1 page.title=Creating a Fragment 2 3 trainingnavtop=true 4 5 @jd:body 6 7 <div id="tb-wrapper"> 8 <div id="tb"> 9 10 <h2>This lesson teaches you to</h2> 11 <ol> 12 <li><a href="#Create">Create a Fragment Class</a></li> 13 <li><a href="#AddInLayout">Add a Fragment to an Activity using XML</a></li> 14 </ol> 15 16 <h2>You should also read</h2> 17 <ul> 18 <li><a href="{@docRoot}guide/components/fragments.html">Fragments</a></li> 19 </ul> 20 21 <h2>Try it out</h2> 22 23 <div class="download-box"> 24 <a href="http://developer.android.com/shareables/training/FragmentBasics.zip" 25 class="button">Download the sample</a> 26 <p class="filename">FragmentBasics.zip</p> 27 </div> 28 29 </div> 30 </div> 31 32 <p>You can think of a fragment as a modular section of an activity, which has its own lifecycle, 33 receives its own input events, and which you can add or remove while the activity is running (sort 34 of like a "sub activity" that you can reuse in different activities). This lesson shows how to 35 extend the {@link android.support.v4.app.Fragment} class using the Support Library so your app 36 remains compatible with devices running system versions as old as Android 1.6.</p> 37 38 <p class="note"><strong>Note:</strong> If you decide for other reasons that the minimum 39 API level your app requires is 11 or higher, you don't need to use the Support 40 Library and can instead use the framework's built in {@link android.app.Fragment} class and related 41 APIs. Just be aware that this lesson is focused on using the APIs from the Support Library, which 42 use a specific package signature and sometimes slightly different API names than the versions 43 included in the platform.</p> 44 45 46 47 <h2 id="Create">Create a Fragment Class</h2> 48 49 <p>To create a fragment, extend the {@link android.support.v4.app.Fragment} class, then override 50 key lifecycle methods to insert your app logic, similar to the way you would with an {@link 51 android.app.Activity} class.</p> 52 53 <p>One difference when creating a {@link android.support.v4.app.Fragment} is that you must use the 54 {@link android.support.v4.app.Fragment#onCreateView onCreateView()} callback to define the layout. 55 In fact, this is the only callback you need in order to get a fragment running. For 56 example, here's a simple fragment that specifies its own layout:</p> 57 58 <pre> 59 import android.os.Bundle; 60 import android.support.v4.app.Fragment; 61 import android.view.LayoutInflater; 62 import android.view.ViewGroup; 63 64 public class ArticleFragment extends Fragment { 65 @Override 66 public View onCreateView(LayoutInflater inflater, ViewGroup container, 67 Bundle savedInstanceState) { 68 // Inflate the layout for this fragment 69 return inflater.inflate(R.layout.article_view, container, false); 70 } 71 } 72 </pre> 73 74 <p>Just like an activity, a fragment should implement other lifecycle callbacks that allow you to 75 manage its state as it is added or removed from the activity and as the activity transitions 76 between its lifecycle states. For instance, when the activity's {@link 77 android.app.Activity#onPause()} method is called, any fragments in the activity also receive a call 78 to {@link android.support.v4.app.Fragment#onPause()}.</p> 79 80 <p>More information about the fragment lifecycle and callback methods is available in the <a 81 href="{@docRoot}guide/components/fragments.html">Fragments</a> developer guide.</p> 82 83 84 85 <h2 id="AddInLayout">Add a Fragment to an Activity using XML</h2> 86 87 <p>While fragments are reusable, modular UI components, each instance of a {@link 88 android.support.v4.app.Fragment} class must be associated with a parent {@link 89 android.support.v4.app.FragmentActivity}. You can achieve this association by defining each 90 fragment within your activity layout XML file.</p> 91 92 <p class="note"><strong>Note:</strong> {@link android.support.v4.app.FragmentActivity} is a 93 special activity provided in the Support Library to handle fragments on system versions older than 94 API level 11. If the lowest system version you support is API level 11 or higher, then you can use a 95 regular {@link android.app.Activity}.</p> 96 97 <p>Here is an example layout file that adds two fragments to an activity when the device 98 screen is considered "large" (specified by the <code>large</code> qualifier in the directory 99 name).</p> 100 101 <p><code>res/layout-large/news_articles.xml:</code></p> 102 <pre> 103 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 104 android:orientation="horizontal" 105 android:layout_width="fill_parent" 106 android:layout_height="fill_parent"> 107 108 <fragment android:name="com.example.android.fragments.HeadlinesFragment" 109 android:id="@+id/headlines_fragment" 110 android:layout_weight="1" 111 android:layout_width="0dp" 112 android:layout_height="match_parent" /> 113 114 <fragment android:name="com.example.android.fragments.ArticleFragment" 115 android:id="@+id/article_fragment" 116 android:layout_weight="2" 117 android:layout_width="0dp" 118 android:layout_height="match_parent" /> 119 120 </LinearLayout> 121 </pre> 122 123 <p class="note"><strong>Tip:</strong> For more information about creating layouts for different 124 screen sizes, read <a href="{@docRoot}training/multiscreen/screensizes.html">Supporting Different 125 Screen Sizes</a>.</p> 126 127 <p>Here's how an activity applies this layout:</p> 128 129 <pre> 130 import android.os.Bundle; 131 import android.support.v4.app.FragmentActivity; 132 133 public class MainActivity extends FragmentActivity { 134 @Override 135 public void onCreate(Bundle savedInstanceState) { 136 super.onCreate(savedInstanceState); 137 setContentView(R.layout.news_articles); 138 } 139 } 140 </pre> 141 142 143 <p class="note"><strong>Note:</strong> When you add a fragment to an activity layout by defining 144 the fragment in the layout XML file, you <em>cannot</em> remove the fragment at runtime. If you plan 145 to swap your fragments in and out during user interaction, you must add the fragment to the activity 146 when the activity first starts, as shown in the next lesson.</p> 147 148 149 150
