navigation.getParam in not an object

问题

I am trying to get an image that is stored in an array in one screen and set it in as a source for an image in another screen. Essentially when a user touches a certain image that exact image will be carried to the next screen. The problem is that I am receiving an error saying undefined is not an object (evaluating 'navigation.getParam')

the code is as follows: Screen 1

this.state = {
  messageItem: null,
  chat: [{
    convo: [Chat1, Chat2, Pic1, Chat4, Chat5, Chat6],
  }]
}

openMessage = (bub) => {
  this.setState({
    messageItem: bub
  });
  console.log({ bub })
}

renderChat = () => {
  return this.state.chat.map((bub, index) => {
    return bub.convo.map((convo, i) => {
      if (bub.convo[i])
        return (
          <Avatar
            key={i}
            size="medium"
            containerStyle={{
              marginRight: 15, shadowOpacity: 0.3,
              shadowRadius: 2,
              shadowColor: 'black'
            }}
            rounded
            source={bub.convo[i]}
            onPress={() => { this.openMessage({ convo: bub.convo[i] }) }
            } />
        )
    })
  })
}

renderChat = () => {
  return this.state.chat.map((bub, index) => {
    return bub.convo.map((convo, i) => {
      if (bub.convo[i])
        return (
          <Avatar
            key={i}
            size="medium"
            containerStyle={{
              marginRight: 15, shadowOpacity: 0.3,
              shadowRadius: 2,
              shadowColor: 'black'
            }}
            rounded
            source={bub.convo[i]}
            onPress={() => { this.openMessage({ convo: bub.convo[i] }) }
            } />
        )
    })
  })
}

render(){
  { this.renderChat() }
  { this.state.messageItem && this.props.navigation.navigate('ChatScreen', { avatarPicture: this.state.messageItem.convo }) }
}

the avatar should be touched which will lead to the ChatScreen, and it's relevant code is as follows:

render() {
  const { navigation } = this.props;
  <Avatar
    size="medium"
    containerStyle={{ alignSelf: 'center', position: 'absolute', justifyContent: 'center', marginTop: 28 }}
    rounded
    source={navigation.getParam('avatarPicture')}
  />
}

回答1:

In Screen1.js

Change below to

onPress={() => { this.openMessage({ convo: bub.convo[i] }) }

openMessage = (bub) => {
  this.setState({
    messageItem: bub
  });
  console.log({ bub })
}

to this

onPress={() => { this.openMessage(bub.convo[i]) }

openMessage = (bub) => {
  this.setState({
    messageItem: bub
  });
  console.log({ bub })
  this.props.navigation.navigate('ChatScreen', { avatarPicture: bub })
}

If your not used the react-redux simply you can access the image like this this.props.navigation.state.params.avatarPicture

If you use react-redux; Bind your navigation params to screens porps like below and then access it using props.

Please remember to import connect form react-redux

import { connect } from 'react-redux';

ChatScreen.js

const mapStateToProps = (state, props) => {
  return {
    ...props.navigation.state.params
  };
};

export default connect(mapStateToProps)(ChatScreen);

And now you will be able access the image like this this.props.avatarPicture

来源：https://stackoverflow.com/questions/58279318/navigation-getparam-in-not-an-object

标签

react-native

navigation

expo