Create a stub content provider
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The sync adapter framework is designed to work with device data managed by the flexible and
highly secure content provider framework. For this reason, the sync adapter framework expects
that an app that uses the framework has already defined a content provider for its local data.
If the sync adapter framework tries to run your sync adapter, and your app doesn't have a
content provider, your sync adapter crashes.
If you're developing a new app that transfers data from a server to the device, you should
strongly consider storing the local data in a content provider. Besides their importance for
sync adapters, content providers offer a variety of security benefits and are specifically
designed to handle data storage on Android systems. To learn more about creating a content
provider, see Creating a Content Provider.
However, if you're already storing local data in another form, you can still use a sync
adapter to handle data transfer. To satisfy the sync adapter framework requirement for a
content provider, add a stub content provider to your app. A stub provider implements the
content provider class, but all of its required methods return null
or 0
. If you
add a stub provider, you can then use a sync adapter to transfer data from any storage
mechanism you choose.
If you already have a content provider in your app, you don't need a stub content provider.
In that case, you can skip this lesson and proceed to the lesson
Creating a Sync Adapter. If you don't yet have a
content provider, this lesson shows you how to add a stub content provider that allows you to
plug your sync adapter into the framework.
Add a stub content provider
To create a stub content provider for your app, extend the class
ContentProvider
and stub out its required methods. The following
snippet shows you how to create the stub provider:
Kotlin
/*
* Define an implementation of ContentProvider that stubs out
* all methods
*/
class StubProvider : ContentProvider() {
/*
* Always return true, indicating that the
* provider loaded correctly.
*/
override fun onCreate(): Boolean = true
/*
* Return no type for MIME type
*/
override fun getType(uri: Uri): String? = null
/*
* query() always returns no results
*
*/
override fun query(
uri: Uri,
projection: Array<String>,
selection: String,
selectionArgs: Array<String>,
sortOrder: String
): Cursor? = null
/*
* insert() always returns null (no URI)
*/
override fun insert(uri: Uri, values: ContentValues): Uri? = null
/*
* delete() always returns "no rows affected" (0)
*/
override fun delete(uri: Uri, selection: String, selectionArgs: Array<String>): Int = 0
/*
* update() always returns "no rows affected" (0)
*/
override fun update(
uri: Uri,
values: ContentValues,
selection: String,
selectionArgs: Array<String>
): Int = 0
}
Java
/*
* Define an implementation of ContentProvider that stubs out
* all methods
*/
public class StubProvider extends ContentProvider {
/*
* Always return true, indicating that the
* provider loaded correctly.
*/
@Override
public boolean onCreate() {
return true;
}
/*
* Return no type for MIME type
*/
@Override
public String getType(Uri uri) {
return null;
}
/*
* query() always returns no results
*
*/
@Override
public Cursor query(
Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String sortOrder) {
return null;
}
/*
* insert() always returns null (no URI)
*/
@Override
public Uri insert(Uri uri, ContentValues values) {
return null;
}
/*
* delete() always returns "no rows affected" (0)
*/
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
return 0;
}
/*
* update() always returns "no rows affected" (0)
*/
public int update(
Uri uri,
ContentValues values,
String selection,
String[] selectionArgs) {
return 0;
}
}
Declare the provider in the manifest
The sync adapter framework verifies that your app has a content provider by checking that your
app has declared a provider in its app manifest. To declare the stub provider in the
manifest, add a <provider>
element with the following attributes:
-
android:name="com.example.android.datasync.provider.StubProvider"
-
Specifies the fully-qualified name of the class that implements the stub content provider.
-
android:authorities="com.example.android.datasync.provider"
-
A URI authority that identifies the stub content provider. Make this value your app's
package name with the string ".provider" appended to it. Even though you're declaring your
stub provider to the system, nothing tries to access the provider itself.
