问题
UIBarButtonItem has multiple icons available. Is it possible to use the icon which appears after setting its identifier to 'trash':
with an UIButton? There is no straighforward method to do that like setting the identifier or style.
回答1:
Download the image from somewhere on the web, add it to your project and set the UIButton's image to the image you just downloaded.
I did not find the same as Apple is using but I found this one. Simply change it's color in Pixelmator or Photoshop.
回答2:
for swift 4.2 (call it on main thread)
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()
For 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;
}
回答3:
Here's a solution that works with ANY System bar button item + it supports 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. Feel free to improve if you know of a better way, thanks.
回答4:
Based on @yycking answer, i wrote an suitable Swift 4 extension:
// 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
}
}
Example with action button (default coloring):
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)
If you want your image to always be treated as a template regardless of context, set renderingMode to .alwaysTemplate
let actionImage = UIImage(systemItem: .action, renderingMode: .alwaysTemplate)
回答5:
All the iOS system icons can be extracted using a handy little app called (fittingly enough) iOS Artwork Extractor. I use it all the time when I want to mimic iOS system behaviors.
Download the Xcode project at:
https://github.com/0xced/iOS-Artwork-Extractor
回答6:
As already mentioned in the comments to @Islam Q's answer, the there presented solution might fail, if the UINavigationItem isn't currently rendered onscreen. It fails, for example, if the view controller isn't currently loaded. In fact the problem seems to be the missing layout of the UINavigationBar in these cases.
A more 'bulletproof' version would be to use a specially created UINavigationBar object just for getting the system item images. This would also make save saving and restoring of any existing UIBarButtonItems obsolete.
I've packed this into a small helper class:
LEABarButtonSystemItemImage.h:
#import <UIKit/UIKit.h>
/**
LEABarButtonSystemItemImage interface
*/
@interface LEABarButtonSystemItemImage : NSObject
+ (UIImage *)imageFromBarButtonSystemItem:(UIBarButtonSystemItem)pBarButtonSystemItem;
+ (UIImage *)customImageForBarButtonSystemItem:(UIBarButtonSystemItem)pBarButtonSystemItem;
+ (NSDictionary<__kindof NSNumber*, __kindof UIImage*> *)barButtonItemImages;
@end
LEABarButtonSystemItemImage.m
#import "LEABarButtonSystemItemImage.h"
/**
LEABarButtonSystemItemImage implementation
*/
@implementation LEABarButtonSystemItemImage
/*
imageFromBarButtonSystemItem:
*/
+ (UIImage *)imageFromBarButtonSystemItem:(UIBarButtonSystemItem)pBarButtonSystemItem {
static const CGFloat defaultNBBtnHW = 44.0;
UINavigationBar * tempNavigationBar = [[UINavigationBar alloc] initWithFrame:CGRectMake(0, 0, defaultNBBtnHW, defaultNBBtnHW)];
UINavigationItem * tempNavigationItem = [[UINavigationItem alloc] init];
UIBarButtonItem * tempBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:pBarButtonSystemItem target:nil action:NULL];
tempNavigationBar.items = @[tempNavigationItem];
tempNavigationItem.rightBarButtonItems = @[tempBarButtonItem];
UIImage * barButtonSystemItemImage = nil;
@try {
UIView * barButtonItemView = [tempBarButtonItem valueForKey:@"view"];
for (UIView* subview in barButtonItemView.subviews) {
if ([subview isKindOfClass:UIImageView.class]) {
barButtonSystemItemImage = ((UIImageView *)subview).image;
break;
}
}
} @catch (...) { NSLog(@"%s: Exception while retrieving image from UIBarButtonItem!", __PRETTY_FUNCTION__); }
return (barButtonSystemItemImage ?: [LEABarButtonSystemItemImage customImageForBarButtonSystemItem:pBarButtonSystemItem]);
}
/*
customImageForBarButtonSystemItem:
*/
+ (UIImage *)customImageForBarButtonSystemItem:(UIBarButtonSystemItem)pBarButtonSystemItem {
NSString * customBarButtonSystemItemImageName = nil;
switch (pBarButtonSystemItem) {
case UIBarButtonSystemItemDone: customBarButtonSystemItemImageName = @"customBarButtonSystemItemDone"; break;
case UIBarButtonSystemItemCancel: customBarButtonSystemItemImageName = @"customBarButtonSystemItemCancel"; break;
case UIBarButtonSystemItemEdit: customBarButtonSystemItemImageName = @"customBarButtonSystemItemEdit"; break;
case UIBarButtonSystemItemSave: customBarButtonSystemItemImageName = @"customBarButtonSystemItemSave"; break;
