建立虛設常式內容供應程式
透過集合功能整理內容
你可以依據偏好儲存及分類內容。
同步轉換介面架構旨在處理由彈性及
高度安全的內容供應器架構因此,同步處理轉換介面架構會預期
使用該架構的應用程式已針對本機資料定義內容供應器。
如果同步轉換介面架構嘗試執行同步轉接程式,而您的應用程式沒有
內容供應器,您的同步轉換介面當機。
如果您正在開發新的應用程式,以便將資料從伺服器轉移到裝置,建議您
強烈建議將本機資料儲存在內容供應器中。除了對
同步轉換介面、內容供應器提供各式各樣的安全性優勢,尤其
專為處理 Android 系統上的資料儲存而設計。進一步瞭解如何建立內容
請參閱建立內容供應器一文。
不過,如果您已以其他形式儲存本機資料,仍然可以使用同步處理功能
處理資料移轉的轉接器。符合
請將虛設常式內容供應器新增至應用程式。虛設常式供應商會
內容供應器類別,但所有的必要方法都會傳回 null
或 0
。如果發生以下情況:
新增虛設常式供應商,即可使用同步轉換介面轉移任何儲存空間中的資料
您選擇的機制
如果應用程式已有內容供應器,則不需要虛設常式內容供應器。
這時,您可以略過本課程,直接繼續完成本課程。
建立同步處理配接器。如果你還沒有
這個單元將說明如何新增虛設常式內容供應器
將同步轉換介面插入架構
新增虛設常式內容供應器
如要為應用程式建立虛設常式內容供應器,請擴充 類別
ContentProvider
並找到其必要方法。下列
下列程式碼片段說明如何建立虛設常式提供者:
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;
}
}
在資訊清單中宣告提供者
同步處理轉換介面架構會檢查您的應用程式
應用程式已在應用程式資訊清單中宣告供應器。如要在
資訊清單,請新增含有下列屬性的 <provider>
元素:
-
android:name="com.example.android.datasync.provider.StubProvider"
-
指定實作虛設常式內容供應器的類別完整名稱。
-
android:authorities="com.example.android.datasync.provider"
-
可識別虛設常式內容供應器的 URI 授權。將此值設為您應用程式的
含有「.provider」字串的套件名稱。即使您宣告
虛設常式供應商傳送至系統,並未嘗試存取供應器本身。
-
android:exported="false"
-
決定其他應用程式是否能存取內容供應器。適合存根內容
提供者,請將值設為
false
,因為您不需要允許其他應用程式查看。
。這個值不會影響同步轉換介面架構之間的互動
和內容供應者
-
android:syncable="true"
-
設定標記,以指出供應商可以同步。如果您將這個標記設為
true
,您不必在程式碼中呼叫 setIsSyncable()
。這個標記可讓同步轉換介面架構建立資料
傳輸作業,但只有在您明確執行時才會轉移。
下列程式碼片段說明如何新增
應用程式資訊清單中的 <provider>
元素:
<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>
現在,您已建立同步轉換介面架構所需的依附元件,您可以
然後建立封裝資料移轉程式碼的元件。這個元件稱為
同步處理轉換介面下一堂課將說明如何將此元件新增至應用程式。
這個頁面中的內容和程式碼範例均受《內容授權》中的授權所規範。Java 與 OpenJDK 是 Oracle 和/或其關係企業的商標或註冊商標。
上次更新時間:2025-07-27 (世界標準時間)。
[[["容易理解","easyToUnderstand","thumb-up"],["確實解決了我的問題","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["缺少我需要的資訊","missingTheInformationINeed","thumb-down"],["過於複雜/步驟過多","tooComplicatedTooManySteps","thumb-down"],["過時","outOfDate","thumb-down"],["翻譯問題","translationIssue","thumb-down"],["示例/程式碼問題","samplesCodeIssue","thumb-down"],["其他","otherDown","thumb-down"]],["上次更新時間:2025-07-27 (世界標準時間)。"],[],[],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."]]