iOS：实现drawRect时要遵循的标准规则：使用可拖动对象

Question

我的应用允许用户在屏幕上拖动圈子。我想知道是否有任何标准步骤来实现这一点，特别是在将视图的正确区域标记为脏的方面。我目前正在做以下事情：

//Get initial touch point and draw a circle there. Use touch point and size of circle to pass the mark the appropriate CGRect as dirty so that it gets redrawn
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

//Get new touchpoint and draw a circle there. Use the union of the previous CGRect and the new one (based on the touch point and circle size) to tell drawRect: what area of the screen to redraw.
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

这看起来是对的，还是我应该做的其他基本部分？

Answer 1

假设你的观点是绘制圆圈的，那么你所做的应该没问题。只需使用[self setNeedsDisplayInRect: circleRect]将圆圈的上一个和新位置标记为脏。