content: /*
   * 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 com.wm.remusic.widget;
  
  import android.os.Bundle;
  import android.os.Parcelable;
  import android.support.v4.app.Fragment;
  import android.support.v4.app.FragmentManager;
  import android.support.v4.app.FragmentTransaction;
  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) {
      }
  
      @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);
          try {
              fragment.getView().clearAnimation();
          } catch (Exception e) {
              e.printStackTrace();
          }
          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.commitAllowingStateLoss();
              mCurTransaction = null;
              mFragmentManager.executePendingTransactions();
          }
      }
  
      @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);
                      }
                  }
              }
          }
      }
  }
  