AuthcodeView.h
#import <UIKit/UIKit.h>
@interface AuthcodeView : UIView
@property (strong, nonatomic) NSArray *dataArray;//字符素材數(shù)組
@property (strong, nonatomic) NSMutableString *authCodeStr;//驗證碼字符串
@end
AuthcodeView.m
#import "AuthcodeView.h"
#define kRandomColor [UIColor colorWithRed:arc4random() % 256 / 256.0 green:arc4random() % 256 / 256.0 blue:arc4random() % 256 / 256.0 alpha:1.0];
#define kLineCount 6
#define kLineWidth 1.0
#define kCharCount 6
#define kFontSize [UIFont systemFontOfSize:arc4random() % 5 + 15]
@implementation AuthcodeView
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
  // Drawing code
}
*/
- (instancetype)initWithFrame:(CGRect)frame
{
  self = [super initWithFrame:frame];
  if (self)
  {
    self.layer.cornerRadius = 5.0f;
    self.layer.masksToBounds = YES;
    self.backgroundColor = kRandomColor;
    [self getAuthcode];//獲得隨機(jī)驗證碼
  }
  return self;
}
#pragma mark 獲得隨機(jī)驗證碼
- (void)getAuthcode
{
  //字符串素材
  _dataArray = [[NSArray alloc] initWithObjects:@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J",@"K",@"L",@"M",@"N",@"O",@"P",@"Q",@"R",@"S",@"T",@"U",@"V",@"W",@"X",@"Y",@"Z",@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",@"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",nil];
  _authCodeStr = [[NSMutableString alloc] initWithCapacity:kCharCount];
  //隨機(jī)從數(shù)組中選取需要個數(shù)的字符串，拼接為驗證碼字符串
  for (int i = 0; i < kCharCount; i++)
  {
    NSInteger index = arc4random() % (_dataArray.count-1);
    NSString *tempStr = [_dataArray objectAtIndex:index];
    _authCodeStr = (NSMutableString *)[_authCodeStr stringByAppendingString:tempStr];
  }
}
#pragma mark 點(diǎn)擊界面切換驗證碼
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
  [self getAuthcode];
  //setNeedsDisplay調(diào)用drawRect方法來實現(xiàn)view的繪制
  [self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect
{
  [super drawRect:rect];
  //設(shè)置隨機(jī)背景顏色
  self.backgroundColor = kRandomColor;
  //根據(jù)要顯示的驗證碼字符串，根據(jù)長度，計算每個字符串顯示的位置
  NSString *text = [NSString stringWithFormat:@"%@",_authCodeStr];
  CGSize cSize = [@"A" sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20]}];
  int width = rect.size.width/text.length - cSize.width;
  int height = rect.size.height - cSize.height;
  CGPoint point;
  //依次繪制每一個字符,可以設(shè)置顯示的每個字符的字體大小、顏色、樣式等
  float pX,pY;
  for ( int i = 0; i<text.length; i++)
  {
    pX = arc4random() % width + rect.size.width/text.length * i;
    pY = arc4random() % height;
    point = CGPointMake(pX, pY);
    unichar c = [text characterAtIndex:i];
    NSString *textC = [NSString stringWithFormat:@"%C", c];
    [textC drawAtPoint:point withAttributes:@{NSFontAttributeName:kFontSize}];
  }
   //調(diào)用drawRect：之前，系統(tǒng)會向棧中壓入一個CGContextRef，調(diào)用UIGraphicsGetCurrentContext()會取棧頂?shù)腃GContextRef
  CGContextRef context = UIGraphicsGetCurrentContext();
  //設(shè)置線條寬度
  CGContextSetLineWidth(context, kLineWidth);
  //繪制干擾線
  for (int i = 0; i < kLineCount; i++)
  {
    UIColor *color = kRandomColor;
    CGContextSetStrokeColorWithColor(context, color.CGColor);//設(shè)置線條填充色
    //設(shè)置線的起點(diǎn)
    pX = arc4random() % (int)rect.size.width;
    pY = arc4random() % (int)rect.size.height;
    CGContextMoveToPoint(context, pX, pY);
    //設(shè)置線終點(diǎn)
    pX = arc4random() % (int)rect.size.width;
    pY = arc4random() % (int)rect.size.height;
    CGContextAddLineToPoint(context, pX, pY);
    //畫線
    CGContextStrokePath(context);
  }
}
@end

@interface AuthCodeViewController ()<UITextFieldDelegate, UIAlertViewDelegate>
{
  AuthcodeView *authCodeView;
  UITextField *_input;
}
@end
@implementation AuthCodeViewController
- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  self.view.backgroundColor = [UIColor whiteColor];
  //顯示驗證碼界面
  authCodeView = [[AuthcodeView alloc] initWithFrame:CGRectMake(30, 100, self.view.frame.size.width-60, 40)];
  [self.view addSubview:authCodeView];
  //提示文字
  UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(50, 160, self.view.frame.size.width-100, 40)];
  label.text = @"點(diǎn)擊圖片換驗證碼";
  label.font = [UIFont systemFontOfSize:12];
  label.textColor = [UIColor grayColor];
  [self.view addSubview:label];
  //添加輸入框
  _input = [[UITextField alloc] initWithFrame:CGRectMake(30, 220, self.view.frame.size.width-60, 40)];
  _input.layer.borderColor = [UIColor lightGrayColor].CGColor;
  _input.layer.borderWidth = 2.0;
  _input.layer.cornerRadius = 5.0;
  _input.font = [UIFont systemFontOfSize:21];
  _input.placeholder = @"請輸入驗證碼!";
  _input.clearButtonMode = UITextFieldViewModeWhileEditing;
  _input.backgroundColor = [UIColor clearColor];
  _input.textAlignment = NSTextAlignmentCenter;
  _input.returnKeyType = UIReturnKeyDone;
  _input.delegate = self;
  [self.view addSubview:_input];
}
#pragma mark 輸入框代理，點(diǎn)擊return 按鈕
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
  //判斷輸入的是否為驗證圖片中顯示的驗證碼
  if ([_input.text isEqualToString:authCodeView.authCodeStr])
  {
    //正確彈出警告款提示正確
    UIAlertView *alview = [[UIAlertView alloc] initWithTitle:@"恭喜您 ^o^" message:@"驗證成功" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alview show];
  }
  else
  {
    //驗證不匹配，驗證碼和輸入框抖動
    CAKeyframeAnimation *anim = [CAKeyframeAnimation animationWithKeyPath:@"transform.translation.x"];
    anim.repeatCount = 1;
    anim.values = @[@-20,@20,@-20];
//    [authCodeView.layer addAnimation:anim forKey:nil];
    [_input.layer addAnimation:anim forKey:nil];
  }
  return YES;
}
#pragma mark 警告框中方法
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
  //清空輸入框內(nèi)容，收回鍵盤
  if (buttonIndex==0)
  {
    _input.text = @"";
    [_input resignFirstResponder];
  }
}