Sqlite 事务阻塞 Android ui

发布于 2024-12-11 23:52:02 字数 568 浏览 3 评论 0原文

在我的 Android 应用程序中，有一个运行时间相对较长的 AsyncTask，我正在运行该任务以在应用程序启动时更新数据库。如果用户在任务完成之前退出应用程序，我需要将其包装在事务中以回滚。然而，由于将代码包装在事务中，它会阻塞 ui，直到任务完成。既然代码已经在单独的线程中运行，为什么会出现这种情况？

我正在使用 ORMLite，这基本上是事务的包装器，更新数据库的代码位于 call() 内部...，在添加代码以更新事务内的数据库之前，没有锁定 ui...

public ConnectionSource source; 
@Override
protected Boolean doInBackground(Context... params) {
    try {
        TransactionManager.callInTransaction(source, new Callable<Void>() {
            public Void call() throws Exception {
                return null;
            }
        });

原文

In my android app there is a relatively long running AsyncTask I'm running to update the database when the app starts up. I'm needing to wrap that in a transaction to roll things back if the user exits the app before the task is finished. However since wrapping the code in a transaction it is blocking the ui untill the task is complete. Why would this be since the code is already running in a separate thread?

I'm using ORMLite and this is the wrapper for the transaction basically,the code to update the db goes inside call().., before adding the code to update the db inside a transaction there was no locking of the ui...

public ConnectionSource source; 
@Override
protected Boolean doInBackground(Context... params) {
    try {
        TransactionManager.callInTransaction(source, new Callable<Void>() {
            public Void call() throws Exception {
                return null;
            }
        });

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蓝眸 2024-12-18 23:52:02

不幸的是，SQLite 事务是独占的，它们会阻止所有其他数据库活动。我怀疑即使您在另一个线程中，UI 线程也正在执行某种必须等待事务完成的数据库活动。

这是一个相关问题。
以下是有关 SQLite 事务级别的文档。

回复收藏 0 原文

夏见 2024-12-18 23:52:02

从 API 11 开始，Android 允许 WAL 模式下有一个写入线程和多个读取线程。您必须切换到 WAL 模式并使用 beginTransactionNonExclusive() 以避免阻塞读取线程。

int flags = SQLiteDatabase.CREATE_IF_NECESSARY;
if(walModeEnabled) {
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
       flags = flags | SQLiteDatabase.ENABLE_WRITE_AHEAD_LOGGING;
   }
}

SQLiteDatabase db = SQLiteDatabase.openDatabase(databasePath.getPath(), null, flags);

// backward compatibility hack to support WAL on pre-jelly-bean devices
if(walModeEnabled) {
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB &&
           Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
       db.enableWriteAheadLogging();
   } else {
       Log.w(TAG, "WAL is not supported on API levels below 11.");
   }
}

查看我的文章，了解有关 SQLite 中 WAL 模式和并发性的更多详细信息：

http://www.skoumal.net/en/parallel-read-and-write-in-sqlite/

Since API 11 Android allows one writing thread and many reading threads in WAL mode. You have to switch to WAL mode and use beginTransactionNonExclusive() to avoid blocking reading threads.

int flags = SQLiteDatabase.CREATE_IF_NECESSARY;
if(walModeEnabled) {
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
       flags = flags | SQLiteDatabase.ENABLE_WRITE_AHEAD_LOGGING;
   }
}

SQLiteDatabase db = SQLiteDatabase.openDatabase(databasePath.getPath(), null, flags);

// backward compatibility hack to support WAL on pre-jelly-bean devices
if(walModeEnabled) {
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB &&
           Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
       db.enableWriteAheadLogging();
   } else {
       Log.w(TAG, "WAL is not supported on API levels below 11.");
   }
}

Check my article for more details about WAL mode and concurency in SQLite:

http://www.skoumal.net/en/parallel-read-and-write-in-sqlite/

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