ContentProvider實現跨程序數據共享，實例如下：
數據庫基于數據存儲中的使用的數據庫，點擊Here
1】ContentProvider類

public class ContentProvider extends android.content.ContentProvider {private static final int BOOK_DIR = 0;private static final int BOOK_ITEM = 1;private static final int CATEGORY_DIR = 2;private static final int CATEGORY_ITEM = 3;private static final String AUTHORITY = "com.example.android.provider";private static UriMatcher mUriMatcher;private MyDatabaseHelper mHelper;static {mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);mUriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);mUriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);mUriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);mUriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);}@Overridepublic boolean onCreate() {mHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 4);return true;}@Nullable@Overridepublic Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {SQLiteDatabase db = mHelper.getWritableDatabase();Cursor cursor = null;switch (mUriMatcher.match(uri)) {case BOOK_DIR:cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);break;case BOOK_ITEM:String bookId = uri.getPathSegments().get(1);cursor = db.query("Book", projection, "id=?", new String[]{bookId}, null, null, sortOrder);break;case CATEGORY_DIR:cursor = db.query("Category", projection, selection, selectionArgs, null, null, sortOrder);break;case CATEGORY_ITEM:String categoryId = uri.getPathSegments().get(1);cursor = db.query("Category", projection, "id=?", new String[]{categoryId}, null, null, sortOrder);break;default:break;}return cursor;}@Nullable@Overridepublic String getType(@NonNull Uri uri) {switch (mUriMatcher.match(uri)) {case BOOK_DIR:return "vnd.android.cursor.dir/vnd.com.example.android.provider.book";case BOOK_ITEM:return "vnd.android.cursor.item/vnd.com.example.android.provider.book";case CATEGORY_DIR:return "vnd.android.cursor.dir/vnd.com.example.android.provider.category";case CATEGORY_ITEM:return "vnd.android.cursor.item/vnd.com.example.android.provider.category";default:break;}return null;}@Nullable@Overridepublic Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {SQLiteDatabase db = mHelper.getWritableDatabase();Uri uriRe = null;switch (mUriMatcher.match(uri)) {case BOOK_DIR:case BOOK_ITEM:long newBookId = db.insert("Book", null, values);uriRe = Uri.parse("context://" + AUTHORITY + "/book" + newBookId);break;case CATEGORY_DIR:case CATEGORY_ITEM:long newCategoryId = db.insert("Category", null, values);uriRe = Uri.parse("context://" + AUTHORITY + "/category" + newCategoryId);break;default:break;}return uriRe;}@Overridepublic int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {SQLiteDatabase db = mHelper.getWritableDatabase();int deleteRows = 0;switch (mUriMatcher.match(uri)) {case BOOK_DIR:deleteRows = db.delete("Book", selection, selectionArgs);break;case BOOK_ITEM:String bookId = uri.getPathSegments().get(1);deleteRows = db.delete("Book", "id=?", new String[]{bookId});break;case CATEGORY_DIR:deleteRows = db.delete("Category", selection, selectionArgs);break;case CATEGORY_ITEM:String categoryId = uri.getPathSegments().get(1);deleteRows = db.delete("Category", "id=?", new String[]{categoryId});break;}return deleteRows;}@Overridepublic int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {SQLiteDatabase db = mHelper.getWritableDatabase();int updateRows = 0;switch (mUriMatcher.match(uri)) {case BOOK_DIR:updateRows = db.update("Book", values, selection, selectionArgs);break;case BOOK_ITEM:String bookId = uri.getPathSegments().get(1);updateRows = db.update("Book", values, "id=?", new String[]{bookId});break;case CATEGORY_DIR:updateRows = db.update("Category", values, selection, selectionArgs);break;case CATEGORY_ITEM:String categoryId = uri.getPathSegments().get(1);updateRows = db.update("Category", values, "id=?", new String[]{categoryId});break;}return updateRows;} }

2】實現增刪改查
查詢數據

private void queryData() {Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);Cursor cursor = getContentResolver().query(uri, null, null, null, null, null);if (cursor != null) {while (cursor.moveToNext()) {// 遍歷Cursor對象，取出數據并打印String category_name = cursor.getString(cursor.getColumnIndex("category_name"));String category_code = cursor.getString(cursor.getColumnIndex("category_code"));Log.d(TAG, "book name is " + category_name);Log.d(TAG, "book author is " + category_code);}}cursor.close();}

更新數據

private void updateData() {Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);ContentValues values = new ContentValues();values.put("category_name", "科幻類");values.put("category_code", 66);getContentResolver().update(uri, values, "category_name=?", new String[]{"科幻類"});}

刪除數據

private void deleteData() {Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY + "/" + newId);getContentResolver().delete(uri, null, null);}

添加數據

private void InsertData() {Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);ContentValues values = new ContentValues();values.put("category_name", "科幻類");values.put("category_code", 11);Uri newUri = getContentResolver().insert(uri, values);newId = newUri.getPathSegments().get(1);}

運行結果，查詢數據pass，其他操作failed

總結

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