Swift 选择框（UIPickerView）的用法

import UIKit

class ViewController: UIViewController        ,UIPickerViewDelegate{
var pickerView:UIPickerView!

override func viewDidLoad() {
super.viewDidLoad()

    var SCREEN_WIDTH  = self.view.frame.width
    var SCREEN_HIGHT = self.view.frame.height

    pickerView = UIPickerView()
    pickerView.delegate = self;
    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);
    
    let button = UIButton(frame: CGRectMake((SCREEN_WIDTH-100)/2,200,100,30))
//        button.center = self.view.center
    button.backgroundColor = UIColor.blueColor()
    button.setTitle("读取", forState: .Normal)
    button.addTarget(self, action: "getPickerViewValue", forControlEvents: .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
//    原文出自：www.hangge.com  转载请保留原文链接：http://www.hangge.com/blog/cache/detail_541.html
//设置列宽
func pickerView(pickerView: UIPickerView,widthForComponent component: Int) -> CGFloat{
    if(0 == component){
        //第一列变宽
        return 50
    }else{
        //第二、三列变窄
        return 50
    }
 }

//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: "hello.png" + 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)
 }

}