Flutter 桌面端保存文件到指定目录 file_picker

 File imageFile = File(
                                  "${dir.path}/uMessage/${DateTime.now().millisecondsSinceEpoch}.png");
                                    imageFile.createSync(recursive: true);
                                    imageFile.writeAsBytesSync(capturedImage);
            
                                    String? outputFile = await FilePicker.platform.saveFile(
                                      dialogTitle: 'Save Your File to desired location',
                                      fileName: "untitled.png",
                                    );

                                    try {
                                      File returnedFile = File('$outputFile');
                                      await returnedFile.writeAsBytes(imageFile.readAsBytesSync());
                                    } catch (e) {
                                      print(e);
                                    }