componentWillMount doesn't get called again when navigating back to my original component - react-native

Question

screen A: calling componentWillMount successfully and then navigating to screen B,
screen B: do some redux changes (that will affect the data in WillMount) and then navigating back to A but componentWillMount doesn't get called and preventing desirable data from appearing on the screen
screen A:
componentWillMount(){
this.props.fetchData();
console.log('fetched')
}
renderItem({item}){
return <Text>{item.name}</Text>
}
render(){
const array = Object.values(this.props.data)
return(
<View style={{flex: 1}}>
<Inline>
<View style={styles.container}>
<View style={styles.headerContainer}>
<Header style={styles.header} HeaderText={'EmployeeList'}
/>
</View>
<TouchableOpacity style={styles.buttonContainer}
onPress={()=> this.props.navigation.navigate('CreateEmp')}
//screen B
>
<Text style={styles.buttonStyle}>Add an Employee</Text>
</TouchableOpacity>
</View>
</Inline>
<FlatList
data={array}
renderItem={this.renderItem}
keyExtractor={array1 => array1.name}
/>
</View>
screen B:
functionOne(){
const {name, phone, createEmployee, shift} = this.props
createEmployee(name, phone, shift)
}
functionTwo(){
this.props.navigation.navigate('EmployeeList')//screen A
}
functionCombined(){
this.functionOne();
this.functionTwo();
}
and calling functionCombined in the class of course

Answer 1

The componentWillMount is executed when the screen is rendered.
However, when navigating to the Navigate command, if the screen is first moved, it is rendered to draw the screen, but if it is already rendered, it is not rendered again.
The function shall be moved using a push commands to run again.
functionTwo(){
this.props.navigation.push('EmployeeList')//screen A
}