消息對象
73. //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
74. msg.arg1 = i;
75. try {
76. Thread.sleep(100);
77. } catch (InterruptedException e) {
78. e.printStackTrace();
79. }
80. //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
81. handler.sendMessage(msg);
82. if(i == progressDialog.getMax()){
83. //當i達到最大值時，從消息隊列中刪除msg
84. handler.removeCallbacks(updateThread, msg);
85. progressDialog.dismiss();
86. }
87. }
89. };
90. }