image for nav bar button item swift

问题:

I want to display an image in the left hand side of my nav bar in swift.

I have tried adding a nav bar button item and setting an image there.

The problem is that I have to use a really small image for it to fit in the nav bar nicely. But making such a small image leads to pixelation especially on the bigger phone iPhone 6 and 6 Plus.

Is there a way to use a good quality image and then set the frame to fit within the bounds of the nav bar?

My attempt:

var image = UIImage(named: "Harp.png")

image = image?.imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)

self.navigationItem.leftBarButtonItem = UIBarButtonItem(image: image, style: UIBarButtonItemStyle.Plain, target: nil, action: nil)
self.navigationItem.leftBarButtonItem.frame = CGRectMake(0, 0, 53, 31)
//image.frame = CGRectMake(0, 0, 53, 31)

I tried putting the frame on the image first and then on the bar button item. But this is throwing up an error:

Type of expression is ambiguous without more context.

回答1:

Try This

let button = UIButton(type: UIButtonType.Custom)
button.setImage(UIImage(named: "yourImageName.png"), forState: UIControlState.Normal)
button.addTarget(self, action:Selector("callMethod"), forControlEvents: UIControlEvents.TouchDragInside)
button.frame=CGRectMake(0, 0, 30, 30)
let barButton = UIBarButtonItem(customView: button)
self.navigationItem.leftBarButtonItems = [newBackButton,barButton]

For Swift 3

let button = UIButton.init(type: .custom)
button.setImage(UIImage.init(named: "yourImageName.png"), for: UIControlState.normal)
button.addTarget(self, action:#selector(ViewController.callMethod), for:.touchUpInside)
button.frame = CGRect.init(x: 0, y: 0, width: 30, height: 30) //CGRectMake(0, 0, 30, 30)
let barButton = UIBarButtonItem.init(customView: button)
            self.navigationItem.leftBarButtonItem = barButton

Here is action

func callMethod() {
//do stuff here
}

回答2:

Use this code:

self.navigationItem.leftBarButtonItem = nil

let button = UIButton(type: .custom)
button.setImage(UIImage (named: "ChatTab"), for: .normal)
button.frame = CGRect(x: 0.0, y: 0.0, width: 35.0, height: 35.0)
//button.addTarget(target, action: nil, for: .touchUpInside)
let barButtonItem = UIBarButtonItem(customView: button)

let button2 = UIButton(type: .custom)
button2.setImage(UIImage (named: "ActivityTab"), for: .normal)
button2.frame = CGRect(x: 0.0, y: 0.0, width: 35.0, height: 35.0)
//button.addTarget(target, action: nil, for: .touchUpInside)

let barButtonItem2 = UIBarButtonItem(customView: button2)
self.navigationItem.rightBarButtonItems = [barButtonItem, barButtonItem2]

Output:

回答3:

There is a way to use images of different sizes, depending on the device. It's called an Asset Catalog. You'll probably already have one in your project, or if not, you can add one with File > New > File > Resource > Asset Catalogue.

Within your Asset Catalog, you can have multiple 'Image Sets' (these will be shown down the left-hand side). Add a new Image Set with the '+' at the bottom. For each Image Set, you can supply different images (e.g. of different sizes) for each of @1x, @2x, and @3x.

Then, to use one of these images in code, you simply use UIImage(named: "name_of_image_set") - note no extension. The correct image will be loaded, depending on the device.

Hope this helps!