case UIBarButtonSystemItemAdd: customBarButtonSystemItemImageName = @"customBarButtonSystemItemAdd"; break;
case UIBarButtonSystemItemCompose: customBarButtonSystemItemImageName = @"customBarButtonSystemItemCompose"; break;
case UIBarButtonSystemItemReply: customBarButtonSystemItemImageName = @"customBarButtonSystemItemReply"; break;
case UIBarButtonSystemItemAction: customBarButtonSystemItemImageName = @"customBarButtonSystemItemAction"; break;
case UIBarButtonSystemItemOrganize: customBarButtonSystemItemImageName = @"customBarButtonSystemItemOrganize"; break;
case UIBarButtonSystemItemBookmarks: customBarButtonSystemItemImageName = @"customBarButtonSystemItemBookmarks"; break;
case UIBarButtonSystemItemSearch: customBarButtonSystemItemImageName = @"customBarButtonSystemItemSearch"; break;
case UIBarButtonSystemItemRefresh: customBarButtonSystemItemImageName = @"customBarButtonSystemItemRefresh"; break;
case UIBarButtonSystemItemStop: customBarButtonSystemItemImageName = @"customBarButtonSystemItemStop"; break;
case UIBarButtonSystemItemCamera: customBarButtonSystemItemImageName = @"customBarButtonSystemItemCamera"; break;
case UIBarButtonSystemItemTrash: customBarButtonSystemItemImageName = @"customBarButtonSystemItemTrash"; break;
case UIBarButtonSystemItemPlay: customBarButtonSystemItemImageName = @"customBarButtonSystemItemPlay"; break;
case UIBarButtonSystemItemPause: customBarButtonSystemItemImageName = @"customBarButtonSystemItemPause"; break;
case UIBarButtonSystemItemRewind: customBarButtonSystemItemImageName = @"customBarButtonSystemItemRewind"; break;
case UIBarButtonSystemItemFastForward: customBarButtonSystemItemImageName = @"customBarButtonSystemItemFastForward"; break;
case UIBarButtonSystemItemUndo: customBarButtonSystemItemImageName = @"customBarButtonSystemItemUndo"; break;
case UIBarButtonSystemItemRedo: customBarButtonSystemItemImageName = @"customBarButtonSystemItemRedo"; break;
case UIBarButtonSystemItemPageCurl: customBarButtonSystemItemImageName = @"customBarButtonSystemItemPageCurl"; break;
default: break;
}
return (customBarButtonSystemItemImageName
? [UIImage imageNamed:customBarButtonSystemItemImageName]
: nil);
}
/*
barButtonItemImages
*/
+ (NSDictionary<__kindof NSNumber*, __kindof UIImage*> *)barButtonItemImages {
NSMutableDictionary<__kindof NSNumber*, __kindof UIImage*> * barButtonItemImages = [NSMutableDictionary dictionary];
// From: https://github.com/nst/iOS-Runtime-Headers/blob/master/Frameworks/UIKit.framework/UIBarButtonItem.h
// unsigned int systemItem : 7;
for (NSUInteger uIndex = 0; uIndex < (1<<7); ++uIndex) {
UIImage* systemImage = [LEABarButtonSystemItemImage imageFromBarButtonSystemItem:uIndex];
if (systemImage) {
[barButtonItemImages setObject:systemImage forKey:@(uIndex)];
}
}
NSLog(@"%s: %@", __PRETTY_FUNCTION__, barButtonItemImages);
return barButtonItemImages;
}
@end
As an add on/fallback , the method returns an custom image, if no system item image could be retrieved. Of course these custom images must be present in the apps bundle.
The last method 'barButtonImages' was implemented just for curiosity... in the UIBarButtonItem header the member systemItem is declared to use 7 bits (0..127). Currently only 22 values are documented from UIBarButtonSystemItemDone to UIBarButtonItemSystemItemPageCurl... and in fact; I found some undocumented images starting with indexes above 100 (tested on iOS 9.3 in the 6S+ simulator) :-)
回答7:
I was using it for imageView in table cell and somehow tint color did not work wherever I set it... So I ended up with this code where you set color for image.
+ (UIImage *)imageFromSystemBarButton:(UIBarButtonSystemItem)systemItem :(UIColor *) color {
UIToolbar *bar = UIToolbar.new;
UIBarButtonItem *buttonItem = [UIBarButtonItem createWithItem:systemItem];
[bar setItems:@[buttonItem] animated:NO];
[bar snapshotViewAfterScreenUpdates:YES];
for (UIView *view in [(id) buttonItem view].subviews)
if ([view isKindOfClass:UIButton.class]) {
UIImage *image = [((UIButton *) view).imageView.image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[color set];
[image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
return nil;
}
回答8:
Using Quartz2D with Swift 4.2
The solutions based in an extension to extract the image from the UIBarButtonSystemItem don't work in iOS 11/12, so I decided to add a custom class to draw the icons without adding any .png
This is implemented for .trash and .action that are the icons I need in my project. Feel free to add the rest.
