FragmentPagerAdapter.java revision 2a4d8518f36346ea25a22a736453ff28f2954165 
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.v13.app;
18
19import android.app.Fragment;
20import android.app.FragmentManager;
21import android.app.FragmentTransaction;
22import android.os.Parcelable;
23import android.support.v4.view.PagerAdapter;
24import android.util.Log;
25import android.view.View;
26
27/**
28 * Implementation of {@link android.support.v4.view.PagerAdapter} that
29 * represents each page as a {@link android.app.Fragment} that is persistently
30 * kept in the fragment manager as long as the user can return to the page.
31 */
32public abstract class FragmentPagerAdapter extends PagerAdapter {
33    private static final String TAG = "FragmentPagerAdapter";
34    private static final boolean DEBUG = false;
35
36    private final FragmentManager mFragmentManager;
37    private FragmentTransaction mCurTransaction = null;
38    private Fragment mCurrentPrimaryItem = null;
39
40    public FragmentPagerAdapter(FragmentManager fm) {
41        mFragmentManager = fm;
42    }
43
44    /**
45     * Return the Fragment associated with a specified position.
46     */
47    public abstract Fragment getItem(int position);
48
49    @Override
50    public void startUpdate(View container) {
51    }
52
53    @Override
54    public Object instantiateItem(View container, int position) {
55        if (mCurTransaction == null) {
56            mCurTransaction = mFragmentManager.beginTransaction();
57        }
58
59        // Do we already have this fragment?
60        String name = makeFragmentName(container.getId(), position);
61        Fragment fragment = mFragmentManager.findFragmentByTag(name);
62        if (fragment != null) {
63            if (DEBUG) Log.v(TAG, "Attaching item #" + position + ": f=" + fragment);
64            mCurTransaction.attach(fragment);
65        } else {
66            fragment = getItem(position);
67            if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
68            mCurTransaction.add(container.getId(), fragment,
69                    makeFragmentName(container.getId(), position));
70        }
71        if (fragment != mCurrentPrimaryItem) {
72            FragmentCompat.setMenuVisibility(fragment, false);
73        }
74
75        return fragment;
76    }
77
78    @Override
79    public void destroyItem(View container, int position, Object object) {
80        if (mCurTransaction == null) {
81            mCurTransaction = mFragmentManager.beginTransaction();
82        }
83        if (DEBUG) Log.v(TAG, "Detaching item #" + position + ": f=" + object
84                + " v=" + ((Fragment)object).getView());
85        mCurTransaction.detach((Fragment)object);
86    }
87
88    @Override
89    public void setPrimaryItem(View container, int position, Object object) {
90        Fragment fragment = (Fragment)object;
91        if (fragment != mCurrentPrimaryItem) {
92            if (mCurrentPrimaryItem != null) {
93                FragmentCompat.setMenuVisibility(mCurrentPrimaryItem, false);
94            }
95            if (fragment != null) {
96                FragmentCompat.setMenuVisibility(fragment, true);
97            }
98            mCurrentPrimaryItem = fragment;
99        }
100    }
101
102    @Override
103    public void finishUpdate(View container) {
104        if (mCurTransaction != null) {
105            mCurTransaction.commitAllowingStateLoss();
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        return null;
119    }
120
121    @Override
122    public void restoreState(Parcelable state, ClassLoader loader) {
123    }
124
125    private static String makeFragmentName(int viewId, int index) {
126        return "android:switcher:" + viewId + ":" + index;
127    }
128}