Question

我需要的是当UIImageView被拖离屏幕时它会在松开时反弹回来。我让它在左侧和上侧工作，这就是我正在做的事情。

    - (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];

        }
    }
}

所以我想为右侧和底侧实现同样的目标。但是我已经坚持了一段时间。任何想法？

Answer 1

如下所示：

- (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];
    }
}

当我阅读你的代码时，“如果偏离左侧，将其重新移回视图的距离与屏幕相同的距离”。说实话，这对我来说没有多大意义（为什么，当弹回时，坐标取决于它离屏幕有多远），但我试图在“屏幕右侧”和“屏幕底部”逻辑。显然我的逻辑是使用superview imageView来确定包含视图的宽度，但是如果这不合适，则用任何东西替换它。

修改

我个人用手势识别器来做这些事情，例如：

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

因此，用于动画移动图像的手势识别器将是：

- (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，如果您想要一个手势识别器，它只是阻止图像首先从屏幕上拖出，那就是：

- (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iOS 7中，您可以将新的animationWithDuration与usingSpringWithDampening和initialSpringVelocity一起使用，将图片视图的动画恢复到原来的位置稍微有点好玩参数：

[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中，您还可以使用UIKit Dynamics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imageView是否已超出self.view。

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

拖出屏幕时弹回UIImageView

2 个答案: