从儿童视图开始触摸移动

Question

我的超级视图里面有一个子视图。在子视图中，我有另一个名为circle的子视图。

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

以下代码放在子视图的类中，用于移动圆圈。

- (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];

    }
}

Answer 1

尝试忽略圆圈视图中没有的触摸？

- (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];

                }
            }