如何使用 Swift 中的 XIB 文件初始化/实例化自定义 UIView class

Question

I have a class called MyClass which is a subclass of UIView , that I want to initialize with a XIB file. I am not sure how to initialize this class with the xib file called View.xib

class MyClass: UIView {

    // what should I do here? 
    //init(coder aDecoder: NSCoder) {} ?? 
}

Answer 1

I tested this code and it works great:

class MyClass: UIView {        
    class func instanceFromNib() -> UIView {
        return UINib(nibName: "nib file name", bundle: nil).instantiateWithOwner(nil, options: nil)[0] as UIView
    }    
}

Initialise the view and use it like below:

var view = MyClass.instanceFromNib()
self.view.addSubview(view)

OR

var view = MyClass.instanceFromNib
self.view.addSubview(view())

UPDATE Swift >=3.x & Swift >=4.x

class func instanceFromNib() -> UIView {
    return UINib(nibName: "nib file name", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! UIView
}

Answer 2

Sam's solution is already great, despite it doesn't take different bundles into account (NSBundle:forClass comes to the rescue) and requires manual loading, aka typing code.

If you want full support for your Xib Outlets, different Bundles (use in frameworks!) and get a nice preview in Storyboard try this:

// NibLoadingView.swift
import UIKit

/* Usage: 
- Subclass your UIView from NibLoadView to automatically load an Xib with the same name as your class
- Set the class name to File's Owner in the Xib file
*/

@IBDesignable
class NibLoadingView: UIView {

    @IBOutlet weak var view: UIView!

    override init(frame: CGRect) {
        super.init(frame: frame)
        nibSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        nibSetup()
    }

    private func nibSetup() {
        backgroundColor = .clearColor()

        view = loadViewFromNib()
        view.frame = bounds
        view.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
        view.translatesAutoresizingMaskIntoConstraints = true

        addSubview(view)
    }

    private func loadViewFromNib() -> UIView {
        let bundle = NSBundle(forClass: self.dynamicType)
        let nib = UINib(nibName: String(self.dynamicType), bundle: bundle)
        let nibView = nib.instantiateWithOwner(self, options: nil).first as! UIView

        return nibView
    }

}

Use your xib as usual, ie connect Outlets to File Owner and set File Owner class to your own class.

Usage: Just subclass your own View class from NibLoadingView & Set the class name to File's Owner in the Xib file

No additional code required anymore.

Credits where credit's due: Forked this with minor changes from DenHeadless on GH. My Gist: https://gist.github.com/winkelsdorf/16c481f274134718946328b6e2c9a4d8

Answer 3

As of Swift 2.0, you can add a protocol extension. In my opinion, this is a better approach because the return type is Self rather than UIView , so the caller doesn't need to cast to the view class.

import UIKit

protocol UIViewLoading {}
extension UIView : UIViewLoading {}

extension UIViewLoading where Self : UIView {

  // note that this method returns an instance of type `Self`, rather than UIView
  static func loadFromNib() -> Self {
    let nibName = "\(self)".characters.split{$0 == "."}.map(String.init).last!
    let nib = UINib(nibName: nibName, bundle: nil)
    return nib.instantiateWithOwner(self, options: nil).first as! Self
  }

}

Answer 4

And this is the answer of Frederik on Swift 3.0

/*
 Usage:
 - make your CustomeView class and inherit from this one
 - in your Xib file make the file owner is your CustomeView class
 - *Important* the root view in your Xib file must be of type UIView
 - link all outlets to the file owner
 */
@IBDesignable
class NibLoadingView: UIView {

    @IBOutlet weak var view: UIView!

    override init(frame: CGRect) {
        super.init(frame: frame)
        nibSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        nibSetup()
    }

    private func nibSetup() {
        backgroundColor = .clear

        view = loadViewFromNib()
        view.frame = bounds
        view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.translatesAutoresizingMaskIntoConstraints = true

        addSubview(view)
    }

    private func loadViewFromNib() -> UIView {
        let bundle = Bundle(for: type(of: self))
        let nib = UINib(nibName: String(describing: type(of: self)), bundle: bundle)
        let nibView = nib.instantiate(withOwner: self, options: nil).first as! UIView

        return nibView
    }
}

Answer 5

Universal way of loading view from xib:

Example:

let myView = Bundle.loadView(fromNib: "MyView", withType: MyView.self)

Implementation:

extension Bundle {

    static func loadView<T>(fromNib name: String, withType type: T.Type) -> T {
        if let view = Bundle.main.loadNibNamed(name, owner: nil, options: nil)?.first as? T {
            return view
        }

        fatalError("Could not load view with type " + String(describing: type))
    }
}

Answer 6

Swift 3 Answer: In my case, I wanted to have an outlet in my custom class that I could modify:

class MyClassView: UIView {
    @IBOutlet weak var myLabel: UILabel!

    class func createMyClassView() -> MyClass {
        let myClassNib = UINib(nibName: "MyClass", bundle: nil)
        return myClassNib.instantiate(withOwner: nil, options: nil)[0] as! MyClassView
    }
}

When in the .xib, make sure that the Custom Class field is MyClassView. Don't bother with the File's Owner.

Also, make sure that you connect the outlet in MyClassView to the label:

To instantiate it:

let myClassView = MyClassView.createMyClassView()
myClassView.myLabel.text = "Hello World!"

Answer 7

Swift 4

Here in my case I have to pass data into that custom view, so I create static function to instantiate the view.