Use it as follows (You need to conform to the SystemIConDelegate protocol, set the Delegate property and add the required method):
let trashIcon = SystemIcon(withType: .trash)
trashIcon.delegate = self
shareButton = UIButton()
shareButton.addSubview(trashIcon)
The SystemIcon class is here. It is optimized for 30 X 30 points:
import UIKit
protocol SystemIconDelegate {
func systemIconButtonClicked()
}
class SystemIcon: UIView {
var type: UIBarButtonItem.SystemItem!
let color = UIColor.blue
var delegate: SystemIconDelegate?
convenience init(withType: UIBarButtonItem.SystemItem) {
self.init(frame: CGRect(x: 0, y: 0, width: 30, height: 30))
self.backgroundColor = .clear
self.type = withType
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
self.delegate?.systemIconButtonClicked()
}
override func draw(_ rect: CGRect) {
let w = self.frame.width
let h = self.frame.height
let context = UIGraphicsGetCurrentContext()
context?.setStrokeColor(color.cgColor)
context?.setLineWidth(1.0)
switch type! {
case .action:
//Box
context?.stroke(CGRect(x: w * 0.16, y: h * 0.3, width: w * 0.69, height: h * 0.69))
context?.setFillColor(UIColor.white.cgColor)
context?.fill(CGRect(x: w * 0.4, y: 0, width: w * 0.2, height: h * 0.5))
//Arrow
context?.move(to: CGPoint(x: w * 0.5, y: h * 0.02))
context?.addLine(to: CGPoint(x: w * 0.5, y: h * 0.64))
context?.move(to: CGPoint(x: w * 0.33, y: h * 0.19))
context?.addLine(to: CGPoint(x: w * 0.5, y: h * 0.02))
context?.addLine(to: CGPoint(x: w * 0.67, y: h * 0.19))
context?.strokePath()
case .trash:
context?.move(to: CGPoint(x: w * 0.1, y: h * 0.15))
context?.addLine(to: CGPoint(x: w * 0.9, y: h * 0.15))
//Can
context?.move(to: CGPoint(x: w * 0.2, y: h * 0.15))
context?.addArc(tangent1End: CGPoint(x: w * 0.25, y: h * 0.95), tangent2End: CGPoint(x: w * 0.5, y:h * 0.95), radius: CGFloat.x(2.0))
context?.addArc(tangent1End: CGPoint(x: w * 0.75, y: h * 0.95), tangent2End: CGPoint(x: w * 0.8, y: h * 0.15), radius: CGFloat.x(2.0))
context?.addLine(to: CGPoint(x: w * 0.8, y: h * 0.15))
// Handle
context?.move(to: CGPoint(x: w * 0.34, y: h * 0.15))
context?.addArc(tangent1End: CGPoint(x: w * 0.34, y: h * 0.02), tangent2End: CGPoint(x: w * 0.5, y: h * 0.02), radius: CGFloat.x(2.0))
context?.addArc(tangent1End: CGPoint(x: w * 0.66, y : h * 0.02), tangent2End: CGPoint(x: w * 0.66, y: h * 0.15), radius: CGFloat.x(2.0))
context?.addLine(to: CGPoint(x: w * 0.66, y: h * 0.15))
//Lines
context?.move(to: CGPoint(x: w * 0.35, y: h * 0.25))
context?.addLine(to: CGPoint(x: w * 0.38, y: h * 0.8))
context?.move(to: CGPoint(x: w * 0.5, y: h * 0.25))
context?.addLine(to: CGPoint(x: w * 0.5, y: h * 0.8))
context?.move(to: CGPoint(x: w * 0.65, y: h * 0.25))
context?.addLine(to: CGPoint(x: w * 0.62, y: h*0.8))
default:
break
}
context?.strokePath()
}
}
回答9:
Based on @yycking answer, here is the Xamarin.iOS C# port:
[DllImport (Constants.ObjectiveCLibrary, EntryPoint = "objc_msgSend")]
static extern IntPtr IntPtr_objc_msgSend (IntPtr receiver, IntPtr selector);
public static UIImage GetImage (UIBarButtonSystemItem systemItem)
{
var tempItem = new UIBarButtonItem (systemItem);
// Add to toolbar and render it
var bar = new UIToolbar ();
bar.SetItems (new [] { tempItem }, false);
bar.SnapshotView (true);
// Get image from real UIButton
var selHandle = Selector.GetHandle ("view");
var itemView = Runtime.GetNSObject<UIView> (IntPtr_objc_msgSend (tempItem.Handle, selHandle));
foreach (var view in itemView?.Subviews) {
if (view is UIButton button)
return button.ImageForState (UIControlState.Normal);
}
return null;
}
来源：https://stackoverflow.com/questions/21187885/use-uibarbuttonitem-icon-in-uibutton