ios - UIView 如何判断自己不在用户的可视范围呢？

Question

要求：方案简单易行，用户无感知（不能占用过高的 CPU）
背景：需要封装一个视图控件，该控件需要根据陀螺仪进行频繁的重绘。

目前需要考虑以下情况：

• alpha

• hidden

• 作为UIScrollView 的子视图，被滚动到视图范围外

• 电话或者进入后台

• 被其它视图遮挡

Answer 1

alpha, hidden——You can know these two UIViews by getting their own properties
UIScrollView subview——You can get the frame of UIView relative to the screen through [scrollView convertRect:self.frame toView:[UIApplication sharedApplication].keyWindow];, and you can also judge whether it is within the view range through specific data
Make a phone call or enter the background - by implementing the corresponding proxy method in appdelegate, a notification will be sent after the proxy method is executed, so that UIView can receive the notification and also know that it is blocked by other views - you can control this thing yourself, write your own app , you will definitely know when the obstruction will occur

Answer 2

/* Return true if rect2' is contained in rect1', false otherwise. `rect2'
is contained in rect1' if the union of rect1' and `rect2' is equal to
`rect1'. */

CG_EXTERN bool CGRectContainsRect(CGRect rect1, CGRect rect2)

CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

Answer 3

Didn’t you list them all?