objective-c - iOS-如何在线程(使用GCD)结束工作时收到通知

Question

我开始使用GCD，我需要知道某个线程何时结束工作。

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。

谢谢，

RL

Answer 1

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:

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，如果您想防止回调阻塞，请使用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);