javascript - 如何在另一个屏幕访问asyncStorage的Key

Question

我的应用程序中存在一些 AsyncStorage 问题，

我需要在另一个屏幕中使用用户名存储的值现在，当我登录屏幕并转到主屏幕时，我需要获取项目存储并向他们展示它的工作正常但是当注销并删除 key 时它使我进入登录屏幕，但是当刷新应用程序时，它会将我移动到主屏幕，2 秒后几乎将我导航到登录屏幕如何在第一次运行应用程序时不这样做

这里是我的两屏代码，

登录界面

import React, { Component } from "react";
import {
  StyleSheet,
  View,
  StatusBar,
  Text,
  TextInput,
  TouchableOpacity,
  AsyncStorage
} from "react-native";
export default class Login extends Component {
  constructor() {
    super();
    this.state = {
      username: "",
      password: ""
    };
  }

  componentDidMount() {
    const login = AsyncStorage.getItem("@myApp:username");
    if (login == null) {
      this.props.navigation.navigate("Login");
    } else {
      this.props.navigation.navigate("Home");
    }
  }
  _onLogin = () => {
    let username = this.state.username;
    let password = this.state.password;
    if (username !== "" && password !== "") {
      AsyncStorage.setItem("@myApp:username", this.state.username).then(
        username => {
          this.setState({ username: username });
        }
      );
      this.props.navigation.navigate("Home");
      console.log(`username is ${username}`);
    } else {
      this.props.navigation.navigate("Login");
    }
  };
  render() {
    return (
      <View style={styles.container}>
        <StatusBar backgroundColor="#333" barStyle="light-content" />
        <Text style={{ fontSize: 28, margin: 10 }}>Login</Text>
        <TextInput
          placeholder="Username"
          onChangeText={username => {
            this.setState({ username: username });
          }}
          value={this.state.username}
          autoCorrect={false}
          returnKeyType="next"
          style={{
            padding: 10,
            margin: 15,
            borderBottomColor: "#333",
            borderBottomWidth: 1,
            width: "80%"
          }}
          editable={true}
        />
        <TextInput
          placeholder="Password"
          onChangeText={password => {
            this.setState({ password: password });
          }}
          secureTextEntry={true}
          value={this.state.password}
          autoCorrect={false}
          returnKeyType="next"
          style={{
            padding: 10,
            margin: 15,
            borderBottomColor: "#333",
            borderBottomWidth: 1,
            width: "80%"
          }}
          editable={true}
        />

        <TouchableOpacity
          style={{
            margin: 20,
            padding: 10,
            width: "70%",
            backgroundColor: "#1a73e8"
          }}
          onPress={this._onLogin}
        >
          <Text style={{ color: "#FFF", textAlign: "center", fontSize: 18 }}>
            Log In
          </Text>
        </TouchableOpacity>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 20,
    justifyContent: "center",
    alignItems: "center",
    backgroundColor: "#fff"
  }
});

主屏幕

import React, { Component } from "react";
import {
  StyleSheet,
  View,
  ImageBackground,
  Text,
  AsyncStorage,
  TouchableOpacity
} from "react-native";
export default class Home extends Component {
  constructor() {
    super();
    this.state = {
      name: ""
    };
  }
  async componentDidMount() {
    try {
      const storedValue = await AsyncStorage.getItem("@myApp:username");
      this.setState({ name: storedValue });
      if (storedValue == null) {
        this.props.navigation.navigate("Login");
      }
      console.log(storedValue); 
    } catch (error) {
      Alert.alert("Error", "There was an error.");
    }
  }
  _onLogout = () => {
    AsyncStorage.removeItem("@myApp:username").then(
      this.props.navigation.navigate("Login")
    );
  };
  render() {
    return (
      <View style={styles.container}>
        <ImageBackground
          source={require("./assets/bg1.jpg")}
          style={{
            flex: 1,
            width: "100%",
            height: "100%"
          }}
        >
          <View
            style={{
              backgroundColor: "rgba(0,0,0,0)",
              flex: 1,
              justifyContent: "center"
            }}
          >
            <Text
              style={{
                alignSelf: "center",
                backgroundColor: "#000fff",
                padding: 10,
                color: "#fff"
              }}
            >
              {`Hello, ${this.state.name} `}
            </Text>
            <TouchableOpacity
              style={{
                margin: 20,
                padding: 10,
                width: "50%",
                backgroundColor: "#1a73e8",
                justifyContent: "center",
                alignSelf: "center"
              }}
              onPress={this._onLogout}
            >
              <Text
                style={{ color: "#FFF", textAlign: "center", fontSize: 18 }}
              >
                Log out?
              </Text>
            </TouchableOpacity>
          </View>
        </ImageBackground>
      </View>
    );
  }
}

Answer 1

您可以创建一个包含常量的 js 文件。然后在您的 Constant.js 文件中，您可以像下面这样添加您的 key :

 export const userNameKey= '@myApp:username';

您可以在屏幕中访问该键，如下所示:

import { userNameKey} from './Constants';

并将其用作:

const login = AsyncStorage.getItem(userNameKey);