#define ScreenHeight [[UIScreen mainScreen] bounds].size.height
#define ScreenWidth [[UIScreen mainScreen] bounds].size.width

@property (nonatomic,strong)NSMutableArray *buttonArr;//全部手势按键的数组
@property (nonatomic,strong)NSMutableArray *selectorArr;//选中手势按键的数组
@property (nonatomic,assign)CGPoint startPoint;//记录开始选中的按键坐标
@property (nonatomic,assign)CGPoint endPoint;//记录结束时的手势坐标
@property (nonatomic,strong)UIImageView *imageView;//画图所需

-(NSMutableArray *)selectorArr
{
  if (!_selectorArr) {
    _selectorArr = [[NSMutableArray alloc]init];
  }
  return _selectorArr;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  self.view.backgroundColor = [UIColor whiteColor];

  
  if (!_buttonArr) {
    _buttonArr = [[NSMutableArray alloc]initWithCapacity:9];
  }
  
  self.imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ScreenWidth, ScreenHeight)];
  [self.view addSubview:self.imageView];

  for (int i=0; i<3; i++) {
    for (int j=0; j<3; j++) {
      UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
      btn.frame = CGRectMake(ScreenWidth/12+ScreenWidth/3*j, ScreenHeight/3+ScreenWidth/3*i, ScreenWidth/6, ScreenWidth/6);
      [btn setImage:[UIImage imageNamed:@"pbg"] forState:UIControlStateNormal];
      [btn setImage:[UIImage imageNamed:@"pbg01"] forState:UIControlStateHighlighted];
      btn.userInteractionEnabled = NO;
      [self.buttonArr addObject:btn];
      [self.imageView addSubview:btn];
    }
    
  }
}

-(UIImage *)drawLine{
  UIImage *image = nil;
  
  UIColor *col = [UIColor colorWithRed:1 green:0 blue:0 alpha:1];
  UIGraphicsBeginImageContext(self.imageView.frame.size);//设置画图的大小为imageview的大小
  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextSetLineWidth(context, 5);
  CGContextSetStrokeColorWithColor(context, col.CGColor);
  
  CGContextMoveToPoint(context, self.startPoint.x, self.startPoint.y);//设置画线起点

  //从起点画线到选中的按键中心，并切换画线的起点
  for (UIButton *btn in self.selectorArr) {
    CGPoint btnPo = btn.center;
    CGContextAddLineToPoint(context, btnPo.x, btnPo.y);
    CGContextMoveToPoint(context, btnPo.x, btnPo.y);
  }
  //画移动中的最后一条线
  CGContextAddLineToPoint(context, self.endPoint.x, self.endPoint.y);
  
  CGContextStrokePath(context);
  
  image = UIGraphicsGetImageFromCurrentImageContext();//画图输出
  UIGraphicsEndImageContext();//结束画线
  return image;
}

//开始手势
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
  UITouch *touch = [touches anyObject];//保存所有触摸事件
  if (touch) {
    
    
    for (UIButton *btn in self.buttonArr) {
      
      CGPoint po = [touch locationInView:btn];//记录按键坐标
      
      if ([btn pointInside:po withEvent:nil]) {//判断按键坐标是否在手势开始范围内,是则为选中的开始按键
        
        [self.selectorArr addObject:btn];
        btn.highlighted = YES;
        self.startPoint = btn.center;//保存起始坐标
      }
    
    }
    
  }
  
}

//移动中触发，画线过程中会一直调用画线方法
-(void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
  UITouch *touch = [touches anyObject];
  if (touch) {
    
    self.endPoint = [touch locationInView:self.imageView];
    for (UIButton *btn in self.buttonArr) {
      CGPoint po = [touch locationInView:btn];
      if ([btn pointInside:po withEvent:nil]) {
        
        BOOL isAdd = YES;//记录是否为重复按键
        for (UIButton *seBtn in self.selectorArr) {
          if (seBtn == btn) {
            isAdd = NO;//已经是选中过的按键，不再重复添加
            break;
          }
        }
        if (isAdd) {//未添加的选中按键，添加并修改状态
          [self.selectorArr addObject:btn];
          btn.highlighted = YES;
        }
        
      }
    }
  }
  self.imageView.image = [self drawLine];//每次移动过程中都要调用这个方法，把画出的图输出显示
  
}
//手势结束触发
-(void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
  self.imageView.image = nil;
  self.selectorArr = nil;
  for (UIButton *btn in self.buttonArr) {
    btn.highlighted = NO;
  }
}