ios - UIPanGestureRecognizer - 立即移动 View

Question

我只需要它根据平移手势移动一些 View 。问题是它不会立即发生，就像 Apple map 一样，如果我将手指放在一个点上，然后快速向任何方向移动， View 会延迟移动，这意味着我将能够看到指出我的手指放在上面，这是我不想要的。

也许由于硬件限制这是不可能的，因为在模拟器中它工作正常。或者也许有我不知道的更好方法。

谢谢。

---

- (IBAction)pan:(UIPanGestureRecognizer *)sender 
{
    CGPoint center = [sender locationInView:sender.view];
    self.myView.center = center; 
}

Answer 1

当我第一次回答时，我假设被拖动的 View 有些复杂(例如，一个大的 CALayer 阴影，这在计算上可能很昂贵)。因此，我的原始答案如下。但在随后的评论交流中，发现其中一个按钮有一个脉冲动画，这更有可能是问题所在。 animation should be suspended如果拖动性能 Not Acceptable ，则在拖动 View 期间。因此:

#import <QuartzCore/QuartzCore.h>

- (IBAction)pan:(UIPanGestureRecognizer *)gesture
{
    static CGPoint originalCenter;

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        originalCenter = gesture.view.center;
        [self pauseLayer:gesture.view.layer];
    }
    else if (gesture.state == UIGestureRecognizerStateChanged)
    {
        CGPoint translate = [gesture translationInView:gesture.view.superview];
        gesture.view.center = CGPointMake(originalCenter.x + translate.x, originalCenter.y + translate.y);
    }
    else if (gesture.state == UIGestureRecognizerStateEnded ||
             gesture.state == UIGestureRecognizerStateFailed ||
             gesture.state == UIGestureRecognizerStateCancelled)
    {
        [self resumeLayer:gesture.view.layer];
    }
}

-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = pausedTime;
}

-(void)resumeLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer timeOffset];
    layer.speed = 1.0;
    layer.timeOffset = 0.0;
    layer.beginTime = 0.0;
    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    layer.beginTime = timeSincePause;
}

显然，这可以与下面讨论的图像光栅化相结合，但我会先像上面那样尝试暂停动画。

---

原答案:

如果被拖动的 View 非常复杂，您可以尝试对其进行栅格化。

1. 将 QuartzCore.framework 添加到目标的 "Link binary with libraries"设置。

2. 然后相应地调整源以进行光栅化。

如:

#import <QuartzCore/QuartzCore.h>

- (IBAction)pan:(UIPanGestureRecognizer *)gesture
{
    static CGPoint originalCenter;

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        originalCenter = gesture.view.center;
        gesture.view.layer.shouldRasterize = YES;
    }
    if (gesture.state == UIGestureRecognizerStateChanged)
    {
        CGPoint translate = [gesture translationInView:gesture.view.superview];
        gesture.view.center = CGPointMake(originalCenter.x + translate.x, originalCenter.y + translate.y);
    }
    if (gesture.state == UIGestureRecognizerStateEnded ||
        gesture.state == UIGestureRecognizerStateFailed ||
        gesture.state == UIGestureRecognizerStateCancelled)
    {
        gesture.view.layer.shouldRasterize = NO;
    }
}

顺便说一句，我建议像这段代码一样保存 originalCenter，这样如果您抓取被拖离中心一点的 View ，它就不会突然跳到您身上。