View分页器内部片段的getActivity返回null [英] getActivity from fragment inside View pager return null
问题描述
我在Fragment Activity内有一个View传呼器,并且View传呼器在活动开始时包含两个片段,我有一个休息请求,当我得到响应时,我想在每个片段和每个片段中更新View我正在使用getActivity,但是我的问题是我总是在平板电脑设备上总是在getActivity上获得空指针异常,但是我没有在手机上得到这个问题
I have a View pager inside of Fragment Activity and the View pager Contain two fragment at the start of the activity i have a rest request and when i get the response i want to update the Views inside of each fragment and in each one i'm using getActivity but my problem is the i always get null pointer exception on getActivity just on tablet Devices but i didn't get this issue on mobile phones
那是我的寻呼机适配器
public class Guide_ViewPager_adapter extends FragmentStatePagerAdapter {
private Guides_fragment guide_frag = new Guides_fragment();
private Maps_fragment maps_frag = new Maps_fragment();
public Guide_ViewPager_adapter(FragmentManager fm){
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return guide_frag;
case 1:
return maps_frag;
}
return null;
}
@Override
public int getCount() {
return 2;
}
}
LogCat代码段:
LogCat snippet:
致命异常:主要流程:android.vi.com.vad,PID:9554java.lang.NullPointerException在android.vi.com.vad.Guides_fragment.update(Guides_fragment.java:138)在android.vi.com.vad.Guide_activity $ GuideTask.onPostExecute(Guide_activity.java:213)在android.vi.com.vad.Guide_activity $ GuideTask.onPostExecute(Guide_activity.java:165)在android.os.AsyncTask.finish(AsyncTask.java:632)在android.os.AsyncTask.access $ 600(AsyncTask.java:177)在android.os.AsyncTask $ InternalHandler.handleMessage(AsyncTask.java:645)在android.os.Handler.dispatchMessage(Handler.java:102)在android.os.Looper.loop(Looper.java:149)在android.app.ActivityThread.main(ActivityThread.java:5234)在java.lang.reflect.Method.invokeNative(本机方法)在java.lang.reflect.Method.invoke(Method.java:515)在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:793)在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)在dalvik.system.NativeStart.main(本机方法)
FATAL EXCEPTION: main Process: android.vi.com.vad, PID: 9554 java.lang.NullPointerException at android.vi.com.vad.Guides_fragment.update(Guides_fragment.java:138) at android.vi.com.vad.Guide_activity$GuideTask.onPostExecute(Guide_activity.java:213) at android.vi.com.vad.Guide_activity$GuideTask.onPostExecute(Guide_activity.java:165) at android.os.AsyncTask.finish(AsyncTask.java:632) at android.os.AsyncTask.access$600(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:149) at android.app.ActivityThread.main(ActivityThread.java:5234) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) at dalvik.system.NativeStart.main(Native Method)
这是我在加载数据时从活动内部调用的方法
This is the method that i call it from inside the activity when the data loaded
public void update(String result) {
if (animation != null) {
animation.reset();
animation.cancel();
}
if (loaderImage != null) {
loaderImage.clearAnimation();
loaderImage.setVisibility(View.GONE);
}
if (result.equalsIgnoreCase("null")) {
if (errorImage != null) {
errorImage.setVisibility(View.VISIBLE);
}
} else {
Guide_GridView_adapter adapter = new Guide_GridView_adapter(activity.getApplicationContext(), Guide_activity.Downloads_Guides);
guides_gridView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
}
在这里,当我将值设置为活动时:
and here when I set value to activity:
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
this.activity = getActivity();
}
推荐答案
我已经通过在Fragment onCreate()中调用setRetainInstance(true)解决了我的问题
I have solved my problem by calling setRetainInstance(true) in Fragment onCreate()
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
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