fragment/fragment/src/main/java/androidx/fragment/app/FragmentPagerAdapter.java - platform/frameworks/support - Git at Google

 /*
  * 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.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;

 /**
  * 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 samples/Support4Demos/src/main/java/com/example/android/supportv4/app/FragmentPagerSupport.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.
  */
 @Deprecated
 public abstract class FragmentPagerAdapter extends PagerAdapter {
     private static final String TAG = "FragmentPagerAdapter";
     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 #FragmentPagerAdapter(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 #FragmentPagerAdapter(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 Fragment mCurrentPrimaryItem = null;
     private boolean mExecutingFinishUpdate;

     /**
      * Constructor for {@link FragmentPagerAdapter} that sets the fragment manager for the adapter.
      * This is the equivalent of calling {@link #FragmentPagerAdapter(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 #FragmentPagerAdapter(FragmentManager, int)} with
      * {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT}
      */
     @Deprecated
     public FragmentPagerAdapter(@NonNull FragmentManager fm) {
         this(fm, BEHAVIOR_SET_USER_VISIBLE_HINT);
     }

     /**
      * Constructor for {@link FragmentPagerAdapter}.
      *
      * If {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT} is passed in, then only the current
      * Fragment is in the {@link Lifecycle.State#RESUMED} state. 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 FragmentPagerAdapter(@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({"ReferenceEquality", "deprecation"})
     @NonNull
     @Override
     public Object instantiateItem(@NonNull 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);
             if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
                 mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.STARTED);
             } else {
                 fragment.setUserVisibleHint(false);
             }
         }

         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, "Detaching item #" + getItemId(position) + ": f=" + object
                 + " v=" + fragment.getView());
         mCurTransaction.detach(fragment);
         if (fragment.equals(mCurrentPrimaryItem)) {
             mCurrentPrimaryItem = null;
         }
     }

     @SuppressWarnings({"ReferenceEquality", "deprecation"})
     @Override
     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() {
         return null;
     }

     @Override
     public void restoreState(@Nullable Parcelable state, @Nullable 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;
     }
 }
	/*
	* 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.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;

	/**
	* 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 samples/Support4Demos/src/main/java/com/example/android/supportv4/app/FragmentPagerSupport.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.
	*/
	@Deprecated
	public abstract class FragmentPagerAdapter extends PagerAdapter {
	private static final String TAG = "FragmentPagerAdapter";
	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 #FragmentPagerAdapter(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 #FragmentPagerAdapter(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 Fragment mCurrentPrimaryItem = null;
	private boolean mExecutingFinishUpdate;

	/**
	* Constructor for {@link FragmentPagerAdapter} that sets the fragment manager for the adapter.
	* This is the equivalent of calling {@link #FragmentPagerAdapter(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 #FragmentPagerAdapter(FragmentManager, int)} with
	* {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT}
	*/
	@Deprecated
	public FragmentPagerAdapter(@NonNull FragmentManager fm) {
	this(fm, BEHAVIOR_SET_USER_VISIBLE_HINT);
	}

	/**
	* Constructor for {@link FragmentPagerAdapter}.
	*
	* If {@link #BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT} is passed in, then only the current
	* Fragment is in the {@link Lifecycle.State#RESUMED} state. 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 FragmentPagerAdapter(@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({"ReferenceEquality", "deprecation"})
	@NonNull
	@Override
	public Object instantiateItem(@NonNull 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);
	if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
	mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.STARTED);
	} else {
	fragment.setUserVisibleHint(false);
	}
	}

	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, "Detaching item #" + getItemId(position) + ": f=" + object
	+ " v=" + fragment.getView());
	mCurTransaction.detach(fragment);
	if (fragment.equals(mCurrentPrimaryItem)) {
	mCurrentPrimaryItem = null;
	}
	}

	@SuppressWarnings({"ReferenceEquality", "deprecation"})
	@Override
	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() {
	return null;
	}

	@Override
	public void restoreState(@Nullable Parcelable state, @Nullable 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;
	}
	}