picker控件詳解與使用，（實現省市的二級聯動）

第一步：新建一個單視圖（single view）的工程，

命名為pickerTest，不要勾選下面兩個選項，第一個是新版本里面的，第二個是單元測試，現在用不着。

點擊next  ->creat之后，打開工具欄：

在下面的控件工具欄中往視圖上拖放一個Picker View控件，一個UIButton控件，一個UILable控件，（所有在前端可以看得見的控件都繼承自UIView）

修改UIButton的title屬性，設置為click 然后點擊分欄按鈕，為控件連線（這種方式相對於手動去寫，要快速很多）。

 

依次為UILable 和 Picker View 控件添加插座變量，並且為UIButton添加Action

右擊picker控件，將 Datesource和delegate連線至File's Owner, 設置它的數據源和代理。

在 cidpViewController.h文件中添加幾個變量和遵循 UIPickerViewDelegate 協議，這樣就可以用UIPickerViewDelegate里面的幾個方法了 。

@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個省份
    aProvince = [[NSMutableArray alloc] initWithObjects:@"北京",@"甘肅",@"山西",@"湖北",@"廣州", nil];
    //初始化5個數組 ，分別初始化為5個省的城市
    NSArray* array1 = [NSArray arrayWithObjects:@"海淀",@"昌平",@"朝陽",@"西城",@"豐台", nil];
    NSArray* array2 = [NSArray arrayWithObjects:@"蘭州",@"白銀",@"張掖",@"隴西",@"天水", nil];
    NSArray* array3 = [NSArray arrayWithObjects:@"太原",@"大同",@"運城",@"晉城",@"五台山", nil];
    NSArray* array4 = [NSArray arrayWithObjects:@"武漢",@"荊州",@"襄陽",@"贛州", nil];
    NSArray* array5 = [NSArray arrayWithObjects:@"廣州",@"佛山",@"尖沙咀",@"中山", nil];
    aCity = [[NSMutableArray alloc] initWithObjects:array1,array2,array3,array4,array5, nil];
    //tempArray 用來初始化第二個 ，並且引用一次，避免提前釋放，內存出錯
    tempArray = [array1 retain];
    // 用來第一次顯示UIlable，負責的話就會顯示 null，null 
    strProvince = [aProvince objectAtIndex:0];
    strCity = [tempArray objectAtIndex:0];
    [aProvince release];
    [aCity release];
    
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView*)pickerView{
    //返回2 表示將有兩個component（滾輪）
    return 2;
}

-(NSInteger)pickerView:(UIPickerView*)pivkerView numberOfRowsInComponent:(NSInteger)component{
    if(component == 0){
        // 返回省份數組的長度
        return [aProvince count];
    }else{
        //返回省份對應城市數組的長度。
        [tempArray count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
        if(component == 0){
            //返回對應row 的數組元素。
            return [aProvince objectAtIndex:row];
        }else{
            
            return [tempArray objectAtIndex:row];
        }
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
    if(component == 0){
        //返回省份對應的城市數組，
        tempArray = [aCity objectAtIndex:row]
        [picker selectRow:0 inComponent:1 animated:YES];
        [picker reloadComponent:1];
        strProvience = [aProvince objectAtIndex:row];
        strCity = [tempArray objectAtIndex:0];
    }else{
        //城市滾輪滾動時，strCity也隨着改變。
       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協議中的五個方法，非必須實現，

@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