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/*
* Copyright 2018 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 androidx.fragment.app;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.IntDef;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager.widget.PagerAdapter;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
/**
* Implementation of {@link PagerAdapter} that
* uses a {@link Fragment} to manage each page. This class also handles
* saving and restoring of fragment's state.
*
* <p>This version of the pager is more useful when there are a large number
* of pages, working more like a list view. When pages are not visible to
* the user, their entire fragment may be destroyed, only keeping the saved
* state of that fragment. This allows the pager to hold on to much less
* memory associated with each visited page as compared to
* {@link FragmentPagerAdapter} at the cost of potentially more overhead when
* switching between pages.
*
* <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 samples/Support4Demos/src/main/java/com/example/android/supportv4/app/FragmentStatePagerSupport.java
* complete}
*
* <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
*
* {@sample samples/Support4Demos/src/main/res/layout/fragment_pager.xml
* complete}
*
* <p>The <code>R.layout.fragment_pager_list</code> resource containing each
* individual fragment's layout is:
*
* {@sample samples/Support4Demos/src/main/res/layout/fragment_pager_list.xml
* complete}
*
* @deprecated Switch to {@link androidx.viewpager2.widget.ViewPager2} and use
* {@link androidx.viewpager2.adapter.FragmentStateAdapter} instead.
*/
@SuppressWarnings("deprecation")
@Deprecated
public abstract class FragmentStatePagerAdapter extends PagerAdapter {
private static final String TAG = "FragmentStatePagerAdapt";
private static final boolean DEBUG = false;
@Retention(RetentionPolicy.SOURCE)
@IntDef({BEHAVIOR_SET_USER_VISIBLE_HINT, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT})
private @interface Behavior { }
/**
* Indicates that {@link Fragment#setUserVisibleHint(boolean)} will be called when the current
* fragment changes.
*
* @deprecated This behavior relies on the deprecated
* {@link Fragment#setUserVisibleHint(boolean)} API. Use
* {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT} to switch to its replacement,
* {@link FragmentTransaction#setMaxLifecycle}.
* @see #FragmentStatePagerAdapter(FragmentManager, int)
*/
@Deprecated
public static final int BEHAVIOR_SET_USER_VISIBLE_HINT = 0;
/**
* Indicates that only the current fragment will be in the {@link Lifecycle.State#RESUMED}
* state. All other Fragments are capped at {@link Lifecycle.State#STARTED}.
*
* @see #FragmentStatePagerAdapter(FragmentManager, int)
*/
public static final int BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT = 1;
private final FragmentManager mFragmentManager;
private final int mBehavior;
private FragmentTransaction mCurTransaction = null;
private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<>();
private ArrayList<Fragment> mFragments = new ArrayList<>();
private Fragment mCurrentPrimaryItem = null;
private boolean mExecutingFinishUpdate;
/**
* Constructor for {@link FragmentStatePagerAdapter} that sets the fragment manager for the
* adapter. This is the equivalent of calling
* {@link #FragmentStatePagerAdapter(FragmentManager, int)} and passing in
* {@link #BEHAVIOR_SET_USER_VISIBLE_HINT}.
*
* <p>Fragments will have {@link Fragment#setUserVisibleHint(boolean)} called whenever the
* current Fragment changes.</p>
*
* @param fm fragment manager that will interact with this adapter
* @deprecated use {@link #FragmentStatePagerAdapter(FragmentManager, int)} with
* {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT}
*/
@Deprecated
public FragmentStatePagerAdapter(@NonNull FragmentManager fm) {
this(fm, BEHAVIOR_SET_USER_VISIBLE_HINT);
}
/**
* Constructor for {@link FragmentStatePagerAdapter}.
*
* If {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT} is passed in, then only the current
* Fragment is in the {@link Lifecycle.State#RESUMED} state, while all other fragments are
* capped at {@link Lifecycle.State#STARTED}. If {@link #BEHAVIOR_SET_USER_VISIBLE_HINT} is
* passed, all fragments are in the {@link Lifecycle.State#RESUMED} state and there will be
* callbacks to {@link Fragment#setUserVisibleHint(boolean)}.
*
* @param fm fragment manager that will interact with this adapter
* @param behavior determines if only current fragments are in a resumed state
*/
public FragmentStatePagerAdapter(@NonNull FragmentManager fm,
@Behavior int behavior) {
mFragmentManager = fm;
mBehavior = behavior;
}
/**
* Return the Fragment associated with a specified position.
*/
@NonNull
public abstract Fragment getItem(int position);
@Override
public void startUpdate(@NonNull ViewGroup container) {
if (container.getId() == View.NO_ID) {
throw new IllegalStateException("ViewPager with adapter " + this
+ " requires a view id");
}
}
@SuppressWarnings("deprecation")
@NonNull
@Override
public Object instantiateItem(@NonNull 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.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
return f;
}
}
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
Fragment fragment = getItem(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);
if (mBehavior == BEHAVIOR_SET_USER_VISIBLE_HINT) {
fragment.setUserVisibleHint(false);
}
mFragments.set(position, fragment);
mCurTransaction.add(container.getId(), fragment);
if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.STARTED);
}
return fragment;
}
// TODO(b/141958824): Suppressed during upgrade to AGP 3.6.
@SuppressWarnings("ReferenceEquality")
@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull 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, fragment.isAdded()
? mFragmentManager.saveFragmentInstanceState(fragment) : null);
mFragments.set(position, null);
mCurTransaction.remove(fragment);
if (fragment.equals(mCurrentPrimaryItem)) {
mCurrentPrimaryItem = null;
}
}
@Override
@SuppressWarnings({"ReferenceEquality", "deprecation"})
public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
Fragment fragment = (Fragment)object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
mCurTransaction.setMaxLifecycle(mCurrentPrimaryItem, Lifecycle.State.STARTED);
} else {
mCurrentPrimaryItem.setUserVisibleHint(false);
}
}
fragment.setMenuVisibility(true);
if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.RESUMED);
} else {
fragment.setUserVisibleHint(true);
}
mCurrentPrimaryItem = fragment;
}
}
@Override
public void finishUpdate(@NonNull ViewGroup container) {
if (mCurTransaction != null) {
// We drop any transactions that attempt to be committed
// from a re-entrant call to finishUpdate(). We need to
// do this as a workaround for Robolectric running measure/layout
// calls inline rather than allowing them to be posted
// as they would on a real device.
if (!mExecutingFinishUpdate) {
try {
mExecutingFinishUpdate = true;
mCurTransaction.commitNowAllowingStateLoss();
} finally {
mExecutingFinishUpdate = false;
}
}
mCurTransaction = null;
}
}
@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
return ((Fragment)object).getView() == view;
}
@Override
@Nullable
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
@SuppressWarnings("deprecation")
public void restoreState(@Nullable Parcelable state, @Nullable 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);
}
}
}
}
}
}