I have an app that needs to present a quick-start set of instructions for using a companion HW product. The instructions are simple fragment with a ViewPager that scrolls through four fragments with an image in them. The first time I instantiate the fragment with he viewpager, I see it's calls to get instantiated, then two calls to get the fragment for page 1 and page 2, and everything works as expected. Then, after hitting the back button to go back to the main app, and bringing up the instructions again, I see the calls to instantiate the fragment with the ViewPager, but no calls to get page 1 and page 2, so the screen is blank.
If I then scroll to page 2 (also blank), I'll see a call to get page 3 (Android is clearly queuing it up). Then I scroll to page 3 which shows up. Then I swipe back to page 2 which is still blank, but then there's a call to get page 1 so when I go back to page 1, it finally shows up.
I can't figure out why the new fragment with the ViewPager doesn't get calls to get pages 1 and 2 when it's instantiated the second time. It seems like it has state associated with it that isn't getting restored, but it should be a new instantiation.
Any help is greatly appreciated!
Here's the code for my fragment with the ViewPager:
public class InstructionsFragment extends Fragment { private static final String TAG = "InstructionsFragment";
public InstructionsFragment() {
// Required empty public constructor
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
Log.d(TAG, "onCreate: " + savedInstanceState);
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView: " + savedInstanceState);
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_instructions, container, false);
// use support.v4 ViewPager, but support.v13 FragmentPagerAdapter
// ViewPager is only in v4, but v13 FragmentPagerAdapter doesn't require support fragments
android.support.v4.view.ViewPager viewPager = (android.support.v4.view.ViewPager) view.findViewById(R.id.viewPager);
viewPager.setAdapter(new android.support.v13.app.FragmentPagerAdapter(getFragmentManager()) {
@Override
public Fragment getItem(int position) {
Log.d(TAG, "getItem: " + position);
switch(position) {
case 0: return ImageFragment.newInstance(R.drawable.instructions0);
case 1: return ImageFragment.newInstance(R.drawable.instructions1);
case 2: return ImageFragment.newInstance(R.drawable.instructions2);
default: return ImageFragment.newInstance(R.drawable.instructions3);
}
}
@Override
public int getCount() {
return 4;
}
});
return view;
}
}
and here's the code for the fragment that shows an image:
public class ImageFragment extends Fragment {
private static final String TAG = "ImageFragment";
private static final String ARG_IMAGE_RESOURCE_ID = "imageResourceId";
private int mImageResourceID;
public ImageFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*/
// TODO: Rename and change types and number of parameters
public static ImageFragment newInstance(int imageResourceID) {
ImageFragment fragment = new ImageFragment();
Bundle args = new Bundle();
args.putInt(ARG_IMAGE_RESOURCE_ID, imageResourceID);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mImageResourceID = getArguments().getInt(ARG_IMAGE_RESOURCE_ID);
}
Log.d(TAG, "onCreate, imageResourceID = " + mImageResourceID);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView, imageResourceID = " + mImageResourceID);
View view = inflater.inflate(R.layout.fragment_image, container, false);
ImageView imageView = (ImageView)view.findViewById(R.id.imageView);
imageView.setImageResource(mImageResourceID);
return view;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Log.d(TAG, "onSaveInstanceState, imageResourceID = " + mImageResourceID);
outState.putInt(ARG_IMAGE_RESOURCE_ID, mImageResourceID);
}
}
