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 class="note"><strong>Note:</strong> If you decide that the minimum 42 API level your app requires is 11 or higher, you don't need to use the Support 43 Library and can instead use the framework's built in {@link android.app.Fragment} class and related 44 APIs. Just be aware that this lesson is focused on using the APIs from the Support Library, which 45 use a specific package signature and sometimes slightly different API names than the versions 46 included in the platform.</p> 47 48 <p>Before you begin this lesson, you must set up your Android project to use the Support Library. 49 If you have not used the Support Library before, set up your project to use the <strong>v4</strong> 50 library by following the <a href="{@docRoot}tools/support-library/setup.html">Support Library 51 Setup</a> document. However, you can also include the <a href= 52 "{@docRoot}guide/topics/ui/actionbar.html">action bar</a> in your activities by instead using the 53 <strong>v7 appcompat</strong> library, which is compatible with Android 2.1 (API level 7) 54 and also includes the {@link android.support.v4.app.Fragment} APIs.</p> 55 56 57 58 <h2 id="Create">Create a Fragment Class</h2> 59 60 <p>To create a fragment, extend the {@link android.support.v4.app.Fragment} class, then override 61 key lifecycle methods to insert your app logic, similar to the way you would with an {@link 62 android.app.Activity} class.</p> 63 64 <p>One difference when creating a {@link android.support.v4.app.Fragment} is that you must use the 65 {@link android.support.v4.app.Fragment#onCreateView onCreateView()} callback to define the layout. 66 In fact, this is the only callback you need in order to get a fragment running. For 67 example, here's a simple fragment that specifies its own layout:</p> 68 69 <pre> 70 import android.os.Bundle; 71 import android.support.v4.app.Fragment; 72 import android.view.LayoutInflater; 73 import android.view.ViewGroup; 74 75 public class ArticleFragment extends Fragment { 76 @Override 77 public View onCreateView(LayoutInflater inflater, ViewGroup container, 78 Bundle savedInstanceState) { 79 // Inflate the layout for this fragment 80 return inflater.inflate(R.layout.article_view, container, false); 81 } 82 } 83 </pre> 84 85 <p>Just like an activity, a fragment should implement other lifecycle callbacks that allow you to 86 manage its state as it is added or removed from the activity and as the activity transitions 87 between its lifecycle states. For instance, when the activity's {@link 88 android.app.Activity#onPause()} method is called, any fragments in the activity also receive a call 89 to {@link android.support.v4.app.Fragment#onPause()}.</p> 90 91 <p>More information about the fragment lifecycle and callback methods is available in the <a 92 href="{@docRoot}guide/components/fragments.html">Fragments</a> developer guide.</p> 93 94 95 96 <h2 id="AddInLayout">Add a Fragment to an Activity using XML</h2> 97 98 <p>While fragments are reusable, modular UI components, each instance of a {@link 99 android.support.v4.app.Fragment} class must be associated with a parent {@link 100 android.support.v4.app.FragmentActivity}. You can achieve this association by defining each 101 fragment within your activity layout XML file.</p> 102 103 <p class="note"><strong>Note:</strong> {@link android.support.v4.app.FragmentActivity} is a 104 special activity provided in the Support Library to handle fragments on system versions older than 105 API level 11. If the lowest system version you support is API level 11 or higher, then you can use a 106 regular {@link android.app.Activity}.</p> 107 108 <p>Here is an example layout file that adds two fragments to an activity when the device 109 screen is considered "large" (specified by the <code>large</code> qualifier in the directory 110 name).</p> 111 112 <p class="code-caption">res/layout-large/news_articles.xml</p> 113 <pre> 114 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 115 android:orientation="horizontal" 116 android:layout_width="fill_parent" 117 android:layout_height="fill_parent"> 118 119 <fragment android:name="com.example.android.fragments.HeadlinesFragment" 120 android:id="@+id/headlines_fragment" 121 android:layout_weight="1" 122 android:layout_width="0dp" 123 android:layout_height="match_parent" /> 124 125 <fragment android:name="com.example.android.fragments.ArticleFragment" 126 android:id="@+id/article_fragment" 127 android:layout_weight="2" 128 android:layout_width="0dp" 129 android:layout_height="match_parent" /> 130 131 </LinearLayout> 132 </pre> 133 134 <p class="note"><strong>Tip:</strong> For more about creating layouts for different 135 screen sizes, read <a href="{@docRoot}training/multiscreen/screensizes.html">Supporting Different 136 Screen Sizes</a>.</p> 137 138 <p>Then apply the layout to your activity:</p> 139 140 <pre> 141 import android.os.Bundle; 142 import android.support.v4.app.FragmentActivity; 143 144 public class MainActivity extends FragmentActivity { 145 @Override 146 public void onCreate(Bundle savedInstanceState) { 147 super.onCreate(savedInstanceState); 148 setContentView(R.layout.news_articles); 149 } 150 } 151 </pre> 152 153 <p>If you're using the <a href="{@docRoot}tools/support-library/features.html#v7-appcompat">v7 154 appcompat library</a>, your activity should instead extend {@link 155 android.support.v7.app.ActionBarActivity}, which is a subclass of {@link 156 android.support.v4.app.FragmentActivity} (for more information, 157 read <a href="{@docRoot}training/basics/actionbar/index.html">Adding the Action Bar</a>).</p> 158 159 160 <p class="note"><strong>Note:</strong> When you add a fragment to an activity layout by defining 161 the fragment in the layout XML file, you <em>cannot</em> remove the fragment at runtime. If you plan 162 to swap your fragments in and out during user interaction, you must add the fragment to the activity 163 when the activity first starts, as shown in the next lesson.</p> 164 165 166 167
