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chrislacy/gist:5998644

Created July 15, 2013 09:30
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  1. chrislacy created this gist Jul 15, 2013.
    231 changes: 231 additions & 0 deletions gistfile1.txt
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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 android.support.v4.app;

    import java.util.ArrayList;

    import android.os.Bundle;
    import android.os.Parcelable;
    import android.support.v4.view.PagerAdapter;
    import android.util.Log;
    import android.view.View;
    import android.view.ViewGroup;

    /**
    * Implementation of {@link android.support.v4.view.PagerAdapter} that
    * uses a {@link Fragment} to manage each page. This class also handles
    * saving and restoring of fragment's state.
    *
    * <p>This version of the pager is more useful when there are a large number
    * of pages, working more like a list view. When pages are not visible to
    * the user, their entire fragment may be destroyed, only keeping the saved
    * state of that fragment. This allows the pager to hold on to much less
    * memory associated with each visited page as compared to
    * {@link FragmentPagerAdapter} at the cost of potentially more overhead when
    * switching between pages.
    *
    * <p>When using FragmentPagerAdapter the host ViewPager must have a
    * valid ID set.</p>
    *
    * <p>Subclasses only need to implement {@link #getItem(int)}
    * and {@link #getCount()} to have a working adapter.
    *
    * <p>Here is an example implementation of a pager containing fragments of
    * lists:
    *
    * {@sample development/samples/Support13Demos/src/com/example/android/supportv13/app/FragmentStatePagerSupport.java
    * complete}
    *
    * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
    *
    * {@sample development/samples/Support13Demos/res/layout/fragment_pager.xml
    * complete}
    *
    * <p>The <code>R.layout.fragment_pager_list</code> resource containing each
    * individual fragment's layout is:
    *
    * {@sample development/samples/Support13Demos/res/layout/fragment_pager_list.xml
    * complete}
    */
    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 ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
    private ArrayList<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);

    // Lacy: add so that a fragment can reliably set its tag
    public String getItemTag(int position) {
    return null;
    }

    @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;
    }
    }

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

    Fragment fragment = getItem(position);
    if (DEBUG) Log.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);
    // Lacy: Add call to getItemTag()
    mCurTransaction.add(container.getId(), fragment, getItemTag(position));

    return fragment;
    }

    @Override
    public void destroyItem(ViewGroup 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, mFragmentManager.saveFragmentInstanceState(fragment));
    mFragments.set(position, null);

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

    @Override
    public void finishUpdate(ViewGroup 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 Parcelable saveState() {
    Bundle state = null;
    if (mSavedState.size() > 0) {
    state = new Bundle();
    Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
    mSavedState.toArray(fss);
    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 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);
    }
    }
    }
    }
    }
    }