让ProgressDialog在setCancelable(false)时按返回键可dismiss
最近发现Android4.0系统中ProgressDialog设置为setCancelable(true)时，点击ProgressDialog以外的区域也可以让ProgressDialog dismiss掉。但有时我们不希望是这样的效果，于是将ProgressDialog设置setCancelable(false)，再点击ProgressDialog以外的区域就不会出现前面所说的情况了，然而这样以来再按返回键时就不起作用了，只能等待程序执行到dissmiss处为止。其实，只要为ProgressDialog添加KeyListener来对返回键予以处理就可以解决这个问题了。

1. package cn.winfirm.examples.base;
   
2. 
   
3. import android.app.Activity;
   
4. import android.app.ProgressDialog;
   
5. import android.content.DialogInterface;
   
6. import android.content.DialogInterface.OnKeyListener;
   
7. import android.os.Bundle;
   
8. import android.view.KeyEvent;
   
9. import android.view.Window;
   
10. 
    
11. /**
    
12. * Activity的基类，带一个ProgressDialog，可双击取消其显示
    
13. *
    
14. * @author savant
    
15. *
    
16. */
    
17. public class BaseActivity extends Activity {
    
18. 
    
19. private ProgressDialog progressDialog = null;
    
20. 
    
21. @Override
    
22. protected void onCreate(Bundle savedInstanceState) {
    
23. super.onCreate(savedInstanceState);
    
24. requestWindowFeature(Window.FEATURE_NO_TITLE);
    
25. }
    
26. 
    
27. /**
    
28. * show loading progress dialog
    
29. */
    
30. public void showDialog() {
    
31. if (null == progressDialog) {
    
32. progressDialog = ProgressDialog.show(BaseActivity.this, "", "正在加载，请稍候...");
    
33. progressDialog.setCancelable(false);
    
34. } else {
    
35. progressDialog.show();
    
36. }
    
37. progressDialog.setOnKeyListener(onKeyListener);
    
38. }
    
39. 
    
40. /**
    
41. * add a keylistener for progress dialog
    
42. */
    
43. private OnKeyListener onKeyListener = new OnKeyListener() {
    
44. @Override
    
45. public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
    
46. if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
    
47. dismissDialog();
    
48. }
    
49. return false;
    
50. }
    
51. };
    
52. 
    
53. /**
    
54. * dismiss dialog
    
55. */
    
56. public void dismissDialog() {
    
57. if (isFinishing()) {
    
58. return;
    
59. }
    
60. if (null != progressDialog && progressDialog.isShowing()) {
    
61. progressDialog.dismiss();
    
62. }
    
63. }
    
64. 
    
65. /**
    
66. * cancel progress dialog if nesseary
    
67. */
    
68. @Override
    
69. public void onBackPressed() {
    
70. if (progressDialog != null && progressDialog.isShowing()) {
    
71. dismissDialog();
    
72. } else {
    
73. super.onBackPressed();
    
74. }
    
75. }
    
76. }