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：

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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         var 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(){         var 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

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//设置列宽 func pickerView(pickerView: UIPickerView！,widthForComponent component: Int) -> CGFloat{     if(00 == 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：

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

4，检测响应选项的选择状态

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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     println(component)     println(row) }