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      1 /*
      2 **
      3 ** Copyright 2013, The Android Open Source Project
      4 **
      5 ** Licensed under the Apache License, Version 2.0 (the "License");
      6 ** you may not use this file except in compliance with the License.
      7 ** You may obtain a copy of the License at
      8 **
      9 **     http://www.apache.org/licenses/LICENSE-2.0
     10 **
     11 ** Unless required by applicable law or agreed to in writing, software
     12 ** distributed under the License is distributed on an "AS IS" BASIS,
     13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 ** See the License for the specific language governing permissions and
     15 ** limitations under the License.
     16 */
     17 package com.android.packageinstaller;
     18 
     19 import android.app.Activity;
     20 import android.content.Context;
     21 import android.graphics.Rect;
     22 import android.support.v4.view.PagerAdapter;
     23 import android.support.v4.view.ViewPager;
     24 import android.view.View;
     25 import android.view.ViewGroup;
     26 import android.widget.TabHost;
     27 import android.widget.TabWidget;
     28 
     29 import java.util.ArrayList;
     30 
     31 /**
     32  * This is a helper class that implements the management of tabs and all
     33  * details of connecting a ViewPager with associated TabHost.  It relies on a
     34  * trick.  Normally a tab host has a simple API for supplying a View or
     35  * Intent that each tab will show.  This is not sufficient for switching
     36  * between pages.  So instead we make the content part of the tab host
     37  * 0dp high (it is not shown) and the TabsAdapter supplies its own dummy
     38  * view to show as the tab content.  It listens to changes in tabs, and takes
     39  * care of switch to the correct paged in the ViewPager whenever the selected
     40  * tab changes.
     41  */
     42 public class TabsAdapter extends PagerAdapter
     43         implements TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener {
     44     private final Context mContext;
     45     private final TabHost mTabHost;
     46     private final ViewPager mViewPager;
     47     private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
     48     private final Rect mTempRect = new Rect();
     49 
     50     static final class TabInfo {
     51         private final String tag;
     52         private final View view;
     53 
     54         TabInfo(String _tag, View _view) {
     55             tag = _tag;
     56             view = _view;
     57         }
     58     }
     59 
     60     static class DummyTabFactory implements TabHost.TabContentFactory {
     61         private final Context mContext;
     62 
     63         public DummyTabFactory(Context context) {
     64             mContext = context;
     65         }
     66 
     67         @Override
     68         public View createTabContent(String tag) {
     69             View v = new View(mContext);
     70             v.setMinimumWidth(0);
     71             v.setMinimumHeight(0);
     72             return v;
     73         }
     74     }
     75 
     76     public TabsAdapter(Activity activity, TabHost tabHost, ViewPager pager) {
     77         mContext = activity;
     78         mTabHost = tabHost;
     79         mViewPager = pager;
     80         mTabHost.setOnTabChangedListener(this);
     81         mViewPager.setAdapter(this);
     82         mViewPager.setOnPageChangeListener(this);
     83     }
     84 
     85     public void addTab(TabHost.TabSpec tabSpec, View view) {
     86         tabSpec.setContent(new DummyTabFactory(mContext));
     87         String tag = tabSpec.getTag();
     88 
     89         TabInfo info = new TabInfo(tag, view);
     90         mTabs.add(info);
     91         mTabHost.addTab(tabSpec);
     92         notifyDataSetChanged();
     93     }
     94 
     95     @Override
     96     public int getCount() {
     97         return mTabs.size();
     98     }
     99 
    100     @Override
    101     public Object instantiateItem(ViewGroup container, int position) {
    102         View view = mTabs.get(position).view;
    103         container.addView(view);
    104         return view;
    105     }
    106 
    107     @Override
    108     public void destroyItem(ViewGroup container, int position, Object object) {
    109         container.removeView((View)object);
    110     }
    111 
    112     @Override
    113     public boolean isViewFromObject(View view, Object object) {
    114         return view == object;
    115     }
    116 
    117     @Override
    118     public void onTabChanged(String tabId) {
    119         int position = mTabHost.getCurrentTab();
    120         mViewPager.setCurrentItem(position);
    121     }
    122 
    123     @Override
    124     public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
    125     }
    126 
    127     @Override
    128     public void onPageSelected(int position) {
    129         // Unfortunately when TabHost changes the current tab, it kindly
    130         // also takes care of putting focus on it when not in touch mode.
    131         // The jerk.
    132         // This hack tries to prevent this from pulling focus out of our
    133         // ViewPager.
    134         TabWidget widget = mTabHost.getTabWidget();
    135         int oldFocusability = widget.getDescendantFocusability();
    136         widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);
    137         mTabHost.setCurrentTab(position);
    138         widget.setDescendantFocusability(oldFocusability);
    139 
    140         // Scroll the current tab into visibility if needed.
    141         View tab = widget.getChildTabViewAt(position);
    142         mTempRect.set(tab.getLeft(), tab.getTop(), tab.getRight(), tab.getBottom());
    143         widget.requestRectangleOnScreen(mTempRect, false);
    144 
    145         // Make sure the scrollbars are visible for a moment after selection
    146         final View contentView = mTabs.get(position).view;
    147         if (contentView instanceof CaffeinatedScrollView) {
    148             ((CaffeinatedScrollView) contentView).awakenScrollBars();
    149         }
    150     }
    151 
    152     @Override
    153     public void onPageScrollStateChanged(int state) {
    154     }
    155 }
    156