1. Create UIView extension

   extension UIView { class func initFromNib<T: UIView>() -> T { return Bundle.main.loadNibNamed(String(describing: self), owner: nil, options: nil)?[0] as! T } }

2. Create MyCustomView

   class MyCustomView: UIView { @IBOutlet weak var messageLabel: UILabel! static func instantiate(message: String) -> MyCustomView { let view: MyCustomView = initFromNib() view.messageLabel.text = message return view } }

3. Set custom class to MyCustomView in .xib file. Connect outlet if necessary as usual.

4. Instantiate view

   let view = MyCustomView.instantiate(message: "Hello World.")

Answer 8

Below code will do the job if anyone wants to load a custom View with XIB Programmatically.

let customView = UINib(nibName:"CustomView",bundle:.main).instantiate(withOwner: nil, options: nil).first as! UIView
customView.frame = self.view.bounds
self.view.addSubview(customView)

Answer 9

Swift 5.2

Create a class named NibLoadingView with the following contents:

import Foundation
import UIKit

/* Usage:
- Subclass your UIView from NibLoadView to automatically load an Xib with the same name as your class
- Set the class name to File's Owner in the Xib file
*/

@IBDesignable
class NibLoadingView: UIView {

    @IBOutlet weak var view: UIView!

    override init(frame: CGRect) {
        super.init(frame: frame)
        
        nibSetup()
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        nibSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        
        nibSetup()
    }

    private func nibSetup() {
        view = loadViewFromNib()
        view.frame = bounds
        view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.translatesAutoresizingMaskIntoConstraints = true

        addSubview(view)
    }

    private func loadViewFromNib() -> UIView {
        let bundle = Bundle(for: type(of: self))
        let nib = UINib(nibName: type(of: self).description().replacingOccurrences(of: "REPLACEME.", with: ""), bundle: bundle)
        let nibView = nib.instantiate(withOwner: self, options: nil).first as! UIView

        return nibView
    }
}

Find REPLACEME in the above code and replace it with your project's name.

Now create a XIB & UIView class pair, set XIB's owner to UIView class and subclass NibLoadingView .

You can now init the class just like ExampleView() , ExampleView(frame: CGRect) , etc.

^{Based on Frederik's answer}

Answer 10

create view from.xib

let nib = UINib(nibName: "View1", bundle: nil) //View1 is a file name(View1.swift)
if let view = nib.instantiate(withOwner: self, options: nil).first as? UIView {
  // logic
}

//or

if let view = Bundle.main.loadNibNamed("View1", owner: self, options: nil)?.first as? UIView {
  // logic
}

Since.xib can contains several view, that is why you are working with array here( .first )

For example

1. Create View1.xib
2. Create View1.swift where set owner in code to create the instance of class(View1)
3. Set File's Owner in View1.xib as View1 . Allows to connect outlets and actions

import UIKit

class View1: UIView {
    @IBOutlet var contentView: UIView!
    
    override init(frame: CGRect) {
            super.init(frame: frame)
            self.commonInit()
        }

        required init?(coder: NSCoder) {
            super.init(coder: coder)
            self.commonInit()
        }
        
        private func commonInit() {
            if let view = Bundle.main.loadNibNamed("View1", owner: self, options: nil)?.first as? UIView {
                addSubview(view)
                view.frame = self.bounds
            }
        }
}

Notes if we move Custom Class from File's owner to Container View we get error(loop). It is because of:

System init instance from Container View where we init it again in commonInit()

.loadNibNamed

Thread 1: EXC_BAD_ACCESS (code=2, address=0x7ff7bf6fbfc8)

Answer 11

override func draw(_ rect: CGRect) 
{
    AlertView.layer.cornerRadius = 4
    AlertView.clipsToBounds = true

    btnOk.layer.cornerRadius = 4
    btnOk.clipsToBounds = true   
}

class func instanceFromNib() -> LAAlertView {
    return UINib(nibName: "LAAlertView", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! LAAlertView
}

@IBAction func okBtnDidClicked(_ sender: Any) {

    removeAlertViewFromWindow()

    UIView.animate(withDuration: 0.4, delay: 0.0, options: .allowAnimatedContent, animations: {() -> Void in
        self.AlertView.transform = CGAffineTransform(scaleX: 0.1, y: 0.1)

    }, completion: {(finished: Bool) -> Void in
        self.AlertView.transform = CGAffineTransform.identity
        self.AlertView.transform = CGAffineTransform(scaleX: 0.0, y: 0.0)
        self.AlertView.isHidden = true
        self.AlertView.alpha = 0.0

        self.alpha = 0.5
    })
}


func removeAlertViewFromWindow()
{
    for subview  in (appDel.window?.subviews)! {
        if subview.tag == 500500{
            subview.removeFromSuperview()
        }
    }
}


public func openAlertView(title:String , string : String ){

    lblTital.text  = title
    txtView.text  = string

    self.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
    appDel.window!.addSubview(self)


    AlertView.alpha = 1.0
    AlertView.isHidden = false

    UIView.animate(withDuration: 0.2, animations: {() -> Void in
        self.alpha = 1.0
    })
    AlertView.transform = CGAffineTransform(scaleX: 0.0, y: 0.0)

    UIView.animate(withDuration: 0.3, delay: 0.2, options: .allowAnimatedContent, animations: {() -> Void in
        self.AlertView.transform = CGAffineTransform(scaleX: 1.1, y: 1.1)

    }, completion: {(finished: Bool) -> Void in
        UIView.animate(withDuration: 0.2, animations: {() -> Void in
            self.AlertView.transform = CGAffineTransform(scaleX: 1.0, y: 1.0)

        })
    })


}