03 - renderInContext:与drawInContext:方法 - 截屏(截图)无法显示子控件

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03 - renderInContext:与drawInContext:方法 - 截屏(截图)无法显示子控件

问题描述

• 前提 : 自定义View:包含若干个子控件
• 理想现象 : 用上下文(UIGraphics)取得View.layer 生成的图片,导到对应路径
• 报错reason : 无报错
• 解决方式 : 渲染方法从drawInContext:改为renderInContext:

创建部分Code:

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
 UIGraphicsBeginImageContextWithOptions(self.drawVIew.bounds.size, NO,0.0);

    //获取当前的上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //把控制器的view的内容画到上下文当中.
         [self.drawVIew.layer drawInContext:ctx];
     // [self.drawVIew.layer renderInContext:ctx];//修改后

    //从上下文当中生成一张图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    //关闭上下文
    UIGraphicsEndImageContext();
    ///Users/apple/Desktop/素材
    //把图片写入到桌面
    //把图片转成二进制流
    //NSData *data = UIImageJPEGRepresentation(newImage, 1);
    NSData *data = UIImagePNGRepresentation(newImage);
    [data writeToFile:@"/Users/a1/Desktop/newImage.png" atomically:YES];
}

分析:

• (void)renderInContext:(CGContextRef)ctx; 该方法为渲染view.layer

/* Defines how the edges of the layer are rasterized. For each of the
     * four edges (left, right, bottom, top) if the corresponding bit is
     * set the edge will be antialiased. Typically this property is used to
     * disable antialiasing for edges that abut edges of other layers, to
     * eliminate the seams that would otherwise occur. The default value is
     * for all edges to be antialiased. */  

• (void)drawInContext:(CGContextRef)ctx; 该方法为渲染UIImage

/* Rendering properties and methods. **/
    /*  Renders the receiver and its sublayers into 'ctx'. This method
     * renders directly from the layer tree. Renders in the coordinate space
     * of the layer.
     * WARNING: currently this method does not implement the full
     * CoreAnimation composition model, use with caution.
     *  */

修改方法:

渲染方法从drawInContext:改为renderInContext: