Swift - 选择框（UIPickerView）的用法

1，选择框可以让用户以滑动的方式选择值。示例如下：

			
									import UIKit
								
									class ViewController:UIViewController, UIPickerViewDelegate, UIPickerViewDataSource{
								
									var pickerView:UIPickerView!
								
									override func viewDidLoad() {
								
									super.viewDidLoad()
								
									pickerView=UIPickerView()
								
									//将dataSource设置成自己
								
									pickerView.dataSource=self
								
									//将delegate设置成自己
								
									pickerView.delegate=self
								
									//设置选择框的默认值
								
									pickerView.selectRow(1,inComponent:0,animated:true)
								
									pickerView.selectRow(2,inComponent:1,animated:true)
								
									pickerView.selectRow(3,inComponent:2,animated:true)
								
									self.view.addSubview(pickerView)
								
									//建立一个按钮，触摸按钮时获得选择框被选择的索引
								
									let button=UIButton(frame:CGRectMake(0,0,100,30))
								
									button.center=self.view.center
								
									button.backgroundColor=UIColor.blueColor()
								
									button.setTitle("获取信息",forState:.Normal)
								
									button.addTarget(self, action:"getPickerViewValue",
								
									forControlEvents: UIControlEvents.TouchUpInside)
								
									self.view.addSubview(button)
								
									}
								
									//设置选择框的列数为3列,继承于UIPickerViewDataSource协议
								
									func numberOfComponentsInPickerView( pickerView: UIPickerView) -> Int{
								
									return 3
								
									}
								
									//设置选择框的行数为9行，继承于UIPickerViewDataSource协议
								
									func pickerView(pickerView: UIPickerView,numberOfRowsInComponent component: Int) -> Int{
								
									return 9
								
									}
								
									//设置选择框各选项的内容，继承于UIPickerViewDelegate协议
								
									func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int)
								
									-> String? {
								
									return String(row)+"-"+String(component)
								
									}
								
									//触摸按钮时，获得被选中的索引
								
									func getPickerViewValue(){
								
									let alertView=UIAlertView();
								
									alertView.title="被选中的索引为"
								
									alertView.message=String(pickerView.selectedRowInComponent(0)) + "-"
								
									+ String(pickerView!.selectedRowInComponent(1)) + "-"
								
									+ String(pickerView.selectedRowInComponent(2))
								
									alertView.addButtonWithTitle("OK")
								
									alertView.show()
								
									}
								
									}

2，调整选择框的尺寸
UIPickerView 用 frame 和 center 两个属性设置整个选择框的大小和位置。
如果要调整内部列的宽度，需要实现 UIPickerViewDelegate 协议类中 pickerView:widthForComponent 方法设置
如果要调整内部行高，则需要实习上述协议类中 pickerView:rowHeightForComponent 方法设置

			
									//设置列宽
								
									func pickerView(pickerView: UIPickerView,widthForComponent component: Int) -> CGFloat{
								
									if(0 == component){
								
									//第一列变宽
								
									return 100
								
									}else{
								
									//第二、三列变窄
								
									return 30
								
									}
								
									}
								
									//设置行高
								
									func pickerView(pickerView: UIPickerView,rowHeightForComponent component: Int) -> CGFloat{
								
									return 50
								
									}

3，将图片作为选择框选项
选择框选项的内容，除了可以使字符串类型的，还可以是任意UIView类型的元素。比如我们将选项内容设置为图片：

			
									func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int,
								
									reusingView view: UIView?) -> UIView {
								
									let image = UIImage(named:"icon_"+String(row))
								
									let imageView = UIImageView()
								
									imageView.image = image
								
									return imageView
								
									}

4，检测响应选项的选择状态

			
									func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
								
									//将在滑动停止后触发，并打印出选中列和行索引
								
									print(component)
								
									print(row)
								
									}