image of UIbutton is stretched in iOS

Question

I have added a right bar button in my navigation bar, and then assign image to the UIButton and set the size to 20px * 20px

the view is good in editor, but when I run the app in simulator, the image is very stretched, can anyone help me please

image is here

Answer 1

在您的UIButton ，设置button.image.contentMode = UIViewContentModeScaleAspectFit

Answer 2

Control Click and Drag from Button to View Controller as IBOutlet

override func viewDidLoad(){
yourButtonOutletName.image.contentMode = .ScaleAspectFit

//        
}