-
android:exported="false"
-
Determines whether other apps can access the content provider. For your stub content
provider, set the value to
false
, since there's no need to allow other apps to see
the provider. This value doesn't affect the interaction between the sync adapter framework
and the content provider.
-
android:syncable="true"
-
Sets a flag that indicates that the provider is syncable. If you set this flag to
true
, you don't have to call setIsSyncable()
in your code. The flag allows the sync adapter framework to make data
transfers with the content provider, but transfers only occur if you do them explicitly.
The following snippet shows you how to add the
<provider>
element to the app manifest:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.network.sync.BasicSyncAdapter"
android:versionCode="1"
android:versionName="1.0" >
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
...
<provider
android:name="com.example.android.datasync.provider.StubProvider"
android:authorities="com.example.android.datasync.provider"
android:exported="false"
android:syncable="true"/>
...
</application>
</manifest>
Now that you have created the dependencies required by the sync adapter framework, you can
create the component that encapsulates your data transfer code. This component is called a
sync adapter. The next lesson shows you how to add this component to your app.
Content and code samples on this page are subject to the licenses described in the Content License. Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
Last updated 2024-01-03 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-01-03 UTC."],[],[],null,["# Create a stub content provider\n\nThe sync adapter framework is designed to work with device data managed by the flexible and\nhighly secure content provider framework. For this reason, the sync adapter framework expects\nthat an app that uses the framework has already defined a content provider for its local data.\nIf the sync adapter framework tries to run your sync adapter, and your app doesn't have a\ncontent provider, your sync adapter crashes.\n\n\nIf you're developing a new app that transfers data from a server to the device, you should\nstrongly consider storing the local data in a content provider. Besides their importance for\nsync adapters, content providers offer a variety of security benefits and are specifically\ndesigned to handle data storage on Android systems. To learn more about creating a content\nprovider, see [Creating a Content Provider](/guide/topics/providers/content-provider-creating).\n\n\nHowever, if you're already storing local data in another form, you can still use a sync\nadapter to handle data transfer. To satisfy the sync adapter framework requirement for a\ncontent provider, add a stub content provider to your app. A stub provider implements the\ncontent provider class, but all of its required methods return `null` or `0`. If you\nadd a stub provider, you can then use a sync adapter to transfer data from any storage\nmechanism you choose.\n\n\nIf you already have a content provider in your app, you don't need a stub content provider.\nIn that case, you can skip this lesson and proceed to the lesson\n[Creating a Sync Adapter](/training/sync-adapters/creating-sync-adapter). If you don't yet have a\ncontent provider, this lesson shows you how to add a stub content provider that allows you to\nplug your sync adapter into the framework.\n\nAdd a stub content provider\n---------------------------\n\n\nTo create a stub content provider for your app, extend the class\n[ContentProvider](/reference/android/content/ContentProvider) and stub out its required methods. The following\nsnippet shows you how to create the stub provider: \n\n### Kotlin\n\n```kotlin\n/*\n * Define an implementation of ContentProvider that stubs out\n * all methods\n */\nclass StubProvider : ContentProvider() {\n /*\n * Always return true, indicating that the\n * provider loaded correctly.