Double save state fix for FragmentStatePagerAdapter

gistfile1.txt

package com.huffingtonpost.android.base.widget;

import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;

import com.fuzz.android.common.GlobalContext;
import com.fuzz.android.util.FZLog;
import com.google.common.io.Files;
import com.huffingtonpost.android.utils.AsyncUtils;
import com.huffingtonpost.android.utils.SafeRunnable;

import java.io.File;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;

public abstract class FragmentStatePagerAdapter2 extends PagerAdapter {
    private static final String TAG = "FragmentStatePagerAdapter";

    private final FragmentManager mFragmentManager;
    private LinkedList<FragmentTransaction> currentTransactions = new LinkedList<>();

    private long[] mItemIds = new long[]{};
    protected ArrayList<Fragment.SavedState> mSavedState = new ArrayList<>();
    private ArrayList<Fragment> mFragments = new ArrayList<>();
    private Fragment mCurrentPrimaryItem = null;

    public FragmentStatePagerAdapter2(FragmentManager fm) {
        mFragmentManager = fm;
        mItemIds = new long[getCount()];
        for (int i = 0; i < mItemIds.length; i++) {
            mItemIds[i] = getItemId(i);
        }
    }

    /**
     * Return the Fragment associated with a specified position.
     */
    public abstract Fragment getItem(int position);

    /**
     * Return a unique identifier for the item at the given position.
     */
    public abstract long getItemId(int position);

    public Fragment getFragmentAtPosition(int position) {
        if (position < 0 || position >= mFragments.size()) {
            return null;
        }
        return mFragments.get(position);
    }

    @Override
    public void notifyDataSetChanged() {
        long[] newItemIds = new long[getCount()];
        for (int i = 0; i < newItemIds.length; i++) {
            newItemIds[i] = getItemId(i);
        }
        FZLog.d(FragmentStatePagerAdapter2.class.getSimpleName(), "newItemIds: " + Arrays.toString(newItemIds));
        FZLog.d(FragmentStatePagerAdapter2.class.getSimpleName(), "mItemIds: " + Arrays.toString(mItemIds));
        boolean arraysEqual = Arrays.equals(mItemIds, newItemIds);
        FZLog.d(FragmentStatePagerAdapter2.class.getSimpleName(), "Arrays are equal: " + arraysEqual);
        if (!arraysEqual) {
            ArrayList<Fragment.SavedState> newSavedState = new ArrayList<>();
            ArrayList<Fragment> newFragments = new ArrayList<>();
            for (int newPosition = 0; newPosition < newItemIds.length; newPosition++) {
                for (int i = 0; i < mItemIds.length; i++) {
                    if (mItemIds.length > i && mFragments.size() > i && mSavedState.size() > i && mItemIds[i] == newItemIds[newPosition]) {
                        newFragments.add(mFragments.get(i));
                        newSavedState.add(mSavedState.get(i));
                        break;
                    }
                }
            }
            mItemIds = newItemIds;
            mSavedState = newSavedState;
            mFragments = newFragments;
        }
        super.notifyDataSetChanged();
    }

    @Override
    public void startUpdate(ViewGroup container) {
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        // If we already have this item instantiated, there is nothing
        // to do.  This can happen when we are restoring the entire pager
        // from its saved state, where the fragment manager has already
        // taken care of restoring the fragments we previously had instantiated.
        if (mFragments.size() > position) {
            Fragment f = mFragments.get(position);
            if (f != null) {
                return f;
            }
        }
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        currentTransactions.add(fragmentTransaction);
        Fragment fragment = getItem(position);
        FZLog.v(TAG, "Adding item #" + position + ": f=" + fragment);
        if (mSavedState.size() > position) {
            Fragment.SavedState fss = mSavedState.get(position);
            if (fss != null) {
                fragment.setInitialSavedState(fss);
            }
        }
        while (mFragments.size() <= position) {
            mFragments.add(null);
        }
        fragment.setMenuVisibility(false);
        fragment.setUserVisibleHint(false);
        mFragments.set(position, fragment);
        fragmentTransaction.add(container.getId(), fragment, generateTag(position));
        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        Fragment fragment = (Fragment) object;
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        currentTransactions.add(fragmentTransaction);
        FZLog.v(TAG, "Removing item #" + position + ": f=" + object + " v=" + ((Fragment) object).getView());
        if (position >= 0) {
            while (mSavedState.size() <= position) {
                mSavedState.add(null);
            }
            while (mFragments.size() <= position) {
                mFragments.add(null);
            }
            try {
                Fragment.SavedState savedState = mFragmentManager.saveFragmentInstanceState(fragment);
                mSavedState.set(position, savedState);
            } catch (Exception e) {
                FZLog.throwable(FragmentStatePagerAdapter2.class.getSimpleName(), e);
            }
            mFragments.set(position, null);
        }
        fragmentTransaction.remove(fragment);
    }

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                mCurrentPrimaryItem.setMenuVisibility(false);
                mCurrentPrimaryItem.setUserVisibleHint(false);
            }
            if (fragment != null) {
                fragment.setMenuVisibility(true);
                if (fragment.getFragmentManager() == null) {
                    try {
                        // this is a hack to not cause a crash if fragment manager does not exist.
                        // however this may be fixed already if fragments getItemPosition and getItemId are set properly.
                        Field[] fields = Fragment.class.getDeclaredFields();
                        for (Field field : fields) {
                            if ("mFragmentManager".equalsIgnoreCase(field.getName())) {
                                field.setAccessible(true);
                                field.set(fragment, mFragmentManager);
                                break;
                            }
                        }

                    } catch (IllegalAccessException e) {
                        FZLog.throwable(FragmentStatePagerAdapter2.class.getSimpleName(), e);
                    }
                }

                fragment.setUserVisibleHint(true);
            }
            mCurrentPrimaryItem = fragment;
        }
    }

    @Override
    public void finishUpdate(ViewGroup container) {
        for (FragmentTransaction fragmentTransaction : currentTransactions) {
            fragmentTransaction.commitAllowingStateLoss();
            mFragmentManager.executePendingTransactions();
        }
        currentTransactions.clear();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return ((Fragment) object).getView() == view;
    }

    @Override
    public Parcelable saveState() {
        Bundle state = new Bundle();
        if (mItemIds.length > 0) {
            state.putLongArray("itemids", mItemIds);
        }
        AsyncUtils.poolExecutor.execute(new SafeRunnable() {
            @Override
            public void safeRun() throws Throwable {
                Parcel parcel = Parcel.obtain();
                parcel.writeList(mSavedState);
                byte[] savedStateBytes = parcel.marshall();
                File cache = new File(GlobalContext.getContext().getCacheDir(), "saved_states");
                cache.mkdir();
                Files.write(savedStateBytes, cache);
            }
        });
        for (int i = 0; i < mFragments.size(); i++) {
            Fragment f = mFragments.get(i);
            if (f != null && f.isAdded()) {
                if (state == null) {
                    state = new Bundle();
                }
                String key = "f" + i;
                mFragmentManager.putFragment(state, key, f);
            }
        }
        return state;
    }

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {
        if (state != null) {
            Bundle bundle = (Bundle) state;
            bundle.setClassLoader(loader);
            mItemIds = bundle.getLongArray("itemids");
            if (mItemIds == null) {
                mItemIds = new long[]{};
            }
            AsyncUtils.poolExecutor.execute(new SafeRunnable() {
                @Override
                public void safeRun() throws Throwable {
                    File cache = new File(GlobalContext.getContext().getCacheDir(), "saved_states");
                    byte[] savedStateBytes = Files.toByteArray(cache);
                    Parcel parcel = Parcel.obtain();
                    parcel.unmarshall(savedStateBytes, 0, savedStateBytes.length);
                    parcel.setDataPosition(0);
                    mSavedState = parcel.readArrayList(Fragment.SavedState.class.getClassLoader());
                    if (mSavedState == null) {
                        mSavedState = new ArrayList<>();
                    }
                    File[] files = cache.listFiles();
                    if (files != null) {
                        for (File file : cache.listFiles()) {
                            file.delete();
                        }
                    }
                }
            });
            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);
                        }
                        mFragments.set(index, f);
                        f.setMenuVisibility(false);
                    } else {
                        FZLog.w(TAG, "Bad fragment at key " + key);
                    }
                }
            }
        }
    }

    public static String generateTag(int position) {
        return "huffington_post_fragment" + position;
    }
}