Question

我有这个代码，其中location和previousLocation是两个CGPoint：

    CGRect  bounds = [self bounds];
UITouch *touch = [[event touchesForView:self] anyObject];
    CGPoint point = [touch locationInView:self];
    location = CGPointMake(point.x,point.y);
    location.y = bounds.size.height - location.y;
    CGPoint prev = [touch previousLocationInView:self];
    previousLocation = CGPointMake(prev.x, prev.y);
previousLocation.y = bounds.size.height - previousLocation.y;
    [self renderLineFromPoint:previousLocation toPoint:location];

好的，这是我的GLPaint应用程序“touchmoved”内部代码的一部分;但我的问题是我想要一个固定点的shift位置和previousLocation，这个点位于imageview的顶点（我这样做是因为我在触摸视图时拖动图像），这一点的值可以是：

CGPoint *vertex = (imageView.center.x-100, imageView.center.y+100);

所以我的代码改变了：

    CGRect  bounds = [self bounds];
UITouch *touch = [[event touchesForView:self] anyObject];
    //CGPoint point = [touch locationInView:self];
    location = CGPointMake(vertex.x,vertex.y);
    location.y = bounds.size.height - location.y;
    //CGPoint prev = [touch previousLocationInView:self];
    previousLocation = CGPointMake(prev.x, prev.y);        <---- ?????
previousLocation.y = bounds.size.height - previousLocation.y;
    [self renderLineFromPoint:previousLocation toPoint:location];

位置可以轻松更改，但我现在的问题是previousLocation，我怎么能改变它？然后我的问题是......知道从位置到previousLocation的差异的方法是什么？我该如何计算其差异？因此，如果我知道dinamic的区别，我可以设置一个正确的转移previousLocation ...

Answer 1

这是解决方案：

CGPoint gap = CGPointMake(cur.x - prev.x, cur.y - prev.y);

IOS：差异化的视角

1 个答案: