Java tutorial
/* * Copyright (C) 2011 The Android Open Source Project * Portions copyright (c) 2013 CommonsWare, LLC * * 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.commonsware.cwac.pager; import android.annotation.TargetApi; import android.app.Fragment; import android.app.FragmentManager; import android.app.FragmentTransaction; import android.os.Build; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.view.PagerAdapter; import android.view.View; import android.view.ViewGroup; import java.util.ArrayList; import java.util.HashMap; import java.util.List; abstract public class ArrayPagerAdapter<T extends Fragment> extends PagerAdapter { public static final RetentionStrategy KEEP = new RetentionStrategy() { @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2) public void attach(Fragment fragment, FragmentTransaction currTransaction) { currTransaction.attach(fragment); } @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2) public void detach(Fragment fragment, FragmentTransaction currTransaction) { currTransaction.detach(fragment); } }; private static final String KEY_DESCRIPTORS = "descriptors"; private final FragmentManager fm; private ArrayList<PageEntry> entries = new ArrayList<PageEntry>(); private FragmentTransaction currTransaction = null; private T currPrimaryItem = null; private HashMap<Fragment, Integer> positionDelta = new HashMap<Fragment, Integer>(); private RetentionStrategy retentionStrategy = null; public ArrayPagerAdapter(FragmentManager fragmentManager, List<PageDescriptor> descriptors) { this(fragmentManager, descriptors, null); } public ArrayPagerAdapter(FragmentManager fragmentManager, List<PageDescriptor> descriptors, RetentionStrategy retentionStrategy) { this.fm = fragmentManager; this.entries = new ArrayList<PageEntry>(); for (PageDescriptor desc : descriptors) { validatePageDescriptor(desc); entries.add(new PageEntry(desc)); } this.retentionStrategy = retentionStrategy; if (this.retentionStrategy == null) { this.retentionStrategy = KEEP; } } abstract protected T createFragment(PageDescriptor desc); @Override public int getCount() { return (entries.size()); } @Override public void startUpdate(ViewGroup container) { } @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) @Override public Object instantiateItem(ViewGroup container, int position) { if (currTransaction == null) { currTransaction = fm.beginTransaction(); } Fragment fragment = getExistingFragment(position); if (fragment != null) { retentionStrategy.attach(fragment, currTransaction); } else { fragment = createFragment(entries.get(position).getDescriptor()); currTransaction.add(container.getId(), fragment, getFragmentTag(position)); } if (fragment != currPrimaryItem) { fragment.setMenuVisibility(false); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) { fragment.setUserVisibleHint(false); } } return (fragment); } @TargetApi(Build.VERSION_CODES.HONEYCOMB) @Override public void destroyItem(ViewGroup container, int position, Object object) { if (currTransaction == null) { currTransaction = fm.beginTransaction(); } retentionStrategy.detach((Fragment) object, currTransaction); } @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) @SuppressWarnings("unchecked") @Override public void setPrimaryItem(ViewGroup container, int position, Object object) { T fragment = (T) object; if (fragment != currPrimaryItem) { if (currPrimaryItem != null) { currPrimaryItem.setMenuVisibility(false); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) { currPrimaryItem.setUserVisibleHint(false); } } if (fragment != null) { fragment.setMenuVisibility(true); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) { fragment.setUserVisibleHint(true); } } currPrimaryItem = fragment; } } @TargetApi(Build.VERSION_CODES.HONEYCOMB) @Override public void finishUpdate(ViewGroup container) { if (currTransaction != null) { currTransaction.commitAllowingStateLoss(); currTransaction = null; fm.executePendingTransactions(); } } @TargetApi(Build.VERSION_CODES.HONEYCOMB) @Override public boolean isViewFromObject(View