Android AsyncTask onPostExecute不会显示AlertDialog

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我在AsyncTask类中遇到了onPostExecute的问题.这是代码.

–EDIT:按要求添加代码的其余部分 –

  1. public class MainActivity extends Activity {
  2. @Override
  3. protected void onCreate(Bundle savedInstanceState) {
  4. super.onCreate(savedInstanceState);
  5. setContentView(R.layout.activity_main);
  6. preliminaryTasks();
  7. }
  8. private void preliminaryTasks() {
  9. //removed more code
  10. new discoverAddresses().execute();
  11. }
  12. public class discoverAddresses extends AsyncTask

但警报对话框从未出现过;当我在调试器中观察时,它将执行alert.show()行,但它永远不会显示在UI上.有没有人对这是为什么有任何想法?谢谢!

编辑:两个AlertDialogs都在调试器中执行,但从未在UI上显示

编辑2:我只是复制了我在这里发布的代码(看看是否是为了简化导致问题而删除代码)进入一个新项目并且实际出现了alertdialog,这意味着我拿出的代码是一个问题.在强制关闭终止应用程序时,我的原始项目中的LogCat即将出现.

  1. 02-02 11:13:28.746: D/AndroidRuntime(11658): Shutting down VM
  2. 02-02 11:13:28.746: W/dalvikvm(11658): threadid=1: thread exiting with uncaught exception (group=0x40fce300)
  3. 02-02 11:13:28.762: E/AndroidRuntime(11658): FATAL EXCEPTION: main
  4. 02-02 11:13:28.762: E/AndroidRuntime(11658): java.lang.NullPointerException
  5. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
  6. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
  7. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.AbsListView.obtainView(AbsListView.java:2257)
  8. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.ListView.measureHeightOfChildren(ListView.java:1244)
  9. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.ListView.onMeasure(ListView.java:1156)
  10. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  11. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4816)
  12. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
  13. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
  14. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
  15. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  16. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4816)
  17. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
  18. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
  19. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
  20. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  21. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4816)
  22. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
  23. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  24. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4816)
  25. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
  26. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  27. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4816)
  28. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
  29. 02-02 11:13:28.762: E/AndroidRuntime(11658): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2148)
  30. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.View.measure(View.java:15172)
  31. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1850)
  32. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1077)
  33. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1275)
  34. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
  35. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4214)
  36. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
  37. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
  38. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.Choreographer.doFrame(Choreographer.java:525)
  39. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
  40. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.os.Handler.handleCallback(Handler.java:615)
  41. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.os.Handler.dispatchMessage(Handler.java:92)
  42. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.os.Looper.loop(Looper.java:137)
  43. 02-02 11:13:28.762: E/AndroidRuntime(11658): at android.app.ActivityThread.main(ActivityThread.java:4899)
  44. 02-02 11:13:28.762: E/AndroidRuntime(11658): at java.lang.reflect.Method.invokeNative(Native Method)
  45. 02-02 11:13:28.762: E/AndroidRuntime(11658): at java.lang.reflect.Method.invoke(Method.java:511)
  46. 02-02 11:13:28.762: E/AndroidRuntime(11658): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
  47. 02-02 11:13:28.762: E/AndroidRuntime(11658): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
  48. 02-02 11:13:28.762: E/AndroidRuntime(11658): at dalvik.system.NativeStart.main(Native Method)
最佳答案
这对我有用,在OnPostExecute方法中.

我在我的AsyncTask类中添加了Activity对象作为propretie,我在AsyncTack的构造函数中实例化,以便我可以调用该活动并在onpostexe中执行runOnUiThread …

  1. AlertDialog.Builder builder = new AlertDialog.Builder(Activity);
  2. builder.setTitle("Connection ?");
  3. builder.setIcon(android.R.drawable.ic_dialog_alert);
  4. builder.setMessage("Test \n ");
  5. builder.setPositiveButton("Ok",null);
  6. final AlertDialog alert = builder.create();
  7. Activity.runOnUiThread(new java.lang.Runnable(){
  8. public void run(){
  9. //show AlertDialog
  10. alert.show();
  11. }
  12. });

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