如何以编程方式为 UIButton 添加系统图标？

Question

It's easy to add a custom image or a background for a UIButton , but there seems to be no programmatic way to set one of the following default iOS icons for a UIButton , I know it can be applied to navigation bar buttons, I don't need that, I want to apply it to a simple UIButton , any hints?

Answer 1

For Swift 5 the syntax is:

button.setImage(UIImage(systemName: "search"), for: .normal)

You can also set the weight of the icon by adding SymbolConfiguration :

let boldConfig = UIImage.SymbolConfiguration(weight: .bold)
let boldSearch = UIImage(systemName: "search", withConfiguration: boldConfig)

button.setImage(boldSearch, for: .normal)

See: Apple documentation for available names (API column) or go to Interface Builder, select UIButton and in the Attributes Inspector select Image which will give you list of all available icons.

Answer 2

import UIKit

extension UIImage {

    public convenience init?(_ systemItem: UIBarButtonItem.SystemItem) {

        guard let sysImage = UIImage.imageFrom(systemItem: systemItem)?.cgImage else {
            return nil
        }

        self.init(cgImage: sysImage)
    }

    private class func imageFrom(systemItem: UIBarButtonItem.SystemItem) -> UIImage? {

        let sysBarButtonItem = UIBarButtonItem(barButtonSystemItem: systemItem, target: nil, action: nil)

        //MARK:- Adding barButton into tool bar and rendering it.
        let toolBar = UIToolbar()
        toolBar.setItems([sysBarButtonItem], animated: false)
        toolBar.snapshotView(afterScreenUpdates: true)

        if  let buttonView = sysBarButtonItem.value(forKey: "view") as? UIView{
            for subView in buttonView.subviews {
                if subView is UIButton {
                    let button = subView as! UIButton
                    let image = button.imageView!.image!
                    return image
                }
            }
        }
        return nil
    }
}

This is an example of how do we use it:

 let button = UIButton() ;
 let systemImage = UIImage(systemItem: .trash) ;
 button.setImage(systemImage, for: .normal)

Answer 3

I found 2521 system icons, as numerated values.

@available(iOS 13.0, *)
@objc public extension UIImage{

    var assetName: String? {
        guard let imageAsset = imageAsset else { return nil }
        return imageAsset.value(forKey:"assetName") as? String
    }

    static var square_and_arrow_up: UIImage? {
        return UIImage(systemName: "square.and.arrow.up")
    }
    static var square_and_arrow_up_fill: UIImage? {
        return UIImage(systemName: "square.and.arrow.up.fill")
    }
    static var square_and_arrow_down: UIImage? {
        return UIImage(systemName: "square.and.arrow.down")
    }
    ...

screenshot: github: link

Answer 4

现在你可以做

button.setImage(UIImage(.search), for: .normal)

Answer 5

来自 Apple 的文档： init(type:)