TouchesMoved与UITouch

Question

我正在创建一个简单的应用程序，您可以通过触摸和拖动UIImageView来移动它。

我的UIImageView叫做imv

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

UITouch * touch = [touches anyObject];

if([touch view] == self.imv){
    CGPoint location = [touch locationInView:self.view];
    self.imv.center = location;

}
}

-(void ) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch * touch = [touches anyObject];

if([touch view] == self.imv){
    CGPoint location = [touch locationInView:self.view];
    self.imv.center = location;

}
}

我整天都在试着解决这个问题，我不知道是怎么回事。如果我禁用If语句，它就无效了。我能做什么?

谢谢你的回答

Answer 1

除非您已经子类UIImageView (不太可能)，否则您的视图将接收触摸事件。

如今，将UIGestureRecognizer用于这类事情变得更简单&更常见，在本例中是UIPanGestureRecognizer。

例如：

UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(dragImageView:)];
[self.imv addGestureRecognizer:pan];


- (void)dragImageView:(UIPanGestureRecognizer *)dragImageView {
    if(UIGestureRecognizerStateBegan  == state) {
        originalCenter = self.imv.center;    // add CGPoint originalCenter; member
    } else if(UIGestureRecognizerStateChanged == state) {
        CGPoint translate = [pan translationInView:self.imv.superview];
        self.imv.center = CGPointMake(originalCenter.x + translate.x, originalCenter.y + translate.y);
    }
}

Answer 2

从一些实验来看，[touch view]似乎返回的是主UIView，而不是您的子视图，因此if语句不工作的问题(我在故事板xib中添加了UIImageView )。编辑--这是因为UIImageView在默认情况下不处理触摸事件--参见这里。当在UIView中添加一个常规的viewDidLoad时，似乎就像您预期的那样起作用了。

无论如何，这个经过修改的代码版本适合我。

-(void)moveImageForTouches:(NSSet*)touches
{
    UITouch * touch = [touches anyObject];
    CGPoint location = [touch locationInView:self.view];

    if(CGRectContainsPoint(self.imv.frame, location))
    {
        self.imv.center = location;
    }

}

-(void ) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self moveImageForTouches:touches];
}

-(void ) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self moveImageForTouches:touches];
}