TextField(
  decoration: InputDecoration(hintText: "请输入用户名"),
  controller: TextEditingController.fromValue(TextEditingValue(
      // 设置内容
      text: _useName.text,
      // 保持光标在最后
      selection: TextSelection.fromPosition(TextPosition(
          affinity: TextAffinity.downstream,
          offset: _useName.text.length)))),
  onChanged: (value) {
    setState(() {
      _useName.text = value;
    });
  },
),复制