Widget content(LoginViewModel viewModel, BoxConstraints constraints) =>
      (viewModel.status != LoadingStatus.loading || viewModel?.type == ScreenState.WELCOME)? new Container(
      child: new Stack(
          fit: StackFit.expand,
          alignment: Alignment.topCenter,
          children: <Widget>[
            new Align(
              alignment: Alignment.topCenter,
              child: new Transform(
                  transform: new Matrix4.translationValues(0.0, _animation.value, 0.0),
                  child: SingleChildScrollView(
                    child: new Column(
                      children: <Widget>[
                       ...
                        viewModel.type == ScreenState.SINGIN?new Column(
                          mainAxisSize: MainAxisSize.max,
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: <Widget>[
                            emailInput(viewModel),
                            (viewModel.status == LoadingStatus.error && viewModel.emailError.isNotEmpty)?emailError(viewModel):const SizedBox(),
                            ...
                            Padding(
                              padding: const EdgeInsets.only(left: 65.0,right: 65.0,top: 16.0),
                              child: Row(
                                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                                mainAxisSize: MainAxisSize.max,
                                children: <Widget>[
                                  ...
                                  loginBtn((){
                                    viewModel.login(viewModel.email,viewModel.password);
                                  })
                                ],
                              ),
                            ),
                            ...
                            termsAndConditions(),
                            new Padding(padding: const EdgeInsets.all(16.0))
                          ],
                        ):Container()
                      ],
                    ),
                  ),
              ),
            ),
          ],
      ),
  ):new Center(
    child: new CircularProgressIndicator(),
  );