在UIButton中使用UIBarButtonItem图标

Question

UIBarButtonItem有多个可用图标。是否可以使用将其标识符设置为“垃圾箱”后出现的图标：

带有UIButton？没有像设置identifier或style那样的直接方法。

Answer 1

从网络上的某处下载图像，将其添加到您的项目中，然后将UIButton的图像设置为刚刚下载的图像。

我没有找到与Apple正在使用的相同，但我发现了this one。只需在Pixelmator或Photoshop中更改其颜色即可。

Answer 2

新 iOS 13现在支持SF SymbolsUIImage(systemName: "trash")

---

对于Swift 4.2 （在主线程上调用它）

extension UIBarButtonItem.SystemItem {
    func image() -> UIImage? {
        let tempItem = UIBarButtonItem(barButtonSystemItem: self,
                                       target: nil,
                                       action: nil)

        // add to toolbar and render it
        let bar = UIToolbar()
        bar.setItems([tempItem],
                     animated: false)
        bar.snapshotView(afterScreenUpdates: true)

        // got image from real uibutton
        let itemView = tempItem.value(forKey: "view") as! UIView
        for view in itemView.subviews {
            if let button = view as? UIButton,
                let image = button.imageView?.image {
                return image.withRenderingMode(.alwaysTemplate)
            }
        }

        return nil
    }
}

UIBarButtonSystemItem.play.image()

对于Objective-C：

+ (UIImage *)imageFromSystemBarButton:(UIBarButtonSystemItem)systemItem {
    UIBarButtonItem* tempItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:systemItem target:nil action:nil];

    // Add to toolbar and render it
    UIToolbar *bar = [[UIToolbar alloc] init];
    [bar setItems:@[tempItem] animated:NO];
    [bar snapshotViewAfterScreenUpdates:YES];

    // Get image from real UIButton
    UIView *itemView = [(id)tempItem view];
    for (UIView* view in itemView.subviews) {
        if ([view isKindOfClass:[UIButton class]]) {
            return [(UIButton*)view imageForState:UIControlStateNormal];
        }
    }

    return nil;
}

Answer 3

这里是与ANY一起使用的解决方案，它支持tintColor：

- (void)viewDidLoad {
    [super viewDidLoad];

    [self.button setImage:[self imageFromSystemBarButton:UIBarButtonSystemItemTrash]
                 forState:UIControlStateNormal];

    self.button.tintColor = [UIColor redColor];
}

- (UIImage *)imageFromSystemBarButton:(UIBarButtonSystemItem)systemItem {
    // Holding onto the oldItem (if any) to set it back later
    // could use left or right, doesn't matter
    UIBarButtonItem *oldItem = self.navigationItem.rightBarButtonItem;

    UIBarButtonItem *tempItem = [[UIBarButtonItem alloc]
                                 initWithBarButtonSystemItem:systemItem
                                 target:nil
                                 action:nil];

    // Setting as our right bar button item so we can traverse its subviews
    self.navigationItem.rightBarButtonItem = tempItem;

    // Don't know whether this is considered as PRIVATE API or not
    UIView *itemView = (UIView *)[self.navigationItem.rightBarButtonItem performSelector:@selector(view)];

    UIImage *image = nil;
    // Traversing the subviews to find the ImageView and getting its image
    for (UIView *subView in itemView.subviews) {
        if ([subView isKindOfClass:[UIImageView class]]) {
            image = ((UIImageView *)subView).image;
            break;
        }
    }

    // Setting our oldItem back since we have the image now
    self.navigationItem.rightBarButtonItem = oldItem;

    return image;
}

P.S。如果您知道更好的方法，请随时进行改进，谢谢。

Answer 4

基于@yycking的答案，我写了一个合适的Swift 4扩展名：

//  UIImage+FromSystemItem.swift

import UIKit

extension UIImage {

    public convenience init?(systemItem sysItem: UIBarButtonItem.SystemItem, renderingMode:UIImage.RenderingMode = .automatic) {
        guard let sysImage = UIImage.imageFromSystemItem(sysItem, renderingMode: renderingMode)?.cgImage else {
            return nil
        }

        self.init(cgImage: sysImage)
    }

    private class func imageFromSystemItem(_ systemItem: UIBarButtonItem.SystemItem, renderingMode:UIImage.RenderingMode = .automatic) -> UIImage? {

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

        // add to toolbar and render it
        let bar = UIToolbar()
        bar.setItems([tempItem], animated: false)
        bar.snapshotView(afterScreenUpdates: true)

        // got image from real uibutton
        let itemView = tempItem.value(forKey: "view") as! UIView

        for view in itemView.subviews {
            if view is UIButton {
                let button = view as! UIButton
                let image = button.imageView!.image!
                image.withRenderingMode(renderingMode)
                return image
            }
        }

        return nil
    }
}

带操作按钮的示例（默认颜色）：

let actionImage = UIImage(systemItem: .action)
let myButton = UIButton(frame: CGRect(x: 0, y: 0, width: 30, height: 30))
myButton.setImage(actionImage, for: .normal)

view.addSubview(myButton)

[如果您希望始终将图像当作模板，上下文，将renderingMode设置为。alwaysTemplate

 let actionImage = UIImage(systemItem: .action, renderingMode: .alwaysTemplate) 

Answer 5

所有iOS系统图标都可以使用一个名为（非常合适）iOS Artwork Extractor的便捷小应用程序进行提取。当我想模仿iOS系统行为时，会一直使用它。

在以下位置下载Xcode项目：>>

https://github.com/0xced/iOS-Artwork-Extractor

Answer 6

正如@Islam Q的答案的注释中已经提到的，如果当前未在屏幕上呈现UINavigationItem

Answer 7

在Swift 4.2中使用Quartz2D

Answer 8

我在表单元格中将它用于imageView，所以无论我在何处设置颜色，着色都无法正常工作。所以我最终得到了这段代码，在其中为图像设置了颜色。

Answer 9

基于@yycking answer，这是Xamarin.iOS C＃端口：