标签栏与选取器的使用

我们要实现下面的效果，就是通过下方的标签栏切换视图来显示不同的选取器






首先创建工程，选择Window－Based Application模板，取项目名称为Picker。生成后选中Classes文件夹，从File中选择new File，再选择UIViewController subclass图标，顺便点选下面的第三项－with xib for user interface，分别取名为DatePicker，SingleComponentPicker，DoubleComponentPicker，生成之后将.xib文件拖入Resources文件夹中。
先添加根视图控制器，单击PickerAppDelegate.h类

#import <UIKit/UIKit.h>
@interface PickersAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
	UITabBarController *rootController;
}
@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *rootController;
@end

单击PickerAppDelegate.m

@synthesize window;
@synthesize rootController;
#pragma mark -
#pragma mark Application lifecycle
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
    [window addSubview:rootController.view];
    [window makeKeyAndVisible];
    return YES;
}
- (void)dealloc {
    [rootController release];
    [window release];
    [super dealloc];
}

双击MainWindow.xib，从库中拖出一个Tab Bar Controller到nib主窗口，这样会出现一个新的窗口

起初下面只有两个标签，图上的3个标签是又添加上去了1个，选中新出现的窗口，按下花＋1打开他的属性，点＋，就能添加标签。

为了使每一个标签都能与对应的nib相关联，我们选中第一个。保留title为空，将nib name指定为DatePickerView，按花＋4，将类改为DatePicker，再点中标签可以改变标签的名称。以此类推，完成剩下标签的相关连。



再nib主窗口中按住Ctrl将Picker App Delegate拖到Tab Bar Controller图标中。
单击DatePicker.h，完成代码

#import <UIKit/UIKit.h>
@interface DatePicker : UIViewController {
	IBOutlet UIDatePicker *datePicker;
}
@property (nonatomic,retain) UIDatePicker *datePicker;
-(IBAction)buttonPressed;
@end

单击DatePicker.m，完成代码

@synthesize datePicker;
-(IBAction)buttonPressed{
	NSData *selected = [datePicker date];
	NSString *message = [[NSString alloc] initWithFormat:@"The date and time is:%@",selected];
	UIAlertView *alert = [[UIAlertView alloc]
						  initWithTitle:@"Data and Time Selected" 
						  message:message 
						  delegate:nil 
						  cancelButtonTitle:@"Yes,I did" 
						  otherButtonTitles:nil];
	[alert show];
	[alert release];
	[message release];
｝
- (void)viewDidLoad {
	NSDate *now = [[NSDate alloc] init];
	[datePicker setDate:now animated:YES];
	[now release];
    [super viewDidLoad];
}
- (void)dealloc {
	[datePicker release];
    [super dealloc];
}

这样第一个视图就完成了。
进行第二个，单个组件选取器，在SingleComponentPicker.h中声明输出口和操作

#import <UIKit/UIKit.h>
@interface SinglecomponentPickerViewController : UIViewController 
	<UIPickerViewDelegate,UIPickerViewDataSource>{
		IBOutlet UIPickerView *singlePicker;
		NSArray *pickerData;
}
@property (nonatomic,retain) UIPickerView *singlePicker;
@property (nonatomic,retain) NSArray *pickerData;
-(IBAction)buttonPressed;
@end

在相应的.xib中创建相应视图，一个Picker View和一个按钮，并完成如下关联




在相应.m文件中进行编码

@synthesize singlePicker;
@synthesize pickerData;
-(IBAction)buttonPressed{
	NSInteger row = [singlePicker selectedRowInComponent:0];
	NSString *selected = [pickerData objectAtIndex:row];
	NSString *title = [[NSString alloc] initWithFormat:@"You selected %@!",selected];
	UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title 
						message:@"Thank you for choosing!" 
						delegate:nil 
						cancelButtonTitle:@"you'are welcome." 
						otherButtonTitles:nil];
	[alert show];
	[alert release];
	[title release];
}
- (void)viewDidLoad {
	NSArray *array = [[NSArray alloc] initWithObjects:@"Inter Milan",@"AC Milan",@"Arsenal",@"Liverpool",@"Chelsea",@"Newcastle",@"Manchester United",@"Real Madrid",nil];
	self.pickerData = array;
	[array release];
}
- (void)dealloc {
	[singlePicker release];
	[pickerData release];
    [super dealloc];
}
#pragma mark -
#pragma mark Picker Data Source Methods
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
	return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
	return [pickerData count];
}
#pragma mark Picker Delegate Methods
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
	return [pickerData objectAtIndex:row];
}
@end

第二个视图也就完成了，下面创建第三个，在DoubleComponentPicker.h中声明输出口和操作

#import <UIKit/UIKit.h>
#define kFillingComponent 0
#define kBreadComponent 1
@interface DoublecomponentPickerViewController : UIViewController 
			<UIPickerViewDelegate,UIPickerViewDataSource>{
				IBOutlet UIPickerView *doublePicker;
				NSArray *fillingTypes;
				NSArray *breadTypes;
}
@property (nonatomic,retain)UIPickerView *doublePicker;
@property (nonatomic,retain)NSArray *fillingTypes;
@property (nonatomic,retain)NSArray *breadTypes;
-(IBAction)buttonPressed;
@end

控件的形式和关联和第二个视图中一样，可以参考。在相应的.m文件中进行编码

@synthesize doublePicker;
@synthesize fillingTypes;
@synthesize breadTypes;
-(IBAction)buttonPressed{
	NSInteger breadRow = [doublePicker selectedRowInComponent:kBreadComponent];
	NSInteger fillingRow = [doublePicker selectedRowInComponent:kFillingComponent];
	NSString *bread = [breadTypes objectAtIndex:breadRow];
	NSString *filling = [fillingTypes objectAtIndex:fillingRow];
	NSString *message = [[NSString alloc] initWithFormat:@"your %@ on %@ bread will be right up.",filling,bread];
	UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Thank you" 
						message:message 
						delegate:nil 
						cancelButtonTitle:@"Great" 
						otherButtonTitles:nil];
	[alert show];
	[alert release];
	[message release];
}
- (void)viewDidLoad {
    NSArray *breadArray = [[NSArray alloc] initWithObjects:@"Inter Milan",@"AC Milan",@"Arsenal",@"Liverpool",@"Chelsea",@"Newcastle",@"Manchester United",@"Real Madrid",nil];
	self.breadTypes = breadArray;
	[breadArray release];
	
	NSArray *fillingArray = [[NSArray alloc] initWithObjects:@"Raul",@"AC Milan",@"Arsenal",@"Liverpool",@"Chelsea",@"Newcastle",@"Manchester United",@"Real Madrid",nil];
	self.fillingTypes = fillingArray;
	[fillingArray release];
}
- (void)dealloc {
	[doublePicker release];
	[breadTypes release];
	[fillingTypes release];
    [super dealloc];
}
#pragma mark -
#pragma mark Picker Data Source Methods

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
	
	return 2;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
	if (component == kBreadComponent) {
		return [self.breadTypes count];
	}
	return [self.fillingTypes count];
}
#pragma mark Picker Delegate Methods
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
	if (component == kBreadComponent) {
		return [self.breadTypes objectAtIndex:row];
	}
	return [self.fillingTypes objectAtIndex:row];
}
@end

这样就结束了