随笔-iOS学习简单绘图

在iOS中，图形的绘制是基于UIView来绘制的，所以，我们要先创建一个用来绘制图形的UIView类。

UIView的类中有一个方法是专门用来绘制图形的：

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
}
*/

我尝试了一些简单的图形绘制命令：

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
 */
- (void)drawRect:(CGRect)rect {
    // Drawing code
    
    //获取当前设备的上下文（画布）
    CGContextRef context = UIGraphicsGetCurrentContext();
    //画笔移到某一点
    CGContextMoveToPoint(context, 0, 0);
    //从一点到某一点画条线
    CGContextAddLineToPoint(context, 100, 100);
    //给线渲染涂色
    CGContextStrokePath(context);
    
    //矩形框
    CGContextAddRect(context, CGRectMake(0, 0, 100, 100));
    CGContextStrokeRect(context, CGRectMake(0, 0, 100, 100));
    //实心矩形
    CGContextFillRect(context, CGRectMake(100, 100, 100, 100));
    //空心圆
    CGContextStrokeEllipseInRect(context, CGRectMake(100, 200, 100, 100));
    //实心圆
    CGContextFillEllipseInRect(context, CGRectMake(100, 300, 100, 100));
    
    //绘制文字
    NSString * str = @"Hello world!";
    [str drawAtPoint:CGPointMake(125, 400) withAttributes:nil];
    //绘制图片
    [img drawAtPoint:CGPointMake(100, 500)];
    [img drawAsPatternInRect:CGRectMake(100, 400, 50, 50)]; //平铺填充
    CGContextDrawImage(context, CGRectMake(100, 500, 80, 80), [img CGImage]);//自由缩放
}

效果看起来笨笨的，哈哈，继续学习ing