FragmentStatePagerAdapter.java revision 7a01f352fa0fe92cfd786ced85129dcc5531c087
1/* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.support.v4.app; 18 19import java.util.ArrayList; 20 21import android.os.Bundle; 22import android.os.Parcelable; 23import android.support.v4.view.PagerAdapter; 24import android.util.Log; 25import android.view.View; 26import android.view.ViewGroup; 27 28/** 29 * Implementation of {@link android.support.v4.view.PagerAdapter} that 30 * uses a {@link Fragment} to manage each page. This class also handles 31 * saving and restoring of fragment's state. 32 */ 33public abstract class FragmentStatePagerAdapter extends PagerAdapter { 34 private static final String TAG = "FragmentStatePagerAdapter"; 35 private static final boolean DEBUG = false; 36 37 private final FragmentManager mFragmentManager; 38 private FragmentTransaction mCurTransaction = null; 39 40 private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>(); 41 private ArrayList<Fragment> mFragments = new ArrayList<Fragment>(); 42 private Fragment mCurrentPrimaryItem = null; 43 44 public FragmentStatePagerAdapter(FragmentManager fm) { 45 mFragmentManager = fm; 46 } 47 48 /** 49 * Return the Fragment associated with a specified position. 50 */ 51 public abstract Fragment getItem(int position); 52 53 @Override 54 public void startUpdate(ViewGroup container) { 55 } 56 57 @Override 58 public Object instantiateItem(ViewGroup container, int position) { 59 // If we already have this item instantiated, there is nothing 60 // to do. This can happen when we are restoring the entire pager 61 // from its saved state, where the fragment manager has already 62 // taken care of restoring the fragments we previously had instantiated. 63 if (mFragments.size() > position) { 64 Fragment f = mFragments.get(position); 65 if (f != null) { 66 return f; 67 } 68 } 69 70 if (mCurTransaction == null) { 71 mCurTransaction = mFragmentManager.beginTransaction(); 72 } 73 74 Fragment fragment = getItem(position); 75 if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment); 76 if (mSavedState.size() > position) { 77 Fragment.SavedState fss = mSavedState.get(position); 78 if (fss != null) { 79 fragment.setInitialSavedState(fss); 80 } 81 } 82 while (mFragments.size() <= position) { 83 mFragments.add(null); 84 } 85 fragment.setMenuVisibility(false); 86 mFragments.set(position, fragment); 87 mCurTransaction.add(container.getId(), fragment); 88 89 return fragment; 90 } 91 92 @Override 93 public void destroyItem(ViewGroup container, int position, Object object) { 94 Fragment fragment = (Fragment)object; 95 96 if (mCurTransaction == null) { 97 mCurTransaction = mFragmentManager.beginTransaction(); 98 } 99 if (DEBUG) Log.v(TAG, "Removing item #" + position + ": f=" + object 100 + " v=" + ((Fragment)object).getView()); 101 while (mSavedState.size() <= position) { 102 mSavedState.add(null); 103 } 104 mSavedState.set(position, mFragmentManager.saveFragmentInstanceState(fragment)); 105 mFragments.set(position, null); 106 107 mCurTransaction.remove(fragment); 108 } 109 110 @Override 111 public void setPrimaryItem(ViewGroup container, int position, Object object) { 112 Fragment fragment = (Fragment)object; 113 if (fragment != mCurrentPrimaryItem) { 114 if (mCurrentPrimaryItem != null) { 115 mCurrentPrimaryItem.setMenuVisibility(false); 116 } 117 if (fragment != null) { 118 fragment.setMenuVisibility(true); 119 } 120 mCurrentPrimaryItem = fragment; 121 } 122 } 123 124 @Override 125 public void finishUpdate(ViewGroup container) { 126 if (mCurTransaction != null) { 127 mCurTransaction.commitAllowingStateLoss(); 128 mCurTransaction = null; 129 mFragmentManager.executePendingTransactions(); 130 } 131 } 132 133 @Override 134 public boolean isViewFromObject(View view, Object object) { 135 return ((Fragment)object).getView() == view; 136 } 137 138 @Override 139 public Parcelable saveState() { 140 Bundle state = null; 141 if (mSavedState.size() > 0) { 142 state = new Bundle(); 143 Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()]; 144 mSavedState.toArray(fss); 145 state.putParcelableArray("states", fss); 146 } 147 for (int i=0; i<mFragments.size(); i++) { 148 Fragment f = mFragments.get(i); 149 if (f != null) { 150 if (state == null) { 151 state = new Bundle(); 152 } 153 String key = "f" + i; 154 mFragmentManager.putFragment(state, key, f); 155 } 156 } 157 return state; 158 } 159 160 @Override 161 public void restoreState(Parcelable state, ClassLoader loader) { 162 if (state != null) { 163 Bundle bundle = (Bundle)state; 164 bundle.setClassLoader(loader); 165 Parcelable[] fss = bundle.getParcelableArray("states"); 166 mSavedState.clear(); 167 mFragments.clear(); 168 if (fss != null) { 169 for (int i=0; i<fss.length; i++) { 170 mSavedState.add((Fragment.SavedState)fss[i]); 171 } 172 } 173 Iterable<String> keys = bundle.keySet(); 174 for (String key: keys) { 175 if (key.startsWith("f")) { 176 int index = Integer.parseInt(key.substring(1)); 177 Fragment f = mFragmentManager.getFragment(bundle, key); 178 if (f != null) { 179 while (mFragments.size() <= index) { 180 mFragments.add(null); 181 } 182 f.setMenuVisibility(false); 183 mFragments.set(index, f); 184 } else { 185 Log.w(TAG, "Bad fragment at key " + key); 186 } 187 } 188 } 189 } 190 } 191} 192