//
//  UIPickerView.h
//  UIKit
//
//  Copyright (c) 2006-2014 Apple Inc. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <CoreGraphics/CoreGraphics.h>
#import <UIKit/UIView.h>
#import <UIKit/UITableView.h>
#import <UIKit/UIKitDefines.h>

@protocol UIPickerViewDataSource, UIPickerViewDelegate;

NS_CLASS_AVAILABLE_IOS(2_0) @interface UIPickerView : UIView <NSCoding, UITableViewDataSource>

@property(nonatomic,assign) id<UIPickerViewDataSource> dataSource;                // default is nil. weak reference 數據源  默認為nil，弱引用
@property(nonatomic,assign) id<UIPickerViewDelegate>   delegate;                // default is nil. weak reference  代理   默認為nil，弱引用
@property(nonatomic)        BOOL                       showsSelectionIndicator;    // default is NO 顯示選中指示器 默認為NO

// info that was fetched and cached from the data source and delegate
//從代理跟數據源中 接收 跟 存儲 信息
@property(nonatomic,readonly) NSInteger numberOfComponents; //返回列數
- (NSInteger)numberOfRowsInComponent:(NSInteger)component; //返回對應列的行數
- (CGSize)rowSizeForComponent:(NSInteger)component; //返回對應列，行的尺寸

// returns the view provided by the delegate via pickerView:viewForRow:forComponent:reusingView:
// or nil if the row/component is not visible or the delegate does not implement
// pickerView:viewForRow:forComponent:reusingView:
- (UIView *)viewForRow:(NSInteger)row forComponent:(NSInteger)component;//返回

// Reloading whole view or single component //刷新全部或者單個列
- (void)reloadAllComponents; //刷新所有列
- (void)reloadComponent:(NSInteger)component; //刷新指定列

// selection. in this case, it means showing the appropriate row in the middle 選擇，在著紅情況下，这意味着在中间显示适当的行
- (void)selectRow:(NSInteger)row inComponent:(NSInteger)component animated:(BOOL)animated;  // scrolls the specified row to center. //滑動指定的列到中心

- (NSInteger)selectedRowInComponent:(NSInteger)component;                                   // returns selected row. -1 if nothing selected  //根據指定列返回指定row，如果，沒有選擇任何東西，返回 ﹣1

@end


@protocol UIPickerViewDataSource<NSObject> //UIPickerView的數據源協議
@required

// returns the number of ‘columns‘ to display.  返回要顯示的總列數
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView;

// returns the # of rows in each component.. 返回每一列的行數
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;
@end


@protocol UIPickerViewDelegate<NSObject>
@optional

// returns width of column and height of row for each component.  返回每列對應每一行的高跟寬
- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component;//返回的是寬
- (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component;//返回的是高

// these methods return either a plain NSString, a NSAttributedString, or a view (e.g UILabel) to display the row for the component.
//這些方法返回，單一的字符串或者帶有屬性修飾的字符串，或者view
// for the view versions, we cache any hidden and thus unused views and pass them back for reuse.
//
// If you return back a different object, the old one will be released. the view will be centered in the row rect  
//如果你返回不同的對象，舊的哪一個會被釋放掉。返回的那個view會在行中心
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component; //返回列對應的行的標題
- (NSAttributedString *)pickerView:(UIPickerView *)pickerView attributedTitleForRow:(NSInteger)row forComponent:(NSInteger)component NS_AVAILABLE_IOS(6_0); // attributed title is favored if both methods are implemented
- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view; //返回自定義的view

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component; //選中對應列對應行的方法

@end

UIPickerView採摘控件的學習