［ios］quartz2d画板功功能实现核心代码

//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];

}