238 lines
8.4 KiB
Java
238 lines
8.4 KiB
Java
/*
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* Copyright (c) 2019 Hemanth Savarala.
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*
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* Licensed under the GNU General Public License v3
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*
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* This is free software: you can redistribute it and/or modify it under
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* the terms of the GNU General Public License as published by
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* the Free Software Foundation either version 3 of the License, or (at your option) any later version.
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*
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* This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
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* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*/
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package code.name.monkey.retromusic.misc;
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import android.os.Bundle;
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import android.os.Parcelable;
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import androidx.annotation.NonNull;
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import androidx.fragment.app.Fragment;
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import androidx.fragment.app.FragmentManager;
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import androidx.fragment.app.FragmentPagerAdapter;
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import androidx.fragment.app.FragmentTransaction;
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import androidx.viewpager.widget.PagerAdapter;
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import android.util.Log;
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import android.view.View;
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import android.view.ViewGroup;
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import java.util.ArrayList;
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/**
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* Implementation of {@link PagerAdapter} that
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* uses a {@link Fragment} to manage each page. This class also handles
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* saving and restoring of fragment's state.
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* <p/>
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* <p>This version of the pager is more useful when there are a large number
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* of pages, working more like a list view. When pages are not visible to
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* the user, their entire fragment may be destroyed, only keeping the saved
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* state of that fragment. This allows the pager to hold on to much less
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* memory associated with each visited page as compared to
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* {@link FragmentPagerAdapter} at the cost of potentially more overhead when
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* switching between pages.
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* <p/>
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* <p>When using FragmentPagerAdapter the host ViewPager must have a
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* valid ID set.</p>
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* <p/>
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* <p>Subclasses only need to implement {@link #getItem(int)}
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* and {@link #getCount()} to have a working adapter.
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* <p/>
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* <p>Here is an example implementation of a pager containing fragments of
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* lists:
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* <p/>
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* {@sample development/samples/Support13Demos/src/com/example/android/supportv13/app/FragmentStatePagerSupport.java
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* complete}
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* <p/>
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* <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
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* <p/>
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* {@sample development/samples/Support13Demos/res/layout/fragment_pager.xml
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* complete}
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* <p/>
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* <p>The <code>R.layout.fragment_pager_list</code> resource containing each
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* individual fragment's layout is:
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* <p/>
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* {@sample development/samples/Support13Demos/res/layout/fragment_pager_list.xml
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* complete}
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*/
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public abstract class CustomFragmentStatePagerAdapter extends PagerAdapter {
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public static final String TAG = CustomFragmentStatePagerAdapter.class.getSimpleName();
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private static final boolean DEBUG = false;
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private final FragmentManager mFragmentManager;
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private FragmentTransaction mCurTransaction = null;
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private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
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private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
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private Fragment mCurrentPrimaryItem = null;
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public CustomFragmentStatePagerAdapter(FragmentManager fm) {
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mFragmentManager = fm;
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}
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/**
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* Return the Fragment associated with a specified position.
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*/
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public abstract Fragment getItem(int position);
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@Override
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public void startUpdate(ViewGroup container) {
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}
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@NonNull
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@Override
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public Object instantiateItem(ViewGroup container, int position) {
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// If we already have this item instantiated, there is nothing
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// to do. This can happen when we are restoring the entire pager
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// from its saved state, where the fragment manager has already
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// taken care of restoring the fragments we previously had instantiated.
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if (mFragments.size() > position) {
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Fragment f = mFragments.get(position);
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if (f != null) {
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return f;
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}
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}
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if (mCurTransaction == null) {
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mCurTransaction = mFragmentManager.beginTransaction();
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}
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Fragment fragment = getItem(position);
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if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
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if (mSavedState.size() > position) {
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Fragment.SavedState fss = mSavedState.get(position);
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if (fss != null) {
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fragment.setInitialSavedState(fss);
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}
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}
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while (mFragments.size() <= position) {
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mFragments.add(null);
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}
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fragment.setMenuVisibility(false);
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fragment.setUserVisibleHint(false);
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mFragments.set(position, fragment);
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mCurTransaction.add(container.getId(), fragment);
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return fragment;
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}
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@Override
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public void destroyItem(ViewGroup container, int position, Object object) {
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Fragment fragment = (Fragment) object;
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if (mCurTransaction == null) {
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mCurTransaction = mFragmentManager.beginTransaction();
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}
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if (DEBUG) Log.v(TAG, "Removing item #" + position + ": f=" + object
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+ " v=" + ((Fragment) object).getView());
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while (mSavedState.size() <= position) {
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mSavedState.add(null);
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}
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mSavedState.set(position, mFragmentManager.saveFragmentInstanceState(fragment));
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mFragments.set(position, null);
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mCurTransaction.remove(fragment);
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}
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@Override
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public void setPrimaryItem(ViewGroup container, int position, Object object) {
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Fragment fragment = (Fragment) object;
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if (fragment != mCurrentPrimaryItem) {
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if (mCurrentPrimaryItem != null) {
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mCurrentPrimaryItem.setMenuVisibility(false);
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mCurrentPrimaryItem.setUserVisibleHint(false);
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}
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if (fragment != null) {
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fragment.setMenuVisibility(true);
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fragment.setUserVisibleHint(true);
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}
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mCurrentPrimaryItem = fragment;
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}
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}
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@Override
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public void finishUpdate(ViewGroup container) {
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if (mCurTransaction != null) {
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mCurTransaction.commitAllowingStateLoss();
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mCurTransaction = null;
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mFragmentManager.executePendingTransactions();
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}
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}
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@Override
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public boolean isViewFromObject(View view, Object object) {
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return ((Fragment) object).getView() == view;
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}
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@Override
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public Parcelable saveState() {
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Bundle state = null;
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if (mSavedState.size() > 0) {
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state = new Bundle();
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Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
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mSavedState.toArray(fss);
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state.putParcelableArray("states", fss);
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}
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for (int i = 0; i < mFragments.size(); i++) {
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Fragment f = mFragments.get(i);
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if (f != null && f.isAdded()) {
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if (state == null) {
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state = new Bundle();
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}
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String key = "f" + i;
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mFragmentManager.putFragment(state, key, f);
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}
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}
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return state;
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}
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@Override
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public void restoreState(Parcelable state, ClassLoader loader) {
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if (state != null) {
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Bundle bundle = (Bundle) state;
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bundle.setClassLoader(loader);
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Parcelable[] fss = bundle.getParcelableArray("states");
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mSavedState.clear();
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mFragments.clear();
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if (fss != null) {
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for (int i = 0; i < fss.length; i++) {
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mSavedState.add((Fragment.SavedState) fss[i]);
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}
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}
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Iterable<String> keys = bundle.keySet();
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for (String key : keys) {
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if (key.startsWith("f")) {
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int index = Integer.parseInt(key.substring(1));
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Fragment f = mFragmentManager.getFragment(bundle, key);
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if (f != null) {
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while (mFragments.size() <= index) {
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mFragments.add(null);
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}
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f.setMenuVisibility(false);
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mFragments.set(index, f);
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} else {
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Log.w(TAG, "Bad fragment at key " + key);
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}
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}
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}
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}
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}
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public Fragment getFragment(int position) {
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if (position < mFragments.size() && position >= 0) {
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return mFragments.get(position);
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}
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return null;
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}
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}
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