在Android的同步处理资料的任务 [英] Syncronizing tasks in Android

问题描述

在我的应用程序有多个地方的AsyncTask可以被调用来连接网页，下载的东西，等它可以从活动或后台服务。

In my application I have multiple places where AsyncTask can be invoked to connect to web, download stuff, etc. It can be from Activity or from background service.

有各种问题，因为我读取和写入SQLite数据库并在多个任务上类似的操作重叠（假设GetMail在后台运行，用户手动启动它）。

There is various issues because I'm reading and writing to SQLite database and when multiple tasks overlap on a similar operation (let's say GetMail runs on background and user started it manually).

我要syncronize类型的这一任务，并写道：code这样。我不知道如何测试它，它似乎是确定运行，但我希望得到你的意见，如果它是有效的。

I want to syncronize types of this tasks and wrote code like this. I'm not sure how to test it, it seems to be running OK but I wanted to get your opinion if it's valid..

public enum AsyncTasks
{
    GetMail,
    PostMail,
}
public class MyApplication extends Application
{
    private final ArrayList<AsyncTasks> mLockedAsyncTasks = new ArrayList<AsyncTasks>();


    public boolean lockAsyncTask(AsyncTasks task)
    {
        synchronized (mLockedAsyncTasks)
        {
            if (!mLockedAsyncTasks.contains(task)) 
            {
                mLockedAsyncTasks.add(task);
                return true;
            }

            return false;            
        }        
    }

    public void unlockAsyncTask(AsyncTasks task)
    {
        synchronized (mLockedAsyncTasks)
        {
            if (mLockedAsyncTasks.contains(task))
            {
                mLockedAsyncTasks.remove(task);
            }
        }
    }
}

在这里的想法是，我打电话 lockAsyncTask ，如果成功 - 我着手进行HTTP的东西，否则跳过，因为它已经运行。

Idea here is that I'm calling lockAsyncTask and if success - I proceed with HTTP stuff, otherwise skip since it's running already.

推荐答案

可能更容易只使用由单一工作线程支持的操作队列。这样的任务也将在他们收到的顺序运行。您可以轻松地使用 执行人 工厂方法。这里有一个简单的例子：

It might be easier to just use an operation queue backed by a single worker thread. That way all tasks will be run in the order they are received. You can easily accomplish this by using the Executors factory methods. Here's a simple example:

private static final ExecutorService mThreadPool =
        Executors.newSingleThreadExecutor();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mThreadPool.execute(new Runnable() {
        public void run() {
            // Do some work here...
        }
    });

    mThreadPool.execute(new Runnable() {
        public void run() {
            // Do some additional work here after
            // the first Runnable has finished...
        }
    });
}

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