iOS:事件指示器停止后如何执行一段代码？

Question

我需要一种方法来执行与下面类似的功能，但不是等待 3 秒，而是等待事件指示器被隐藏 [UIApplication sharedApplication].networkActivityIndi​​catorVisible = NO;。任何提示或建议表示赞赏。

double delayInSeconds = 3.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds *    NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
   // lines of code
 });

Answer 1

你如何使用Key-Value Observing :

声明上下文

static int NetworkActivityContext;

添加您的观察员

[[UIApplication sharedApplication] addObserver:self forKeyPath:@"networkActivityIndicatorVisible" options:NSKeyValueObservingOptionNew context:&NetworkActivityContext];

实现 KVO 回调

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if (context == &NetworkActivityContext) {
        BOOL isNetworkActivityVisible = [UIApplication sharedApplication].networkActivityIndicatorVisible;
        if(!isNetworkActivityVisible){
          //Do whatever work you need to do now that it's hidden
        }
    }
}