Java tutorial
/* * 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.sbrukhanda.fragmentviewpager.adapters; 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.support.v4.view.PagerAdapter; import android.util.Log; import android.view.View; import android.view.ViewGroup; import java.util.ArrayList; /** * A modified copy of the {@link android.support.v4.app.FragmentStatePagerAdapter}, which retains its * original behaviour, but incorporates some additions and changes to its methods. <p /> * * Firstly, method {@link android.support.v4.app.FragmentStatePagerAdapter#getItem(int)} was replaced * with a more appropriately named {@link #instantiateFragment(int)} method. <p /> * * Secondly, method {@link #getFragment(int)} was added in order to allow access to the underlying * mechanism of stored {@code Fragment}s. <p /> * * <b>Note:</b> The Support-v4 v23.1.1 {@link android.support.v4.app.FragmentStatePagerAdapter}'s * source was used as a base. * * @author Serhiy Brukhanda <http://lnkd.in/dMuBjh8> */ public abstract class FragmentStatePagerAdapter extends PagerAdapter { // ============================================================================================= // Constants // ============================================================================================= private static final String TAG = FragmentStatePagerAdapter.class.getSimpleName(); private static final boolean DEBUG = true; // ============================================================================================= // Fields // ============================================================================================= 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; // ============================================================================================= // Constructors & Methods // ============================================================================================= // ********************************************************************************************* public FragmentStatePagerAdapter(FragmentManager fm) { mFragmentManager = fm; } // ********************************************************************************************* @Override public void startUpdate(ViewGroup container) { // Nothing needed } /** * Returns the {@code Fragment} associated with the specified position. * * @param position The position of the {@code Fragment} to fetch. * @return The {@code Fragment} associated with the specified position if such exists, else * {@code null}. */ public Fragment getFragment(int position) { return ((mFragments.size() > position) ? mFragments.get(position) : null); } /** * Create the {@code Fragment} for the specified position. * * @param position The position of the {@code Fragment} to create. * @return The newly created {@code Fragment}. */ public abstract Fragment instantiateFragment(int position); // ********************************************************************************************* @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. // ----------------------------------------------------------------------------------------- Fragment existingFragment = getFragment(position); if (existingFragment != null) { return existingFragment; } // ----------------------------------------------------------------------------------------- // Else, continue with normal flow. // ----------------------------------------------------------------------------------------- if (mCurTransaction == null) { mCurTransaction = mFragmentManager.beginTransaction(); } Fragment fragment = instantiateFragment(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); mCurTransaction.add(container.getId(), fragment); 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 && 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); 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); } } } } } }