如何裁剪小部件，或切出特定大小的小部件的正方形部分？

Question

我想裁剪 CameraPreview 小部件，以便只获得我想要裁剪它的确切大小和位置。

目前我可以使用ClipRect 对其进行剪辑， 但是我在小部件被剪掉的地方周围出现了这个黑色区域，我想删除它（请参阅下面的替换图）

假设我们有一个这样的小部件

 --------------                       
|88888888888888|                               
|88888888888888|                   
|88888888888888|                     
|88888888888888|                      
|88888888888888|                     
|88888888888888|                     
 --------------  

我需要裁剪小部件，（不是剪辑）

 --------------                       
|              |                               
|              |                    
|         888  |                      -----
|         888  |                     | 888 | 
|         888  |                     | 888 | 
|              |                     | 888 |
 --------------                       -----
     CLIPPING                        CROPPING

谁能帮我裁剪一个小部件？

Answer 1

没关系，我自己设法解决了， 感觉 Flutter 框架以神秘的方式工作，直到我弄清楚了这一点

return Container( // just a parent
      child: Align( // important
        alignment: Alignment.center,
        child: Container( // just a parent
          width: some_width,  
          height: some_height,  
          child: SizedBox(
            width: width,  // final width of cropped portion
            height: width,  // final height of cropped portion
            child: OverflowBox(
              alignment: Alignment(-1,-1), // gives you top left portion of the size above, (1,1) gives bottom right, right direction is positive x, downward direction is positive y, see about Alignment on flutter docs for more details 
              maxWidth: double.infinity,
              maxHeight: double.infinity,
              child: Container(
                width: width,
                height: width,
                child: ClipRect(
                  clipper: RectClipper(i, width / 4),// this is a custom clipper i made of type CustomClipper<Rect>
                  child: CameraPreview(controller),
                ),
              ),
            ),
          ),
        ),
      ),
    );

Answer 2

试试这个

final Size size = controller.value.size;
return ClipRect(
  child: OverflowBox(
    maxWidth: double.infinity,
    maxHeight: double.infinity,
    alignment: Alignment.center,
    child: FittedBox(
      fit: BoxFit.cover,
      alignment: Alignment.center,
      child: new Container(
        width: size.width,
        height: size.height,
        child: CameraPreview(controller)
      )
    )
  )
);