iOS-如何在线程(使用GCD)结束工作时收到通知 [英] iOS - how to be notified when a thread (using GCD) ends it's job

问题描述

我开始使用GCD，我需要知道某个线程何时结束它的工作.

I'm start to use GCD, and I need to know when a certain thread has ended it's job.

我的代码:

dispatch_queue_t registerDeviceQueue = dispatch_queue_create("RegisterDevice", NULL);
dispatch_async(registerDeviceQueue, ^{
    [self registerDevice];

    dispatch_async(dispatch_get_main_queue(), ^{
        [aiRegisterDevice stopAnimating];
    });
});
dispatch_release(registerDeviceQueue);

我需要知道此步结束的时间，以便UIActivityView可以停止. 现在的样子，它在线程结束之前就停止了.

I need to know when this tread has ended, so that the UIActivityView can stop. The way it is now, it's stops before the thread ends.

谢谢

RL

推荐答案

我将建立一个组，并使用dispatch_group_wait仅在计算完成后才继续.举个例子:

I'd set up a group and use dispatch_group_wait to continue only when the computation has finished. To take your example:

dispatch_queue_t registerDeviceQueue = dispatch_queue_create("RegisterDevice", NULL);
dispatch_group_t group = dispatch_group_create();

dispatch_group_async(group, registerDeviceQueue, ^{
    [self registerDevice];
});

dispatch_group_wait(group, DISPATCH_TIME_FOREVER); // Block until we're ready
// Now we're good to call it:
[aiRegisterDevice stopAnimating];

dispatch_release(registerDeviceQueue);
dispatch_release(group);

或者，如果要防止回调阻止，请使用dispatch_group_notify:

Or, if you want to prevent the callback blocking use dispatch_group_notify:

dispatch_queue_t registerDeviceQueue = dispatch_queue_create("RegisterDevice", NULL);
dispatch_group_t group = dispatch_group_create();

dispatch_group_async(group, registerDeviceQueue, ^{
    [self registerDevice];
}); // In this version, the group won't block


// This block gets called asynchronously when the above code is done:
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    [aiRegisterDevice stopAnimating];
});

dispatch_release(registerDeviceQueue);
dispatch_release(group);

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