\n */\n override fun onCreate(): Boolean = true\n\n /*\n * Return no type for MIME type\n */\n override fun getType(uri: Uri): String? = null\n\n /*\n * query() always returns no results\n *\n */\n override fun query(\n uri: Uri,\n projection: Array\u003cString\u003e,\n selection: String,\n selectionArgs: Array\u003cString\u003e,\n sortOrder: String\n ): Cursor? = null\n\n /*\n * insert() always returns null (no URI)\n */\n override fun insert(uri: Uri, values: ContentValues): Uri? = null\n\n /*\n * delete() always returns \"no rows affected\" (0)\n */\n override fun delete(uri: Uri, selection: String, selectionArgs: Array\u003cString\u003e): Int = 0\n\n /*\n * update() always returns \"no rows affected\" (0)\n */\n override fun update(\n uri: Uri,\n values: ContentValues,\n selection: String,\n selectionArgs: Array\u003cString\u003e\n ): Int = 0\n}\n```\n\n### Java\n\n```java\n/*\n * Define an implementation of ContentProvider that stubs out\n * all methods\n */\npublic class StubProvider extends ContentProvider {\n /*\n * Always return true, indicating that the\n * provider loaded correctly.\n */\n @Override\n public boolean onCreate() {\n return true;\n }\n /*\n * Return no type for MIME type\n */\n @Override\n public String getType(Uri uri) {\n return null;\n }\n /*\n * query() always returns no results\n *\n */\n @Override\n public Cursor query(\n Uri uri,\n String[] projection,\n String selection,\n String[] selectionArgs,\n String sortOrder) {\n return null;\n }\n /*\n * insert() always returns null (no URI)\n */\n @Override\n public Uri insert(Uri uri, ContentValues values) {\n return null;\n }\n /*\n * delete() always returns \"no rows affected\" (0)\n */\n @Override\n public int delete(Uri uri, String selection, String[] selectionArgs) {\n return 0;\n }\n /*\n * update() always returns \"no rows affected\" (0)\n */\n public int update(\n Uri uri,\n ContentValues values,\n String selection,\n String[] selectionArgs) {\n return 0;\n }\n}\n```\n\nDeclare the provider in the manifest\n------------------------------------\n\n\nThe sync adapter framework verifies that your app has a content provider by checking that your\napp has declared a provider in its app manifest. To declare the stub provider in the\nmanifest, add a [\u003cprovider\u003e](/guide/topics/manifest/provider-element) element with the following attributes:\n\n\n`android:name=\"com.example.android.datasync.provider.StubProvider\"`\n:\n Specifies the fully-qualified name of the class that implements the stub content provider.\n\n\n`android:authorities=\"com.example.android.datasync.provider\"`\n:\n A URI authority that identifies the stub content provider. Make this value your app's\n package name with the string \".provider\" appended to it. Even though you're declaring your\n stub provider to the system, nothing tries to access the provider itself.\n\n\n`android:exported=\"false\"`\n:\n Determines whether other apps can access the content provider. For your stub content\n provider, set the value to `false`, since there's no need to allow other apps to see\n the provider. This value doesn't affect the interaction between the sync adapter framework\n and the content provider.\n\n\n`android:syncable=\"true\"`\n:\n Sets a flag that indicates that the provider is syncable. If you set this flag to\n `true`, you don't have to call [setIsSyncable()](/reference/android/content/ContentResolver#setIsSyncable(android.accounts.Account, java.lang.String, int)) in your code. The flag allows the sync adapter framework to make data\n transfers with the content provider, but transfers only occur if you do them explicitly.\n\n\nThe following snippet shows you how to add the\n[\u003cprovider\u003e](/guide/topics/manifest/provider-element) element to the app manifest: \n\n```xml\n\u003cmanifest xmlns:android=\"http://schemas.android.com/apk/res/android\"\n package=\"com.example.android.network.sync.BasicSyncAdapter\"\n android:versionCode=\"1\"\n android:versionName=\"1.0\" \u003e\n \u003capplication\n android:allowBackup=\"true\"\n android:icon=\"@drawable/ic_launcher\"\n android:label=\"@string/app_name\"\n android:theme=\"@style/AppTheme\" \u003e\n ...\n \u003cprovider\n android:name=\"com.example.android.datasync.provider.StubProvider\"\n android:authorities=\"com.example.android.datasync.provider\"\n android:exported=\"false\"\n android:syncable=\"true\"/\u003e\n ...\n \u003c/application\u003e\n\u003c/manifest\u003e\n```\n\n\nNow that you have created the dependencies required by the sync adapter framework, you can\ncreate the component that encapsulates your data transfer code. This component is called a\nsync adapter. The next lesson shows you how to add this component to your app."]]