到最后1秒，还是要到主线程中更新UI

[appke]

不在主线程中更新界面，会有一点延迟

if (timeOut <= 0) {
    dispatch_source_cancel(timer);

    dispatch_async(dispatch_get_main_queue(), ^{
        weakSelf.backgroundColor = mColor;
        [weakSelf setTitle:title forState:UIControlStateNormal];
        weakSelf.userInteractionEnabled = YES;
    });
}