[iOS基础控件

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 3;
}

/** 对应列的行数 */
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    return 5;
}

/** 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 0:
            self.fruitLabel.text = food;
            break;
        case 1:
            self.mainLabel.text = food;
            break;
        case 2:
            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=0; 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];
    }
}