前言

    NS_CLASS_AVAILABLE_IOS(2_0) __TVOS_PROHIBITED @interface UIPickerView : UIView <NSCoding, UITableViewDataSource>
    @available(iOS 2.0, *)                      public class UIPickerView : UIView, NSCoding, UITableViewDataSource 

• 选择框可以让用户以滑动的方式选择值。

1、UIPickerView 的创建

• 遵守协议 UIPickerViewDataSource, UIPickerViewDelegate

• Objective-C

      // 实例化 UIPickerView 对象
      UIPickerView *pickerView = [[UIPickerView alloc] init];
  
      // 设置代理
      pickerView.dataSource = self;
      pickerView.delegate = self;
  
      // 将 pickerView 添加到屏幕
      [self.view addSubview:pickerView];
  
      // 设置列数，必须设置，UIPickerViewDataSource 协议方法
      - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
  
          return 3;
      }
  
      // 设置行数 ，必须设置，UIPickerViewDataSource 协议方法
      - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
  
          return 10;
      }
  
      // 设置各行内容，必须设置，UIPickerViewDelegate 方法
      - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
  
          return [NSString stringWithFormat:@"%li行 - %li列", row, component];
      }

• Swift

      // 实例化 UIPickerView 对象
      let pickerView:UIPickerView = UIPickerView()
  
      // 设置代理
      pickerView.dataSource = self
      pickerView.delegate = self
  
      // 将 pickerView 添加到屏幕
      self.view.addSubview(pickerView)
  
      // 设置列数，必须设置，UIPickerViewDataSource 协议方法
      func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
  
          return 3
      }
  
      // 设置行数，必须设置，UIPickerViewDataSource 协议方法
      func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
  
          return 10
      }
  
      // 设置各行内容，必须设置，UIPickerViewDelegate 方法
      func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
  
          return String(format: "%li行 - %li列", row, component)
      }

2、UIPickerView 的设置

• Objective-C

      // 设置默认值
      [pickerView selectRow:1 inComponent:0 animated:YES];      // 第 0 列的默认值为 1
      [pickerView selectRow:2 inComponent:1 animated:YES];      // 第 1 列的默认值为 2
      [pickerView selectRow:3 inComponent:2 animated:YES];      // 第 2 列的默认值为 3
  
      // 设置 frame
      /*
          高度只有三个值：162, 180 和 216，默认为 216，设置为其它的值无效
      */
      pickerView.frame = CGRectMake(10, 30, self.view.bounds.size.width - 20, 162);
  
      // 设置位置
      pickerView.center = self.view.center;
  
      // 设置背景颜色
      pickerView.backgroundColor = [UIColor orangeColor];
  
      // 是否显示指示器
      /*
          default is NO
      */
      pickerView.showsSelectionIndicator = YES;
  
      // 刷新指定的列
      [pickerView reloadComponent:0];
  
      // 刷新所有的列
      [pickerView reloadAllComponents];
  
      // 获取列数，只读
      NSInteger numberOfComponents = pickerView.numberOfComponents;
  
      // 获取指定列的行数
      NSInteger numberOfRows = [pickerView numberOfRowsInComponent:0];
  
      // 获取指定行的尺寸
      CGSize rowSize = [pickerView rowSizeForComponent:0];
  
      // 获取指定列被选中的行数索引
      NSInteger selectedIndex = [pickerView selectedRowInComponent:0];
  
      // 获取指定行列的视图
      UIView *view = [pickerView viewForRow:3 forComponent:0];
  
      // 设置列宽
      /*
          不设置时为默认宽度，UIPickerViewDelegate 方法
      */
      - (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
  
          return 50;
      }
  
      // 设置行高
      /*
          不设置时为默认高度 32，UIPickerViewDelegate 方法
      */
      - (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component {
  
          return 50;
      }

• Swift

      // 设置默认值
      pickerView.selectRow(1, inComponent: 0, animated: true)      // 第 0 列的默认值为 1
      pickerView.selectRow(2, inComponent: 1, animated: true)      // 第 1 列的默认值为 2
      pickerView.selectRow(3, inComponent: 2, animated: true)      // 第 2 列的默认值为 3
  
      // 设置 frame
      /*
          高度只有三个值：162, 180 和 216，默认为 216，设置为其它的值无效
      */
      pickerView.frame = CGRectMake(10, 30, self.view.bounds.size.width - 20, 162)
  
      // 设置位置
      pickerView.center = self.view.center
  
      // 设置背景颜色
      pickerView.backgroundColor = UIColor.orangeColor()
  
      // 是否显示指示器
      /*
          default is NO
      */
      pickerView.showsSelectionIndicator = true
  
      // 刷新指定的列
      pickerView.reloadComponent(0)
  
      // 刷新所有的列
      pickerView.reloadAllComponents()
  
      // 获取列数，只读
      let numberOfComponents:Int = pickerView.numberOfComponents
  
      // 获取指定列的行数
      let numberOfRows:Int = pickerView.numberOfRowsInComponent(0)
  
      // 获取指定行的尺寸
      let rowSize:CGSize = pickerView.rowSizeForComponent(0)
  
      // 获取指定列被选中的行数索引
      let selectedIndex:Int = pickerView.selectedRowInComponent(0)
  
      // 获取指定行列的视图
      let view:UIView? = pickerView.viewForRow(3, forComponent: 0)
  
      // 设置列宽
      /*
          不设置时为默认宽度，UIPickerViewDelegate 方法
      */
      func pickerView(pickerView: UIPickerView, widthForComponent component: Int) -> CGFloat {
  
          return 50
      }
  
      // 设置行高
      /*
          不设置时为默认高度 32，UIPickerViewDelegate 方法
      */
      func pickerView(pickerView: UIPickerView, rowHeightForComponent component: Int) -> CGFloat {
  
          return 50
      }

3、UIPickerViewDataSource 协议方法

• Objective-C

      // 设置列数
      - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
  
      }
  
      // 设置行数
      - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
  
      }

• Swift

      // 设置列数
      func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
  
      }
  
      // 设置行数
      func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
  
      }

4、UIPickerViewDelegate 协议方法

• Objective-C

      // 设置各行内容为 字符串
      - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
  
      }
  
      // 设置各行内容为 NSAttributedString 型字符串
      - (NSAttributedString *)pickerView:(UIPickerView *)pickerView attributedTitleForRow:(NSInteger)row forComponent:(NSInteger)component {
  
      }
  
      // 设置各行内容为 view
      - (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view {
  
      }
  
      // 设置列宽
      - (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
  
      }
  
      // 设置行高
      - (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component {
  
      }
  
      // 检测行的选择状态，在滑动停止后触发
      - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
  
      }

• Swift

      // 设置各行内容为 字符串
      func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
  
      }
  
      // 设置各行内容为 NSAttributedString 型字符串
      func pickerView(pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
  
      }
  
      // 设置各行内容为 view
      func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusingView view: UIView?) -> UIView {
  
      }
  
      // 设置列宽
      func pickerView(pickerView: UIPickerView, widthForComponent component: Int) -> CGFloat {
  
      }
  
      // 设置行高
      func pickerView(pickerView: UIPickerView, rowHeightForComponent component: Int) -> CGFloat {
  
      }
  
      // 检测行的选择状态，在滑动停止后触发
      func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
  
      }