[iOS基础控件 - 6.10.1] PickerView 餐点搭配Demo

A.需求

1.使用PickerView做出有3列餐点（水果、主菜、饮料）的搭配Demo

2.选择的餐点实时显示在“显示区”

3.提供“随机”按钮，随机选择菜品搭配

 

B.实现步骤

1.拖入一个PickerView

 

2.用控制器配置dataSource和delegate

 // 遵守UIPickerViewDataSource,UIPickerViewDelegate
 @interface ViewController () <UIPickerViewDataSource, UIPickerViewDelegate>

 /** 选择器 */
 @property (weak, nonatomic) IBOutlet UIPickerView *pickerView;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];
     // Do any additional setup after loading the view, typically from a nib.

     // 设置dataSource
     self.pickerView.dataSource = self;
     // 设置delegage
     self.pickerView.delegate = self;
 }

 

3.实现代理方法

 #pragma mark - 代理方法
 /** 列数 */
 - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
     return ;
 }

 /** 对应列的行数 */
 - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
     return ;
 }

 /** 对应列和行的显示内容 */
 - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
     return @"内容";
 }

 

 

4.引入plist文件，读取数据

 

 /** 加载数据，延迟加载 */
 - (NSArray *) foodCategories {
     if (nil == _foodCategories) {
         _foodCategories = [NSArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"foods.plist" ofType:nil]];
     }

     return _foodCategories;
 }

 #pragma mark - dataSource方法
 /** 列数 */
 - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
     return self.foodCategories.count;
 }

 /** 对应列的行数 */
 - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
     NSArray *foods = self.foodCategories[component];
     return foods.count;
 }

 #pragma mark - delegate方法
 /** 对应列和行的显示内容 */
 - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
     NSArray *foods = self.foodCategories[component];
     return foods[row];
 }

 

 

 

5.制作显示区

 

 /** 水果 */
 @property (weak, nonatomic) IBOutlet UILabel *fruitLabel;
 /** 主菜 */
 @property (weak, nonatomic) IBOutlet UILabel *mainLabel;
 /** 饮料 */
 @property (weak, nonatomic) IBOutlet UILabel *drinkLabel;

 

6.响应选择事件

 /** 响应选择餐点事件 */
 - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
     NSArray *foods = self.foodCategories[component];
     NSString *food = foods[row];

     switch (component) {
         case :
             self.fruitLabel.text = food;
             break;
         case :
             self.mainLabel.text = food;
             break;
         case :
             self.drinkLabel.text = food;
             break;
         default:
             break;
     }

 

 

7.制作“随机”功能

 /** 随机选择餐点 */
 - (IBAction)onRandomClicked {
     // 循环所有餐点种类
     for (int i=; i<self.foodCategories.count; i++) {
         // 之前选择的餐点行数
         NSInteger originalRow = [self.pickerView selectedRowInComponent:i];

         NSInteger row = originalRow;

         // 此种类内含有的所有餐点
         NSArray *foods = self.foodCategories[i];
         // 如果随机的餐点跟上一次的相同，继续随机
         while (row == originalRow) {
             row = arc4random() % foods.count;
         }

         // 通知pickerView改变选择
         [self.pickerView selectRow:row inComponent:i animated:YES];

         // 改变显示区
         [self pickerView:self.pickerView didSelectRow:row inComponent:i];
     }
 }