TextFormField创建键盘以快速打开和关闭

Question

我有一个TextFormField窗口小部件，该窗口小部件嵌入在页面上，旨在接受用户的评论。用户键入评论后，我将对其进行验证并将其发布到Firebase。当我启用了硬件键盘，然后单击并键入时，一切正常。

但是，当我禁用硬件键盘并想要抬起手机的键盘时，它开始抬起，然后立即折叠起来，重新加载页面。

如何防止这种情况发生？

class CommentCollector extends StatefulWidget {
  final String articleID;
  final String articleDate;
  final String articleTitle;
  final String userName;
  final String firstName;
  final String lastName;
  final String user_id;
  const CommentCollector(
      {Key key,
      this.articleID,
      this.articleTitle,
      this.userName,
      this.firstName,
      this.lastName,
      this.user_id,
      this.articleDate})
      : super(key: key);

  @override
  _CommentCollectorState createState() => new _CommentCollectorState();
}

class _PostData {
  String comment = '';
}

class _CommentCollectorState extends State<CommentCollector> {
  final _formKey = GlobalKey<FormState>();
  bool _commentPosted = false;
  _PostData _data = new _PostData();

  void submit() {
    // First validate form.
    if (this._formKey.currentState.validate()) {
      _formKey.currentState.save(); // Save our form now.

      addPost({
        'article': widget.articleID,
        'article_title': widget.articleTitle,
        'author': widget.userName,
        'comment': _data.comment,
        'firstName': widget.firstName,
        'lastName': widget.lastName,
        'user_id': widget.user_id,
        'respect_count': 0,
      });
      setState(() {
        _commentPosted = true;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    print(_formKey);
    switch (_commentPosted) {
      case (true):
        return new UserPostGetter(
          articleHeader: widget.articleTitle,
          articleId: widget.articleID,
        );

      case (false):
        return new Container(
          child: new Center(
            child: new Container(
              padding: EdgeInsets.all(8.0),
              child: new Card(
                shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(20.0)),
                elevation: 5.0,
                child: new Form(
                  key: this._formKey,
                  child: new Column(
                    mainAxisSize: MainAxisSize.min,
                    children: <Widget>[
                      new Padding(
                        padding: EdgeInsets.all(10.0),
                        child: new Text(
                          "What's your take on the issue?",
                          style: new TextStyle(fontSize: 18.0),
                        ),
                      ),
                      new Padding(
                        padding: EdgeInsets.all(20.0),
                        child: new Card(
                          elevation: 5.0,
                          child: new TextFormField(
                              validator: (value) {
                                if (value.isEmpty) {
                                  return 'Please enter some text';
                                }
                                if (value.length > 250) {
                                  return 'Please shorten comment';
                                }
                              },
                              decoration: new InputDecoration(
                                contentPadding: EdgeInsets.all(10.0),
                                border: InputBorder.none,
                                hintText: 'Your thoughts?',
                              ),
                              keyboardType: TextInputType.multiline,
                              maxLines: 6,
                              maxLength: 250,
                              onSaved: (String value) {
                                this._data.comment = value;
                              }),
                        ),
                      ),
                      new RaisedButton(
                        onPressed: this.submit,
                        child: new Text(
                          "SUBMIT",
                          style: new TextStyle(color: Colors.white),
                        ),
                        color: purpleColor(),
                      )
                    ],
                  ),
                ),
              ),
            ),
          ),
        );
    }
  }
}

//add post to Firebase
Future<void> addPost(postData) async {
  Firestore.instance.collection('post').add(postData).catchError((e) {
    print(e);
  });
  Firestore.instance.collection('respect_count').add({
    'count': 0,
  }).catchError((e) {
    print(e);
  });
}