iOS >> UIButton ImageView Property >> How to set C

Is there a way to set a UIButton Image, BackgroundImage or ImageView Properties Content Mode Property?

I've tried the direct approach (it didn't work, of course...):

self.imageButton.imageView.contentMode = UIViewContentModeScaleAspectFit;

It's nice to have a button with an image, but if there's no way to set it properly, it's not very handy...

回答1:

Using iOS7/8 with auto-layout, button.imageView doesn't get scaled when button is laid out, e.g. for iPhone 6:

(lldb) po button
<UIButton: 0x7fb4f501d7d0; frame = (0 0; 375 275); opaque = NO; autoresize = RM+BM; tag = 102; layer = <CALayer: 0x7fb4f501d160>>

(lldb) po button.imageView
<UIImageView: 0x7fb4f51d21f0; frame = (0 0; 0 0); clipsToBounds = YES; hidden = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x7fb4f5152860>>

After setting button's image, button.imageView assumed the size of the image, e.g. for a 320x240 image:

(lldb) po button.imageView
<UIImageView: 0x7fb4f51d21f0; frame = (27.5 17.5; 320 240); clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x7fb4f5152860>>

It looks like button.imageView does not respect its content mode, but actually, it is the size of the button.imageView that is the problem.

The answer is to set button's content alignment as well.

The following sets button's image, sets button.imageView's content mode, and makes button.imageView fit the size of button:

[button setImage:image forState:UIControlStateNormal];
button.imageView.contentMode = UIViewContentModeScaleAspectFill;
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentFill;
button.contentVerticalAlignment = UIControlContentVerticalAlignmentFill;

Now, button.imageView is the same size as button, and has the desired content mode.

(lldb) po button.imageView
<UIImageView: 0x7faac219a5c0; frame = (0 0; 375 275); clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x7faac219a6c0>>

The desired result is thereby achieved. Very handy!

回答2:

if you don't want to subclass UIButton than you can try this,

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    for (UIView *view in button.subviews) {
        if ([view isKindOfClass:[UIImageView class]]) {
            [view setContentMode:UIViewContentModeScaleAspectFit];
        }
    }

回答3:

Every UIButton has one hidden UIImageView of its own. So we have to set the content mode like the way given below...

[[btn imageView] setContentMode: UIViewContentModeScaleAspectFit];