React native 如何在ReactNative中使用异步存储

我在ReactJS中创建了运行良好的localstorage。 但我想用这段代码来反应。 我不知道怎样才能申请工作 这段代码是由js编写的

...
  componentWillMount(){
    const contactData = localStorage.contactData;
    if(contactData){
      this.setState({
        contactData:JSON.parse(contactData)
      })
    }
  }
...
...
  componentWillMount(){
    const contactData = localStorage.contactData;
    if(contactData){
      this.setState({
        contactData:JSON.parse(contactData)
      })
    }
  }
...

我读了这个

---

但是我不太明白。

对于React本机存储，您必须使用异步存储。上述代码在react native中将变为

...
async componentWillMount(){
const contactData = await AsyncStorage.getItem('contactData');
if(contactData){
  this.setState({
    contactData:JSON.parse(contactData)
  })
}
}
...
...
async componentWillMount(){
const contactData = localStorage.getItem('contactData');
if(contactData){
  this.setState({
    contactData:JSON.parse(contactData)
  })
}
}
...

---

您可以使用async wait或then/catch承诺来处理数据。

对于React本机存储，您必须使用async存储。上述代码在react native中将变为

...
async componentWillMount(){
const contactData = await AsyncStorage.getItem('contactData');
if(contactData){
  this.setState({
    contactData:JSON.parse(contactData)
  })
}
}
...
...
async componentWillMount(){
const contactData = localStorage.getItem('contactData');
if(contactData){
  this.setState({
    contactData:JSON.parse(contactData)
  })
}
}
...

    this.retrieveItem(goalCategory).then((goals) => {
              //this callback is executed when your Promise is resolved
              }).catch((error) => {
              //this callback is executed when your Promise is rejected
              console.log('Promise is rejected with error: ' + error);
              }); 

//the functionality of the retrieveItem is shown below
async retrieveItem(key) {
    try {
      const retrievedItem =  await AsyncStorage.getItem(key);
      const item = JSON.parse(retrievedItem);
      return item;
    } catch (error) {
      console.log(error.message);
    }
    return
  }

您可以使用async wait或then/catch承诺来处理数据

    this.retrieveItem(goalCategory).then((goals) => {
              //this callback is executed when your Promise is resolved
              }).catch((error) => {
              //this callback is executed when your Promise is rejected
              console.log('Promise is rejected with error: ' + error);
              }); 

//the functionality of the retrieveItem is shown below
async retrieveItem(key) {
    try {
      const retrievedItem =  await AsyncStorage.getItem(key);
      const item = JSON.parse(retrievedItem);
      return item;
    } catch (error) {
      console.log(error.message);
    }
    return
  }

保存到异步存储

从异步存储中检索值

从异步存储中删除

保存到异步存储

从异步存储中检索值

从异步存储中删除

const deleteUserId = async () => {
  try {
    await AsyncStorage.removeItem('userId');
  } catch (error) {
    // Error retrieving data
    console.log(error.message);
  }
}