此问题可能在两个位置发生，您可能会错过使用globalKey。请尝试在使用!之前检查null。

Future<void> _captureAndSharePng() async {
    try {
      RenderRepaintBoundary? boundary = globalKey.currentContext?.findRenderObject() as RenderRepaintBoundary?;
      if(boundary ==null){ 
         debugPrint("got null boundary");
         return;
       }
      var image = await boundary.toImage();
      ByteData? byteData = await image.toByteData(format: ImageByteFormat.png);
      Uint8List? pngBytes = byteData?.buffer.asUint8List();
      
      if(pngBytes==null){
       debugPrint("got null pngBytes");
         return;
       }

    ....