黑马程序员——iOS 开发学习---UIPickerView控件的应用

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIPickerViewDataSource,UIPickerViewDelegate>
{
NSMutableArray* _provinceArray;
NSMutableArray* _cityArray;
}

@end

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
[super viewDidLoad];

//处理数据源
_provinceArray=[[NSMutableArray alloc]initWithObjects:@"河南省",@"安徽省",@"四川省", nil];
NSMutableArray* array1=[[NSMutableArray alloc]initWithObjects:@"郑州", @"新郑",@"周口",@"信阳",@"新乡",nil];
NSMutableArray* array2=[[NSMutableArray alloc]initWithObjects:@"合肥",@"芜湖",@"六安",nil];
NSMutableArray* array3=[[NSMutableArray alloc]initWithObjects:@"汶川",@"南充",@"绵阳",nil];
//把三个小数组装进一个大数组（模范二维数组）
_cityArray=[[NSMutableArray alloc ]initWithObjects:array1,array2,array3, nil];
//处理UI  下面两者继承的父类不同，没有直接关系。
//UIDatePicker : UIControl
//UIPickerView : UIView   它的高度是固定的：162 180 216
UIPickerView *pickerView=[[UIPickerView alloc]initWithFrame:CGRectMake(30, 150, 260, 180)];
pickerView.backgroundColor=[UIColor grayColor];

//设置数据源代理
//@optional：表明这些方法是可选的
//@requied： 表明这些方法是必选的（必须实现的，不实现就找不到方法，就会崩溃）
//设置代理
pickerView.dataSource=self;
pickerView.delegate=self;
pickerView.showsSelectionIndicator=YES;

//默认选择那一列的哪一行
[pickerView selectRow:0 inComponent:0 animated:YES];//(第0列的第0行)
[self.view addSubview:pickerView];

//输出一个空间的的坐标大小
//NSLog(@"%@",NSStringFromCGRect(pickerView.frame));
// Do any additional setup after loading the view, typically from a nib.
}

#pragma mark  UIPickerViewDataSource
//设置PickerView列数
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return 2;
}
//设置PickerView行数
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
//如果是第0列返回三行
//如果不是第0列，那么需要根据第0列选择第几行，分别来设置第1列行数
if (component==0) {
return _provinceArray.count;
}else{
//获取第0列你选择的哪一行
int number=[pickerView selectedRowInComponent:0];
//根据number（第0列选择了第number）
NSMutableArray *array=[_cityArray objectAtIndex:number];

return array.count;
}

}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
if (component==0) {
NSString* title=[_provinceArray objectAtIndex:row];
return title;

}else{
int number=[pickerView selectedRowInComponent:0];
//取出对应的小数组
NSMutableArray *array=[_cityArray objectAtIndex:number];
//返回小数组元素
NSString* title=[array objectAtIndex:row];
return title;
}
}

#pragma mark  刷新数据源  UIPickerViewDelegate代理
//只要行发生了变化都会调用该方法
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
if (component==0) {
//[pickerView reloadAllComponents];//刷新所有的列 效率比较低，因为刷新的是所有的列
//指定列刷新,
[pickerView reloadComponent:1];//第一列的行数改变的时候要刷新
}
}

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

@end