当我滚动时,颤动的表格数据消失了

@override
  Widget build(BuildContext context) {
    var _children = <Widget>[
      new Center(
        child: new Text(widget.prov.fname + widget.prov.lname,style: new TextStyle(fontSize: 20.0,fontWeight: FontWeight.bold),),new Center(
          child: new Container(
            padding: new EdgeInsets.only(
                left: 125.0,right: 125.0,bottom: 50.0),child: new Image.network('http://174.138.61.246:8080/getimage/'+widget.prov.pic.assetName),)
      ),new Form(
          key: _formKey,autovalidate: _autovalidate,onWillPop: _warnUserAboutInvalidData,child: new Expanded(
              child: new ListView(
                padding: const EdgeInsets.symmetric(horizontal: 16.0),children: <Widget>[
                  new TextFormField(
                    decoration: const InputDecoration(
                      icon: const Icon(Icons.person),hintText: 'First Name?',labelText: 'First Name *',onSaved: (String value) { referral.fname = value; },validator: _validateName,new TextFormField(
                    decoration: const InputDecoration(
                      icon: const Icon(Icons.person),hintText: 'Last Name?',labelText: 'Last Name *',onSaved: (String value) { referral.lname = value; },new TextFormField(
                    decoration: const InputDecoration(
                        icon: const Icon(Icons.phone),hintText: 'How to contact?',labelText: 'Phone Number *',prefixText: '+1'
                    ),keyboardType: TextInputType.phone,onSaved: (String value) { referral.contact = value; },validator: _validatePhoneNumber,// TextInputFormatters are applied in sequence.
                    inputFormatters: <TextInputFormatter> [
                      WhitelistingTextInputFormatter.digitsOnly,// Fit the validating format.
                      _phoneNumberFormatter,],new TextFormField(
                    decoration: const InputDecoration(
                      hintText: 'Tell us about patient',helperText: 'It does not have to be detailed yet',labelText: 'Referral Details',maxLines: 5,new _DateTimePicker(
                    labelText: 'DOB',selectedDate: _fromDate,selectDate: (DateTime date) {
                      setState(() {
                        referral.dob = date;
                      });
                    },new InputDecorator(
                    decoration: const InputDecoration(
                      labelText: 'Type of Appointment',hintText: 'Choose an Appointment Type',isEmpty: _typeAppt == null,child: new DropdownButton<String>(
                      value: _typeAppt,isDense: true,onChanged: (String newValue) {
                        setState(() {
                          _typeAppt = newValue;
                        });
                      },items: _allTypeAppt.map((String value) {
                        return new DropdownMenuItem<String>(
                          value: value,child: new Text(value),);
                      }).toList(),)
          )
      ),/*new RefreshIndicator(
        child: new ListView.builder(
          itemBuilder: _itemBuilder,itemCount: listcount,onRefresh: _onRefresh,*/

    ];
    return new Scaffold(
      appBar: new AppBar(title: new Text("My Provider")),body: new Column(
        children: _children,);
  }