Objective-C ,ios,iphone开发基础:picker控件详解与使用，（实现省市的二级联动）

第一步：新建一个单视图（single view）的工程，

命名为pickerTest，不要勾选下面两个选项，第一个是新版本里面的，第二个是单元测试，现在用不着。

点击next ->creat之后，打开工具栏：

在下面的控件工具栏中往视图上拖放一个Picker View控件，一个UIButton控件，一个UILable控件，（所有在前端可以看得见的控件都继承自UIView）

修改UIButton的title属性，设置为click 然后点击分栏按钮，为控件连线（这种方式相对于手动去写，要快速很多）。

依次为UILable 和 Picker View 控件添加插座变量，并且为UIButton添加Action

右击picker控件，将 Datesource和delegate连线至File's Owner, 设置它的数据源和代理。

在 cidpViewController.h文件中添加几个变量和遵循 UIPickerViewDelegate 协议，这样就可以用UIPickerViewDelegate里面的几个方法了 。

@interface cidpViewController : UIViewController<UIPickerViewDelegate>

#import <UIKit/UIKit.h>@interface cidpViewController : UIViewController<UIPickerViewDelegate> {    UILabel *lblTitle;    UIPickerView *picker;    NSString* strProvince;    NSString* strCity;    NSMutableArray* aProvince;    NSMutableArray* aCity;    NSArray* tempArray;}@property (strong, nonatomic) IBOutlet UIPickerView *picker;@property (strong, nonatomic) IBOutlet UILabel *lblTitle;- (IBAction)btnClick:(id)sender;@end

#import "cidpViewController.h"@implementation cidpViewController@synthesize picker;@synthesize lblTitle;- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Release any cached data, images, etc that aren't in use.}#pragma mark - View lifecycle- (void)viewDidLoad{    [super viewDidLoad];    //初始哈5个省份    aProvince = [[NSMutableArray alloc] initWithObjects:@"北京",@"甘肃",@"山西",@"湖北",@"广州", nil];    //初始化5个数组 ，分别初始化为5个省的城市    NSArray* array1 = [NSArray arrayWithObjects:@"海淀",@"昌平",@"朝阳",@"西城",@"丰台", nil];    NSArray* array2 = [NSArray arrayWithObjects:@"兰州",@"白银",@"张掖",@"陇西",@"天水", nil];    NSArray* array3 = [NSArray arrayWithObjects:@"太原",@"大同",@"运城",@"晋城",@"五台山", nil];    NSArray* array4 = [NSArray arrayWithObjects:@"武汉",@"荆州",@"襄阳",@"赣州", nil];    NSArray* array5 = [NSArray arrayWithObjects:@"广州",@"佛山",@"尖沙咀",@"中山", nil];    aCity = [[NSMutableArray alloc] initWithObjects:array1,array2,array3,array4,array5, nil];    //tempArray 用来初始化第二个 ，并且引用一次，避免提前释放，内存出错    tempArray = [array1 retain];    // 用来第一次显示UIlable，负责的话就会显示 null，null     strProvince = [aProvince objectAtIndex:0];    strCity = [tempArray objectAtIndex:0];    [aProvince release];    [aCity release];    }-(NSInteger)numberOfComponentsInPickerView:(UIPickerView*)pickerView{    //返回2 表示将有两个component（滚轮）    return 2;}-(NSInteger)pickerView:(UIPickerView*)pivkerView numberOfRowsInComponent:(NSInteger)component{    if(component == 0){        // 返回省份数组的长度        return [aProvince count];    }else{        //返回省份对应城市数组的长度。        [tempArray count];}- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{        if(component == 0){            //返回对应row 的数组元素。            return [aProvince objectAtIndex:row];        }else{                        return [tempArray objectAtIndex:row];        }}- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{    if(component == 0){        //返回省份对应的城市数组，        tempArray = [aCity objectAtIndex:row]        [picker selectRow:0 inComponent:1 animated:YES];        [picker reloadComponent:1];        strProvience = [aProvince objectAtIndex:row];        strCity = [tempArray objectAtIndex:0];    }else{        //城市滚轮滚动时，strCity也随着改变。       strCity =  [tempArray objectAtIndex:0];    }    lblTitle.text = [[NSString alloc] initWithFormat:@"%@,%@",strProvince,strCity,nil];}    - (void)viewDidUnload{    [self setLblTitle:nil];    [self setPicker:nil];    [super viewDidUnload];}- (void)viewWillAppear:(BOOL)animated{    [super viewWillAppear:animated];}- (void)viewDidAppear:(BOOL)animated{    [super viewDidAppear:animated];}- (void)viewWillDisappear:(BOOL)animated{    [super viewWillDisappear:animated];}- (void)viewDidDisappear:(BOOL)animated{    [super viewDidDisappear:animated];}- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation{    // Return YES for supported orientations    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);}- (IBAction)btnClick:(id)sender {    lblTitle.text = [[NSString alloc] initWithFormat:@"%@,%@",strProvince,strCity,nil];}-(void)dealloc{    [aProvince release];    [aCity release];    [lblTitle release];    [strCity release];    [strProvince release];    [picker release];    [super  dealloc];    }@end

@protocol UIPickerViewDataSource<NSObject>@required// returns the number of 'columns' to display.- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView;// returns the # of rows in each component..- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;@end

UIPickerViewDelegate协议中的五个方法，非必须实现，

@protocol UIPickerViewDelegate<NSObject>@optional// returns width of column and height of row for each component. - (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component;- (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component;// these methods return either a plain UIString, or a view (e.g UILabel) to display the row for the component.// for the view versions, we cache any hidden and thus unused views and pass them back for reuse. // If you return back a different object, the old one will be released. the view will be centered in the row rect  - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component;- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view;- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component;@end