Question

按下登录按钮时，我想显示一个toast，以成功或“未找到”消息显示用户详细信息。

 new RaisedButton(
     onPressed: () {
        Future<User> user = _sendToServer();

        if (user != null) {
              Toast.show("You have logged as ${user.toString()}", context,
                  duration: Toast.LENGTH_SHORT, gravity: Toast.BOTTOM);
        } else {
              Toast.show("Not found", context,
                  duration: Toast.LENGTH_SHORT, gravity: Toast.BOTTOM);
        }
     },
     child: new Text('log in'),
  ),

我知道我收到了正确的回复，但无法使用吐司显示它。

Future<User> _sendToServer() async {
  DatabaseHelper helper = DatabaseHelper.instance;
  if (_key.currentState.validate()) {
    // No any error in validation
    _key.currentState.save();
    User user = await helper.getLogin(email, password);
    print("login user ${user.email}");
    return user;
  } else {
    // validation error
    setState(() {
      _validate = true;
    });
    return null;
  }
}

Answer 1

您应将onPressed设为异步，并在等待状态下调用函数或将其用作承诺。

对于exa-

yourFunctiomWithFuture().then((value) {
    // Run code here
  }, onError: (error) {
    print(error);
  });

Answer 2

RaisedButton(
  onPressed: () async{ // mark it async
    User user = await _sendToServer(); // await to get user

    if (user != null) {
      Toast.show("You have logged as ${user.toString()}", context,
          duration: Toast.LENGTH_SHORT, gravity: Toast.BOTTOM);
    } else {
      Toast.show("Not found", context,
          duration: Toast.LENGTH_SHORT, gravity: Toast.BOTTOM);
    }
  },
  child: new Text('log in'),
)

单击凸起按钮时如何在烤面包上显示消息？

2 个答案: