Ios 从子视图开始触摸移动

我的superview中有一个子视图。在子视图中，我有另一个子视图，名为circle

这个圆是一个可拖动的圆。我可以通过触摸圆并移动来拖动圆。问题是，如果我触摸子视图上的任何其他位置并移动，则圆将移动。我如何防止这种情况发生

以下代码放置在子视图的类中，用于移动圆

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    startPoint = [[touches anyObject] locationInView:circle];
}

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

    for (UITouch *touch in touches){

        CGPoint newPoint = [touch locationInView:self];
        newPoint.x -= startPoint.x;
        newPoint.y -= startPoint.y;
        CGRect frm = [circle frame];
        frm.origin = newPoint;
        [circle setFrame:frm];

    }
}

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尝试忽略圆圈视图中不存在的触摸

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
                UITouch *touch1 = [touches anyObject];
                if(touch1.view == circle)
                {
                    startPoint = [[touches anyObject] locationInView:self];
                }
                else
                {
                    startPoint = nil;
                }
            }

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

                if (!startPoint) //If touch didnt start on circle view then ignore it
                {
                    return;
                }
                for (UITouch *touch in touches){

                    CGPoint newPoint = [touch locationInView:self];
                    newPoint.x -= startPoint.x;
                    newPoint.y -= startPoint.y;
                    CGRect frm = [circle frame];
                    frm.origin = newPoint;
                    [circle setFrame:frm];

                }
            }

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据我所知，有三种视图SuperView-->SubView1-->子视图（圆形）。我假设代码是子视图1中的编写器。是吗？是的。代码位于子视图1中。