Android 重新创建活动时,viewpager适配器为空
我正在实现包含viewpager的android应用程序。问题是,当应用程序在后台被终止时,当我在asynctask onPostExecute方法中使用适配器实例设置viewpager时,我的行上有空指针。下面是我的代码。希望得到帮助: 发生崩溃的片段类中的片段Android 重新创建活动时,viewpager适配器为空,android,android-viewpager,adapter,Android,Android Viewpager,Adapter,我正在实现包含viewpager的android应用程序。问题是,当应用程序在后台被终止时,当我在asynctask onPostExecute方法中使用适配器实例设置viewpager时,我的行上有空指针。下面是我的代码。希望得到帮助: 发生崩溃的片段类中的片段 protected void onPostExecute(ArrayList<CategoryChild> result) { super.onPostExecute(result);
protected void onPostExecute(ArrayList<CategoryChild> result) {
super.onPostExecute(result);
if (this.fragmentWeakRef.get() != null) {
if (result != null) {
mHomeCategories = result;
if(mBannerViewPager != null){
mBannerViewPager.setAdapter(new BannerViewpagerAdapter(
getChildFragmentManager(), getActivity()
.getApplicationContext())); // here app crashes after being killed in background
// and restored
}
mcategoryViewPager.setAdapter(new CategoryViewpagerAdapter(
getChildFragmentManager(), getActivity()
.getApplicationContext(),setFragmentsArray()));
} else {
Toast.makeText(getActivity().getApplicationContext(),
"No Internet Connection", Toast.LENGTH_SHORT)
.show();
}
}
}
}
这是我的适配器
public class BannerViewpagerAdapter extends FragmentPagerAdapter {
private SparseArray<BannerFragment> registeredFragments = new SparseArray<BannerFragment>();
private static HashMap<Integer, Integer> myHashmap = new HashMap<Integer, Integer>();
static {
myHashmap.put(0, R.drawable.img);
myHashmap.put(1, R.drawable.stopex);
}
public BannerViewpagerAdapter(android.support.v4.app.FragmentManager fm, Context context) {
super(fm);
// TODO Auto-generated constructor stub
}
@Override
public Fragment getItem(int position) {
// TODO Auto-generated method stub
BannerFragment myFragment = null;
myFragment = registeredFragments.get(position);
if(myFragment == null){
myFragment = BannerFragment.newInstance(myHashmap.get(position));
registeredFragments.put(position, myFragment);
}
return myFragment;
}
@Override
public Object instantiateItem(ViewGroup arg0, int arg1) {
// TODO Auto-generated method stub
return super.instantiateItem(arg0, arg1);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return 2;
}
}
这是合乎逻辑的。活动被杀死,其成员也被杀死。所以,在这种情况下,您应该解决应用程序的行为。您还可以添加验证ViewPager是否存在的对话框,就像您在上面的几行中所做的那样:
if (mcategoryViewPager != null) {
mcategoryViewPager.setAdapter(new CategoryViewpagerAdapter(
getChildFragmentManager(), getActivity()
.getApplicationContext(),setFragmentsArray()))
}
哦。您的活动被终止,因此getActivity将返回null。因此,只需在前面添加:
if (getActivity() == null) { return; }
应用程序在此行崩溃mBannerViewPager.setAdapterNewBannerviewPager AdapterGetChildFragmentManager,getActivity.getApplicationContext;你是对的,我的朋友getactivity为空。你真的骗了我谢谢: