com.vincestyling.traversaless.FragmentStatePagerAdapter.java Source code

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/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.vincestyling.traversaless;

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

import java.util.ArrayList;
import java.util.List;

public abstract class FragmentStatePagerAdapter extends PagerAdapter {
    private static final String TAG = "FragmentStatePagerAdapter";
    private static final boolean DEBUG = false;

    private final FragmentManager mFragmentManager;
    private FragmentTransaction mCurTransaction = null;

    private List<SavedStateInfo> mSavedState = new ArrayList<SavedStateInfo>();
    private List<Fragment> mFragments = new ArrayList<Fragment>();
    private Fragment mCurrentPrimaryItem = null;

    public FragmentStatePagerAdapter(FragmentManager fm) {
        mFragmentManager = fm;
    }

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

    @Override
    public void startUpdate(ViewGroup container) {
    }

    @Override
    public Object instantiateItem(View 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;
            }
        }

        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }

        Fragment fragment = getItem(position);
        if (DEBUG)
            Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
        if (mSavedState.size() > position) {
            SavedStateInfo fsi = mSavedState.get(position);
            if (fsi != null) {
                fragment.setInitialSavedState(fsi.state);
            }
        }
        while (mFragments.size() <= position) {
            mFragments.add(null);
        }
        fragment.setMenuVisibility(false);
        mFragments.set(position, fragment);
        mCurTransaction.add(container.getId(), fragment);

        return fragment;
    }

    @Override
    public void destroyItem(View container, int position, Object object) {
        Fragment fragment = (Fragment) object;

        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG)
            Log.v(TAG, "Removing item #" + position + ": f=" + object + " v=" + ((Fragment) object).getView());
        while (mSavedState.size() <= position) {
            mSavedState.add(null);
        }
        mSavedState.set(position, new SavedStateInfo(getItemIdentifier(position),
                mFragmentManager.saveFragmentInstanceState(fragment)));
        mFragments.set(position, null);

        mCurTransaction.remove(fragment);
    }

    @Override
    public void dismissItem(View container, int position, Object object) {
        Fragment fragment = (Fragment) object;

        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG)
            Log.v(TAG, "Dismiss item #" + position + ": f=" + object + " v=" + ((Fragment) object).getView());

        if (mSavedState.size() > position)
            mSavedState.set(position, null);
        mFragments.set(position, null);

        mCurTransaction.remove(fragment);
    }

    @Override
    public void rearrangeItems(List<Fragment> fragments) {
        this.mFragments = fragments;
    }

    @Override
    public void setPrimaryItem(View container, int position, Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                mCurrentPrimaryItem.setMenuVisibility(false);
            }
            if (fragment != null) {
                fragment.setMenuVisibility(true);
            }
            mCurrentPrimaryItem = fragment;
        }
    }

    @Override
    public void finishUpdate(View container) {
        if (mCurTransaction != null) {
            mCurTransaction.commitAllowingStateLoss();
            mCurTransaction = null;
            mFragmentManager.executePendingTransactions();
        }
    }

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

    @Override
    public void rearrangeSavedStates(int newItemCount) {
        List<SavedStateInfo> savedStates = new ArrayList<SavedStateInfo>(newItemCount);
        while (savedStates.size() < newItemCount)
            savedStates.add(null);
        for (SavedStateInfo state : mSavedState) {
            if (state == null)
                continue;
            int newPos = getItemPosition(state.identifier);
            if (newPos >= 0 && savedStates.size() > newPos) {
                savedStates.set(newPos, state);
            }
        }
        mSavedState = savedStates;
    }

    @Override
    public Parcelable saveState() {
        Bundle state = null;
        if (mSavedState.size() > 0) {
            state = new Bundle();
            Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
            for (int i = 0; i < mSavedState.size(); i++) {
                SavedStateInfo fsi = mSavedState.get(i);
                fss[i] = fsi != null ? fsi.state : null;
            }
            state.putParcelableArray("states", fss);
        }
        for (int i = 0; i < mFragments.size(); i++) {
            Fragment f = mFragments.get(i);
            if (f != null) {
                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);
            Parcelable[] fss = bundle.getParcelableArray("states");
            mSavedState.clear();
            mFragments.clear();
            if (fss != null) {
                for (int pos = 0; pos < fss.length; pos++) {
                    Parcelable fs = fss[pos];
                    mSavedState
                            .add(fs != null ? new SavedStateInfo(getItemIdentifier(pos), (Fragment.SavedState) fs)
                                    : null);
                }
            }
            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);
                    }
                }
            }
        }
    }

    private class SavedStateInfo {
        Object identifier;
        Fragment.SavedState state;

        public SavedStateInfo(Object identifier, Fragment.SavedState state) {
            this.identifier = identifier;
            this.state = state;
        }
    }
}