在自定义大小View上显示Camera预览，不变形

需求：
在项目里某一界面大约2 / 3面积用于显示camera预览， 预览Size不确定，要求预览不变形。
如图：

显示预览控件用的textureview
核心代码：

 private void fixPreviewFrame()
       {
           if (camera != null)
           {
               if (TextureWidth == 0 || TextureHeight == 0)
               {
                   return;
               }
               Matrix matrix = textureView.Matrix;
               global::Android.Hardware.Camera.Size preSize = camera.GetParameters().PreviewSize;
               int previewWid = shouldRotate() ? preSize.Height : preSize.Width;
               int previewHei = shouldRotate() ? preSize.Width : preSize.Height;
               float scaleWid = (float)previewWid / TextureWidth;
               float scaleHei = (float)previewHei / TextureHeight;

             /*  if(scaleWid<1 || scaleHei < 1)
               {*/
                   if(scaleWid < scaleHei)
                   {   
                       float secondScale = 1f / scaleWid;
                       scaleWid = 1;
                       scaleHei *= secondScale;
                   }
                   else
                   {
                       float secondScale = 1f / scaleHei;
                       scaleHei = 1;
                       scaleWid *= secondScale;
                   }
/*
               }
               else
               {
                   if (scaleWid < scaleHei)
                   {
                       float secondScale = 1f / scaleWid;
                       scaleWid = 1;
                       scaleHei *= secondScale;
                   }
                   else
                   {
                       float secondScale = 1f / scaleHei;
                       scaleHei = 1;
                       scaleWid *= secondScale;
                   }
               }*/

            

               matrix.SetScale(scaleWid, scaleHei, TextureWidth / 2, TextureHeight / 2);
               textureView.SetTransform(matrix);
           }
       }