1 page.title=Creating a Stub Content Provider 2 3 trainingnavtop=true 4 @jd:body 5 6 7 <div id="tb-wrapper"> 8 <div id="tb"> 9 10 <h2>This lesson teaches you to</h2> 11 <ol> 12 <li> 13 <a href="#CreateProvider">Add a Stub Content Provider</a> 14 </li> 15 <li> 16 <a href="#DeclareProvider">Declare the Provider in the Manifest</a> 17 </li> 18 </ol> 19 20 <h2>You should also read</h2> 21 <ul> 22 <li> 23 <a href="{@docRoot}guide/topics/providers/content-provider-basics.html" 24 >Content Provider Basics</a> 25 </li> 26 </ul> 27 28 <h2>Try it out</h2> 29 30 <div class="download-box"> 31 <a href="http://developer.android.com/shareables/training/BasicSyncAdapter.zip" class="button">Download the sample</a> 32 <p class="filename">BasicSyncAdapter.zip</p> 33 </div> 34 35 </div> 36 </div> 37 <p> 38 The sync adapter framework is designed to work with device data managed by the flexible and 39 highly secure content provider framework. For this reason, the sync adapter framework expects 40 that an app that uses the framework has already defined a content provider for its local data. 41 If the sync adapter framework tries to run your sync adapter, and your app doesn't have a 42 content provider, your sync adapter crashes. 43 </p> 44 <p> 45 If you're developing a new app that transfers data from a server to the device, you should 46 strongly consider storing the local data in a content provider. Besides their importance for 47 sync adapters, content providers offer a variety of security benefits and are specifically 48 designed to handle data storage on Android systems. To learn more about creating a content 49 provider, see <a href="{@docRoot}guide/topics/providers/content-provider-creating.html" 50 >Creating a Content Provider</a>. 51 </p> 52 <p> 53 However, if you're already storing local data in another form, you can still use a sync 54 adapter to handle data transfer. To satisfy the sync adapter framework requirement for a 55 content provider, add a stub content provider to your app. A stub provider implements the 56 content provider class, but all of its required methods return {@code null} or {@code 0}. If you 57 add a stub provider, you can then use a sync adapter to transfer data from any storage 58 mechanism you choose. 59 </p> 60 <p> 61 If you already have a content provider in your app, you don't need a stub content provider. 62 In that case, you can skip this lesson and proceed to the lesson 63 <a href="creating-sync-adapter.html">Creating a Sync Adapter</a>. If you don't yet have a 64 content provider, this lesson shows you how to add a stub content provider that allows you to 65 plug your sync adapter into the framework. 66 </p> 67 <h2 id="CreateProvider">Add a Stub Content Provider</h2> 68 <p> 69 To create a stub content provider for your app, extend the class 70 {@link android.content.ContentProvider} and stub out its required methods. The following 71 snippet shows you how to create the stub provider: 72 </p> 73 <pre> 74 /* 75 * Define an implementation of ContentProvider that stubs out 76 * all methods 77 */ 78 public class StubProvider extends ContentProvider { 79 /* 80 * Always return true, indicating that the 81 * provider loaded correctly. 82 */ 83 @Override 84 public boolean onCreate() { 85 return true; 86 } 87 /* 88 * Return an empty String for MIME type 89 */ 90 @Override 91 public String getType() { 92 return new String(); 93 } 94 /* 95 * query() always returns no results 96 * 97 */ 98 @Override 99 public Cursor query( 100 Uri uri, 101 String[] projection, 102 String selection, 103 String[] selectionArgs, 104 String sortOrder) { 105 return null; 106 } 107 /* 108 * insert() always returns null (no URI) 109 */ 110 @Override 111 public Uri insert(Uri uri, ContentValues values) { 112 return null; 113 } 114 /* 115 * delete() always returns "no rows affected" (0) 116 */ 117 @Override 118 public int delete(Uri uri, String selection, String[] selectionArgs) { 119 return 0; 120 } 121 /* 122 * update() always returns "no rows affected" (0) 123 */ 124 public int update( 125 Uri uri, 126 ContentValues values, 127 String selection, 128 String[] selectionArgs) { 129 return 0; 130 } 131 } 132 </pre> 133 <h2 id="DeclareProvider">Declare the Provider in the Manifest</h2> 134 <p> 135 The sync adapter framework verifies that your app has a content provider by checking that your 136 app has declared a provider in its app manifest. To declare the stub provider in the 137 manifest, add a <code><a href="{@docRoot}guide/topics/manifest/provider-element.html" 138 ><provider></a></code> element with the following attributes: 139 </p> 140 <dl> 141 <dt> 142 <code>android:name="com.example.android.datasync.provider.StubProvider"</code> 143 </dt> 144 <dd> 145 Specifies the fully-qualified name of the class that implements the stub content provider. 146 </dd> 147 <dt> 148 <code>android:authorities="com.example.android.datasync.provider"</code> 149 </dt> 150 <dd> 151 A URI authority that identifies the stub content provider. Make this value your app's 152 package name with the string ".provider" appended to it. Even though you're declaring your 153 stub provider to the system, nothing tries to access the provider itself. 154 </dd> 155 <dt> 156 <code>android:exported="false"</code> 157 </dt> 158 <dd> 159 Determines whether other apps can access the content provider. For your stub content 160 provider, set the value to {@code false}, since there's no need to allow other apps to see 161 the provider. This value doesn't affect the interaction between the sync adapter framework 162 and the content provider. 163 </dd> 164 <dt> 165 <code>android:syncable="true"</code> 166 </dt> 167 <dd> 168 Sets a flag that indicates that the provider is syncable. If you set this flag to 169 {@code true}, you don't have to call {@link android.content.ContentResolver#setIsSyncable 170 setIsSyncable()} in your code. The flag allows the sync adapter framework to make data 171 transfers with the content provider, but transfers only occur if you do them explicitly. 172 </dd> 173 </dl> 174 <p> 175 The following snippet shows you how to add the 176 <code><a href="{@docRoot}guide/topics/manifest/provider-element.html" 177 ><provider></a></code> element to the app manifest: 178 </p> 179 <pre> 180 <manifest xmlns:android="http://schemas.android.com/apk/res/android" 181 package="com.example.android.network.sync.BasicSyncAdapter" 182 android:versionCode="1" 183 android:versionName="1.0" > 184 <application 185 android:allowBackup="true" 186 android:icon="@drawable/ic_launcher" 187 android:label="@string/app_name" 188 android:theme="@style/AppTheme" > 189 ... 190 <provider 191 android:name="com.example.android.datasync.provider.StubProvider" 192 android:authorities="com.example.android.datasync.provider" 193 android:exported="false" 194 android:syncable="true"/> 195 ... 196 </application> 197 </manifest> 198 </pre> 199 <p> 200 Now that you have created the dependencies required by the sync adapter framework, you can 201 create the component that encapsulates your data transfer code. This component is called a 202 sync adapter. The next lesson shows you how to add this component to your app. 203 </p> 204
