#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 kRandomColor [UIColor grayColor];#define kLineCount 6#define kLineWidth 1.0#define kCharCount 4#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; //设置layer圆角半径    self.layer.masksToBounds = YES; //隐藏边界    self.backgroundColor = kRandomColor;    //    [UIColor grayColor]    //显示一个随机验证码    [self changeCaptcha];  }  return self;}#pragma mark 更换验证码,得到更换的验证码的字符串-(void)changeCaptcha{  //<一>从字符数组中随机抽取相应数量的字符，组成验证码字符串  //数组中存放的是全部可选的字符，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",nil];  //如果能确定最大需要的容量，使用initWithCapacity:来设置，好处是当元素个数不超过容量时，添加元素不需要重新分配内存  NSMutableString *getStr = [[NSMutableString alloc] initWithCapacity:kCharCount];  self.changeString = [[NSMutableString alloc] initWithCapacity:kCharCount];  //随机从数组中选取需要个数的字符，然后拼接为一个字符串  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];  }}#pragma mark 点击view时调用，因为当前类自身就是UIView，点击更换验证码可以直接写到这个方法中，不用再额外添加手势-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{  //点击界面，切换验证码  [self changeCaptcha];  //setNeedsDisplay调用drawRect方法来实现view的绘制  [self setNeedsDisplay];}#pragma mark 绘制界面（1.UIView初始化后自动调用； 2.调用setNeedsDisplay方法时会自动调用）- (void)drawRect:(CGRect)rect {  // 重写父类方法，首先要调用父类的方法  [super drawRect:rect];  //设置随机背景颜色  self.backgroundColor = kRandomColor;  //获得要显示验证码字符串，根据长度，计算每个字符显示的大概位置  NSString *text = [NSString stringWithFormat:@"%@",self.changeString];  CGSize cSize = [@"S" sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20.0]}];  int width = rect.size.width / text.length - cSize.width;  int height = rect.size.height - cSize.height;  CGPoint point;  //依次绘制每一个字符,可以设置显示的每个字符的字体大小、颜色、样式等  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}];  }    //调用drawRect：之前，系统会向栈中压入一个CGContextRef，调用UIGraphicsGetCurrentContext()会取栈顶的CGContextRef    CGContextRef context = UIGraphicsGetCurrentContext();    //设置画线宽度    CGContextSetLineWidth(context, kLineWidth);    //绘制干扰的彩色直线    for(int i = 0; i < kLineCount; i++)    {      //设置线的随机颜色      UIColor *color = kRandomColor;      CGContextSetStrokeColorWithColor(context, [color CGColor]);      //设置线的起点      pX = arc4random() % (int)rect.size.width;      pY = arc4random() % (int)rect.size.height;      CGContextMoveToPoint(context, pX, pY);      //设置线终点      pX = arc4random() % (int)rect.size.width;      pY = arc4random() % (int)rect.size.height;      CGContextAddLineToPoint(context, pX, pY);      //画线      CGContextStrokePath(context);    }}@end