效果图

#import "ViewController.h"

@interface ViewController ()
@property(strong,nonatomic)UIPickerView *myPickView1;
@property(strong,nonatomic)NSArray *guo;
@property(strong,nonatomic)NSMutableArray *sheng;
@property(strong,nonatomic)NSMutableArray *shixian;
@property(strong,nonatomic)NSDictionary *shi;
@property(strong,nonatomic)UIButton *btn;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.sheng=[NSMutableArray array];
    self.shixian=[NSMutableArray array];
//    self.guo=[NSArray array];

    //添加UIPickerView
    self.myPickView1=[[UIPickerView alloc]initWithFrame:CGRectMake(10, 100, 400, 300)];
    self.myPickView1.backgroundColor=[UIColor colorWithRed:0.945 green:1.000 blue:0.359 alpha:1.000];
    self.myPickView1.delegate=self;
    self.myPickView1.dataSource=self;

    //读取plist文件
    NSBundle *bundle=[NSBundle mainBundle];
    NSString *path=[bundle pathForResource:@"area.plist" ofType:nil];
   self.guo=[NSArray arrayWithContentsOfFile:path];
    
    //遍历  省
    for (NSDictionary *arr in self.guo) {
      [self.sheng addObject:arr[@"State"]];
    }
    
    
    [self.view addSubview:self.myPickView1];

    
}



#pragma mark - 数据源
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{

    return 2;
}

#pragma mark - 数据源，返回长度
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
    if (compOnent==FIRST) {
         return self.sheng.count;
    }
    return self.shixian.count;
}

#pragma mark - 显示信息
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
    if (compOnent==FIRST) {
        return [self.sheng objectAtIndex:row];
    }
   

        return [self.shixian objectAtIndex:row];
    
    
}

#pragma mark - 选中选的信息
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
    
    if (compOnent==FIRST) {
        //清除上次选择的城市
        [self.shixian removeAllObjects];
        //更具城市的索引，遍历串城市
        NSDictionary *a=[self.guo objectAtIndex:row];
        //遍历城市信息
        NSArray *array=a[@"Cities"];
        NSMutableArray *s=[NSMutableArray array];
        for (NSDictionary *a in array) {
            [s addObject:a[@"city"]];
        }
        //把值传给 self.shixian
        self.shixian=s;
        
        //把第一个加到第二个中
        [self.myPickView1 selectRow:row inComponent:FIRST animated:YES];
        
        //刷新组件
        [self.myPickView1 reloadComponent:SECOND];
    
    }
    //如果选中第二个，弹出信息
    if (compOnent==SECOND) {
        NSInteger firstRow=[self.myPickView1 selectedRowInComponent:FIRST];
        NSInteger secOndRow=[self.myPickView1 selectedRowInComponent:SECOND];
        
        NSString *firstString=[self.sheng objectAtIndex:firstRow];
        NSString *secOndString=[self.shixian objectAtIndex:secondRow];
        
        
        NSString *message=[NSString stringWithFormat:@"您确定要选择%@%@吗？",firstString,secondString];
        UIAlertController *alertMessage=[UIAlertController alertControllerWithTitle:@"提示" message:message preferredStyle:UIAlertControllerStyleAlert];
        
        UIAlertAction *cancle=[UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:nil];
        
        UIAlertAction *ok=[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
        
        [alertMessage addAction:cancle];
        [alertMessage addAction:ok];
        [self presentViewController:alertMessage animated:YES completion:nil];
    }
}

#pragma  mark - 行高
-(CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component{
    return 30;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

ViewController.h文件

#import 
#define FIRST 0
#define SECOND 1
 @interface ViewController : UIViewController

@end

 

注：plist文件结构