将UIImageView弹回屏幕时退回

Question

我需要的是当UIImageView从屏幕上拖出时，它会在放开时弹回。我在左边和上边工作，这是我正在做的事情。

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

     if (!CGRectContainsPoint(self.view.frame, imageView.frame.origin)){ 

      CGFloat newX = 0.0f; 
      CGFloat newY = 0.0f; 

      // If off screen upper and left 

      if (imageView.frame.origin.x < 0.0f){ 
       CGFloat negX = imageView.frame.origin.x * -1; 
       newX = negX; 
      }else{ 
       newX = imageView.frame.origin.x; 
      } 

      if (imageView.frame.origin.y < 0.0f){ 
       CGFloat negY = imageView.frame.origin.y * -1; 
       newY = negY; 
      }else{ 
       newY = imageView.frame.origin.y; 
      } 


      CGRect newPoint = CGRectMake(newX, newY, imageView.frame.size.width, imageView.frame.size.height); 

      [UIView beginAnimations:@"BounceAnimations" context:nil]; 
      [UIView setAnimationDuration:.5]; 
      [letterOutOfBounds play]; 
      [imageView setFrame:newPoint]; 

      [UIView commitAnimations]; 

     } 
    } 
} 

所以，我想实现右侧和底侧的相同的事情。但我一直坚持这一点。有任何想法吗？

Answer 1

下面是怎么样的？

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

    UIImageView *imageView = nil; 

    BOOL moved = NO; 
    CGRect newPoint = imageView.frame; 

    // If off screen left 

    if (newPoint.origin.x < 0.0f){ 
     newPoint.origin.x *= -1.0; 
     moved = YES; 
    } 

    // if off screen up 

    if (newPoint.origin.y < 0.0f){ 
     newPoint.origin.y *= -1.0; 
     moved = YES; 
    } 

    // if off screen right 

    CGFloat howFarOffRight = (newPoint.origin.x + newPoint.size.width) - imageView.superview.frame.size.width; 
    if (howFarOffRight > 0.0) 
    { 
     newPoint.origin.x -= howFarOffRight * 2; 
     moved = YES; 
    } 

    // if off screen bottom 

    CGFloat howFarOffBottom = (newPoint.origin.y + newPoint.size.height) - imageView.superview.frame.size.height; 
    if (howFarOffBottom > 0.0) 
    { 
     newPoint.origin.y -= howFarOffBottom * 2; 
     moved = YES; 
    } 

    if (moved) 
    { 
     [UIView beginAnimations:@"BounceAnimations" context:nil]; 
     [UIView setAnimationDuration:.5]; 
     [letterOutOfBounds play]; 
     [imageView setFrame:newPoint]; 

     [UIView commitAnimations]; 
    } 
} 

当我读到你的代码，逻辑“如果关闭左侧，回到将其移动到相同的距离是关闭屏幕的看法。”说实话，这对我来说并不合适（为什么当反弹时，坐标取决于屏幕有多远），但我试图在“屏幕右侧”对其进行兑现，并且“屏幕底部”逻辑。显然，我的逻辑是使用superview的imageView来确定包含视图的宽度，但如果不合适，请将其替换为任何内容。

编辑：

我亲自做这个东西与手势识别，如：

UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]; 
[self.imageView addGestureRecognizer:pan]; 
self.imageView.userInteractionEnabled = YES; 

因此，手势识别动画移动图像后面将是：

- (void)handlePan:(UIPanGestureRecognizer *)gesture 
{ 
    static CGRect originalFrame; // you could make this an ivar if you want, but just for demonstration purposes 

    if (gesture.state == UIGestureRecognizerStateBegan) 
    { 
     originalFrame = self.imageView.frame; 
    } 
    else if (gesture.state == UIGestureRecognizerStateChanged) 
    { 
     CGPoint translate = [gesture translationInView:gesture.view]; 

     CGRect newFrame = originalFrame; 

     newFrame.origin.x += translate.x; 
     newFrame.origin.y += translate.y; 

     gesture.view.frame = newFrame; 
    } 
    else if (gesture.state == UIGestureRecognizerStateEnded || gesture.state == UIGestureRecognizerStateCancelled) 
    { 
     CGRect newFrame = gesture.view.frame; 

     newFrame.origin.x = fmaxf(newFrame.origin.x, 0.0); 
     newFrame.origin.x = fminf(newFrame.origin.x, gesture.view.superview.bounds.size.width - newFrame.size.width); 

     newFrame.origin.y = fmaxf(newFrame.origin.y, 0.0); 
     newFrame.origin.y = fminf(newFrame.origin.y, gesture.view.superview.bounds.size.height - newFrame.size.height); 

     // animate how ever you want ... I generally just do animateWithDuration 

     [UIView animateWithDuration:0.5 animations:^{ 
      gesture.view.frame = newFrame; 
     }]; 
    } 
} 

或者，如果你想要一个手势识别器，只是防止首先从屏幕上拖出图像，它就会LD是：

- (void)handlePan:(UIPanGestureRecognizer *)gesture 
{ 
    static CGRect originalFrame; 

    if (gesture.state == UIGestureRecognizerStateBegan) 
    { 
     originalFrame = self.imageView.frame; 
    } 
    else if (gesture.state == UIGestureRecognizerStateChanged) 
    { 
     CGPoint translate = [gesture translationInView:gesture.view]; 

     CGRect newFrame = originalFrame; 

     newFrame.origin.x += translate.x; 
     newFrame.origin.x = fmaxf(newFrame.origin.x, 0.0); 
     newFrame.origin.x = fminf(newFrame.origin.x, gesture.view.superview.bounds.size.width - newFrame.size.width); 

     newFrame.origin.y += translate.y; 
     newFrame.origin.y = fmaxf(newFrame.origin.y, 0.0); 
     newFrame.origin.y = fminf(newFrame.origin.y, gesture.view.superview.bounds.size.height - newFrame.size.height); 

     gesture.view.frame = newFrame; 
    } 
} 

---

顺便说一句，在搭载iOS 7，您可以通过使用新的animationWithDuration与usingSpringWithDampening和initialSpringVelocity参数给图像视图的动画回到它原来的位置一点点反弹力：

[UIView animateWithDuration:1.0 
         delay:0.0 
    usingSpringWithDamping:0.3 
     initialSpringVelocity:0.1 
        options:0 
       animations:^{ 
        // set the new `frame` (or update the constraint constant values that 
        // will dictate the `frame` and call `layoutViewsIfNeeded`) 
       } 
       completion:nil]; 

或者，在iOS7，你也可以使用UIKit的动态添加UISnapBehavior：

self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view]; 
self.animator.delegate = self; 

UISnapBehavior *snap = [[UISnapBehavior alloc] initWithItem:self.viewToAnimate snapToPoint:CGPointMake(self.viewToAnimate.center.x, self.view.frame.size.height - 50)]; 

// optionally, you can control how much bouncing happens when it finishes, e.g., for a lot of bouncing: 
// 
// snap.damping = 0.2; 

// you can also slow down the snap by adding some resistance 
// 
// UIDynamicItemBehavior *resistance = [[UIDynamicItemBehavior alloc] initWithItems:@[self.viewToAnimate]]; 
// resistance.resistance = 20.0; 
// resistance.angularResistance = 200.0; 
// [self.animator addBehavior:resistance]; 

[self.animator addBehavior:snap]; 

Answer 2

我认为最简单的方法是检查您的imageView是否已经从您的self.view中消失。

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { 
    if (!CGRectContainsRect(self.view.frame, imageView.frame)){ 
     // Your animation to bounce. 
    } 
}