UIButton 不会在 iPhone 中使用 AspectFit

I've had that problem before. I solved it by putting my image in a UIImageView, where contentMode settings actually work, and putting a transparent custom UIButton over top of that.

EDIT: This answer is obsolete. See @Werner Altewischer's answer for the correct answer in modern versions of iOS.

I had the same issue, but I couldn't get it to work (perhaps it's a bug with the SDK).

Eventually, as a workaround, I placed a UIImageView behind my button and set the options I wanted on that, then simply placed a blank UIButton on top of it.

UIView content modes apply to the corresponding CALayer's "content". This works for UIImageViews because they set the CALayer content to the corresponding CGImage.

drawRect: ultimately renders to the layer content.

A custom UIButton (as far as I know) has no content (the rounded-rect style buttons might be rendered using content). The button has subviews: the background UIImageView, the image UIImageView, and the title UILabel. Setting the contentMode on the subviews may do what you want, but messing around with the UIButton view hierarchy is a bit of a no-no.

The solution is to set the contentMode on the imageView property of the UIButton. The UIButton has to be created with custom type for this to work I believe (otherwise nil is returned for this property).

If you put the image in an UIImageView behind the button, you'll loose the built-in functionality of the UIButton class, such as adjustsImageWhenHighlighted and adjustsImageWhenDisabled, and of course the ability to set different images for different states (without the hazzle of doing this yourself).

If we want to have an image unstreched for all control states, one approuch is to get the image using imageWithCGImage:scale:orientation, as in the following method:

- (UIImage *) getScaledImage:(UIImage *)img insideButton:(UIButton *)btn {


// Check which dimension (width or height) to pay respect to and
// calculate the scale factor
CGFloat imgRatio = img.size.width / img.size.height,
btnRatio = btn.frame.size.width / btn.frame.size.height,
scaleFactor = (imgRatio > btnRatio
? img.size.width / btn.frame.size.width
: img.size.height / btn.frame.size.height;


// Create image using scale factor
UIImage *scaledImg = [UIImage imageWithCGImage:[img CGImage]
scale:scaleFactor
orientation:UIImageOrientationUp];
return scaledImg;
}

To implement this we would write:

UIImage *scaledImg = [self getScaledImage:myBtnImg insideButton:myBtn];
[myBtn setImage:scaledImg forState:UIControlStateNormal];

This should prevent the image from stretching in all control states. It worked for me, but let me know if it doesn't!

NOTE: Here we are addressing a problem relating to UIButton, but the insideButton: might as well be insideView:, or whatever one would like to fit the image into.

You can use imageWithCGImage as shown above (but without the missing parentheses).

Also... millions of non-4.0 phones won't work with that code at all.

I had problems with the image not resizing proportionately so the way I fixed it was using edge insets.

fooButton.contentEdgeInsets = UIEdgeInsetsMake(10, 15, 10, 15);

[button sizeToFit] worked for me.

I had this problem a while back. The issue I had was i was trying to apply this effect to the background UIButton which is limited and therefore means you cannot adjust it as easy.

The trick is to set it as just an image then apply @ayreguitar's technique and that should fix it!

UIButton *myButton = [UIButton buttonWithType:UIButtonTypeCustom];
[myButton setContentMode:UIViewContentModeScaleAspectFill];
[myButton setImage:@"myImage.png" forState:UIControlStateNormal];

This answer is based on @WernerAltewischer's answer.

To avoid having connect my button to an IBOutlet to execute the code on it, I subclassed UIButton's class:

// .h
@interface UIButtonWithImageAspectFit : UIButton
@end


// .m
@implementation UIButtonWithImageAspectFit


- (void) awakeFromNib {
[self.imageView setContentMode:UIViewContentModeScaleAspectFit];
}


@end

Now create a custom button in your xib, and set its image (not the background image):

Then, set its class:

You're done!
Instead of

your button's image aspect fit is now as expected:

ios 12. You need to add also the content Alignment

class FitButton: UIButton {


required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)




}


override func layoutSubviews() {
self.imageView?.contentMode = .scaleAspectFill
self.contentHorizontalAlignment = .fill
self.contentVerticalAlignment = .fill
super.layoutSubviews()




}


}

This worked for me

[button.imageView setContentMode:UIViewContentModeScaleAspectFit];

Thanks to @ayreguitar for his comment

Here's an alternative answer in swift:

myButton.imageView?.contentMode = .ScaleAspectFit

Changing UIButton.imageView.contentMode does not worked for me.
I solved the problem by setting the image to 'Background' property.
You can add ratio constraint if you need

This method worked for me very well.:

In Xib select the button and set user defined runtime attributes:

• Key path: self.imageView.contentMode
• Type: Number
• Value: 1

We use number because you cant use enum there. But the UIViewContentModeScaleAspectFit is equal to 1.

btn.imageView.contentMode = UIViewContentModeScaleAspectFit;

This overlaps many of the other answers, but the solution for me was to

• set the contentMode of the UIImageView for the button to .ScaleAspectFit – which can either be done in the ”User Defined Runtime Attributes” in Interface Builder (ie. self.imageView.contentMode, Number, 1) or in a UIButton subclass;
• disable ”Autoresize Subviews”;
• set ”Edge” to ”Image” and appropriate ”Top” and ”Bottom” values for ”Inset” (which might only be needed if you, like me, used a PDF as image).

Similar to @Guillaume, I have created a subclass of UIButton as a Swift-File. Then set my custom class in the Interface Builder:

.

And here the Swift file:

import UIKit


class TRAspectButton : UIButton {
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.imageView?.contentMode = .ScaleAspectFit
}
}

Use button's imageView for contentMode. Not directly on the button itself.

homeButton.imageView.contentMode = UIViewContentModeScaleAspectFit;
homeButton.contentHorizontalAlignment = UIControlContentHorizontalAlignmentFill;
homeButton.contentVerticalAlignment = UIControlContentVerticalAlignmentFill;
[homeButton setImage:[UIImage imageNamed:kPNGLogo] forState:UIControlStateNormal];

Combining together a few different answers into one solution-- create a button with a custom type, set the button's imageView contentMode property, and set the image for the button (not the background image, which will still scale to fill).

//Objective-C:
UIImage *image = [UIImage imageNamed:"myImageName.png"];
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button setImage:image forState:UIControlStateNormal];
button.imageView.contentMode = UIViewContentModeScaleAspectFit;


//Swift:
let image = UIImage(named: "myImageName.png")
let button = UIButton(type: .custom)
button.imageView?.contentMode = .scaleAspectFit
button.setImage(image, for: .normal)

If you are doing this in Interface Builder, you can use the Runtime attributes inspector to set this directly without any code.

Set your Key Path on the button to be "imageView.contentMode" with a type of "Number" and a value of "1" (or whichever mode you would like).