UIPickerView选择控件实现选择轮播效果（转轮效果）

UIPickerView为用户提供了选择器功能，使用户以更好的体验方式实现数据的选择，如图：

UIPickerView控件的使用方法：（创建好根视图：MainViewController）

#import <UIKit/UIKit.h>  
  
@interface MainViewController : UIViewController<UIPickerViewDelegate>  
{  
    UIPickerView *pickerView;  
    UILabel *contentview;  
    NSArray *content;  // 星座;  
}  
  
@end  

实现部分：

- (void)viewDidLoad  
{  
    [super viewDidLoad];  
    // Do any additional setup after loading the view.  
}  
-(void)loadView  
{  
    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];  
    self.view = view;  
    view.backgroundColor = [UIColor yellowColor];  
    [view release];  
    // 初始化数据， 这些数据将显示在picker中  
    content = [[NSArray alloc] initWithObjects:@"水瓶座", @"双鱼座", @"白羊座        ", @"金牛座", @"双子座", @"巨蟹座", @"狮子座", @"处女座", @"天秤座", @"天蝎座", @"射手座", @"白羊座",nil];  
    // 设置选择器  
    pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 150, 320, 216)];  
    // 设置代理  
    pickerView.delegate = self;  
    pickerView.showsSelectionIndicator = YES;  
    [self.view addSubview:pickerView];  
    contentview = [[UILabel alloc] initWithFrame:CGRectMake(80, 80, 100, 40)];  
    contentview.backgroundColor = [UIColor clearColor];  
    [self.view addSubview:contentview];  
}  
#pragma mark--处理方法  
// 返回显示的数列  
- (NSInteger)numberOfRowsInComponent:(NSInteger)component  
{  
    return 1;  
}  
// 返回当前列显示的行数  
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component  
{  
    return [content count];  
}  
// 设置当前的内容，如果行没有显示则自动释放  
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component  
{  
    return [content objectAtIndex:row];  
}  
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component  
{  
//    NSString *result = [pickerView pickView:pickerView titleForRow:row forComponent:component];  
      
    NSString *result = nil;  
    result = [content objectAtIndex:row];  
    NSLog(@"result:%@", result);  
    contentview.text = result;  
    [result release];  
}  
- (void)didReceiveMemoryWarning  
{  
    [super didReceiveMemoryWarning];  
    // Dispose of any resources that can be recreated.  
}