我有一个 Activity 进行远程服务器调用并尝试填充列表。对服务器的调用工作正常，并且调用返回一些很好的 JSON。
但随后系统抛出此异常：
04-06 18:43:19.626: D/AndroidRuntime(2564): Shutting down VM
04-06 18:43:19.626: W/dalvikvm(2564): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
04-06 18:43:19.686: E/AndroidRuntime(2564): FATAL EXCEPTION: main
04-06 18:43:19.686: E/AndroidRuntime(2564): java.lang.NullPointerException
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.AbsListView.obtainView(AbsListView.java:2033)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.ListView.measureHeightOfChildren(ListView.java:1244)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.ListView.onMeasure(ListView.java:1155)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.View.measure(View.java:12723)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.View.measure(View.java:12723)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.View.measure(View.java:12723)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.View.measure(View.java:12723)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
04-06 18:43:19.686: E/AndroidRuntime(2564): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.View.measure(View.java:12723)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.os.Handler.dispatchMessage(Handler.java:99)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.os.Looper.loop(Looper.java:137)
04-06 18:43:19.686: E/AndroidRuntime(2564): at android.app.ActivityThread.main(ActivityThread.java:4424)
04-06 18:43:19.686: E/AndroidRuntime(2564): at java.lang.reflect.Method.invokeNative(Native Method)
04-06 18:43:19.686: E/AndroidRuntime(2564): at java.lang.reflect.Method.invoke(Method.java:511)
04-06 18:43:19.686: E/AndroidRuntime(2564): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-06 18:43:19.686: E/AndroidRuntime(2564): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-06 18:43:19.686: E/AndroidRuntime(2564): at dalvik.system.NativeStart.main(Native Method)
为什么会发生这种情况？它没有指向我的任何代码，所以有点奇怪。
永远不会在回调中protected void onPostExecute(String result)被调用。
谢谢！