UIPickerView詳解

//模型層定義

#import <Foundation/Foundation.h>

@interface CityModel : NSObject

@property (nonatomic, copy) NSString *proName;

@property (nonatomic, strong) NSArray *cities;

@end

//實作

#import "ViewController.h"

#import "CityModel.h"

@interface ViewController ()

@property (nonatomic, strong) NSMutableArray *proArr;

@end

@implementation ViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.flag_Zu=YES;

    UIPickerView *pickerView = [[UIPickerView alloc]initWithFrame:CGRectMake(0, 350, 0, 0)];

    pickerView.delegate = self;

    pickerView.dataSource = self;

    pickerView.showsSelectionIndicator = YES;

    [self.view addSubview:pickerView];

    self.proArr = [NSMutableArray arrayWithCapacity:0];

    NSBundle *bundle = [NSBundle mainBundle];

    NSString *path = [bundle pathForResource:@"city" ofType:@"plist"];

    NSArray *cityArr = [[NSArray alloc]initWithContentsOfFile:path];

    for (NSDictionary *dic in cityArr) {

        CityModel *model = [[CityModel alloc]init];

        model.cities = [dic objectForKey:@"cities"];

        model.proName = [dic objectForKey:@"state"];

        [self.proArr addObject:model];

    }

}

//傳回組數

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView

{

    return 2;

}

// 傳回組中的行數

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component

{

    if (component == 0) {

        return self.proArr.count;

    }else{

        //傳回第一列選擇行的索引

        NSInteger selectedRow = [pickerView selectedRowInComponent:0];

        CityModel *model = [self.proArr objectAtIndex:selectedRow];

        return model.cities.count;

    }

}

//傳回每個item中的title

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component

{

    if (component == 0) {

        CityModel *model = [self.proArr objectAtIndex:row];

        self.flag_Zu=NO;

        return model.proName;

    }else {

        NSInteger selectedRow = [pickerView selectedRowInComponent:0];

        CityModel *model = [self.proArr objectAtIndex:selectedRow];

        if(self.flag_Zu)

            return [model.cities objectAtIndex:row];

        else

            return [model.cities objectAtIndex:0];

    }

}

//設定列的寬度

- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {

    if (component == 0) {

        return 100;

    }

    return 220;

}

//選擇行的事件

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    if (component == 0) {

        self.flag_Zu=YES;

        //重新整理指定列中的行

        [pickerView reloadComponent:1];

        //選擇指定的item

        [pickerView selectRow:0 inComponent:1 animated:YES];

    }

}

在這個過程中遇到的問題就是當第一列沒停止的時候，去華東第二列，程式很容易崩潰。解決的方法就是就是加個BOOL變量去判斷一下

效果如下圖所示: