touchesBegan、touchesEnded、touchesMoved 用于移动 UIView [英] touchesBegan, touchesEnded, touchesMoved for moving UIView

问题描述

我需要拖动我的 UIView 对象.我使用此代码，但它不起作用

I need to drag my UIView object. I use this code, but it does not work

float oldX, oldY;
BOOL dragging;

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

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLocation = [touch locationInView:self];

    if ([[touch.view class] isSubclassOfClass:[UILabel class]]) {
        UILabel *label = (UILabel *)touch.view;
        if (CGRectContainsPoint(label.frame, touchLocation)) {
            dragging = YES;
            oldX = touchLocation.x;
            oldY = touchLocation.y;
        }
    }


}

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

    dragging = NO;
}

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

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLocation = [touch locationInView:self];

    if ([[touch.view class] isSubclassOfClass:[UILabel class]]) {
        UILabel *label = (UILabel *)touch.view;

        if (dragging) {
            CGRect frame = label.frame;
            frame.origin.x = label.frame.origin.x + touchLocation.x - oldX;
            frame.origin.y =  label.frame.origin.y + touchLocation.y - oldY;
            label.frame = frame;
        }

    }


}

推荐答案

你的代码有些奇怪.

您在 self 中询问位置，一些 UIView 大概包含您要检查的 UILabel.这就引出了一个问题，即为什么不将 touchesXXX 添加到您的某些 UILabel 子类中.

You ask for the location in self, some UIView which presumably contains the UILabel you want to check. This begs the question as to why you do not add the touchesXXX to some UILabel subclass of yours.

当您使用根据其 superview.bounds 定义的 label.frame(您询问触摸位置的父 UIView)时，这会取消，但这并不是最直接的方式关注正在发生的事情.

This cancels out as you're using the label.frame which is defined in terms of its superview.bounds (your parent UIView you asked the touch location with respect to), but this doesn't make for the most straightforward way to follow what's going on.

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