com.facebook.react.bridge.readablenativemap cannot be cast to java.lang.string

问题

My code:

const file = {
  uri: this.state.imageSource,
  name: this.state.imageName,
  type: 'image/jpg',
};

const data = new FormData();
data.append('file', file);

fetch(config.server + '/upload', {
  method: 'POST',
  body: data,
})
  .then((res) => res.json())
  .then((responseData) => {
    alert(JSON.stringify(responseData));
  })
  .catch((err) => {
    alert(err);
  });

Without FormData code doesnt display error. What I should do to fix? Debugging on android.

回答1:

The error was because I was passing in the url as an array but it expected a string.

回答2:

I was getting this error because my URL was incorrect

回答3:

This will resolve the issue : alert(JSON.stringify(data))

回答4:

In my case I was not running the api server.

回答5:

I also faced the same issue and the below line of code can be a solution.

var formdata = new FormData();
formdata.append("mobile", phonenumber);

var requestOptions = {
method: 'POST',
body: formdata,
redirect: 'follow'
};

fetch("http://your_url", requestOptions)
.then(response => response.text())
.then(result => console.log(result))
.catch(error => console.log('error', error));

回答6:

react-native link

Use this command to resolve this issue. This worked for me.

Note : Only for react-native < 60.x

来源：https://stackoverflow.com/questions/50623080/com-facebook-react-bridge-readablenativemap-cannot-be-cast-to-java-lang-string