Can’t find variable: navigate

I am trying to navigate between two screen with the help of react-navigation. I am able to access navigate inside the render method as its scope is also inside that method.

Where should I declare so I can access it any method of this component. I am trying to access navigate inside the onPressButton method but it giving an error.

Can’t find variable: navigate

import React, { Component } from "react";
import { View, Text, Image, Button, Alert, StyleSheet } from "react-native";
import styles from "./Styles";
import * as strings from "./Strings";
import RoundButton from "./RoundButton";
var DialogAndroid = require("react-native-dialogs");
import { StackNavigator } from "react-navigation";

export default class CreateMessageScreen extends Component {
  render() {  
    const { navigate } = this.props.navigation;

    return (
      <View style={styles.container}>
        <Image source={require("./img/create_message.png")} />
        <Text style={styles.textStyle}>{strings.create_message}</Text>

        <RoundButton
          textStyle={styles.roundTextStyle}
          buttonStyle={styles.roundButtonStyle}
          onPress={this.onPressButton}
        >
          CREATE MESSAGE
        </RoundButton>

      </View>
    );
  }

  onPressButton() {
    var options = {
      title: strings.app_name,
      content: strings.create_message,
      positiveText: strings.OK,
      onPositive: () => navigate("DashboardScreen")
    };
    var dialog = new DialogAndroid();
    dialog.set(options);
    dialog.show();
  }
}


Source: stackoverflow-javascript