设置 UITouch 的移动范围

Question

我为大小为 (30, 50) 的标签创建了一个触摸移动事件。这是代码

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {    
    UITouch *touch = [touches anyObject];
    UIView *superView = self.superview;
}

但我需要确保标签只能在超级视图内移动。也就是说UILabel在“接触”到view的边缘时会停止移动，如何设置label的移动范围？

Answer 1

1. 将标签设置为您的触摸位置
2. 检查label的frame是否在superView里面
3. 如果在外面，换框架，把userInteractionEnabled设为NO

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    self.center = [touches.anyObject locationInView:self.superview];

    CGRect bounds = self.superview.bounds;
    CGRect newFrame = self.frame;

    if (newFrame.origin.x < 0) {
        newFrame.origin.x = 0;
        self.userInteractionEnabled = NO;
    }
    if (newFrame.origin.y<0) {
        newFrame.origin.y = 0;
        self.userInteractionEnabled = NO;
    }
    if (newFrame.origin.x + newFrame.size.width > bounds.size.width) {
        newFrame.origin.x = bounds.size.width - newFrame.size.width;
        self.userInteractionEnabled = NO;
    }
    if (newFrame.origin.y + newFrame.size.height > bounds.size.height) {
        newFrame.origin.y = bounds.size.height - newFrame.size.height;
        self.userInteractionEnabled = NO;
    }

    self.frame = newFrame;
}