Question

为什么我无法在以下代码中导航至屏幕“ App”。我收到错误消息：

无法读取未定义的属性“ navigate”

  async signIn() {
    const { username, password } = this.state
    await Auth.signIn(username, password)
    .then(user => {
      this.setState({ user })
      this.props.navigation.navigate("App");
      Alert.alert('Signed In Successful!')
    })
    .catch(err => {
        console.log('Error when signing in: ', err)
        Alert.alert('Error when signing in: ', err)
    })
  }
}

Answer 1

您正在兑现承诺并等待。您要么等待登录，要么删除异步/等待并将其视为承诺。另外，可能是您尚未绑定函数，因此“ this”指向未定义。

要么：

async signIn = () => {
    const { username, password } = this.state
    let user = await Auth.signIn(username, password);
     this.setState({ user })
      this.props.navigation.navigate("App");
      Alert.alert('Signed In Successful!')

  }
}

或

signIn = () => {
    const { username, password } = this.state
    Auth.signIn(username, password)
    .then(user => {
      this.setState({ user })
      this.props.navigation.navigate("App");
      Alert.alert('Signed In Successful!')
    })
    .catch(err => {
        console.log('Error when signing in: ', err)
        Alert.alert('Error when signing in: ', err)
    })
  }
}

无法读取.then（）=> {}中未定义的属性“ navigate”

1 个答案: