OS X开发.第一章,1.10, NSComboBox

1.10 NSComboBox
NSComboBox是Cocoa中用以提供下拉选择的控件。可提前设置好下拉选择框条目，也可动态进行增删。

1.10.1 基本声明

import Cocoa

class WidgetController: NSViewController, NSComboBoxDelegate {
    
    var mView: NSView!
    var comboBox: NSComboBox!
    
    override func loadView() {
        self.view = NSView(frame: NSRect(x: 0, y: 0, width: 500, height: 300))
    }

    private func initView(){
        mView = NSView(frame: NSRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
        
        comboBox = NSComboBox(frame: NSRect(x: (self.view.frame.width / 2) - 30, y: self.view.frame.height - 50, width: 70, height: 25))
        comboBox.addItem(withObjectValue: "C")
        comboBox.addItem(withObjectValue: "Java")
        comboBox.addItem(withObjectValue: "Swift")
        comboBox.addItem(withObjectValue: "C#")
        comboBox.addItem(withObjectValue: "C  ")
        comboBox.addItem(withObjectValue: "Objective-C")
        comboBox.numberOfVisibleItems = 3
        comboBox.delegate = self
        
        self.view.addSubview(comboBox)
    }
    
    private func initConfig(){
        self.title = "NSWidget-Family"
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do view setup here.
        
        initView()
        initConfig()
    }

    func comboBoxSelectionDidChange(_ notification: Notification) {
        let combo = notification.object as! NSComboBox
        print("DidChange------> SELECT AT:\(combo.indexOfSelectedItem), AND CONTENT: \(combo.stringValue)")
    }
    
    func comboBoxSelectionIsChanging(_ notification: Notification) {
        let combo = notification.object as! NSComboBox
        print("IsChanging------> SELECT AT:\(combo.indexOfSelectedItem), AND CONTENT: \(combo.stringValue)")
    }
}

说明：NSComboBox的功能就是展示下拉数据选项，因此在这里看到了addItem(withObjectValue: ) 这个方法，通过该方法我们可以增加下拉选择条目。当然也可以通过comboBox.removeItem(at: Int) 这个方法根据索引来动态地删除item。其NSViewController实现了NSComboBox实现了NSComboBoxDelegate ，目的是为了进行事件监听，可实现的方法有正在变化、已经变化这两种。numberOfVisibleItems 这个属性是设置当前最多能展示的item数量，超过后则以滚动条形式展示。

1.10.2 数据源展示
NSComboBox也可用数据源形式进行展示。如下：

class WidgetController: NSViewController, NSComboBoxDelegate, NSComboBoxDataSource {
    
    var mView: NSView!

    var comboBox: NSComboBox!
   
    var language: Array<String> = ["C", "Java", "Swift", "Objective-C", "C#"]
    
    override func loadView() {
        self.view = NSView(frame: NSRect(x: 0, y: 0, width: 500, height: 300))
    }

    private func initView2(){
        mView = NSView(frame: NSRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
        
        comboBox = NSComboBox(frame: NSRect(x: (self.view.frame.width / 2) - 30, y: self.view.frame.height - 50, width: 70, height: 25))
        comboBox.numberOfVisibleItems = 3
        comboBox.delegate = self
        comboBox.usesDataSource = true
        comboBox.dataSource = self

        self.view.addSubview(comboBox)
    }
    
    private func initConfig(){
        self.title = "NSWidget-Family"
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do view setup here.
        
        initView2()
        initConfig()
    }
    
    func comboBoxSelectionDidChange(_ notification: Notification) {
        let combo = notification.object as! NSComboBox
        
        print("DidChange------> SELECT AT:\(combo.indexOfSelectedItem), AND CONTENT: \(combo.stringValue)")
    }
    
    func comboBoxSelectionIsChanging(_ notification: Notification) {
        let combo = notification.object as! NSComboBox
        
        print("IsChanging------> SELECT AT:\(combo.indexOfSelectedItem), AND CONTENT: \(combo.stringValue)")
    }
    
    func numberOfItems(in comboBox: NSComboBox) -> Int {
        return language.count
    }
    
    func comboBox(_ comboBox: NSComboBox, objectValueForItemAt index: Int) -> Any? {
        return language[index]
    }
}

说明：继续实现NSComboBoxDataSource 该协议，并设置其usesDataSource 属性为true然后完成相关方法即可。

运行截图：

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