Setting an image for a UIButton in code

Objective-C

UIImage *btnImage = [UIImage imageNamed:@"image.png"];
[btnTwo setImage:btnImage forState:UIControlStateNormal];

Swift 5.1

let btnImage = UIImage(named: "image")
btnTwo.setImage(btnImage , for: .normal)

Mike's solution will just show the image, but any title set on the button will not be visible, because you can either set the title or the image.

If you want to set both (your image and title) use the following code:

btnImage = [UIImage imageNamed:@"image.png"];
[btnTwo setBackgroundImage:btnImage forState:UIControlStateNormal];
[btnTwo setTitle:@"Title" forState:UIControlStateNormal];

Before this would work for me I had to resize the button frame explicitly based on the image frame size.

UIImage *listImage = [UIImage imageNamed:@"list_icon.png"];
UIButton *listButton = [UIButton buttonWithType:UIButtonTypeCustom];

// get the image size and apply it to the button frame
CGRect listButtonFrame = listButton.frame;
listButtonFrame.size = listImage.size;
listButton.frame = listButtonFrame;

[listButton setImage:listImage forState:UIControlStateNormal];
[listButton addTarget:self.navigationController.parentViewController 
               action:@selector(revealToggle:) 
     forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *jobsButton = 
  [[UIBarButtonItem alloc] initWithCustomView:listButton];

self.navigationItem.leftBarButtonItem = jobsButton;

In case of Swift User

// case of normal image
let image1 = UIImage(named: "your_image_file_name_without_extension")!
button1.setImage(image1, forState: UIControlState.Normal) 

// in case you don't want image to change when "clicked", you can leave code below
// case of when button is clicked
let image2 = UIImage(named: "image_clicked")!
button1.setImage(image2, forState: UIControlState.Highlight) 

You can do it like this

[btnTwo setImage:[UIImage imageNamed:@"image.png"] forState:UIControlStateNormal];

UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame = CGRectMake(0, 0, 150, 44);
[btn setBackgroundImage:[UIImage imageNamed:@"buttonimage.png"] 
               forState:UIControlStateNormal];
[btn addTarget:self 
     action:@selector(btnSendComment_pressed:) 
     forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:btn];

You can put the image in either of the way:

UIButton *btnTwo = [UIButton buttonWithType:UIButtonTypeRoundedRect]; 
btnTwo.frame = CGRectMake(40, 140, 240, 30);
[btnTwo setTitle:@"vc2:v1" forState:UIControlStateNormal];
[btnTwo addTarget:self 
           action:@selector(goToOne) 
 forControlEvents:UIControlEventTouchUpInside];


[btnTwo setImage:[UIImage imageNamed:@"name.png"] forState:UIControlStateNormal];

//OR setting as background image

[btnTwo setBackgroundImage:[UIImage imageNamed:@"name.png"] 
                  forState:UIControlStateNormal];

[self.view addSubview:btnTwo];

I was looking for a solution to add an UIImage to my UIButton. The problem was just it displays the image bigger than needed. Just helped me with this:

_imageViewBackground = [[UIImageView alloc] initWithFrame:rectImageView];
_imageViewBackground.image = [UIImage imageNamed:@"gradientBackgroundPlain"];
[self addSubview:_imageViewBackground];
[self insertSubview:_imageViewBackground belowSubview:self.label];
_imageViewBackground.hidden = YES;

Every time I want to display my UIImageView I just set the var hidden to YES or NO. There might be other solutions but I got confused so many times with this stuff and this solved it and I didn't need to deal with internal stuff UIButton is doing in background.

Don't worry so much framing the button from code, you can do that on the storyboard. This worked for me, one line...more simple.

[self.button setBackgroundImage:[UIImage imageNamed: @"yourPic.png"] forState:UIControlStateNormal];

-(void)buttonTouched:(id)sender
{
    UIButton *btn = (UIButton *)sender;

    if( [[btn imageForState:UIControlStateNormal] isEqual:[UIImage imageNamed:@"icon-Locked.png"]])
    {
        [btn setImage:[UIImage imageNamed:@"icon-Unlocked.png"] forState:UIControlStateNormal];
        // other statements....
    }
    else
    {
        [btn setImage:[UIImage imageNamed:@"icon-Locked.png"] forState:UIControlStateNormal];
        // other statements....
    }
}

Swift 3 version (butt_img must be an Image Set into Assets.xcassets or Images.xcassets folder in Xcode):

btnTwo.setBackgroundImage(UIImage(named: "butt_img"), for: .normal)
btnTwo.setTitle("My title", for: .normal)

Anyway, if you want the image to be scaled to fill the button's size, you may add a UIImageView over it and assign it your image:

let img = UIImageView()
img.frame = btnTwo.frame
img.contentMode = .scaleAspectFill
img.clipsToBounds = true
img.image = UIImage(named: "butt_img")
btnTwo.addSubview(img)

For swift 5+

let image = UIImage(named: "icons-multiply")?.withRenderingMode(.alwaysTemplate)
btn.setImage(image, for: .normal)