- (void)viewDidLoad {      [super viewDidLoad];      // Do any additional setup after loading the view, typically from a nib.            UIImageView *imageV = [[UIImageView alloc]initWithFrame:CGRectMake(10, 120, screen_Width-20, screen_Height-150)];      imageV.image = [UIImage imageNamed:@"640-960-1.jpg"];      [self.view addSubview:imageV];            UIButton *testBtn = [[UIButton alloc]initWithFrame:CGRectMake(screen_Width/2.0-60, 60, 120, 36)];      [testBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];      [testBtn setTitle:@"添加直线" forState:UIControlStateNormal];      [testBtn addTarget:self action:@selector(addLineAct:) forControlEvents:UIControlEventTouchUpInside];      [self.view addSubview:testBtn];  }    - (void)addLineAct:(id)sender{      NSLog(@"测试按钮");  } 

@property(nonatomic,strong) NSMutableArray * completeLines; //已经画好的线条 存入数组  @property(nonatomic,strong) NSMutableDictionary* LinesInProscess; //正在画的线条 存入字典  @property(nonatomic,strong) UIColor *lineColor;//线条颜色  @property (nonatomic)float lineWidth;//线条的粗细 

//初始化  - (id)initWithFrame:(CGRect)frame{      if (self = [super initWithFrame:frame]) {          //初始化变量          _completeLines = [[NSMutableArray alloc]init];          _LinesInProscess = [[NSMutableDictionary alloc]init];          //设置透明背景          self.backgroundColor = [UIColor clearColor];                }            return  self;  } 

#import <Foundation/Foundation.h>  #import <UIKit/UIKit.h>    @interface Line : NSObject    @property(nonatomic)CGPoint begin; //线条开始点    @property(nonatomic)CGPoint end; //线条结束点    @end 

// Only override drawRect: if you perform custom drawing.  // An empty implementation adversely affects performance during animation.  - (void)drawRect:(CGRect)rect {      // Drawing code            //获取上下文      CGContextRef cgt=UIGraphicsGetCurrentContext();      //设置线条宽度      CGContextSetLineWidth(cgt, self.lineWidth);      //设置线条两端形状为圆角      CGContextSetLineCap(cgt, kCGLineCapRound);            //设置颜色      [self.lineColor set];      //绘制已经完成的线段      for (Line *line in _completeLines){          CGContextMoveToPoint(cgt, [line begin].x, [line begin].y);          CGContextAddLineToPoint(cgt, [line end].x, [line end].y );          CGContextStrokePath(cgt);      }                  //绘制正在画的线段      for (NSArray *v in _LinesInProscess) {          Line *line =[_LinesInProscess objectForKey:v];          CGContextMoveToPoint(cgt, [line begin].x, [line begin].y);          CGContextAddLineToPoint(cgt, [line end].x, [line end].y );          CGContextStrokePath(cgt);      }        } 

//清空画板  -(void)clearAll  {      [_completeLines removeLastObject];      [_LinesInProscess removeAllObjects];      [self setNeedsDisplay];  }      -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event  {      //判断是否连按      for (UITouch *t in touches) {          if ([t tapCount]>1) {              //第二次画线时第一条线还未完成时结束画线              [self clearAll];              return;          }                    //NSValue 作为键使用          NSValue *key=[NSValue valueWithNonretainedObject:t];                    // 根据触摸位置创建Line对象          CGPoint loc=[t locationInView:self];          Line *newLine=[[Line alloc]init ];          newLine.begin=loc;          newLine.end=loc;          //将当前正在画的线存入字典          [_LinesInProscess setObject:newLine forKey:key];                }  }    -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event  {      //手指移动过程中按照当前手指的位置动态更新线条      for (UITouch * t in touches) {          NSValue *key=[NSValue valueWithNonretainedObject:t];          // 找对象当前UITouch对象的Line对象          Line *line =[_LinesInProscess objectForKey:key];                    CGPoint loc=[t locationInView:self];          line.end=loc;      }      [self setNeedsDisplay];  }    -(void)endTouches:(NSSet *) touches  {      //画线完成之后将当前线条加入_completeLines 数组中 同时删除字典_LinesInProscess里的线条      for (UITouch *t in touches) {          NSValue *key=[NSValue valueWithNonretainedObject:t];          Line *line =[_LinesInProscess objectForKey:key];          if (line) {              [_completeLines addObject:line];              [_LinesInProscess removeObjectForKey:key];          }      }      [self setNeedsDisplay];  }    -(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event  {      [self endTouches:touches];  }    -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event  {      [self endTouches:touches];  } 

- (void)addLineAct:(id)sender{      NSLog(@"测试按钮");            DrawLine *touchdrawView = [[DrawLine alloc]initWithFrame:imageV.frame];        touchdrawView.lineColor = [UIColor yellowColor];      touchdrawView.lineWidth = 5.0;      touchdrawView.tag = 902;      [self.view addSubview:touchdrawView];              } 

//添加剪头  double r = sqrt((line.end.x-line.begin.x)*(line.end.x-line.begin.x)+(line.begin.y-line.end.y)*(line.begin.y-line.end.y));//线条长度  CGContextMoveToPoint(cgt,line.end.x,line.end.y);  //P1  CGContextAddLineToPoint(cgt,line.end.x-(10*(line.begin.y-line.end.y)/r),line.end.y-(10*(line.end.x-line.begin.x)/r));  //P3  CGContextAddLineToPoint(cgt,line.end.x+(20*(line.end.x-line.begin.x)/r), line.end.y-(20*(line.begin.y-line.end.y)/r));  //P2  CGContextAddLineToPoint(cgt,line.end.x+(10*(line.begin.y-line.end.y)/r),line.end.y+(10*(line.end.x-line.begin.x)/r));    CGContextAddLineToPoint(cgt, line.end.x,line.end.y);  CGContextDrawPath(cgt,kCGPathFillStroke);  CGContextStrokePath(cgt);