Android的线程和数据库锁定 [英] Android threading and database locking

问题描述

我们使用的是 AsyncTasks 来访问数据库中的表和游标。

We are using AsyncTasks to access database tables and cursors.

不幸的是，我们看到关于数据库偶然的例外被锁定。

Unfortunately we are seeing occasional exceptions regarding the database being locked.

E/SQLiteOpenHelper(15963): Couldn't open iviewnews.db for writing (will try read-only):
E/SQLiteOpenHelper(15963): android.database.sqlite.SQLiteException: database is locked
E/SQLiteOpenHelper(15963):  at     android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method)
E/SQLiteOpenHelper(15963):  at     android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:1637)
E/SQLiteOpenHelper(15963):  at     android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1587)
E/SQLiteOpenHelper(15963):  at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:638)
E/SQLiteOpenHelper(15963):  at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:659)
E/SQLiteOpenHelper(15963):  at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:652)
E/SQLiteOpenHelper(15963):  at android.app.ApplicationContext.openOrCreateDatabase(ApplicationContext.java:482)
E/SQLiteOpenHelper(15963):  at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:193)
E/SQLiteOpenHelper(15963):  at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
E/SQLiteOpenHelper(15963):  at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:158)
E/SQLiteOpenHelper(15963):  at com.iview.android.widget.IViewNewsTopStoryWidget.initData(IViewNewsTopStoryWidget.java:73)
E/SQLiteOpenHelper(15963):  at com.iview.android.widget.IViewNewsTopStoryWidget.updateNewsWidgets(IViewNewsTopStoryWidget.java:121)
E/SQLiteOpenHelper(15963):  at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:338)
E/SQLiteOpenHelper(15963):  at com.iview.android.async.GetNewsTask.doInBackground(GetNewsTask.java:1)
E/SQLiteOpenHelper(15963):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
E/SQLiteOpenHelper(15963):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256)
E/SQLiteOpenHelper(15963):  at java.util.concurrent.FutureTask.run(FutureTask.java:122)
E/SQLiteOpenHelper(15963):  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648)
E/SQLiteOpenHelper(15963):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673)
E/SQLiteOpenHelper(15963):  at java.lang.Thread.run(Thread.java:1060)

没有任何人有一个普遍的例子为code的写入到数据库，从不同的线程比一个读数，以及我们如何能保证线程安全。

Does anybody have a general example for code which writes to a database from a different thread than the one reading and how can we ensure thread safety.

一个建议我已经是使用的ContentProvider ，因为这将处理的数据库从多个线程访问。我要看看这个，但这是处理这种问题的推荐方法？它似乎相当重量级的考虑，我们正在谈论的前面或后面。

One suggestion I've had is to use a ContentProvider, as this would handle the access of the database from multiple threads. I am going to look at this, but is this the recommended method of handling such a problem? It seems rather heavyweight considering we're talking about in front or behind.

推荐答案

我只是确保我所有的数据库解决了这个相同的异常打开已经关闭，以及（更重要的），以确保这一点，使每一个数据库实例的范围局部仅向需要它的方法。 ContentProvider的是一个良好的，安全的访问类的多线程分贝时使用，而且还要确保您使用的是良好的分贝做法：

I solved this same exception just by making sure all my database opens have closes, and (more importantly) to assure this, making the scope of each database instance local ONLY to the method that needs it. ContentProvider is a good, safe class to use when accessing a db from multiple threads, but also make sure you're using good db practices:

• 在保持数据库实例的地方（不SQLiteDatabase类成员！）
• 呼叫关闭（）在其中它打开了数据库中相同的方法
• 呼叫关闭（）你从DB
获得光标
• 听LogCat中的任何投诉SQLiteDatabse可能有

• Keep db instances local (no SQLiteDatabase class members!)
• call close() on the db in the same method in which it's opened
• call close() on the cursors you get from the db
• listen to LogCat for any complaints that SQLiteDatabse might have

这篇关于Android的线程和数据库锁定的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！