Question

我添加了一个选项，为我的Android手机应用不同的主题。申请时，我正在启动异步任务。如果我在应用它时改变方向，我会得到一个错误，如下所示。

01-01 00:19:25.140: ERROR/AndroidRuntime(3553): FATAL EXCEPTION: main
01-01 00:19:25.140: ERROR/AndroidRuntime(3553): java.lang.RuntimeException: Unable to resume activity {com.android.settings/com.android.settings.ThemeSettingsActivity}: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=null} to activity {com.android.settings/com.android.settings.ThemeSettingsActivity}: java.lang.NullPointerException
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2471)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2499)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1994)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3375)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.access$700(ActivityThread.java:125)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1153)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.os.Looper.loop(Looper.java:137)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.main(ActivityThread.java:4368)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at java.lang.reflect.Method.invokeNative(Native Method)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at java.lang.reflect.Method.invoke(Method.java:511)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at dalvik.system.NativeStart.main(Native Method)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553): Caused by: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=null} to activity {com.android.settings/com.android.settings.ThemeSettingsActivity}: java.lang.NullPointerException
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3004)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2458)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     ... 13 more
01-01 00:19:25.140: ERROR/AndroidRuntime(3553): Caused by: java.lang.NullPointerException
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at com.android.settings.ThemeSettingsActivity.onActivityResult(ThemeSettingsActivity.java:308)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.Activity.dispatchActivityResult(Activity.java:4649)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3000)
01-01 00:19:25.140: ERROR/AndroidRuntime(3553):     ... 14 more

我无法找到这个原因请求帮助。

Answer 1

查看代码会很有帮助，特别是包含第308行的ThemeSettingsActivity.java的onActivityResult方法。

然而，AsyncTask的设计存在一个弱点，可能会导致这种情况。更改方向时，您的活动将被销毁并重新创建。但是，AsyncTask（特别是如果它是活动的内部类）仍然与被破坏的活动进行交互。 Android文档建议在活动被销毁时保存任务状态并销毁任务，然后在重新创建活动时从已保存状态构建新任务。请参阅Google网上论坛上的this discussion thread，其中讨论了以允许任务继续的方式解决问题的几个想法。

Answer 2

正如Ted所说，你可能会被糟糕的AsyncTask使用所困扰。我写了一篇关于AsyncTask陷阱的博客文章。您可能会发现它与您的情况有关。

http://www.shanekirk.com/2012/04/asynctask-missteps/

-Shane

在我的Android手机中更改方向时出错。

2 个答案: