FragmentStatePagerAdapter.java revision 5c1637087453de15e31861f073eae5133c4e9f7b 
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;
26
27public abstract class FragmentStatePagerAdapter extends PagerAdapter {
28    private static final String TAG = "FragmentStatePagerAdapter";
29    private static final boolean DEBUG = false;
30
31    private final FragmentManager mFragmentManager;
32    private FragmentTransaction mCurTransaction = null;
33
34    private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
35    private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
36
37    public FragmentStatePagerAdapter(FragmentManager fm) {
38        mFragmentManager = fm;
39    }
40
41    /**
42     * Return the Fragment associated with a specified position.
43     */
44    public abstract Fragment getItem(int position);
45
46    @Override
47    public void startUpdate(View container) {
48    }
49
50    @Override
51    public Object instantiateItem(View container, int position) {
52        // If we already have this item instantiated, there is nothing
53        // to do.  This can happen when we are restoring the entire pager
54        // from its saved state, where the fragment manager has already
55        // taken care of restoring the fragments we previously had instantiated.
56        if (mFragments.size() > position) {
57            Fragment f = mFragments.get(position);
58            if (f != null) {
59                return f;
60            }
61        }
62
63        if (mCurTransaction == null) {
64            mCurTransaction = mFragmentManager.beginTransaction();
65        }
66
67        Fragment fragment = getItem(position);
68        if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
69        if (mSavedState.size() > position) {
70            Fragment.SavedState fss = mSavedState.get(position);
71            if (fss != null) {
72                fragment.setInitialSavedState(fss);
73            }
74        }
75        while (mFragments.size() <= position) {
76            mFragments.add(null);
77        }
78        mFragments.set(position, fragment);
79        mCurTransaction.add(container.getId(), fragment);
80
81        return fragment;
82    }
83
84    @Override
85    public void destroyItem(View container, int position, Object object) {
86        Fragment fragment = (Fragment)object;
87
88        if (mCurTransaction == null) {
89            mCurTransaction = mFragmentManager.beginTransaction();
90        }
91        if (DEBUG) Log.v(TAG, "Removing item #" + position + ": f=" + object
92                + " v=" + ((Fragment)object).getView());
93        while (mSavedState.size() <= position) {
94            mSavedState.add(null);
95        }
96        mSavedState.set(position, mFragmentManager.saveFragmentInstanceState(fragment));
97        mFragments.set(position, null);
98
99        mCurTransaction.remove(fragment);
100    }
101
102    @Override
103    public void finishUpdate(View container) {
104        if (mCurTransaction != null) {
105            mCurTransaction.commit();
106            mCurTransaction = null;
107            mFragmentManager.executePendingTransactions();
108        }
109    }
110
111    @Override
112    public boolean isViewFromObject(View view, Object object) {
113        return ((Fragment)object).getView() == view;
114    }
115
116    @Override
117    public Parcelable saveState() {
118        Bundle state = null;
119        if (mSavedState.size() > 0) {
120            state = new Bundle();
121            Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
122            mSavedState.toArray(fss);
123            state.putParcelableArray("states", fss);
124        }
125        for (int i=0; i<mFragments.size(); i++) {
126            Fragment f = mFragments.get(i);
127            if (f != null) {
128                if (state == null) {
129                    state = new Bundle();
130                }
131                String key = "f" + i;
132                mFragmentManager.putFragment(state, key, f);
133            }
134        }
135        return state;
136    }
137
138    @Override
139    public void restoreState(Parcelable state, ClassLoader loader) {
140        if (state != null) {
141            Bundle bundle = (Bundle)state;
142            bundle.setClassLoader(loader);
143            Parcelable[] fss = bundle.getParcelableArray("states");
144            mSavedState.clear();
145            mFragments.clear();
146            if (fss != null) {
147                for (int i=0; i<fss.length; i++) {
148                    mSavedState.add((Fragment.SavedState)fss[i]);
149                }
150            }
151            Iterable<String> keys = bundle.keySet();
152            for (String key: keys) {
153                if (key.startsWith("f")) {
154                    int index = Integer.parseInt(key.substring(1));
155                    Fragment f = mFragmentManager.getFragment(bundle, key);
156                    if (f != null) {
157                        while (mFragments.size() <= index) {
158                            mFragments.add(null);
159                        }
160                        mFragments.set(index, f);
161                    } else {
162                        Log.w(TAG, "Bad fragment at key " + key);
163                    }
164                }
165            }
166        }
167    }
168}
169