const { BackButtonService } = require ( '../services/back-button.js' ) ; const DialogBox = require ( 'react-native-dialogbox' ) . default ; export default class BackButtonDialogBox extends DialogBox { constructor ( props ) { super ( props ) ; this . backHandler_ = ( ) => { if ( this . state . isVisible ) { this . close ( ) ; return true ; } return false ; } ; } async componentDidUpdate ( ) { if ( this . state . isVisible ) { BackButtonService . addHandler ( this . backHandler_ ) ; } else { BackButtonService . removeHandler ( this . backHandler_ ) ; } } }