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      1 /*
      2  * Copyright 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 
     17 package com.example.android.effectivenavigation;
     18 
     19 import android.app.ActionBar;
     20 import android.content.Intent;
     21 import android.os.Bundle;
     22 import android.support.v4.app.Fragment;
     23 import android.support.v4.app.FragmentActivity;
     24 import android.support.v4.app.FragmentManager;
     25 import android.support.v4.app.FragmentStatePagerAdapter;
     26 import android.support.v4.app.NavUtils;
     27 import android.support.v4.app.TaskStackBuilder;
     28 import android.support.v4.view.ViewPager;
     29 import android.view.LayoutInflater;
     30 import android.view.MenuItem;
     31 import android.view.View;
     32 import android.view.ViewGroup;
     33 import android.widget.TextView;
     34 
     35 public class CollectionDemoActivity extends FragmentActivity {
     36 
     37     /**
     38      * The {@link android.support.v4.view.PagerAdapter} that will provide fragments representing
     39      * each object in a collection. We use a {@link android.support.v4.app.FragmentStatePagerAdapter}
     40      * derivative, which will destroy and re-create fragments as needed, saving and restoring their
     41      * state in the process. This is important to conserve memory and is a best practice when
     42      * allowing navigation between objects in a potentially large collection.
     43      */
     44     DemoCollectionPagerAdapter mDemoCollectionPagerAdapter;
     45 
     46     /**
     47      * The {@link android.support.v4.view.ViewPager} that will display the object collection.
     48      */
     49     ViewPager mViewPager;
     50 
     51     public void onCreate(Bundle savedInstanceState) {
     52         super.onCreate(savedInstanceState);
     53         setContentView(R.layout.activity_collection_demo);
     54 
     55         // Create an adapter that when requested, will return a fragment representing an object in
     56         // the collection.
     57         //
     58         // ViewPager and its adapters use support library fragments, so we must use
     59         // getSupportFragmentManager.
     60         mDemoCollectionPagerAdapter = new DemoCollectionPagerAdapter(getSupportFragmentManager());
     61 
     62         // Set up action bar.
     63         final ActionBar actionBar = getActionBar();
     64 
     65         // Specify that the Home button should show an "Up" caret, indicating that touching the
     66         // button will take the user one step up in the application's hierarchy.
     67         actionBar.setDisplayHomeAsUpEnabled(true);
     68 
     69         // Set up the ViewPager, attaching the adapter.
     70         mViewPager = (ViewPager) findViewById(R.id.pager);
     71         mViewPager.setAdapter(mDemoCollectionPagerAdapter);
     72     }
     73 
     74     @Override
     75     public boolean onOptionsItemSelected(MenuItem item) {
     76         switch (item.getItemId()) {
     77             case android.R.id.home:
     78                 // This is called when the Home (Up) button is pressed in the action bar.
     79                 // Create a simple intent that starts the hierarchical parent activity and
     80                 // use NavUtils in the Support Package to ensure proper handling of Up.
     81                 Intent upIntent = new Intent(this, MainActivity.class);
     82                 if (NavUtils.shouldUpRecreateTask(this, upIntent)) {
     83                     // This activity is not part of the application's task, so create a new task
     84                     // with a synthesized back stack.
     85                     TaskStackBuilder.from(this)
     86                             // If there are ancestor activities, they should be added here.
     87                             .addNextIntent(upIntent)
     88                             .startActivities();
     89                     finish();
     90                 } else {
     91                     // This activity is part of the application's task, so simply
     92                     // navigate up to the hierarchical parent activity.
     93                     NavUtils.navigateUpTo(this, upIntent);
     94                 }
     95                 return true;
     96         }
     97         return super.onOptionsItemSelected(item);
     98     }
     99 
    100     /**
    101      * A {@link android.support.v4.app.FragmentStatePagerAdapter} that returns a fragment
    102      * representing an object in the collection.
    103      */
    104     public static class DemoCollectionPagerAdapter extends FragmentStatePagerAdapter {
    105 
    106         public DemoCollectionPagerAdapter(FragmentManager fm) {
    107             super(fm);
    108         }
    109 
    110         @Override
    111         public Fragment getItem(int i) {
    112             Fragment fragment = new DemoObjectFragment();
    113             Bundle args = new Bundle();
    114             args.putInt(DemoObjectFragment.ARG_OBJECT, i + 1); // Our object is just an integer :-P
    115             fragment.setArguments(args);
    116             return fragment;
    117         }
    118 
    119         @Override
    120         public int getCount() {
    121             // For this contrived example, we have a 100-object collection.
    122             return 100;
    123         }
    124 
    125         @Override
    126         public CharSequence getPageTitle(int position) {
    127             return "OBJECT " + (position + 1);
    128         }
    129     }
    130 
    131     /**
    132      * A dummy fragment representing a section of the app, but that simply displays dummy text.
    133      */
    134     public static class DemoObjectFragment extends Fragment {
    135 
    136         public static final String ARG_OBJECT = "object";
    137 
    138         @Override
    139         public View onCreateView(LayoutInflater inflater, ViewGroup container,
    140                 Bundle savedInstanceState) {
    141             View rootView = inflater.inflate(R.layout.fragment_collection_object, container, false);
    142             Bundle args = getArguments();
    143             ((TextView) rootView.findViewById(android.R.id.text1)).setText(
    144                     Integer.toString(args.getInt(ARG_OBJECT)));
    145             return rootView;
    146         }
    147     }
    148 }
    149