問題描述

我有一個 UIImageView 放置在 UIScrollView 中，基本上這個 UIImageView 擁有非常大的地圖，并在帶有箭頭"指向導航方向的預定義路徑上創(chuàng)建動畫.

I have a UIImageView placed in UIScrollView, Basicly this UIImageView holds very big map, and created animation on a predefined path with "arrows" pointed navigation direction.

但是，每當發(fā)生 uiscrollevents 時，我認為 MainLoop 會凍結并且 NSTimer 不會被觸發(fā)，并且動畫會停止.

But, whenever uiscrollevents occurs, I think MainLoop freezes and NSTimer being not fired, and animation stopped.

在 UIScrollView、CAKeyFrameAnimation 或 NSTimer 上是否存在解決此問題的任何現有屬性?

Are there any existing property, which solves this problem, on UIScrollView, CAKeyFrameAnimation or NSTimer?

//viewDidLoad
   self.myTimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(drawLines:) userInfo:nil repeats:YES];

- (void)drawLines:(NSTimer *)timer {

   CALayer *arrow = [CALayer layer];
   arrow.bounds = CGRectMake(0, 0, 5, 5);
   arrow.position = CGPointMake(line.x1, line.y1);
   arrow.contents = (id)([UIImage imageNamed:@"arrow.png"].CGImage);

   [self.contentView.layer addSublayer:arrow];

   CAKeyframeAnimation* animation = [CAKeyframeAnimation animation];
   animation.path = path;
   animation.duration = 1.0;
   animation.rotationMode = kCAAnimationRotateAuto; // object auto rotates to follow the path
   animation.repeatCount = 1;
   animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
   animation.fillMode = kCAFillModeForwards;

   [arrow addAnimation:animation forKey:@"position"];
}

推薦答案

iOS 應用程序在 NSRunLoop 上運行.每個 NSRunLoop 對不同的任務都有不同的執(zhí)行模式.例如，默認的 nstimer 計劃在 NSRunLoop 上的 NSDefaultRunMode 下運行.然而，這意味著某些 UIEvents，scrollviewing 是一個，將中斷計時器，并將其放在隊列中，以便在事件停止更新時立即運行.在您的情況下，為了讓計時器不被中斷，您需要將其安排為不同的模式，即 NSRunLoopCommonModes，如下所示:

iOS Applications run on an NSRunLoop. Each NSRunLoop has different modes of execution for different tasks. For example, the default nstimer is scheduled to run under the NSDefaultRunMode on the NSRunLoop. What this means however is that certain UIEvents, scrollviewing being one, will interrupt the timer, and place it on a queue to be run as soon as the event stops updating. In your case, in order to get the timer to not be interrupted, you need to schedule it for a different mode, namely NSRunLoopCommonModes, like so:

  self.myTimer =  [NSTimer scheduledTimerWithTimeInterval:280
                                                                 target:self
                                                               selector:@selector(doStuff)
                                                               userInfo:nil
                                                                repeats:NO];
  [[NSRunLoop currentRunLoop] addTimer:self.myTimer forMode:NSRunLoopCommonModes]; 

此模式將允許您的計時器不會被滾動打斷.您可以在此處找到有關此信息的更多信息:https://developer.apple.com/documentation/foundation/nsrunloop在底部，您將看到可以選擇的模式的定義.還有，傳說有，你可以編寫自己的自定義模式，但恐怕很少有人能活著講述這個故事.

This mode will allow your timer to not be interrupted by scrolling. You can find more about this info here: https://developer.apple.com/documentation/foundation/nsrunloop At the bottom you will see the definitions of the modes you can choose from. Also, legend has it, you can write your own custom modes, but few have ever lived to tell the tale im afraid.

這篇關于發(fā)生 uiscrollview 事件時未觸發(fā) NSTimer的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！