React-Native refs undefined on text input - user-interface

Question

we are currently running React-Native 0.33
We are trying to use the refs to go from 1 text input to another when they hit the next button. Classic username to password.
Anyone have any idea? Below is the code we are using. From other posts I've found on stack this is what they've done; however, it's telling us that this.refs is undefined.
UPDATE
So I've narrowed the problem down to
render() {
return (
<Navigator
renderScene={this.renderScene.bind(this)}
navigator={this.props.navigator}
navigationBar={
<Navigator.NavigationBar style={{backgroundColor: 'transparent'}}
routeMapper={NavigationBarRouteMapper} />
} />
);
}
If I just render the code below in the renderScene function inside of the original render it works, however with the navigator it won't work. Does anyone know why? Or how to have the navigator show as well as render the code in renderScene to appear in the original render?
class LoginIOS extends Component{
constructor(props) {
super(props);
this.state={
username: '',
password: '',
myKey: '',
};
}
render() {
return (
<Navigator
renderScene={this.renderScene.bind(this)}
navigator={this.props.navigator}
navigationBar={
<Navigator.NavigationBar style={{backgroundColor: 'transparent'}}
routeMapper={NavigationBarRouteMapper} />
} />
);
}
renderScene() {
return (
<View style={styles.credentialContainer}>
<View style={styles.inputContainer}>
<Icon style={styles.inputPassword} name="person" size={28} color="#FFCD00" />
<View style={{flexDirection: 'row', flex: 1, marginLeft: 2, marginRight: 2, borderBottomColor: '#e0e0e0', borderBottomWidth: 2}}>
<TextInput
ref = "FirstInput"
style={styles.input}
placeholder="Username"
autoCorrect={false}
autoCapitalize="none"
returnKeyType="next"
placeholderTextColor="#e0e0e0"
onChangeText={(text) => this.setState({username: text})}
value={this.state.username}
onSubmitEditing={(event) => {
this.refs.SecondInput.focus();
}}
>
</TextInput>
</View>
</View>
<View style={styles.inputContainer}>
<Icon style={styles.inputPassword} name="lock" size={28} color="#FFCD00" />
<View style={{flexDirection: 'row', flex: 1, marginLeft: 2, marginRight: 2, borderBottomColor: '#e0e0e0', borderBottomWidth: 2}}>
<TextInput
ref = "SecondInput"
style={styles.input}
placeholder="Password"
autoCorrect={false}
secureTextEntry={true}
placeholderTextColor="#e0e0e0"
onChangeText={(text) => this.setState({password: text})}
value={this.state.password}
returnKeyType="done"
onSubmitEditing={(event)=> {
this.login();
}}
focus={this.state.focusPassword}
>
</TextInput>
</View>
</View>
</View>
);
}

Answer 1

Try setting the reference using a function. Like this:
<TextInput ref={(ref) => { this.FirstInput = ref; }} />
Then you can access to the reference with this.FirstInput instead of this.refs.FirstInput

Answer 2

For a functional component using the useRef hook. You can use achieve this easily, with...
import React, { useRef } from 'react';
import { TextInput, } from 'react-native';
function MyTextInput(){
const textInputRef = useRef<TextInput>(null);;
return (
<TextInput ref={textInputRef} />
)
}

Answer 3

Try changing the Navigator's renderScene callback to the following (based on Navigator documentation) cause you will need the navigator object later.
renderScene={(route, navigator) => this.renderScene(route, navigator)}
Then, use 'navigator' instead of 'this' to get the refs.
navigator.refs.SecondInput.focus()