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Diffstat (limited to 'src/android/support/v4/view/PagerAdapter.java')
| -rw-r--r-- | src/android/support/v4/view/PagerAdapter.java | 340 |
1 files changed, 340 insertions, 0 deletions
diff --git a/src/android/support/v4/view/PagerAdapter.java b/src/android/support/v4/view/PagerAdapter.java new file mode 100644 index 0000000..c321292 --- /dev/null +++ b/src/android/support/v4/view/PagerAdapter.java @@ -0,0 +1,340 @@ +/* + * 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.view; + +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 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(ViewGroup, int)}</li> + * <li>{@link #destroyItem(ViewGroup, int, Object)}</li> + * <li>{@link #getCount()}</li> + * <li>{@link #isViewFromObject(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(ViewGroup)} indicates that the contents of the ViewPager + * are about to change. One or more calls to {@link #instantiateItem(ViewGroup, int)} + * and/or {@link #destroyItem(ViewGroup, int, Object)} will follow, and the end + * of an update will be signaled by a call to {@link #finishUpdate(ViewGroup)}. + * By the time {@link #finishUpdate(ViewGroup) finishUpdate} returns the views + * associated with the key objects returned by + * {@link #instantiateItem(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(ViewGroup, int, Object) destroyItem} + * should be removed. The method {@link #isViewFromObject(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(ViewGroup, int)} + * after creation and adding them to the parent ViewGroup. A matching + * {@link #destroyItem(ViewGroup, int, Object)} implementation would remove the + * View from the parent ViewGroup and {@link #isViewFromObject(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> + */ +@SuppressWarnings("javadoc") +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(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(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(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(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(ViewGroup)} + */ + @Deprecated + @SuppressWarnings("static-method") + public void startUpdate(View container) { + return; + } + + /** + * 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(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(ViewGroup, int)} + */ + @Deprecated + @SuppressWarnings("static-method") + 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(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(View, int)}. + * + * @deprecated Use {@link #destroyItem(ViewGroup, int, Object)} + */ + @Deprecated + @SuppressWarnings("static-method") + 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(View, int)}. + * + * @deprecated Use {@link #setPrimaryItem(ViewGroup, int, Object)} + */ + @Deprecated + @SuppressWarnings("static-method") + public void setPrimaryItem(View container, int position, Object object) { + return; + } + + /** + * 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(ViewGroup)} + */ + @Deprecated + @SuppressWarnings("static-method") + public void finishUpdate(View container) { + return; + } + + /** + * Determines whether a page View is associated with a specific key object + * as returned by {@link #instantiateItem(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 + */ + @SuppressWarnings("static-method") + 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 + */ + @SuppressWarnings("static-method") + public void restoreState(Parcelable state, ClassLoader loader) { + return; + } + + /** + * 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(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. + */ + @SuppressWarnings("static-method") + 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 + */ + @SuppressWarnings("static-method") + 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 + */ + @SuppressWarnings("static-method") + public float getPageWidth(int position) { + return 1.f; + } +} |