在Android上正确使用的SQLite（SQLiteOpenHelper，连接，主线程，等...） [英] Correct use of Sqlite on Android (SQLiteOpenHelper, connections, main thread, etc...)

问题描述

我在寻找有关SQLite的在Android上的信息，并阅读Android上编程一些书部分章节，但我不知道如何真正使用SQLite在Android上运行。

I'm searching info about SQLite on Android, and read some chapters of some books on Android Programming, but I don't know how to really use SQLite on Android correctly.

我正在开发一个应用程序，有活动，服务和BroadcastReceivers，和所有的人都必须在数据库中读取和写入数据。所以，我有一些问题：

I'm developing an app that has Activities, Services and BroadcastReceivers, and all of them must read and write data in the database. So I have some questions:

• 在哪里是创建 SQLiteOpenHelper 实例最好的地方？我读到这，它似乎是最好的办法是只具有 SQLiteOpenHelper 为所有的应用程序。
• 在何时，何地，我需要获得 SQLiteDatabase 对象通过调用 dbHelper.getReadableDatabase（）（或 getWritableDatabase ）？我需要做的每一个查询，每次查询后关闭它？
• 在我看，我不应该做的数据库操作在主线程，所以我创建一个异步任务对每个数据库操作我做的一个活动，这是最好的方法是什么？

• Where is the best place to create the SQLiteOpenHelper instance? I read about this, and it seems that the best way is to have only SQLiteOpenHelper for all the app.
• When, and where, do I need to get SQLiteDatabase object by calling dbHelper.getReadableDatabase() (or getWritableDatabase)? I need to do it on each query, closing it after each query?
• I read that I should never do database operations in the main thread, so I'm creating an Async task for each database operation I do in an Activity, is this the best way?

推荐答案

大部分的问题是相当主观的。但是，让我来刺它

Most of the question is rather subjective. But let me take a stab at it

在哪里是创建SQLiteOpenHelper实例最好的地方？一世   readed关于这一点，似乎是最好的办法是只让   SQLiteOpenHelper的所有应用程序。

Where is the best place to create the SQLiteOpenHelper instance? I readed about this, and seems that the best way is to have only SQLiteOpenHelper for all the app.

您可以在您的项目扩展 SQLiteOpenHelper 创建的类的。这是有帮助的，当你将访问相同的数据库的在你的应用程序的多个活动。

You can create a Class in your project that extends SQLiteOpenHelper. This is helpful when you would be accessing the same Database in multiple Activities in your application.

当，何地，我需要得到SQLiteDatabase对象通过调用   dbHelper.getReadableDatabase（）（或getWritableDatabase）？我需要做的   它的每个查询，每次查询后关闭它？

When, and where, do I need to get SQLiteDatabase object by calling dbHelper.getReadableDatabase() (or getWritableDatabase)? I need to do it on each query, closing it after each query?

这将在完成的类的扩展的 SQLiteOpenHelper 的。例如：（这是在文章最后的提供的Vogella文章摘录）

This would be done in the Class that extends SQLiteOpenHelper. For example: (this is an excerpt from a Vogella article provided at the end of this post)

public void open() throws SQLException {
    database = dbHelper.getWritableDatabase();
}

和中，将使用类的活动：

And in an Activity that will use the Class:

CommentsDataSource datasource = new CommentsDataSource(this);
datasource.open();

和一个光标和数据库的连接的从<$ C $发C>活动应关闭，当你与取完成后，修改，添加等与数据库。

And a Cursor and the Database connection made from the Activity should be closed when you are done with fetching, modifying, adding, etc with the Database.

的code以上才有意义，当你看过之后链接的网页。的

我readed，我不应该做的数据库操作的主   线程，所以我创建一个异步任务对每个数据库操作怎么办   在活动，这是最好的方法是什么？

I readed that I should never do database operations in the main thread, so I'm creating an Async task for each database operation I do in an Activity, this is the best way?

在理想情况下，是的。我个人推荐使用的的AsyncTask 的尤其是当你将处理大型记录集。

Ideally, yes. I would personally recommend using an Asynctask especially when you would be dealing with large record sets.

最后，我建议你读了本教程由拉尔斯Vogella：<一href="http://www.vogella.com/articles/AndroidSQLite/article.html">http://www.vogella.com/articles/AndroidSQLite/article.html.这将解决大部分的问题和疑问。祝你好运。 ： - ）

Finally, I would suggest that you read up on this tutorial by Lars Vogella: http://www.vogella.com/articles/AndroidSQLite/article.html. It will address most of your concerns and queries. Good luck. :-)

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