TabScreen.js

import React, { Component } from "react";
import {
  Image,
  Text,
  TextInput,
  Platform,
  StyleSheet,
  TouchableOpacity
} from "react-native";
import {
  Container,
  Tabs,
  Tab,
  Header,
  Title,
  ScrollableTab,
  View,
  Form,
  Label,
  Left,
  Right
} from "native-base";
import { NavigationActions, StackActions } from "react-navigation";
import { connect } from "react-redux";
import globalStyles, { height, width, colors } from "../customLib/globalStyle";
import RegisterScreen from "./RegisterScreen";
import { updateInitTab } from "../Redux/actions/auth";

class LoginScreen extends Component {
  constructor(props) {
    super(props);
    this.state = {
      email: "",
      password: ""
    };
  }

  render() {
    return (
      <Container>
        ...
        <Tabs
          onChangeTab={val => this.props.updateInitTab(val.i)}
          initialPage={this.props.initPage}
          tabBarUnderlineStyle={{ backgroundColor: colors.BLUE }}
        >
          <Tab heading="Masuk" >
            <Text> Masuk </Text>
          </Tab>
          <Tab heading="Daftar" >
            <RegisterScreen {...this.props} updatePage={val => this.props.updateInitTab(val)} />
          </Tab>
        </Tabs>
      </Container>
    );
  }
}

const mapStateToProps = ({ auth }) => ({
  initPage: auth.initPage
});

const mapDispatchToProps = dispatch => ({
  updateInitTab: int => dispatch(updateInitTab(int))
});

export default connect(
  mapStateToProps,
  mapDispatchToProps
)(LoginScreen);