［ios］新手笔记－。－UIPickerView 关于伪造循环效果和延时滚动效果

查找了网上资料，循环效果绝大部分都是增加行数来制造循环的错觉，延时滚动就是利用NSTimer间隔出发滚动事件来制造滚动效果。

代码：

#import <UIKit/UIKit.h>
#import "UserEntity.h"

@interface PickerViewController : UIViewController
{
NSTimer *times;
int j;//设置延时滚动的行数
}

@property (retain,nonatomic) UserEntity *userEntity;
@property (strong,nonatomic) NSMutableArray *pickerData;//设置可变数组存放数据
@property (weak, nonatomic) IBOutlet UIPickerView *pickerView;

- (IBAction)backButton:(id)sender;

@end

-------------------------------------------------------------------------------------------------------------------

@implementation PickerViewController
@synthesize pickerView;
@synthesize pickerData;

@synthesize userEntity;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
       return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    NSLog(@"min:%d,max:%d",self.userEntity.minNum,self.userEntity.maxNum);
    //设置滚动初始位置等于扩大行数后的位置（1000/2）
      j＝500；
    int startNum= self.userEntity.minNum;
    int endNum =self.userEntity.maxNum;
    int value=endNum-startNum;

    NSMutableArray *numArray =[NSMutableArray arrayWithCapacity:value+1];
    for(int i=startNum;i<=endNum;i++)
    {
        NSString* str = [NSString stringWithFormat:@"%d",i];
        [numArray addObject:str];

    }
    self.pickerData = numArray;
    [pickerView selectRow:1000/2 inComponent:0 animated:NO];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(int)getRandomNumber:(int)from to:(int)to
{
    return (int)(from + (arc4random() % (to - from + 1)));
}

- (IBAction)backButton:(id)sender {
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (IBAction)selectButton:(id)sender {
    times=[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(scollPicker) userInfo:nil repeats:YES];
}

-(void)scollPicker
{
    j++;
    if(j%100==0)
    {

        [times invalidate];
        times=nil;

        int startNum= self.userEntity.minNum;
        int endNum =self.userEntity.maxNum;
        int value=endNum-startNum;
        int getNum = [self getRandomNumber:0 to:1000];

        [pickerView selectRow:getNum%value inComponent:0 animated:YES];
        [pickerView reloadComponent:0];


        NSInteger row = [self.pickerView selectedRowInComponent:0];
        NSString *selected = [self.pickerData objectAtIndex:row];

        NSString *title=[[NSString alloc] initWithFormat:@"You selected %@!", selected];
        UIAlertView *alert=[[UIAlertView alloc] initWithTitle:title message:@"Thanks for choosing." delegate:self cancelButtonTitle:@"You're Welcome" otherButtonTitles:nil,nil];
        [alert show];


        j=0;
      // button.enabled=YES;
}

@implementation PickerViewController
@synthesize pickerView;
@synthesize pickerData;

@synthesize userEntity;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
       return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    NSLog(@"min:%d,max:%d",self.userEntity.minNum,self.userEntity.maxNum);
    //设置滚动初始位置等于扩大行数后的位置（1000/2）
    j＝500；
    获取随机数范围
    int startNum= self.userEntity.minNum;
    int endNum =self.userEntity.maxNum;
    int value=endNum-startNum;

   //初始话数组并赋值
    NSMutableArray *numArray =[NSMutableArray arrayWithCapacity:value+1];
    for(int i=startNum;i<=endNum;i++)
    {
        NSString* str = [NSString stringWithFormat:@"%d",i];
        [numArray addObject:str];
    }
   //绑定数据
    self.pickerData = numArray;
   //初始Picker位置
    [pickerView selectRow:1000/2 inComponent:0 animated:NO];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

//获取随机数
-(int)getRandomNumber:(int)from to:(int)to
{
    return (int)(from + (arc4random() % (to - from + 1)));
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
   //扩大行数制造循环
    return 1000;
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    //求余赋值使扩大后的数与数组值相同，制造循环效果
    return [pickerData objectAtIndex:(row%(self.userEntity.maxNum-self.userEntity.minNum+1))];
}

    }
    else
    {for (int i=0; i<3; i++) {
        [pickerView selectRow:j inComponent:0 animated:YES];
        [pickerView reloadComponent:0];
     //   button.enabled=NO;
    }
    }

}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    return 1000;
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    return [pickerData objectAtIndex:(row%(self.userEntity.maxNum-self.userEntity.minNum+1))];
}
可能有些理解有错，希望求指出指点。