v4/java/android/support/v4/app/FragmentStatePagerAdapter.java - platform/frameworks/support - Git at Google

 /*
  * 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.app;

 import android.os.Bundle;
 import android.os.Parcelable;
 import android.support.v4.view.PagerAdapter;
 import android.util.Log;
 import android.view.View;
 import android.view.ViewGroup;

 import java.util.ArrayList;

 /**
  * Implementation of {@link android.support.v4.view.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 development/samples/Support13Demos/src/com/example/android/supportv13/app/FragmentStatePagerSupport.java
  *      complete}
  *
  * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
  *
  * {@sample development/samples/Support13Demos/res/layout/fragment_pager.xml
  *      complete}
  *
  * <p>The <code>R.layout.fragment_pager_list</code> resource containing each
  * individual fragment's layout is:
  *
  * {@sample development/samples/Support13Demos/res/layout/fragment_pager_list.xml
  *      complete}
  */
 public abstract class FragmentStatePagerAdapter extends PagerAdapter {
     private static final String TAG = "FragmentStatePagerAdapter";
     private static final boolean DEBUG = false;

     private final FragmentManager mFragmentManager;
     private FragmentTransaction mCurTransaction = null;

     private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
     private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
     private Fragment mCurrentPrimaryItem = null;

     public FragmentStatePagerAdapter(FragmentManager fm) {
         mFragmentManager = fm;
     }

     /**
      * Return the Fragment associated with a specified position.
      */
     public abstract Fragment getItem(int position);

     @Override
     public void startUpdate(ViewGroup container) {
         if (container.getId() == View.NO_ID) {
             throw new IllegalStateException("ViewPager with adapter " + this
                     + " requires a view id");
         }
     }

     @Override
     public Object instantiateItem(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);
         fragment.setUserVisibleHint(false);
         mFragments.set(position, fragment);
         mCurTransaction.add(container.getId(), fragment);

         return fragment;
     }

     @Override
     public void destroyItem(ViewGroup container, int position, 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);
     }

     @Override
     public void setPrimaryItem(ViewGroup container, int position, Object object) {
         Fragment fragment = (Fragment)object;
         if (fragment != mCurrentPrimaryItem) {
             if (mCurrentPrimaryItem != null) {
                 mCurrentPrimaryItem.setMenuVisibility(false);
                 mCurrentPrimaryItem.setUserVisibleHint(false);
             }
             if (fragment != null) {
                 fragment.setMenuVisibility(true);
                 fragment.setUserVisibleHint(true);
             }
             mCurrentPrimaryItem = fragment;
         }
     }

     @Override
     public void finishUpdate(ViewGroup container) {
         if (mCurTransaction != null) {
             mCurTransaction.commitNowAllowingStateLoss();
             mCurTransaction = null;
         }
     }

     @Override
     public boolean isViewFromObject(View view, Object object) {
         return ((Fragment)object).getView() == view;
     }

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

	import android.os.Bundle;
	import android.os.Parcelable;
	import android.support.v4.view.PagerAdapter;
	import android.util.Log;
	import android.view.View;
	import android.view.ViewGroup;

	import java.util.ArrayList;

	/**
	* Implementation of {@link android.support.v4.view.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 development/samples/Support13Demos/src/com/example/android/supportv13/app/FragmentStatePagerSupport.java
	* complete}
	*
	* <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
	*
	* {@sample development/samples/Support13Demos/res/layout/fragment_pager.xml
	* complete}
	*
	* <p>The <code>R.layout.fragment_pager_list</code> resource containing each
	* individual fragment's layout is:
	*
	* {@sample development/samples/Support13Demos/res/layout/fragment_pager_list.xml
	* complete}
	*/
	public abstract class FragmentStatePagerAdapter extends PagerAdapter {
	private static final String TAG = "FragmentStatePagerAdapter";
	private static final boolean DEBUG = false;

	private final FragmentManager mFragmentManager;
	private FragmentTransaction mCurTransaction = null;

	private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
	private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
	private Fragment mCurrentPrimaryItem = null;

	public FragmentStatePagerAdapter(FragmentManager fm) {
	mFragmentManager = fm;
	}

	/**
	* Return the Fragment associated with a specified position.
	*/
	public abstract Fragment getItem(int position);

	@Override
	public void startUpdate(ViewGroup container) {
	if (container.getId() == View.NO_ID) {
	throw new IllegalStateException("ViewPager with adapter " + this
	+ " requires a view id");
	}
	}

	@Override
	public Object instantiateItem(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);
	fragment.setUserVisibleHint(false);
	mFragments.set(position, fragment);
	mCurTransaction.add(container.getId(), fragment);

	return fragment;
	}

	@Override
	public void destroyItem(ViewGroup container, int position, 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);
	}

	@Override
	public void setPrimaryItem(ViewGroup container, int position, Object object) {
	Fragment fragment = (Fragment)object;
	if (fragment != mCurrentPrimaryItem) {
	if (mCurrentPrimaryItem != null) {
	mCurrentPrimaryItem.setMenuVisibility(false);
	mCurrentPrimaryItem.setUserVisibleHint(false);
	}
	if (fragment != null) {
	fragment.setMenuVisibility(true);
	fragment.setUserVisibleHint(true);
	}
	mCurrentPrimaryItem = fragment;
	}
	}

	@Override
	public void finishUpdate(ViewGroup container) {
	if (mCurTransaction != null) {
	mCurTransaction.commitNowAllowingStateLoss();
	mCurTransaction = null;
	}
	}

	@Override
	public boolean isViewFromObject(View view, Object object) {
	return ((Fragment)object).getView() == view;
	}

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