| /* |
| * 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 android.support.v4.app; |
| |
| import android.os.Parcelable; |
| import android.support.v4.view.PagerAdapter; |
| import android.util.Log; |
| import android.view.View; |
| import android.view.ViewGroup; |
| |
| /** |
| * Implementation of {@link PagerAdapter} that |
| * represents each page as a {@link Fragment} that is persistently |
| * kept in the fragment manager as long as the user can return to the page. |
| * |
| * <p>This version of the pager is best for use when there are a handful of |
| * typically more static fragments to be paged through, such as a set of tabs. |
| * The fragment of each page the user visits will be kept in memory, though its |
| * view hierarchy may be destroyed when not visible. This can result in using |
| * a significant amount of memory since fragment instances can hold on to an |
| * arbitrary amount of state. For larger sets of pages, consider |
| * {@link FragmentStatePagerAdapter}. |
| * |
| * <p>When using FragmentPagerAdapter the host ViewPager must have a |
| * valid ID set.</p> |
| * |
| * <p>Subclasses only need to implement {@link #getItem(int)} |
| * and {@link #getCount()} to have a working adapter. |
| * |
| * <p>Here is an example implementation of a pager containing fragments of |
| * lists: |
| * |
| * {@sample frameworks/support/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentPagerSupport.java |
| * complete} |
| * |
| * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is: |
| * |
| * {@sample frameworks/support/samples/Support4Demos/res/layout/fragment_pager.xml |
| * complete} |
| * |
| * <p>The <code>R.layout.fragment_pager_list</code> resource containing each |
| * individual fragment's layout is: |
| * |
| * {@sample frameworks/support/samples/Support4Demos/res/layout/fragment_pager_list.xml |
| * complete} |
| */ |
| public abstract class FragmentPagerAdapter extends PagerAdapter { |
| private static final String TAG = "FragmentPagerAdapter"; |
| private static final boolean DEBUG = false; |
| |
| private final FragmentManager mFragmentManager; |
| private FragmentTransaction mCurTransaction = null; |
| private Fragment mCurrentPrimaryItem = null; |
| |
| public FragmentPagerAdapter(FragmentManager fm) { |
| mFragmentManager = fm; |
| } |
| |
| /** |
| * Return the Fragment associated with a specified position. |
| */ |
| public abstract Fragment getItem(int position); |
| |
| @Override |
| public void startUpdate(ViewGroup container) { |
| if (container.getId() == View.NO_ID) { |
| throw new IllegalStateException("ViewPager with adapter " + this |
| + " requires a view id"); |
| } |
| } |
| |
| @SuppressWarnings("ReferenceEquality") |
| @Override |
| public Object instantiateItem(ViewGroup container, int position) { |
| if (mCurTransaction == null) { |
| mCurTransaction = mFragmentManager.beginTransaction(); |
| } |
| |
| final long itemId = getItemId(position); |
| |
| // Do we already have this fragment? |
| String name = makeFragmentName(container.getId(), itemId); |
| Fragment fragment = mFragmentManager.findFragmentByTag(name); |
| if (fragment != null) { |
| if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment); |
| mCurTransaction.attach(fragment); |
| } else { |
| fragment = getItem(position); |
| if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment); |
| mCurTransaction.add(container.getId(), fragment, |
| makeFragmentName(container.getId(), itemId)); |
| } |
| if (fragment != mCurrentPrimaryItem) { |
| fragment.setMenuVisibility(false); |
| fragment.setUserVisibleHint(false); |
| } |
| |
| return fragment; |
| } |
| |
| @Override |
| public void destroyItem(ViewGroup container, int position, Object object) { |
| if (mCurTransaction == null) { |
| mCurTransaction = mFragmentManager.beginTransaction(); |
| } |
| if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object |
| + " v=" + ((Fragment)object).getView()); |
| mCurTransaction.detach((Fragment)object); |
| } |
| |
| @SuppressWarnings("ReferenceEquality") |
| @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.commitNowAllowingStateLoss(); |
| mCurTransaction = null; |
| } |
| } |
| |
| @Override |
| public boolean isViewFromObject(View view, Object object) { |
| return ((Fragment)object).getView() == view; |
| } |
| |
| @Override |
| public Parcelable saveState() { |
| return null; |
| } |
| |
| @Override |
| public void restoreState(Parcelable state, ClassLoader loader) { |
| } |
| |
| /** |
| * Return a unique identifier for the item at the given position. |
| * |
| * <p>The default implementation returns the given position. |
| * Subclasses should override this method if the positions of items can change.</p> |
| * |
| * @param position Position within this adapter |
| * @return Unique identifier for the item at position |
| */ |
| public long getItemId(int position) { |
| return position; |
| } |
| |
| private static String makeFragmentName(int viewId, long id) { |
| return "android:switcher:" + viewId + ":" + id; |
| } |
| } |