问题
I have an Activity that have two Fragments and those fragments are presented to user by a ViewPager. So, I created a class extends FragmentStatePagerAdapter for ViewPager's adapter (MainFragsAdapter class) and I overrided some methods of it. I want to get my fragment's instances in my ViewPager from host Activity and get current fragment's root View by getView() method.
I got the instances of fragments by typing followings in Activity's onCreate() But getView() of that instance returns null :
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mainFragsAdapter = new MainFragsAdapter(getSupportFragmentManager());
viewPager = (ViewPager)findViewById(R.id.Pager);
viewPager.setAdapter(mainFragsAdapter);
int index = viewPager.getCurrentItem();
if(index == 0) {
Fragment1 fragment = (Fragment1)viewPager.getAdapter().instantiateItem(viewPager, index);
View v = fragment.getView();
Log.e("Frag1View",v.toString()); //At this point, I'm getting NullPointerException
//because getView() returns null.(Fragment isn't null)
}else if(index == 1){
Fragment2 fragment =(Fragment2)viewPager.getAdapter().instantiateItem(viewPager, index);
}
}
My FragmentStatePagerAdapter :
public class MainFragsAdapter extends FragmentStatePagerAdapter {
private SparseArray<Fragment> fragments = new SparseArray<>();
private Fragment currentFragment;
private int NUM_ITEMS = 2;
public MainFragsAdapter(FragmentManager fm,Context context) {
super(fm);
}
@Override
public int getCount() {
return NUM_ITEMS;
}
@Override
public Fragment getItem(int position) {
if(position == 0){
this.currentFragment = Fragment1.createInstance();
}
if(position == 1){
this.currentFragment =Fragment2.createInstance();
}
return this.currentFragment;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment = (Fragment)super.instantiateItem(container,position);
fragments.put(position,fragment);
return fragment; }
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
fragments.remove(position);
super.destroyItem(container,position,object);
}
public Fragment getRegisteredFragment(int position) {
return fragments.get(position);
}
}
How can i solve this issue ? Thank you for helps.
来源：https://stackoverflow.com/questions/44437839/it-returns-null-when-i-use-getview-to-get-root-view-of-the-fragment-in-the-vie