Question

为什么当我将片段放入我的适配器并且它应该在我运行它时从片段获取上下文时，log cat会给我错误：

@Override
public void onActivityCreated(Bundle arg0)
{
    super.onActivityCreated(arg0);
    mygrid= (GridView) getActivity().findViewById(R.id.gridView2);
    mygrid.setAdapter(new Myaddapter(getActivity().getApplicationContext()));

Logcat输出：

05-23 22:28:33.862: E/AndroidRuntime(1650): FATAL EXCEPTION: main
05-23 22:28:33.862: E/AndroidRuntime(1650): Process: com.amirhossein.simon, PID: 1650
05-23 22:28:33.862: E/AndroidRuntime(1650): java.lang.NullPointerException
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.amirhossein.simon.FragmentA.<init>(FragmentA.java:33)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.amirhossein.simon.Myadapter.getItem(Fragment1.java:100)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:97)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:832)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.support.v4.view.ViewPager.populate(ViewPager.java:982)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.View.measure(View.java:16497)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.View.measure(View.java:16497)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.View.measure(View.java:16497)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.View.measure(View.java:16497)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.Choreographer.doCallbacks(Choreographer.java:574)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.Choreographer.doFrame(Choreographer.java:544)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.os.Handler.handleCallback(Handler.java:733)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.os.Handler.dispatchMessage(Handler.java:95)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.os.Looper.loop(Looper.java:136)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at android.app.ActivityThread.main(ActivityThread.java:5017)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at java.lang.reflect.Method.invokeNative(Native Method)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at java.lang.reflect.Method.invoke(Method.java:515)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-23 22:28:33.862: E/AndroidRuntime(1650):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

GridView mygrid= (GridView) getView().findViewById(R.id.gridView1);

您无法在成员初始值设定项中获取视图。您可以保留成员声明，但是初始化代码应该移动到片段onCreateView()中（在您要返回的视图上使用findViewById()，而不是getView()）。

上下文到片段中的适配器错误

1 个答案: