上下文到片段中的适配器错误答案

【问题标题】：context into adapter error in fragment上下文到片段中的适配器错误
【发布时间】：2014-07-13 09:44:24
【问题描述】：

为什么当我将片段放入我的适配器并且当我运行它时它应该从片段中获取上下文时，log cat 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)

【问题讨论】：

看起来像一个导致异常的成员初始化程序。 FragmentA.java 第 33 行有什么内容？
它在第 33 行：GridView mygrid= (GridView) getView().findViewById(R.id.gridView1);

标签： android gridview fragment android-adapter android-context

【解决方案1】：

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

您无法在成员初始化程序中获取视图。您可以保留成员声明，但初始化代码应移动到 Fragment 的 onCreateView() 中（通过在您返回的视图上使用 findViewById()，而不是在 getView() 上）。

【讨论】：