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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 package com.example.android.supportv13.app;
     17 
     18 import android.app.ActionBar;
     19 import android.app.ActionBar.Tab;
     20 import android.app.Activity;
     21 import android.app.Fragment;
     22 import android.app.FragmentTransaction;
     23 import android.content.Context;
     24 import android.os.Bundle;
     25 
     26 import androidx.legacy.app.FragmentPagerAdapter;
     27 import androidx.viewpager.widget.ViewPager;
     28 
     29 import com.example.android.supportv13.R;
     30 
     31 import java.util.ArrayList;
     32 
     33 //BEGIN_INCLUDE(complete)
     34 public class FragmentNestingPagerSupport extends Activity {
     35     ViewPager mViewPager;
     36     TabsAdapter mTabsAdapter;
     37 
     38     @Override
     39     protected void onCreate(Bundle savedInstanceState) {
     40         super.onCreate(savedInstanceState);
     41 
     42         mViewPager = new ViewPager(this);
     43         mViewPager.setId(R.id.pager);
     44         setContentView(mViewPager);
     45 
     46         final ActionBar bar = getActionBar();
     47         bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
     48         bar.setDisplayOptions(0, ActionBar.DISPLAY_SHOW_TITLE);
     49 
     50         mTabsAdapter = new TabsAdapter(this, mViewPager);
     51         mTabsAdapter.addTab(bar.newTab().setText("Simple"),
     52                 CountingFragment.class, null);
     53         mTabsAdapter.addTab(bar.newTab().setText("List"),
     54                 FragmentPagerSupport.ArrayListFragment.class, null);
     55         mTabsAdapter.addTab(bar.newTab().setText("Cursor"),
     56                 CursorFragment.class, null);
     57         mTabsAdapter.addTab(bar.newTab().setText("Tabs"),
     58                 FragmentTabsFragment.class, null);
     59 
     60         if (savedInstanceState != null) {
     61             bar.setSelectedNavigationItem(savedInstanceState.getInt("tab", 0));
     62         }
     63     }
     64 
     65     @Override
     66     protected void onSaveInstanceState(Bundle outState) {
     67         super.onSaveInstanceState(outState);
     68         outState.putInt("tab", getActionBar().getSelectedNavigationIndex());
     69     }
     70 
     71     /**
     72      * This is a helper class that implements the management of tabs and all
     73      * details of connecting a ViewPager with associated TabHost.  It relies on a
     74      * trick.  Normally a tab host has a simple API for supplying a View or
     75      * Intent that each tab will show.  This is not sufficient for switching
     76      * between pages.  So instead we make the content part of the tab host
     77      * 0dp high (it is not shown) and the TabsAdapter supplies its own dummy
     78      * view to show as the tab content.  It listens to changes in tabs, and takes
     79      * care of switch to the correct paged in the ViewPager whenever the selected
     80      * tab changes.
     81      */
     82     public static class TabsAdapter extends FragmentPagerAdapter
     83             implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
     84         private final Context mContext;
     85         private final ActionBar mActionBar;
     86         private final ViewPager mViewPager;
     87         private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
     88 
     89         static final class TabInfo {
     90             private final Class<?> clss;
     91             private final Bundle args;
     92 
     93             TabInfo(Class<?> _class, Bundle _args) {
     94                 clss = _class;
     95                 args = _args;
     96             }
     97         }
     98 
     99         public TabsAdapter(Activity activity, ViewPager pager) {
    100             super(activity.getFragmentManager());
    101             mContext = activity;
    102             mActionBar = activity.getActionBar();
    103             mViewPager = pager;
    104             mViewPager.setAdapter(this);
    105             mViewPager.addOnPageChangeListener(this);
    106         }
    107 
    108         public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
    109             TabInfo info = new TabInfo(clss, args);
    110             tab.setTag(info);
    111             tab.setTabListener(this);
    112             mTabs.add(info);
    113             mActionBar.addTab(tab);
    114             notifyDataSetChanged();
    115         }
    116 
    117         @Override
    118         public int getCount() {
    119             return mTabs.size();
    120         }
    121 
    122         @Override
    123         public Fragment getItem(int position) {
    124             TabInfo info = mTabs.get(position);
    125             return Fragment.instantiate(mContext, info.clss.getName(), info.args);
    126         }
    127 
    128         @Override
    129         public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
    130         }
    131 
    132         @Override
    133         public void onPageSelected(int position) {
    134             mActionBar.setSelectedNavigationItem(position);
    135         }
    136 
    137         @Override
    138         public void onPageScrollStateChanged(int state) {
    139         }
    140 
    141         @Override
    142         public void onTabSelected(Tab tab, FragmentTransaction ft) {
    143             Object tag = tab.getTag();
    144             for (int i=0; i<mTabs.size(); i++) {
    145                 if (mTabs.get(i) == tag) {
    146                     mViewPager.setCurrentItem(i);
    147                 }
    148             }
    149         }
    150 
    151         @Override
    152         public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    153         }
    154 
    155         @Override
    156         public void onTabReselected(Tab tab, FragmentTransaction ft) {
    157         }
    158     }
    159 }
    160 //END_INCLUDE(complete)
    161