Question

ContentProvider中SQLite更新的奇怪行为。

更新方法：

@Override
public int update(Uri uri, ContentValues updateValues, String whereClause, String[] whereValues) {

    SQLiteDatabase db = TasksContentProvider.dbHelper.getWritableDatabase();
    int updatedRowsCount;
    String finalWhere;

    db.beginTransaction();
    // Perform the update based on the incoming URI's pattern
    try {
        switch (uriMatcher.match(uri)) {
        case MATCHER_TASKS:

                updatedRowsCount = db.update(TasksTable.TABLE_NAME, updateValues, whereClause, whereValues);
                break;

        case MATCHER_TASK:
                String id = uri.getPathSegments().get(TasksTable.TASK_ID_PATH_POSITION);
                finalWhere = TasksTable._ID + " = " + id;

                // if we were passed a 'where' arg, add that to our 'finalWhere'
                if (whereClause != null) {
                    finalWhere = finalWhere + " AND " + whereClause;
                }
                updatedRowsCount = db.update(TasksTable.TABLE_NAME, updateValues, finalWhere, whereValues);
                break;

        default:
                // Incoming URI pattern is invalid: halt & catch fire.
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
    } finally {
        db.endTransaction();
    }

    if (updatedRowsCount > 0) {
        DVSApplication.getContext().getContentResolver().notifyChange(uri, null);
    }

    return updatedRowsCount;
}

查询方法：

    @Override
    public Cursor query(Uri uri, String[] selectedColumns, String whereClause, String[] whereValues, String sortOrder) {

        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

        // Choose the projection and adjust the "where" clause based on URI pattern-matching.
        switch (uriMatcher.match(uri)) {
        case MATCHER_TASKS:
            qb.setTables(TasksTable.TABLE_NAME);
            qb.setProjectionMap(tasksProjection);
            break;

        // asking for a single comic - use the rage comics projection, but add a where clause to only return the one
        // comic
        case MATCHER_TASK:
            qb.setTables(TasksTable.TABLE_NAME);
            qb.setProjectionMap(tasksProjection);

            // Find the comic ID itself in the incoming URI
            String taskId = uri.getPathSegments().get(TasksTable.TASK_ID_PATH_POSITION);
            qb.appendWhere(TasksTable._ID + "=" + taskId);
            break;
        case MATCHER_TASK_COMMENTS:
            qb.setTables(TaskCommentsTable.TABLE_NAME);
            qb.setProjectionMap(taskCommentsProjection);
            break;

        case MATCHER_TASK_COMMENT:
            qb.setTables(TaskCommentsTable.TABLE_NAME);
            qb.setProjectionMap(taskCommentsProjection);

            String commentId = uri.getPathSegments().get(TaskCommentsTable.TASK_COMMENT_ID_PATH_POSITION);
            qb.appendWhere(TaskCommentsTable._ID + "=" + commentId);
            break;
        default:
            // If the URI doesn't match any of the known patterns, throw an exception.
            throw new IllegalArgumentException("Unknown URI " + uri);
        }

        SQLiteDatabase db = TasksContentProvider.dbHelper.getReadableDatabase();
        // the two nulls here are 'grouping' and 'filtering by group'
        Cursor cursor = qb.query(db, selectedColumns, whereClause, whereValues, null, null, sortOrder);

        // Tell the Cursor about the URI to watch, so it knows when its source data changes
        cursor.setNotificationUri(DVSApplication.getContext().getContentResolver(), uri);

        return cursor;
    }

尝试更新并排队。

int affectedRowsCount = provider.update(Uri.parse(TasksTable.CONTENT_URI.toString() + "/"+ taskId), task.getContentValues(), null, null);

affectedRowsCount对1

是eqaul

检查行是否已更新

Cursor cs = provider.query(TasksTable.CONTENT_URI, new String[] {TasksTable.TASK_STATE_VALUE}, TasksTable._ID +" = ?", new String[] {String.valueOf(taskId)}, null);
if(cs.moveToFirst()) {
    String state = cs.getString(cs.getColumnIndex(TasksTable.TASK_STATE_VALUE));
}

state与更新前相同。虽然更新成功，因为affectedRowsCount等于1但是选择相同的ID，同一行似乎根本没有更新行。

Answer 1

在update方法中，您使用的是transaction，但您从未将结果设置为成功，因此每次到达db.endTransaction()时都会执行rollback。这就是为什么不存储您的更新。

如果没有结束任何交易，将回滚更改被标记为干净（通过调用setTransactionSuccessful）。除此以外他们会承诺。

您需要使用

db.setTransactionSuccessful();

更新完成后没有错误。在您的代码中，它应该在您的db.update。

之后

更新后SQLite相同的结果

1 个答案: