iOS 生成本地驗證碼

在應用程式註冊、登陸或者有關支付確認的介面，經常會用到驗證碼，驗證碼有的是通過手機傳送獲取的，有的是在本地點選獲取的，通過手機傳送獲取的動態驗證碼可以使用第三方類庫實現，本地點選獲取的是在本地自己繪製的，下面我們來詳細講解一下本地生成動態驗證碼的過程。

匯入CoreGraphics.framework

驗證碼封裝了一個UIView，在使用的時候直接把這個View加到介面上使用

CaptchaView.h

#import <UIKit/UIKit.h>

@interface CaptchaView : UIView

@property (nonatomic, retain) NSArray *changeArray; //字元素材陣列
@property (nonatomic, retain) NSMutableString *changeString;  //驗證碼的字串

@end

CaptchaView.m

#import "CaptchaView.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 CaptchaView
@synthesize changeString,changeArray;

- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {

        self.layer.cornerRadius = 5.0; //設定layer圓角半徑
        self.layer.masksToBounds = YES; //隱藏邊界
        self.backgroundColor = kRandomColor;

        //顯示一個隨機驗證碼
        [self changeCaptcha];
    }

    return self;
}
#pragma mark 更換驗證碼,得到更換的驗證碼的字串
-(void)changeCaptcha
{
//<一>從字元陣列中隨機抽取相應數量的字元，組成驗證碼字串
    //陣列中存放的是全部可選的字元，可以是字母，也可以是中文
    self.changeArray = [[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",@"傑",@"瑞",@"教",@"育",nil];

    //如果能確定最大需要的容量，使用initWithCapacity:來設定，好處是當元素個數不超過容量時，新增元素不需要重新分配記憶體
    NSMutableString *getStr = [[NSMutableString alloc] initWithCapacity:kCharCount];
    self.changeString = [[NSMutableString alloc] initWithCapacity:kCharCount];

    //隨機從陣列中選取需要個數的字元，然後拼接為一個字串
    for(int i = 0; i < kCharCount; i++)
    {
        NSInteger index = arc4random() % ([self.changeArray count] - 1);
        getStr = [self.changeArray objectAtIndex:index];

        self.changeString = (NSMutableString *)[self.changeString stringByAppendingString:getStr];
    }

//<2>從網路獲取字串，然後把得到的字串在本地繪製出來（網路獲取步驟在這省略）
//    self.changeString = [NSMutableString stringWithString:@"傑瑞教育"];
}

#pragma mark 點選view時呼叫，因為當前類自身就是UIView，點選更換驗證碼可以直接寫到這個方法中，不用再額外新增手勢
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //點選介面，切換驗證碼
    [self changeCaptcha];

    //setNeedsDisplay呼叫drawRect方法來實現view的繪製
    [self setNeedsDisplay];
}

#pragma mark 繪製介面（1.UIView初始化後自動呼叫； 2.呼叫setNeedsDisplay方法時會自動呼叫）
- (void)drawRect:(CGRect)rect {
    // 重寫父類方法，首先要呼叫父類的方法
    [super drawRect:rect];

    //設定隨機背景顏色
    self.backgroundColor = kRandomColor;

    //獲得要顯示驗證碼字串，根據長度，計算每個字元顯示的大概位置
    NSString *text = [NSString stringWithFormat:@"%@",self.changeString];
    CGSize cSize = [@"S" sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20]}]; int width = rect.size.width / text.length - cSize.width;
    int height = rect.size.height - cSize.height;
    CGPoint point;

    //依次繪製每一個字元,可以設定顯示的每個字元的字型大小、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}];
    }

    //呼叫drawRect：之前，系統會向棧中壓入一個CGContextRef，呼叫UIGraphicsGetCurrentContext()會取棧頂的CGContextRef
    CGContextRef context = UIGraphicsGetCurrentContext();
    //設定畫線寬度
    CGContextSetLineWidth(context, kLineWidth);

    //繪製干擾的彩色直線
    for(int i = 0; i < kLineCount; i++)
    {
        //設定線的隨機顏色
        UIColor *color = kRandomColor;
        CGContextSetStrokeColorWithColor(context, [color CGColor]);
        //設定線的起點
        pX = arc4random() % (int)rect.size.width;
        pY = arc4random() % (int)rect.size.height;
        CGContextMoveToPoint(context, pX, pY);
        //設定線終點
        pX = arc4random() % (int)rect.size.width;
        pY = arc4random() % (int)rect.size.height;
        CGContextAddLineToPoint(context, pX, pY);
        //畫線
        CGContextStrokePath(context);
    }
}

@end

<三>在介面上新增驗證碼

ViewController.m

#import "ViewController.h"
#import "CaptchaView.h"

@interface ViewController ()<UITextFieldDelegate,UIAlertViewDelegate>
{
    CaptchaView *_captchaView;
    UITextField *_input;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //顯示驗證碼介面
    _captchaView = [[CaptchaView alloc] initWithFrame:CGRectMake(20, 40, 150, 40)];
    [self.view addSubview:_captchaView];

    //提示文字
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(190, 40, 100, 40)];
    label.text = @"點選圖片換驗證碼";
    label.font = [UIFont systemFontOfSize:12];
    label.textColor = [UIColor grayColor];
    [self.view addSubview:label];

    //新增輸入框
    _input = [[UITextField alloc] initWithFrame:CGRectMake(20, 100, 150, 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 輸入框協議中方法,點選return按鈕
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    //判斷輸入的是否為驗證圖片顯示的驗證碼
    if ([_input.text isEqualToString:_captchaView.changeString]) {
        //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，驗證碼和輸入框晃動
        CAKeyframeAnimation *anim = [CAKeyframeAnimation animationWithKeyPath:@"transform.translation.x"];
        anim.repeatCount = 1;
        anim.values = @[@-20, @20, @-20];
        [_captchaView.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
{
    //清空輸入框內容，收回鍵盤
    if (buttonIndex==0) {
        _input.text = @"";
        [_input resignFirstResponder];
    }
}
@end