Question

我正在尝试以水平和垂直方式预览图像的幻灯片，我希望能够在用户停止滚动时做一些事情，并在5秒后做这些事情。我使用2个计时器来处理这个，但我需要一些同步，或者我的方法可能不对！为什么我使用2个计时器：因为我想在主视图（-(void)touchesBegan和-(void)touchesEnded）中处理滚动并在scrollView（UIScrollView delegate）上滚动。我的代码在下面，我希望有人可以帮助:)。感谢。

// This is the slideShow view controller
// It display all the images with preview (right, left, up and down)
@interface ImageSlideShowViewController : UIViewController<UIScrollViewDelegate>
{

    UIScrollView *scrollViewForSlideShow;    
    // Timers
    NSTimer *autoscrollTimer;
    NSTimer *mainViewTimer;
}

@end

@implementation ImageSlideShowViewController

#pragma mark Touch handling

-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event{
    ....
    // Invalidate all timers
   [autoscrollTimer invalidate];
   autoscrollTimer = nil;
   [mainViewTimer invalidate];
   mainViewTimer = nil;
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    ....

    assert(mainViewTimer == nil);

    mainViewTimer = [NSTimer scheduledTimerWithTimeInterval:5.0
                                                       target:self
                                                     selector:@selector(allViewTimerFireMethod:)
                                                     userInfo:nil
                                                      repeats:NO];   


    // prev image horizontal
        ...

    // next image horizontal
        ....    

    // prev image vertical
            ...

    // next image vertical
            ....
}   


#pragma mark -
#pragma mark UIScrollView delegate

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    // Invalidate all timers
    [autoscrollTimer invalidate];
    autoscrollTimer = nil;
    [mainViewTimer invalidate];
    mainViewTimer = nil;
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView 
{
    //Doing some management stuff here
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    if (!scrollView.dragging)
    {
        //Doing some management stuff here

        assert(autoscrollTimer == nil);


        autoscrollTimer = [NSTimer scheduledTimerWithTimeInterval:5.0
                                                           target:self
                                                         selector:@selector(timerFireMethod:)
                                                         userInfo:nil
                                                          repeats:NO];

    }
}

#pragma mark -
#pragma mark Timers methods

- (void)timerFireMethod:(NSTimer*)theTimer
{
    autoscrollTimer = nil;
    // Call a method that dispaly the image
}

- (void)allViewTimerFireMethod:(NSTimer *)theTimer
{
    mainViewTimer = nil;
    // Call a method that dispaly the image (same as the method called above)
}

@end

Answer 1

我认为你可以摆脱两个定时器并定义一个中间函数，比如enableTimerFor:，你可以从-scrollViewDidEndDecelerating:和-touchesEnded:withEvent:调用，而不是在那里创建2个定时器

enableTimerFor:基本上会创建计时器并安排它：

-(void)enableTimerFor:(NSUInteger)callerId {
    viewTimer = [NSTimer scheduledTimerWithTimeInterval:5.0
                                                   target:self
                                                 selector:@selector(timerFired:)
                                                 userInfo:nil
                                                  repeats:NO];   
}

-(void)timerFired {
   // do whatever you need to
}

它将被称为：

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    ....
    [self enableTimerFor:kTouchesEnded];
    ....
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    if (!scrollView.dragging) {
        //Doing some management stuff here
        [self enableTimerFor:kScrollEnded];
    }
    ....
}

就像那样，你在同步方面没有问题。另请注意，我认为enableTimerFor:有一个参数可以让您识别它是从一个函数还是另一个函数调用的，但是如果您不需要区分，您可以轻松地决定将其删除这两个案例。

我不确定这个建议是否适合您，因为我不知道您的解决方案的所有细节，但我认为这是我提供的最直接的建议。

UIScrollView带有图像幻灯片和计时器

1 个答案: