ContentObserver和DatasetObserver之间的区别？ [英] Difference between ContentObserver and DatasetObserver?

问题描述

之间是什么 ContentObserver 区别和 DatasetObserver ？

在一个或另一个应该使用？

When one or another should be used?

我得到光标单排。我想收到有关数据的变化 - 例如。当行被更新。

I get Cursor with single row. I want to be notified about data changes - eg. when row is updated.

我要注册哪一个观察者类？

Which observer class should I register?

推荐答案

如果您使用的是的ContentProvider （通过 ContentResolver的或 Activity.managedQuery（）），让您的数据，只需连接一个 ContentObserver 您光标。在code。在的onChange（）将被称为每当 ContentResolver的广播通知的乌里与光标相关。

If you are using a ContentProvider (via ContentResolver or Activity.managedQuery()) to get your data, simply attach a ContentObserver to your Cursor. The code in onChange() will be called whenever the ContentResolver broadcasts a notification for the Uri associated with your cursor.

Cursor myCursor = managedQuery(myUri, projection, where, whereArgs, sortBy);
myCursor.registerContentObserver(new ContentObserver() {
    @Override
    public void onChange(boolean selfChange) {
        // This cursor's Uri has been notified of a change
        // Call cursor.requery() or run managedQuery() again
    }

    @Override
    public boolean deliverSelfNotifications() {
        return true;
    }
}

请确保您的的ContentProvider 是一个好公民，并注册了乌里与查询之后光标：

Make sure your ContentProvider is a "good citizen" and registers the Uri with the cursor after a query:

cursor.setNotificationUri(getContentResolver(), uri);

这也应该通知 ContentResolver的的底层数据（你的SQLite数据库，例如，插入过程中，删除和更新操作）的任何变化：

It should also notify the ContentResolver of any changes to the underlying data (for instance, during insert, delete, and update operations on your SQLite database):

getContentResolver().notifyChange(uri, null);

此方法是面向对象设计的观察者模式的一个很好的例子。

This approach is a good example of the Observer Pattern of object-oriented design.

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