Copy ViewPager and PagerAdapter into framework-internal widgets (75fd8f9f) · Commits · e / os / android_frameworks_base

core/java/com/android/internal/widget/PagerAdapter.java

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		/*
		* Copyright (C) 2015 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 com.android.internal.widget;

		import android.database.DataSetObservable;
		import android.database.DataSetObserver;
		import android.os.Parcelable;
		import android.view.View;
		import android.view.ViewGroup;

		/**
		* Base class providing the adapter to populate pages inside of
		* a {@link android.support.v4.view.ViewPager}. You will most likely want to use a more
		* specific implementation of this, such as
		* {@link android.support.v4.app.FragmentPagerAdapter} or
		* {@link android.support.v4.app.FragmentStatePagerAdapter}.
		*
		* <p>When you implement a PagerAdapter, you must override the following methods
		* at minimum:</p>
		* <ul>
		* <li>{@link #instantiateItem(android.view.ViewGroup, int)}</li>
		* <li>{@link #destroyItem(android.view.ViewGroup, int, Object)}</li>
		* <li>{@link #getCount()}</li>
		* <li>{@link #isViewFromObject(android.view.View, Object)}</li>
		* </ul>
		*
		* <p>PagerAdapter is more general than the adapters used for
		* {@link android.widget.AdapterView AdapterViews}. Instead of providing a
		* View recycling mechanism directly ViewPager uses callbacks to indicate the
		* steps taken during an update. A PagerAdapter may implement a form of View
		* recycling if desired or use a more sophisticated method of managing page
		* Views such as Fragment transactions where each page is represented by its
		* own Fragment.</p>
		*
		* <p>ViewPager associates each page with a key Object instead of working with
		* Views directly. This key is used to track and uniquely identify a given page
		* independent of its position in the adapter. A call to the PagerAdapter method
		* {@link #startUpdate(android.view.ViewGroup)} indicates that the contents of the ViewPager
		* are about to change. One or more calls to {@link #instantiateItem(android.view.ViewGroup, int)}
		* and/or {@link #destroyItem(android.view.ViewGroup, int, Object)} will follow, and the end
		* of an update will be signaled by a call to {@link #finishUpdate(android.view.ViewGroup)}.
		* By the time {@link #finishUpdate(android.view.ViewGroup) finishUpdate} returns the views
		* associated with the key objects returned by
		* {@link #instantiateItem(android.view.ViewGroup, int) instantiateItem} should be added to
		* the parent ViewGroup passed to these methods and the views associated with
		* the keys passed to {@link #destroyItem(android.view.ViewGroup, int, Object) destroyItem}
		* should be removed. The method {@link #isViewFromObject(android.view.View, Object)} identifies
		* whether a page View is associated with a given key object.</p>
		*
		* <p>A very simple PagerAdapter may choose to use the page Views themselves
		* as key objects, returning them from {@link #instantiateItem(android.view.ViewGroup, int)}
		* after creation and adding them to the parent ViewGroup. A matching
		* {@link #destroyItem(android.view.ViewGroup, int, Object)} implementation would remove the
		* View from the parent ViewGroup and {@link #isViewFromObject(android.view.View, Object)}
		* could be implemented as <code>return view == object;</code>.</p>
		*
		* <p>PagerAdapter supports data set changes. Data set changes must occur on the
		* main thread and must end with a call to {@link #notifyDataSetChanged()} similar
		* to AdapterView adapters derived from {@link android.widget.BaseAdapter}. A data
		* set change may involve pages being added, removed, or changing position. The
		* ViewPager will keep the current page active provided the adapter implements
		* the method {@link #getItemPosition(Object)}.</p>
		*/
		public abstract class PagerAdapter {
		private DataSetObservable mObservable = new DataSetObservable();

		public static final int POSITION_UNCHANGED = -1;
		public static final int POSITION_NONE = -2;

		/**
		* Return the number of views available.
		*/
		public abstract int getCount();

		/**
		* Called when a change in the shown pages is going to start being made.
		* @param container The containing View which is displaying this adapter's
		* page views.
		*/
		public void startUpdate(ViewGroup container) {
		startUpdate((View) container);
		}

		/**
		* Create the page for the given position. The adapter is responsible
		* for adding the view to the container given here, although it only
		* must ensure this is done by the time it returns from
		* {@link #finishUpdate(android.view.ViewGroup)}.
		*
		* @param container The containing View in which the page will be shown.
		* @param position The page position to be instantiated.
		* @return Returns an Object representing the new page. This does not
		* need to be a View, but can be some other container of the page.
		*/
		public Object instantiateItem(ViewGroup container, int position) {
		return instantiateItem((View) container, position);
		}

		/**
		* Remove a page for the given position. The adapter is responsible
		* for removing the view from its container, although it only must ensure
		* this is done by the time it returns from {@link #finishUpdate(android.view.ViewGroup)}.
		*
		* @param container The containing View from which the page will be removed.
		* @param position The page position to be removed.
		* @param object The same object that was returned by
		* {@link #instantiateItem(android.view.View, int)}.
		*/
		public void destroyItem(ViewGroup container, int position, Object object) {
		destroyItem((View) container, position, object);
		}

		/**
		* Called to inform the adapter of which item is currently considered to
		* be the "primary", that is the one show to the user as the current page.
		*
		* @param container The containing View from which the page will be removed.
		* @param position The page position that is now the primary.
		* @param object The same object that was returned by
		* {@link #instantiateItem(android.view.View, int)}.
		*/
		public void setPrimaryItem(ViewGroup container, int position, Object object) {
		setPrimaryItem((View) container, position, object);
		}

