UIPanGestureRecognizer - 立即移动视图

Question

我只需要它来根据平移手势移动一些视图。 问题是它不会立即发生，就像苹果地图一样，如果我将手指放在一个点上，然后快速移动到任何方向，视图会延迟移动，这意味着我将能够看到我的手指点，那是我不想要的。

可能由于硬件限制而无法实现，因为在模拟器中它可以正常工作。 或者也许有更好的方法我不知道。

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，我假设被拖动的视图有些复杂（例如，很大的 CALayer 阴影，计算量可能很大）。因此，我的原始答案如下。但在随后的cmet交流中，发现其中一个按钮有跳动的动画，这更有可能是问题所在。 animation should be suspended 在拖动视图时如果拖动性能不可接受。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，但我会先尝试像上面那样暂停动画。

---

原答案：

如果您拖动的视图非常复杂，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" 设置中。

2. 然后将源调整为相应的光栅化。

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，这样如果你抓住被拖离中心一点的视图，它就不会突然跳到你身上。

Answer 2

在为中心点设置新值时尝试禁用动画。

- (IBAction)pan:(UIPanGestureRecognizer *)sender 
{
    CGPoint center = [sender locationInView:sender.view];
    [CATransaction begin];
    [CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
    self.myView.center = center; 
    [CATransaction commit];
}

如果这有帮助，您可以尝试使用更快的动画来平滑它。

您也可以尝试禁用动画，如下所述： Explicitly disabling UIView animation in iOS4+

很快：

- (IBAction)pan:(UIPanGestureRecognizer *)sender 
{
    CGPoint center = [sender locationInView:sender.view];
    [UIView setAnimationsEnabled:NO];
    self.myView.center = center; 
    [UIView setAnimationsEnabled:YES];
}

一旦您设法在重新定位期间禁用所有动画，这取决于硬件和代码的速度。