Hardware back button Issue in ionic 4.10.3

I am using Latest android studio, with every thing up to date . i just created a application with ionic current version . but problem is . when i debag it in my android device . i can’t close the application using back button . i am just confused . whats wrong with my application , i tryed all off step like ```
this.platform.exitApp();

this.platform.exitApp();

or
navigator.app.exitApp()

or
navigator[‘app’].exitApp()

but nothing is worked , just confused . why ionic doing ths with us every time . its really a good idea to update. but with proper gideline .

Pour suivre car je voudrais aussi quitter l’app avrc le bouttin back de l’appareil

not sure what are you talking about . -" To follow because I would also like to leave the app with the back of the device ". not sure what is ??

I say to follow because I want my back button hardware to leave the app but I can not make it work er I would like to see the answers that will be given to you

excuse my english which is not too correct because am french and I use the google translator

its ok. i think ionic should take a look on it