//触摸开始
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
// 1，获取对应的touch对象
UITouch *touch = [touches anyObject];
// 2，通过touch对象获取手指触摸对象
CGPoint startPoint = [touch locationInView:touch.view];
// 3，创建小数组，保存当前路径所有点
NSMutableArray *subPoints = [NSMutableArray array];
// 4，手指触摸对象起点存于数组
[subPoints addObject:[NSValue valueWithCGPoint:startPoint]];
// 5，小数组存入大数组
[self.totalPoints addObject:subPoints];
}
//移动
-(void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
// 1，获取对应的touch对象
UITouch *touch = [touches anyObject];
// 2，通过touch对象获取手指触摸对象
CGPoint movePoint = [touch locationInView:touch.view];
// 3，从大数组中取出当前路径对应的小数组
NSMutableArray *subPoints = [self.totalPoints lastObject];
// 4，手指触摸对象起点存于数组
[subPoints addObject:[NSValue valueWithCGPoint:movePoint]];
// 5，调用drawRect方法重回视图
[self setNeedsDisplay];
}
//触摸结束
-(void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
[self touchesMoved:touches withEvent:event];
}
//画图
- (void)drawRect:(CGRect)rect {
// 1.获取图形上下文
CGContextRef ctx = UIGraphicsGetCurrentContext();
// 2.遍历大数组取出小数组
for(NSMutableArray *subPointArray in self.totalPoints)
{
for (int index = 0 ; index < subPointArray.count ; index++)
{
// 3.1取出小数组
CGPoint point = [subPointArray[index] CGPointValue];
// 3.2绘制线段
if(0 == index){
// 绘制起点
CGContextMoveToPoint(ctx, point.x, point.y);
}else{
// 绘制终点
CGContextAddLineToPoint(ctx, point.x, point.y);
}
}
}
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextSetLineJoin(ctx, kCGLineJoinRound);
CGContextSetLineWidth(ctx, 10);
// 渲染
CGContextStrokePath(ctx);
}
// 清屏
-(void)clean
{
[self.totalPoints removeAllObjects];
[self setNeedsDisplay];
}
// 撤销
-(void)back
{
[self.totalPoints removeLastObject];
[self setNeedsDisplay];
}