view, Object object) { return ((Fragment) object).getView() == view; } @Override public Parcelable saveState() { Bundle state = new Bundle(); state.putParcelableArrayList(KEY_DESCRIPTORS, entries); return (state); } @Override public void restoreState(Parcelable state, ClassLoader loader) { if (state != null) { Bundle b = (Bundle) state; b.setClassLoader(getClass().getClassLoader()); entries = ((Bundle) state).getParcelableArrayList(KEY_DESCRIPTORS); notifyDataSetChanged(); } } @Override public String getPageTitle(int position) { return (getPageDescriptor(position).getTitle()); } @Override public int getItemPosition(Object o) { Integer result = positionDelta.get(o); if (result == null) { return (PagerAdapter.POSITION_UNCHANGED); } return (result); } public PageDescriptor getPageDescriptor(int position) { return (entries.get(position).getDescriptor()); } public int getPositionForTag(String tag) { for (int i = 0; i < entries.size(); i++) { PageEntry entry = entries.get(i); if (entry.getDescriptor().getFragmentTag().equals(tag)) { return (i); } } return (-1); } public void add(PageDescriptor desc) { validatePageDescriptor(desc); positionDelta.clear(); entries.add(new PageEntry(desc)); notifyDataSetChanged(); } public void insert(PageDescriptor desc, int position) { validatePageDescriptor(desc); positionDelta.clear(); for (int i = position; i < entries.size(); i++) { Fragment f = getExistingFragment(i); if (f != null) { positionDelta.put(f, i + 1); } } entries.add(position, new PageEntry(desc)); notifyDataSetChanged(); } public void remove(int position) { positionDelta.clear(); Fragment f = getExistingFragment(position); if (f != null) { positionDelta.put(f, PagerAdapter.POSITION_NONE); } for (int i = position + 1; i < entries.size(); i++) { f = getExistingFragment(i); if (f != null) { positionDelta.put(f, i - 1); } } entries.remove(position); notifyDataSetChanged(); } public void move(int oldPosition, int newPosition) { if (oldPosition != newPosition) { PageDescriptor desc = getPageDescriptor(oldPosition); remove(oldPosition); insert(desc, newPosition); } } @TargetApi(Build.VERSION_CODES.HONEYCOMB) @SuppressWarnings("unchecked") public T getExistingFragment(int position) { return (T) (fm.findFragmentByTag(getFragmentTag(position))); } public T getCurrentFragment() { return (currPrimaryItem); } private String getFragmentTag(int position) { return (getPageDescriptor(position).getFragmentTag()); } private void validatePageDescriptor(PageDescriptor desc) { for (PageEntry entry : entries) { if (desc.getFragmentTag().equals(entry.getDescriptor().getFragmentTag())) { throw new IllegalArgumentException("PageDescriptor tag not unique: " + desc.getFragmentTag()); } } } public interface RetentionStrategy { void attach(Fragment fragment, FragmentTransaction currTransaction); void detach(Fragment fragment, FragmentTransaction currTransaction); } // public static final RetentionStrategy REMOVE=new // RetentionStrategy() { // public void attach(Fragment fragment, // FragmentTransaction currTransaction) { // currTransaction.attach(fragment); // } // // public void detach(Fragment fragment, // FragmentTransaction currTransaction) { // currTransaction.detach(fragment); // } // }; private static class PageEntry implements Parcelable { public static final Creator<PageEntry> CREATOR = new Creator<PageEntry>() { public PageEntry createFromParcel(Parcel in) { return new PageEntry(in); } public PageEntry[] newArray(int size) { return new PageEntry[size]; } }; private PageDescriptor descriptor = null; private Fragment.SavedState state = null; PageEntry(PageDescriptor descriptor) { this.descriptor = descriptor; } PageEntry(Parcel in) { this.descriptor = in.readParcelable(getClass().getClassLoader()); this.state = in.readParcelable(getClass().getClassLoader()); } PageDescriptor getDescriptor() { return (descriptor); } @Override public int describeContents() { return (0); } @Override public void writeToParcel(Parcel out, int flags) { out.writeParcelable(descriptor, 0); out.writeParcelable(state, 0); } } }