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

问题描述

我需要拖动UIView对象.我使用了这段代码，但是它不起作用

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

您的代码中有些奇怪.

您要求在self中的位置，某些UIView可能包含要检查的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(您询问的触摸位置的父UIView)定义的label.frame时，这会取消，但这并不是最直接的方法跟踪发生的事情.

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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