如何使用Touch移动UIImageView

Question

我正在尝试为我的imageView(下面的代码中的maskPreview)创建移动功能,以便用户可以在屏幕周围移动maskPreview中包含的图片.这是触摸开始和触摸移动的代码:

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
if ([touches count]==1) {
    UITouch *touch= [touches anyObject];
    originalOrigin = [touch locationInView:maskPreview];
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
if ([touches count]==1) {
    UITouch *touch = [touches anyObject];
    CGPoint lastTouch = [touch previousLocationInView:self.view];
    CGFloat movedDistanceX = originalOrigin.x-lastTouch.x;
    CGFloat movedDistanceY = originalOrigin.y-lastTouch.y;
    [maskPreview setFrame:CGRectMake(maskPreview.frame.origin.x+movedDistanceX, maskPreview.frame.origin.y + movedDistanceY, maskPreview.frame.size.width, maskPreview.frame.size.height)];
}
}

但我从应用程序得到一些奇怪的回应.我没有限制图像视图可以移动多远,即防止它移出屏幕,但即使这是一个小动作,我的图像视图也会疯狂消失.

非常感谢所有的帮助

Answer 1

touchesBegan在这个现代世界中,实施等等是过度的.你只是混淆了自己,你的代码将很快变得无法理解或维护.使用UIPanGestureRecognizer; 这就是它的用途.使用UIPanGestureRecognizer进行可拖动视图是微不足道的.这是UIPanGestureRecognizer的动作处理程序,它使视图可拖动:

- (void) dragging: (UIPanGestureRecognizer*) p {
    UIView* vv = p.view;
    if (p.state == UIGestureRecognizerStateBegan ||
        p.state == UIGestureRecognizerStateChanged) {
        CGPoint delta = [p translationInView: vv.superview];
        CGPoint c = vv.center;
        c.x += delta.x; c.y += delta.y;
        vv.center = c;
        [p setTranslation: CGPointZero inView: vv.superview];
    }
}