		/**
		* Called when the a change in the shown pages has been completed. At this
		* point you must ensure that all of the pages have actually been added or
		* removed from the container as appropriate.
		* @param container The containing View which is displaying this adapter's
		* page views.
		*/
		public void finishUpdate(ViewGroup container) {
		finishUpdate((View) container);
		}

		/**
		* Called when a change in the shown pages is going to start being made.
		* @param container The containing View which is displaying this adapter's
		* page views.
		*
		* @deprecated Use {@link #startUpdate(android.view.ViewGroup)}
		*/
		public void startUpdate(View container) {
		}

		/**
		* Create the page for the given position. The adapter is responsible
		* for adding the view to the container given here, although it only
		* must ensure this is done by the time it returns from
		* {@link #finishUpdate(android.view.ViewGroup)}.
		*
		* @param container The containing View in which the page will be shown.
		* @param position The page position to be instantiated.
		* @return Returns an Object representing the new page. This does not
		* need to be a View, but can be some other container of the page.
		*
		* @deprecated Use {@link #instantiateItem(android.view.ViewGroup, int)}
		*/
		public Object instantiateItem(View container, int position) {
		throw new UnsupportedOperationException(
		"Required method instantiateItem was not overridden");
		}

		/**
		* Remove a page for the given position. The adapter is responsible
		* for removing the view from its container, although it only must ensure
		* this is done by the time it returns from {@link #finishUpdate(android.view.View)}.
		*
		* @param container The containing View from which the page will be removed.
		* @param position The page position to be removed.
		* @param object The same object that was returned by
		* {@link #instantiateItem(android.view.View, int)}.
		*
		* @deprecated Use {@link #destroyItem(android.view.ViewGroup, int, Object)}
		*/
		public void destroyItem(View container, int position, Object object) {
		throw new UnsupportedOperationException("Required method destroyItem was not overridden");
		}

		/**
		* Called to inform the adapter of which item is currently considered to
		* be the "primary", that is the one show to the user as the current page.
		*
		* @param container The containing View from which the page will be removed.
		* @param position The page position that is now the primary.
		* @param object The same object that was returned by
		* {@link #instantiateItem(android.view.View, int)}.
		*
		* @deprecated Use {@link #setPrimaryItem(android.view.ViewGroup, int, Object)}
		*/
		public void setPrimaryItem(View container, int position, Object object) {
		}

		/**
		* Called when the a change in the shown pages has been completed. At this
		* point you must ensure that all of the pages have actually been added or
		* removed from the container as appropriate.
		* @param container The containing View which is displaying this adapter's
		* page views.
		*
		* @deprecated Use {@link #finishUpdate(android.view.ViewGroup)}
		*/
		public void finishUpdate(View container) {
		}

		/**
		* Determines whether a page View is associated with a specific key object
		* as returned by {@link #instantiateItem(android.view.ViewGroup, int)}. This method is
		* required for a PagerAdapter to function properly.
		*
		* @param view Page View to check for association with <code>object</code>
		* @param object Object to check for association with <code>view</code>
		* @return true if <code>view</code> is associated with the key object <code>object</code>
		*/
		public abstract boolean isViewFromObject(View view, Object object);

		/**
		* Save any instance state associated with this adapter and its pages that should be
		* restored if the current UI state needs to be reconstructed.
		*
		* @return Saved state for this adapter
		*/
		public Parcelable saveState() {
		return null;
		}

		/**
		* Restore any instance state associated with this adapter and its pages
		* that was previously saved by {@link #saveState()}.
		*
		* @param state State previously saved by a call to {@link #saveState()}
		* @param loader A ClassLoader that should be used to instantiate any restored objects
		*/
		public void restoreState(Parcelable state, ClassLoader loader) {
		}

		/**
		* Called when the host view is attempting to determine if an item's position
		* has changed. Returns {@link #POSITION_UNCHANGED} if the position of the given
		* item has not changed or {@link #POSITION_NONE} if the item is no longer present
		* in the adapter.
		*
		* <p>The default implementation assumes that items will never
		* change position and always returns {@link #POSITION_UNCHANGED}.
		*
		* @param object Object representing an item, previously returned by a call to
		* {@link #instantiateItem(android.view.View, int)}.
		* @return object's new position index from [0, {@link #getCount()}),
		* {@link #POSITION_UNCHANGED} if the object's position has not changed,
		* or {@link #POSITION_NONE} if the item is no longer present.
		*/
		public int getItemPosition(Object object) {
		return POSITION_UNCHANGED;
		}

		/**
		* This method should be called by the application if the data backing this adapter has changed
		* and associated views should update.
		*/
		public void notifyDataSetChanged() {
		mObservable.notifyChanged();
		}

		/**
		* Register an observer to receive callbacks related to the adapter's data changing.
		*
		* @param observer The {@link android.database.DataSetObserver} which will receive callbacks.
		*/
		public void registerDataSetObserver(DataSetObserver observer) {
		mObservable.registerObserver(observer);
		}

		/**
		* Unregister an observer from callbacks related to the adapter's data changing.
		*
		* @param observer The {@link android.database.DataSetObserver} which will be unregistered.
		*/
		public void unregisterDataSetObserver(DataSetObserver observer) {
		mObservable.unregisterObserver(observer);
		}

		/**
		* This method may be called by the ViewPager to obtain a title string
		* to describe the specified page. This method may return null
		* indicating no title for this page. The default implementation returns
		* null.
		*
		* @param position The position of the title requested
		* @return A title for the requested page
		*/
		public CharSequence getPageTitle(int position) {
		return null;
		}

		/**
		* Returns the proportional width of a given page as a percentage of the
		* ViewPager's measured width from (0.f-1.f]
		*
		* @param position The position of the page requested
		* @return Proportional width for the given page position
		*/
		public float getPageWidth(int position) {
		return 1.f;
		}
		}

core/java/com/android/internal/widget/ViewPager.java

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