iOS绘图功能

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

{

    NSMutableArray *pointArray = [NSMutableArray arrayWithCapacity:1];

    [_lineArry addObject:pointArray];

}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

{

    UITouch *touch = [touches anyObject];

    // 获取当前点的位置

    CGPoint point = [touch locationInView:self];

    NSLog(@"point = %@", NSStringFromCGPoint(point));

    // 拿到最后一个对象

    NSMutableArray *pointArray = [_lineArry lastObject];

    // 转换成对象类型

    NSValue *pointValue = [NSValue valueWithCGPoint:point];

    // 添加到数组对象中

    [pointArray addObject:pointValue];

    

    [self setNeedsDisplay];

}

- (void)drawRect:(CGRect)rect

{

    // 拿到绘图的配置信息（绘画的属性信息）

    // 通过图片得到上下文

    CGContextRef context = UIGraphicsGetCurrentContext();

    // 设置画笔的颜色

    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);

    // 设置画笔的粗细

    CGContextSetLineWidth(context, 2.0);

    for (int i = 0; i < [_lineArry count]; i++) {

        NSMutableArray *pointArry = [_lineArry objectAtIndex:i];

        for (int j = 0; j < (int)pointArry.count-1; j++) {

            NSValue *firstPointValue = [pointArry objectAtIndex:j];

            NSValue *secondPointValue = [pointArry objectAtIndex:j + 1];

            CGPoint firstPoint  =  [firstPointValue CGPointValue];

            CGPoint secondPoint = [secondPointValue CGPointValue];

            // 把笔触移动到一个点

            CGContextMoveToPoint(context, firstPoint.x, firstPoint.y);

            // 笔触和另一点形成一个路径(从move到point)

            CGContextAddLineToPoint(context, secondPoint.x, secondPoint.y);

        }

    }// 绘制图形

    CGContextStrokePath(context);

}