swift 5+

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

objective - c

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

斯威夫特5.1

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

Mike的解决方案将只显示图像，但在按钮上设置的任何标题都将不可见，因为您可以设置标题或图像。

如果你想同时设置(你的图片和标题)，请使用以下代码:

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

如果是Swift用户

// 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) 

你可以把图像放在两种方式中的任何一种:

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];

Swift 3版本(butt_img必须是Image Set into Assets。xcassets或图像。xcassets文件夹在Xcode):

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

无论如何，如果你想让图像缩放到按钮的大小，你可以在它上面添加一个UIImageView，并给它分配你的图像:

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