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）

 1 #import <UIKit/UIKit.h>
 2
 3 @interface MainViewController : UIViewController<UIPickerViewDelegate>
 4 {
 5     UIPickerView *pickerView;
 6     UILabel *contentview;
 7     NSArray *content;  // 星座;
 8 }
 9
10 @end  

实现部分：

 1 - (void)viewDidLoad
 2 {
 3     [super viewDidLoad];
 4     // Do any additional setup after loading the view.
 5 }
 6 -(void)loadView
 7 {
 8     UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
 9     self.view = view;
10     view.backgroundColor = [UIColor yellowColor];
11     [view release];
12     // 初始化数据， 这些数据将显示在picker中
13     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];
14     // 设置选择器
15     pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 150, 320, 216)];
16     // 设置代理
17     pickerView.delegate = self;
18     pickerView.showsSelectionIndicator = YES;
19     [self.view addSubview:pickerView];
20     contentview = [[UILabel alloc] initWithFrame:CGRectMake(80, 80, 100, 40)];
21     contentview.backgroundColor = [UIColor clearColor];
22     [self.view addSubview:contentview];
23 }
24 #pragma mark--处理方法
25 // 返回显示的数列
26 - (NSInteger)numberOfRowsInComponent:(NSInteger)component
27 {
28     return 1;
29 }
30 // 返回当前列显示的行数
31 - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
32 {
33     return [content count];
34 }
35 // 设置当前的内容，如果行没有显示则自动释放
36 - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
37 {
38     return [content objectAtIndex:row];
39 }
40 - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
41 {
42 //    NSString *result = [pickerView pickView:pickerView titleForRow:row forComponent:component];
43
44     NSString *result = nil;
45     result = [content objectAtIndex:row];
46     NSLog(@"result:%@", result);
47     contentview.text = result;
48     [result release];
49 }
50 - (void)didReceiveMemoryWarning
51 {
52     [super didReceiveMemoryWarning];
53     // Dispose of any resources that can be recreated.
54 }