Geek Answers Handbook

IOS function says "CGRectMinY" which should be the bottom left corner

According to Apple documentation

CGRectMinY (CGRect) rect returns the y coordinate of the upper right corner of the specified rectangle

Isn't that the bottom left corner of the rectangle? Because I think the Y axis is down.

+7
source share
2 answers

If it is for iOS, I think your function is wrong.

http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Reference/CGGeometry/Reference/reference.html

CGRectGetMinY

Returns the y coordinate that sets the bottom edge of the rectangle.

CGFloat CGRectGetMinY (CGRect rect);

Options

Rect

The rectangle to examine.

Return value

The y-coordinate of the lower left corner of the specified rectangle. Availability

 Available in iOS 2.0 and later.

Sample code

 HeadsUpUI oalTouch PhotoScroller QuartzDemo SpeakHere

Declared in CGGeometry.h

Edit : Remove Confucius. "CGRectGetMinY" is a function that will be used on CGRect, which means that it will return the result as if it were only looking at a rectangle. eg:

 // With a self created element CGRect rect = CGRectMake(0, 429, 100, 44); NSLog(@"rect.origin.y: %f",rect.origin.y); NSLog(@"rect.size.height: %f",rect.size.height); NSLog(@"CGRectGetMinY(rect): %f",CGRectGetMinY(rect)); NSLog(@"CGRectGetMaxY(rect): %f",CGRectGetMaxY(rect));

returns

 2012-06-04 10:55:49.737 test[7613:707] rect.origin.y: 429.000000 2012-06-04 10:55:49.739 test[7613:707] rect.size.height: 44.000000 2012-06-04 10:55:49.741 test[7613:707] CGRectGetMinY(rect): 429.000000 2012-06-04 10:55:49.748 test[7613:707] CGRectGetMaxY(rect): 473.000000

The key is to just think about it, if you ask for min, you will get a lower value than if you asked for max. Even if you think about it without using the ios coordinate system.

NOW ios IS is inverted, so you have to consider this, the previous function will work, but visually speaking, the result is inverted, because the system is inverted.

 // With an element on the screen NSLog(@"gpsButton.frame.origin.y: %f",gpsButton.frame.origin.y); NSLog(@"gpsButton.frame.size.height: %f",gpsButton.frame.size.height); NSLog(@"CGRectGetMinY(gpsButton.frame): %f",CGRectGetMinY(gpsButton.frame)); NSLog(@"CGRectGetMaxY(gpsButton.frame): %f",CGRectGetMaxY(gpsButton.frame));

returns

 2012-06-04 10:55:49.725 test[7613:707] gpsButton.frame.origin.y: 429.000000 2012-06-04 10:55:49.727 test[7613:707] gpsButton.frame.size.height: 44.000000 2012-06-04 10:55:49.732 test[7613:707] CGRectGetMinY(gpsButton.frame): 429.000000 2012-06-04 10:55:49.735 test[7613:707] CGRectGetMaxY(gpsButton.frame): 473.000000

For a person who sees this, there is nothing wrong, min less than max.

So the confusion is in the ios inverted system, since you want to get a visually lower value from the inverted system.

That's why it seems strange, the description in CGGeometry is made for the "human world". Not for ios inverted system.

+14
source

The Y axis points down, starting at the top left point in the view. Thus, lower y values ​​are closer to the top of the view.

0
source

More articles:


All Articles