null is not an object (evaluating 'ShareDialog.canShow')

问题

I have an code like this:

import React, { Component } from 'react';
import {AppRegistry, StyleSheet, Text, TouchableHighlight, View,} from 'react-native';
import {LoginButton, ShareDialog} from 'react-native-fbsdk';

class RNSample extends Component {
constructor(props) {
super(props);
const shareLinkContent = {
  contentType: 'link',
  contentUrl: 'https://www.facebook.com/',
  contentDescription: 'Facebook sharing is easy!'
};

this.state = {shareLinkContent: shareLinkContent,};
}

shareLinkWithShareDialog() {
var tmp = this;
ShareDialog.canShow(this.state.shareLinkContent).then(
  function(canShow) {
    if (canShow) {
      return ShareDialog.show(tmp.state.shareLinkContent);
    }
  }
).then(
  function(result) {
    if (result.isCancelled) {
      alert('Share cancelled');
    } else {
      alert('Share success with postId: ' + result.postId);
    }
  },
  function(error) {
    alert('Share fail with error: ' + error);
  }
);
}

   render() {
return (
  <View style={styles.container}>
    <LoginButton
      onLoginFinished={
        (error, result) => {
          if (error) {
            alert("Login failed with error: " + error.message);
          } else if (result.isCancelled) {
            alert("Login was cancelled");
          } else {
            alert("Login was successful with permissions: " + result.grantedPermissions)
          }
        }
      }
      onLogoutFinished={() => alert("User logged out")}/>
    <TouchableHighlight onPress={this.shareLinkWithShareDialog.bind(this)}>
      <Text style={styles.shareText}>Share link with ShareDialog</Text>
    </TouchableHighlight>
  </View>
    );
 }
 }

const styles = StyleSheet.create({
  container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
 },
 shareText: {
fontSize: 20,
margin: 10,
},
});

AppRegistry.registerComponent('RNSample', () => RNSample);

But I get an error like this: 'null is not an object (evaluating 'ShareDialog.canShow')

here the screenshot

I'm using react native. I don't understand why I get this error. React Native and React latest version I use. I did the Facebook SDK settings for my app.

I tested more than one times but it gets still error. And by the way, why stackoverflow says "It looks like your post is mostly code; please add some more details." It's very annoying!

回答1:

You referred this to a local variable in shareLinkWithShareDialog function but to canShow you are passing state using this.state.shareLinkContent which isn’t correct. It should be tmp.state.shareLinkContent

So Change

    ShareDialog.canShow(this.state.shareLinkContent)

    ShareDialog.canShow(tmp.state.shareLinkContent)

Would fix your issue

来源：https://stackoverflow.com/questions/54696944/null-is-not-an-object-evaluating-sharedialog-canshow

标签

reactjs

react-native