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我正在尝试ProgressDialog.But我很困惑.

1.pd=ProgressDialog.show(MainActivity.this, "", "Fething data");

当我使用(MainActivity.this)然后它没关系.但

2.pd=ProgressDialog.show(getApplicationContext(), "", "Fething data");

当我使用(getApplicationContext())时,它是错误的.

这个progressDialog有什么问题？

(MainActivity.this)vs(getApplicationContext())之间有什么不同

当我用它完美时间？

对于getApplicationContext()错误是:

04-09 15:05:37.453: E/AndroidRuntime(9980): FATAL EXCEPTION: main
04-09 15:05:37.453: E/AndroidRuntime(9980): android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.view.ViewRootImpl.setView(ViewRootImpl.java:571)
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:246)
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.app.Dialog.show(Dialog.java:281)
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.app.ProgressDialog.show(ProgressDialog.java:116)
04-09 15:05:37.453: E/AndroidRuntime(9980):     at android.app.ProgressDialog.show(ProgressDialog.java:99)
04-09 …