1 page.title=Creating a Fragment 2 page.tags=fragments 3 helpoutsWidget=true 4 5 trainingnavtop=true 6 7 @jd:body 8 9 <div id="tb-wrapper"> 10 <div id="tb"> 11 12 <h2>This lesson teaches you to</h2> 13 <ol> 14 <li><a href="#Create">Create a Fragment Class</a></li> 15 <li><a href="#AddInLayout">Add a Fragment to an Activity using XML</a></li> 16 </ol> 17 18 <h2>You should also read</h2> 19 <ul> 20 <li><a href="{@docRoot}guide/components/fragments.html">Fragments</a></li> 21 </ul> 22 23 <h2>Try it out</h2> 24 25 <div class="download-box"> 26 <a href="http://developer.android.com/shareables/training/FragmentBasics.zip" 27 class="button">Download the sample</a> 28 <p class="filename">FragmentBasics.zip</p> 29 </div> 30 31 </div> 32 </div> 33 34 <p>You can think of a fragment as a modular section of an activity, which has its own lifecycle, 35 receives its own input events, and which you can add or remove while the activity is running (sort 36 of like a "sub activity" that you can reuse in different activities). This lesson shows how to 37 extend the {@link android.support.v4.app.Fragment} class using the <a 38 href="{@docRoot}tools/support-library/index.html">Support Library</a> so your app 39 remains compatible with devices running system versions as low as Android 1.6.</p> 40 41 <p>Before you begin this lesson, you must set up your Android project to use the Support Library. 42 If you have not used the Support Library before, set up your project to use the <strong>v4</strong> 43 library by following the <a href="{@docRoot}tools/support-library/setup.html">Support Library 44 Setup</a> document. However, you can also include the <a href= 45 "{@docRoot}training/appbar/index.html">app bar</a> in your activities by instead using the 46 <strong>v7 appcompat</strong> library, which is compatible with Android 2.1 (API level 7) 47 and also includes the {@link android.support.v4.app.Fragment} APIs.</p> 48 49 50 51 <h2 id="Create">Create a Fragment Class</h2> 52 53 <p>To create a fragment, extend the {@link android.support.v4.app.Fragment} class, then override 54 key lifecycle methods to insert your app logic, similar to the way you would with an {@link 55 android.app.Activity} class.</p> 56 57 <p>One difference when creating a {@link android.support.v4.app.Fragment} is that you must use the 58 {@link android.support.v4.app.Fragment#onCreateView onCreateView()} callback to define the layout. 59 In fact, this is the only callback you need in order to get a fragment running. For 60 example, here's a simple fragment that specifies its own layout:</p> 61 62 <pre> 63 import android.os.Bundle; 64 import android.support.v4.app.Fragment; 65 import android.view.LayoutInflater; 66 import android.view.ViewGroup; 67 68 public class ArticleFragment extends Fragment { 69 @Override 70 public View onCreateView(LayoutInflater inflater, ViewGroup container, 71 Bundle savedInstanceState) { 72 // Inflate the layout for this fragment 73 return inflater.inflate(R.layout.article_view, container, false); 74 } 75 } 76 </pre> 77 78 <p>Just like an activity, a fragment should implement other lifecycle callbacks that allow you to 79 manage its state as it is added or removed from the activity and as the activity transitions 80 between its lifecycle states. For instance, when the activity's {@link 81 android.app.Activity#onPause()} method is called, any fragments in the activity also receive a call 82 to {@link android.support.v4.app.Fragment#onPause()}.</p> 83 84 <p>More information about the fragment lifecycle and callback methods is available in the <a 85 href="{@docRoot}guide/components/fragments.html">Fragments</a> developer guide.</p> 86 87 88 89 <h2 id="AddInLayout">Add a Fragment to an Activity using XML</h2> 90 91 <p>While fragments are reusable, modular UI components, each instance of a {@link 92 android.support.v4.app.Fragment} class must be associated with a parent {@link 93 android.support.v4.app.FragmentActivity}. You can achieve this association by defining each 94 fragment within your activity layout XML file.</p> 95 96 <p class="note"><strong>Note:</strong> {@link android.support.v4.app.FragmentActivity} is a 97 special activity provided in the Support Library to handle fragments on system versions older than 98 API level 11. If the lowest system version you support is API level 11 or higher, then you can use a 99 regular {@link android.app.Activity}.</p> 100 101 <p>Here is an example layout file that adds two fragments to an activity when the device 102 screen is considered "large" (specified by the <code>large</code> qualifier in the directory 103 name).</p> 104 105 <p class="code-caption">res/layout-large/news_articles.xml</p> 106 <pre> 107 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 108 android:orientation="horizontal" 109 android:layout_width="fill_parent" 110 android:layout_height="fill_parent"> 111 112 <fragment android:name="com.example.android.fragments.HeadlinesFragment" 113 android:id="@+id/headlines_fragment" 114 android:layout_weight="1" 115 android:layout_width="0dp" 116 android:layout_height="match_parent" /> 117 118 <fragment android:name="com.example.android.fragments.ArticleFragment" 119 android:id="@+id/article_fragment" 120 android:layout_weight="2" 121 android:layout_width="0dp" 122 android:layout_height="match_parent" /> 123 124 </LinearLayout> 125 </pre> 126 127 <p class="note"><strong>Tip:</strong> For more about creating layouts for different 128 screen sizes, read <a href="{@docRoot}training/multiscreen/screensizes.html">Supporting Different 129 Screen Sizes</a>.</p> 130 131 <p>Then apply the layout to your activity:</p> 132 133 <pre> 134 import android.os.Bundle; 135 import android.support.v4.app.FragmentActivity; 136 137 public class MainActivity extends FragmentActivity { 138 @Override 139 public void onCreate(Bundle savedInstanceState) { 140 super.onCreate(savedInstanceState); 141 setContentView(R.layout.news_articles); 142 } 143 } 144 </pre> 145 146 <p>If you're using the <a href="{@docRoot}tools/support-library/features.html#v7-appcompat">v7 147 appcompat library</a>, your activity should instead extend {@link 148 android.support.v7.app.AppCompatActivity}, which is a subclass of {@link 149 android.support.v4.app.FragmentActivity}. For more information, 150 read <a href="{@docRoot}training/appbar/index.html">Adding the App Bar</a>).</p> 151 152 153 <p class="note"><strong>Note:</strong> When you add a fragment to an activity layout by defining 154 the fragment in the layout XML file, you <em>cannot</em> remove the fragment at runtime. If you plan 155 to swap your fragments in and out during user interaction, you must add the fragment to the activity 156 when the activity first starts, as shown in the next lesson.</p> 157 158 159 160
