1 page.title=Creating a Fragment 2 parent.title=Building a Dynamic UI with Fragments 3 parent.link=index.html 4 5 trainingnavtop=true 6 previous.title=Using the Android Support Library 7 previous.link=support-lib.html 8 next.title=Building a Flexible UI 9 next.link=fragment-ui.html 10 11 @jd:body 12 13 <div id="tb-wrapper"> 14 <div id="tb"> 15 16 <h2>This lesson teaches you to</h2> 17 <ol> 18 <li><a href="#Create">Create a Fragment Class</a></li> 19 <li><a href="#AddInLayout">Add a Fragment to an Activity using XML</a></li> 20 </ol> 21 22 <h2>You should also read</h2> 23 <ul> 24 <li><a href="{@docRoot}guide/components/fragments.html">Fragments</a></li> 25 </ul> 26 27 <h2>Try it out</h2> 28 29 <div class="download-box"> 30 <a href="http://developer.android.com/shareables/training/FragmentBasics.zip" 31 class="button">Download the sample</a> 32 <p class="filename">FragmentBasics.zip</p> 33 </div> 34 35 </div> 36 </div> 37 38 <p>You can think of a fragment as a modular section of an activity, which has its own lifecycle, 39 receives its own input events, and which you can add or remove while the activity is running (sort 40 of like a "sub activity" that you can reuse in different activities). This lesson shows how to 41 extend the {@link android.support.v4.app.Fragment} class using the Support Library so your app 42 remains compatible with devices running system versions as old as Android 1.6.</p> 43 44 <p class="note"><strong>Note:</strong> If you decide for other reasons that the minimum 45 API level your app requires is 11 or higher, you don't need to use the Support 46 Library and can instead use the framework's built in {@link android.app.Fragment} class and related 47 APIs. Just be aware that this lesson is focused on using the APIs from the Support Library, which 48 use a specific package signature and sometimes slightly different API names than the versions 49 included in the platform.</p> 50 51 52 53 <h2 id="Create">Create a Fragment Class</h2> 54 55 <p>To create a fragment, extend the {@link android.support.v4.app.Fragment} class, then override 56 key lifecycle methods to insert your app logic, similar to the way you would with an {@link 57 android.app.Activity} class.</p> 58 59 <p>One difference when creating a {@link android.support.v4.app.Fragment} is that you must use the 60 {@link android.support.v4.app.Fragment#onCreateView onCreateView()} callback to define the layout. 61 In fact, this is the only callback you need in order to get a fragment running. For 62 example, here's a simple fragment that specifies its own layout:</p> 63 64 <pre> 65 import android.os.Bundle; 66 import android.support.v4.app.Fragment; 67 import android.view.LayoutInflater; 68 import android.view.ViewGroup; 69 70 public class ArticleFragment extends Fragment { 71 @Override 72 public View onCreateView(LayoutInflater inflater, ViewGroup container, 73 Bundle savedInstanceState) { 74 // Inflate the layout for this fragment 75 return inflater.inflate(R.layout.article_view, container, false); 76 } 77 } 78 </pre> 79 80 <p>Just like an activity, a fragment should implement other lifecycle callbacks that allow you to 81 manage its state as it is added or removed from the activity and as the activity transitions 82 between its lifecycle states. For instance, when the activity's {@link 83 android.app.Activity#onPause()} method is called, any fragments in the activity also receive a call 84 to {@link android.support.v4.app.Fragment#onPause()}.</p> 85 86 <p>More information about the fragment lifecycle and callback methods is available in the <a 87 href="{@docRoot}guide/components/fragments.html">Fragments</a> developer guide.</p> 88 89 90 91 <h2 id="AddInLayout">Add a Fragment to an Activity using XML</h2> 92 93 <p>While fragments are reusable, modular UI components, each instance of a {@link 94 android.support.v4.app.Fragment} class must be associated with a parent {@link 95 android.support.v4.app.FragmentActivity}. You can achieve this association by defining each 96 fragment within your activity layout XML file.</p> 97 98 <p class="note"><strong>Note:</strong> {@link android.support.v4.app.FragmentActivity} is a 99 special activity provided in the Support Library to handle fragments on system versions older than 100 API level 11. If the lowest system version you support is API level 11 or higher, then you can use a 101 regular {@link android.app.Activity}.</p> 102 103 <p>Here is an example layout file that adds two fragments to an activity when the device 104 screen is considered "large" (specified by the <code>large</code> qualifier in the directory 105 name).</p> 106 107 <p><code>res/layout-large/news_articles.xml:</code></p> 108 <pre> 109 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 110 android:orientation="horizontal" 111 android:layout_width="fill_parent" 112 android:layout_height="fill_parent"> 113 114 <fragment android:name="com.example.android.fragments.HeadlinesFragment" 115 android:id="@+id/headlines_fragment" 116 android:layout_weight="1" 117 android:layout_width="0dp" 118 android:layout_height="match_parent" /> 119 120 <fragment android:name="com.example.android.fragments.ArticleFragment" 121 android:id="@+id/article_fragment" 122 android:layout_weight="2" 123 android:layout_width="0dp" 124 android:layout_height="match_parent" /> 125 126 </LinearLayout> 127 </pre> 128 129 <p class="note"><strong>Tip:</strong> For more information about creating layouts for different 130 screen sizes, read <a href="{@docRoot}training/multiscreen/screensizes.html">Supporting Different 131 Screen Sizes</a>.</p> 132 133 <p>Here's how an activity applies this layout:</p> 134 135 <pre> 136 import android.os.Bundle; 137 import android.support.v4.app.FragmentActivity; 138 139 public class MainActivity extends FragmentActivity { 140 @Override 141 public void onCreate(Bundle savedInstanceState) { 142 super.onCreate(savedInstanceState); 143 setContentView(R.layout.news_articles); 144 } 145 } 146 </pre> 147 148 149 <p class="note"><strong>Note:</strong> When you add a fragment to an activity layout by defining 150 the fragment in the layout XML file, you <em>cannot</em> remove the fragment at runtime. If you plan 151 to swap your fragments in and out during user interaction, you must add the fragment to the activity 152 when the activity first starts, as shown in the next lesson.</p> 153 154 155 156
