Question

我正在尝试在objective-c中编写一个for循环，它将显示一堆注释视图，这些注释视图中的每一个都将创建一个自定义的标注视图（只是一个UIView子类）屏幕中间有一张图片）。

但是，我希望用户能够保持标注视图并暂停for循环（延迟循环继续直到用户放开屏幕）并且当他们放开屏幕时，for循环应该继续并立即转到下一个annotationView。

示例代码：

-(void)displayAnnotation:(MKAnnotationView *)view
{
    // ..blah blah blah
    // ..display some UIView

    // ..delay a second before returning
}

-(void)displayAllAnnotations:(NSMutableArray *)arrayOfAnnotationViews
{
    for (id annotationView in arrayOfAnnotationViews)
    {
        [self displayAnnotation:annotationView]

        // <NEED CODE HERE>
        // <If user holds screen, pause this loop from continuing>
        // <If user lets go, continue loop immediately to next picture>
    }
}

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Answer 1

你不能使用for循环，因为你在执行for循环时阻塞了主线程。这意味着在for循环结束之前，您的视图将不会收到触摸事件。

我建议改用dispatch_async。一个粗略的例子是：

@interface MyClass : NSObject
@property (nonatomic) NSUInteger viewIdx;
@property (nonatomic) NSArray *arrayOfAnnotationViews;
@property (nonatomic) BOOL userIsTappingScreen;
@end

@implementation MyClass

-(void)displayAnnotation:(MKAnnotationView *)view
{
    // ..blah blah blah
    // ..display some UIView
}

-(void)continueIteration
{
    dispatch_async(dispatch_get_main_queue(), ^{
        MKAnnotationView *view = self.arrayOfAnnotationViews[self.viewIdx];
        [self displayAnnotation:view];
        self.viewIdx++;
        if (user is tapping the screen) {
            self.userIsTappingScreen = YES;
        }
        else {
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                [self continueIteration];
            });
        }
    });
 }

 -(void)displayAllAnnotations:(NSMutableArray *)arrayOfAnnotationViews
 {
     self.viewIdx = 0;
     self.arrayOfAnnotationViews = arrayOfAnnotationViews;
 }

 // This method need to be called by your code when the user lifts the finger from the screen
 -(void)userHasSoppedTappingTheScreen
 {
    if (self.userIsTappingScreen) {
        [self continueIteration];
    }
 }

 @end

Answer 2

为了延迟尝试：

double delayInSeconds = 1.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    //code to be executed on the main queue after delay
});

Objective-C延迟循环运行时

2 个答案: