绘图 - 3

来源：互联网发布：国家顶级域名是编辑：程序博客网时间：2024/06/10 21:47

绘图这块，我慢慢地会整理一番，前期肯定会比较混乱，毕竟知识面太广泛了。

好文章：http://gypgyp.iteye.com/blog/1552067

现在主要为集成一些涉及到的方法和类及实现。

- (CGPoint)convertPoint:(CGPoint)point toView:(nullable UIView *)view;- (CGPoint)convertPoint:(CGPoint)point fromView:(nullable UIView *)view;

UIView的两个方法，十分有意思，首先要对一个概念熟悉，Coordinate system ，相信有初中的知识就可以够用了。而这个方法顾名思义，就是将一个点从基于的一个坐标系转换到基于另外一个的坐标系。

http://stackoverflow.com/questions/8465659/understand-convertrecttoview-convertrectfromview-convertpointtoview-and

这里给出的一个例子，但是上面需要一点地修改是point参数其实最好给出常数，这里的例子给了view1.bounds.origin，其实就是{ 0 , 0 }这个数，只是很容易让人误解这个参数的意义。这个point 的意义就是偏移值。

    UIView* containView = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 300, 300)];    [containView setBackgroundColor:[UIColor lightGrayColor]];    [self.view addSubview:containView];            UILabel* label = [[UILabel alloc] init];    [label setFrame:CGRectMake(50, 50, 100, 100)];    [label setBackgroundColor:[UIColor yellowColor]];    [containView addSubview:label];        CGPoint originInContainViewCoordinates = [containView convertPoint:CGPointZero fromView:label];;    NSLog(@"convertPointer:fromView : %@", NSStringFromCGPoint(originInContainViewCoordinates));            CGPoint originInLabelCoordinates = [containView convertPoint:CGPointZero toView:label];    NSLog(@"convertPointer:toView : %@", NSStringFromCGPoint(originInLabelCoordinates));            CGPoint originInContainViewCoordiatesConst = [containView convertPoint:CGPointMake(10, 10) fromView:label];    NSLog(@"originInContainViewCoordiatesConst : %@ ", NSStringFromCGPoint(originInContainViewCoordiatesConst));        CGPoint originInLabelCoordiatesConst = [containView convertPoint:CGPointMake(10, 10) toView:label];    NSLog(@"originInLabelCoordiatesConst : %@", NSStringFromCGPoint(originInLabelCoordiatesConst));        CGPoint originInView_LabelCoordinates = [self.view convertPoint:CGPointZero fromView:label];    NSLog(@"originInViewCoordinates : %@", NSStringFromCGPoint(originInView_LabelCoordinates));            CGPoint originInLabel_ViewCoordinates = [self.view convertPoint:CGPointZero toView:label];    NSLog(@"originInLabel_ViewCoordinates : %@", NSStringFromCGPoint(originInLabel_ViewCoordinates));            CGPoint originInView_LabelCoordinatesConst = [self.view convertPoint:CGPointMake(10, 10) toView:label];    NSLog(@"originInView_LabelCoordinatesConst : %@", NSStringFromCGPoint(originInView_LabelCoordinatesConst));

好好思考就很容易明白，上面的名字也非常好理解： originInContainViewCoordinates 和 originInLabelCoordinates 分别是基于ContainView的坐标系和基于Label的坐标系

这样的输出结果就非常好理解了：抓住 from to的意义。

说白了就是坐标系和偏移度的选取罢了。

还有一处注意的地方，你可以这样倒置，效果是一样的：

    CGPoint originInContainViewCoordinates = [containView convertPoint:CGPointZero fromView:label];    CGPoint originInContainViewCoordinates = [label convertPoint:CGPointZero toView:containView];

在头文件中我们可以见到另外两个相似的方法：

- (CGRect)convertRect:(CGRect)rect toView:(nullable UIView *)view;- (CGRect)convertRect:(CGRect)rect fromView:(nullable UIView *)view;

效果和用法都是一样的啦，只是改成了以CGRect作结果罢了。

参考：

http://stackoverflow.com/questions/8465659/understand-convertrecttoview-convertrectfromview-convertpointtoview-and

http://blog.csdn.net/xuhuan_wh/article/details/8486337

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