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class _FormTestRouteState extends State<FormTestRoute> {
  bool _hasFocusOnFocusNode2 = false;
  TextEditingController _unameController = TextEditingController();

  FocusNode focusNode1 = FocusNode();
  FocusNode focusNode2 = FocusNode();
  FocusScopeNode? focusScopeNode;

  TextEditingController _uname2Controller = TextEditingController();
  TextEditingController _pwdController = TextEditingController();
  GlobalKey _formKey = GlobalKey<FormState>();

  @override
  void initState() {
    super.initState();
    _unameController.text = "hello world!";
    _unameController.selection = TextSelection(
        baseOffset: 2, extentOffset: _unameController.text.length);
    //监听输入改变
    _unameController.addListener(() {
      print(_unameController.text);
    });

    focusNode2.addListener(() {
      setState(() {
        print(_hasFocusOnFocusNode2);
        _hasFocusOnFocusNode2 = focusNode2.hasFocus;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        TextField(
          controller: _unameController,
          autofocus: true,
          focusNode: focusNode1,
          decoration: InputDecoration(
            labelText: "用户名",
            hintText: "用户名或邮箱",
            prefixIcon: Icon(Icons.person),
            enabledBorder: UnderlineInputBorder(
              borderSide: BorderSide(color: Colors.grey),
            ),
            //获得焦点下划线设为蓝色
            focusedBorder: UnderlineInputBorder(
              borderSide: BorderSide(color: Colors.blue),
            ),
          ),
        ),
        Container(
          decoration: BoxDecoration(
              border: Border(
                  bottom: _hasFocusOnFocusNode2
                      ? BorderSide(color: Colors.orange, width: 1.0)
                      : BorderSide(color: Colors.grey, width: 1.0))),
          child: TextField(
            decoration: InputDecoration(
                labelText: "密码",
                hintText: "您的登录密码",
                prefixIcon: Icon(Icons.lock),
                border: InputBorder.none),
            focusNode: focusNode2,
            obscureText: true,
          ),
        ),
        Builder(
          builder: (ctx) {
            return Column(
              children: <Widget>[
                ElevatedButton(
                  child: Text("移动焦点"),
                  onPressed: () {
                    // 将焦点从第一个TextField移到第二个TextField
                    // 这是一种写法 
                    // FocusScope.of(context).requestFocus(focusNode2);
                    // 这是第二种写法
                    focusScopeNode ??= FocusScope.of(context);
                    focusNode1.unfocus();
                    focusScopeNode?.requestFocus(focusNode2);
                  },
                ),
                ElevatedButton(
                  child: Text("隐藏键盘"),
                  onPressed: () {
                    // 当所有编辑框都失去焦点时键盘就会收起
                    focusNode1.unfocus();
                    focusNode2.unfocus();
                  },
                ),
              ],
            );
          },
        ),
        Form(
          key: _formKey, //设置globalKey，用于后面获取FormState
          autovalidateMode: AutovalidateMode.onUserInteraction,
          child: Column(
            children: <Widget>[
              Padding(
                  padding: const EdgeInsets.only(left: 20.0, right: 20.0),
                  child: Column(
                    children: [
                      TextFormField(
                        autofocus: true,
                        controller: _uname2Controller,
                        decoration: InputDecoration(
                          labelText: "用户名",
                          hintText: "用户名或邮箱",
                          icon: Icon(Icons.person),
                        ),
                        // 校验用户名
                        validator: (v) {
                          return v!.trim().isNotEmpty ? null : "用户名不能为空";
                        },
                      ),
                      TextFormField(
                        controller: _pwdController,
                        decoration: InputDecoration(
                          labelText: "密码",
                          hintText: "您的登录密码",
                          icon: Icon(Icons.lock),
                        ),
                        obscureText: true,
                        //校验密码
                        validator: (v) {
                          return v!.trim().length > 5 ? null : "密码不能少于6位";
                        },
                      ),
                    ],
                  )),

              // 登录按钮
              Padding(
                padding:
                    const EdgeInsets.only(left: 38.0, right: 38.0, top: 10.0),
                child: Row(
                  children: <Widget>[
                    Expanded(
                      child: ElevatedButton(
                        child: Padding(
                          padding: const EdgeInsets.all(16.0),
                          child: Text(
                            "登录",
                            style: TextStyle(color: Colors.white, fontSize: 14),
                          ),
                        ),
                        onPressed: () {
                          // 通过_formKey.currentState 获取FormState后，
                          // 调用validate()方法校验用户名密码是否合法，校验
                          // 通过后再提交数据。
                          if ((_formKey.currentState as FormState).validate()) {
                            //验证通过提交数据
                          }
                        },
                      ),
                    ),
                  ],
                ),
              )
            ],
          ),
        )
      ],
    );
  }
}