Question

I’ve got Fragments which can be instantiated in two different ways according to the current layout.
These fragment are loaded in a PageViewer using an Adapter derived from the FragmentStatePageAdapter.
If I run the app just in portrait or landscape mode everything is fine. The fragment are loaded correctly and look ok.
The problem is when I change orientation: The fragment doesn’t change, it seems that it reuse the one loaded for a certain orientation, in fact if I scroll the pager after the next one (wich it was already loaded in the previous orientation) the new fragment are loaded correctly and when I scroll back again even that “starting fragment” is reloaded correctly.

I would like to fix the problem by forcing the recreation of the current and the adjacents fragments but the solution I’ve tried seems to be incomplete/not working.

I’ve overridden the Adapter startUpdate method this way:

    public void startUpdate(ViewGroup container) {
        if(isPortrait != isLastOrientationPortrait){
            container.removeAllViews();
            instantiateItem(container, lastPosition);
        }
        super.startUpdate(container);
    }   

This force the elimination of the fragments from the containers. But I don’t know if it’s a correct approach and how to put the newly instatiated item back to the container.

Any suggestions?

Answer 1

I found a solution to this problem:

Instead of extends the FragmentStatePagerAdapter class I modified its source code (In case you need it you can find it here: https://android.googlesource.com/platform/frameworks/support/+/refs/heads/master/v4/java/android/support/v4/app/FragmentStatePagerAdapter.java)

What I did was just to modify the restoreStateMethod this way:

public void restoreState(Parcelable state, ClassLoader loader) {
        Log.d(TAG, "restoreState");
        //We don't want to restore the fragments if the orientation changes!
        if(isLastOrientationPortrait != isPortrait){
            if(state != null){
                Bundle bundle = (Bundle) state;
                bundle.setClassLoader(loader);
                Iterable<String> keys = bundle.keySet();
                if (mCurTransaction == null) {
                    mCurTransaction = mFragmentManager.beginTransaction();
                }
                for (String key : keys) {
                    if (key.startsWith("f")) {
                        Fragment f = mFragmentManager.getFragment(bundle,
                                key);
                        mCurTransaction.remove(f);
                    }
                }
            }
            isLastOrientationPortrait = isPortrait;
        }else{
            if (state != null) {
                Bundle bundle = (Bundle)state;
                bundle.setClassLoader(loader);
                Parcelable[] fss = bundle.getParcelableArray("states");
                mSavedState.clear();
                mFragments.clear();
                if (fss != null) {
                    for (int i=0; i<fss.length; i++) {
                        mSavedState.add((Fragment.SavedState)fss[i]);
                    }
                }
                Iterable<String> keys = bundle.keySet();
                for (String key: keys) {
                    if (key.startsWith("f")) {
                        int index = Integer.parseInt(key.substring(1));
                        Fragment f = mFragmentManager.getFragment(bundle, key);
                        if (f != null) {
                            while (mFragments.size() <= index) {
                                mFragments.add(null);
                            }
                            f.setMenuVisibility(false);
                            mFragments.set(index, f);
                        } else {
                            Log.w(TAG, "Bad fragment at key " + key);
                        }
                    }
                }
            }
        }
    }

what i basically added is this first if statement:

if(isLastOrientationPortrait != isPortrait){
            if(state != null){
                Bundle bundle = (Bundle) state;
                bundle.setClassLoader(loader);
                Iterable<String> keys = bundle.keySet();
                if (mCurTransaction == null) {
                    mCurTransaction = mFragmentManager.beginTransaction();
                }
                for (String key : keys) {
                    if (key.startsWith("f")) {
                        Fragment f = mFragmentManager.getFragment(bundle,
                                key);
                        mCurTransaction.remove(f);
                    }
                }
            }
            isLastOrientationPortrait = isPortrait;
        }

where isPortrait is the boolean value for the current orientation and isLastOrientationPortrait is the previous orientation saved via the onSaveInstanceState

This force to discard all the saved fragments and recreate them again on orientation change.