UIPickerView和UIDatePicker的简单应用（双级联动防止崩溃）

  1 #import "ViewController.h"
  2 #import "DataModel.h"
  3 
  4 @interface ViewController ()<UIPickerViewDataSource, UIPickerViewDelegate>
  5 ///日期输入框
  6 @property (weak, nonatomic) IBOutlet UITextField *dateField;
  7 ///地点输入框
  8 @property (weak, nonatomic) IBOutlet UITextField *placeField;
  9 
 10 @property (nonatomic, strong) UIPickerView *myPickerView;
 11 @property (nonatomic, strong) UIDatePicker *datePicker;
 12 //当省列表和城市列表同时滑动时，刷新不及时，造成数组越界，程序崩溃，该变量用于记录当前省份在provinceArray中的角标,防止崩溃
 13 @property (nonatomic, assign) NSInteger provinceIndex;
 14 
 15 ///加载plist文件数据所需属性
 16 @property (nonatomic, strong) NSMutableArray *provinceArray;
 17 
 18 @end
 19 
 20 @implementation ViewController
 21 //懒加载读取plist文件中的数据
 22 - (NSMutableArray *)provinceArray {
 23     if (_provinceArray == nil) {
 24         _provinceArray = [NSMutableArray array];
 25         NSString *pathString = [[NSBundle mainBundle] pathForResource:@"provinces.plist" ofType:nil];
 26         NSArray *arry = [NSArray arrayWithContentsOfFile:pathString];
 27         for (NSDictionary *dict in arry) {
 28             DataModel *model = [[DataModel alloc] init];
 29             [model setValuesForKeysWithDictionary:dict];
 30             [_provinceArray addObject:model];
 31         }
 32 
 33     }
 34     return _provinceArray;
 35 }
 36 
 37 - (void)viewDidLoad {
 38     [super viewDidLoad];
 39     // Do any additional setup after loading the view, typically from a nib.
 40     
 41 }
 42 
 43 #pragma mark - 日期选择按钮的响应方法
 44 - (IBAction)dateAction:(UIButton *)sender {
 45     [self.myPickerView removeFromSuperview];
 46     if (self.datePicker == nil) {
 47         
 48         //设置UIDatePicker;只创建一次，防止多次点击按钮，创建多个对象，占用过多内存
 49         self.datePicker = [[UIDatePicker alloc] initWithFrame:CGRectMake(0, 300, self.view.frame.size.width, 200)];
 50     }
 51     //设置本地时间为中国
 52     self.datePicker.locale = [NSLocale localeWithLocaleIdentifier:@"ch"];
 53     //日期显示格式
 54     self.datePicker.datePickerMode = UIDatePickerModeDate;
 55     [self.view addSubview:self.datePicker];
 56     [self changeValue:self.datePicker];
 57     //添加监听，当滑动选择的时候触发changeValue：方法
 58     [self.datePicker addTarget:self action:@selector(changeValue:) forControlEvents:UIControlEventValueChanged];
 59     
 60 }
 61 //监听触发方法的实现，将self.datePicker显示的日期转换成字符串显示在self.dateField上
 62 - (void)changeValue:(UIDatePicker *)datePicker {
 63         NSDateFormatter *format = [[NSDateFormatter alloc] init];
 64         format.dateFormat = @"yyyy-MM-dd";
 65         NSString *dateString = [format stringFromDate:datePicker.date];
 66     self.dateField.text = dateString;
 67 }
 68 #pragma mark - 地点选择按钮的响应方法
 69 - (IBAction)placeAction:(UIButton *)sender {
 70     //先将self.datePicker从父视图移除，再添加self.myPickerView
 71     [self.datePicker removeFromSuperview];
 72     //设置UIPickerView
 73     if (self.myPickerView == nil) {//只创建一次，防止多次点击按钮，创建多个对象，占用过多内存
 74          self.myPickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 300, self.view.frame.size.width, 200)];
 75     }
 76     [self.view addSubview:self.myPickerView];
 77     //设置代理
 78     self.myPickerView.dataSource = self;
 79     self.myPickerView.delegate = self;
 80     [self pickerView:self.myPickerView didSelectRow:0 inComponent:0];//给placeField赋初始值
 81     
 82 }
 83 //设置列数
 84 - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
 85     return 2;
 86 }
 87 //设置每列的行数
 88 - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
 89     if (component == 0) {
 90        return self.provinceArray.count;//第一列显示各个省份
 91     }else {
 92         DataModel *model = self.provinceArray[self.provinceIndex];
 93        return model.cities.count;//第二列根据第一列选中的省份，显示该省的城市，
 94     }
 95 }
 96 //设置每行显示的内容，若不设置，默认显示的都是？
 97 - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
 98     if (component == 0) {
 99         DataModel *model = self.provinceArray[row];
100         return model.name;
101     }else {
102        // NSInteger *index = [self.myPickerView selectedRowInComponent:0]
103         //DataModel *model = self.provinceArray[index];//之所以不用该句，是因为该句获取的是当前省份的城市，当省列表和城市列表同时滑动时，刷新不及时（UI刷新之后row的范围才能改变，例如UI刷新之前row的范围是1-10，省列表和城市列表同时滑动时，使用上面两句代码，当前省份随着滚动而改变，若某个省份的城市数量小于10，后面代码“return model.cities[row];”就会数组越界，程序崩溃），造成数组越界，程序崩溃，所以在开始的时候声明一个记录当前省份的变量provinceIndex。
104         DataModel *model = self.provinceArray[self.provinceIndex];
105         return model.cities[row];
106     }
107 }
108 //滚动的时候，触发的方法
109 - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
110     if (component == 0) {
111         //记录当前选中的省份
112         self.provinceIndex = [self.myPickerView selectedRowInComponent:0];
113         [self.myPickerView reloadComponent:1];
114     }
115     DataModel *model = self.provinceArray[self.provinceIndex];
116     NSInteger index = [self.myPickerView selectedRowInComponent:1];
117     NSString *string = [model.name stringByAppendingString:model.cities[index]];//注意：这里model.cities[index]，要获取当前列选中的行数，不能使用model.cities[row],否则会造成数组越界
118     self.placeField.text = string;
119 }
120 
121 @end

1 #import <Foundation/Foundation.h>
2 
3 @interface DataModel : NSObject
4 ///存放城市
5 @property (nonatomic, strong) NSArray *cities;
6 ///省的名称
7 @property (nonatomic, strong) NSString *name;
8 
9 @end

1 #import "DataModel.h"
2 
3 @implementation DataModel
4 //使用KVC赋值，防止程序崩溃
5 - (void)setValue:(id)value forUndefinedKey:(NSString *)key {
6     
7 }
8 
9 @end