back to android in navigation flet

[SofExp]

Question

I am facing an issue with handling the Android "Back" button in navigation using Flet. The behavior doesn't seem to work as expected. When I press the Back button.
Android "Back" button minimizes the application and does not participate in routing.
How to detect and intercept the back button in android?

I build the application using flet build apk.

Code sample

import flet
from flet import Page, View, Text, ElevatedButton

def main(page: Page):

    def route_change(route):
        page.views.clear()
        
        if page.route == "/":
            page.views.append(
                View(
                    "/",
                    controls=[
                        Text("Home"),
                        ElevatedButton("page 1", on_click=lambda _: page.go("/screen1")),
                        ElevatedButton("page 2", on_click=lambda _: page.go("/screen2")),
                    ],
                )
            )
        elif page.route == "/screen1":
            page.views.append(
                View(
                    "/screen1",
                    controls=[
                        Text("page 1"),
                        ElevatedButton("Back", on_click=lambda _: page.go("/")),
                    ],
                )
            )
        elif page.route == "/screen2":
            page.views.append(
                View(
                    "/screen2",
                    controls=[
                        Text("page 2"),
                        ElevatedButton("Back", on_click=lambda _: page.go("/")),
                    ],
                )
            )
        page.update()

    def view_pop(view):
        page.views.pop()
        page.go(page.views[-1].route if page.views else "/")
    
    page.on_route_change = route_change
    page.on_view_pop = view_pop

    page.go(page.route)


flet.app(target=main)

Error message

No response

------------------------------------------------------

• I have searched for answers to my question both in the issues and in previous discussions.

[GreenDringo42]

Same problem, please helppp

[SIRGPrice]

I solved the problem, to use other tools you can use routing with page.go (to_desired ROUTE) but with back button page.views.append (desired_VIEW) must be used directly so that the previous or desired view is now above and is the one that looks Used this line instead of page.go (page.views[-1].route if page.views else "/"). If it doesn't work for you, tell me and I share code with you.

[GreenDringo42]

Hola, gracias por responder. Apliqué la solución que diste pero me sigue cerrando la app :(
Me podrías compartir el codigo por favor?

[SIRGPrice]

def Dialog(title,content,lista):

        d=AlertDialog(
            open=False,
            title=Text(title, color=W),
            content=Text(content, color=W),
            actions=lista,
            bgcolor=BG,
            icon=Icon(icons.ERROR_OUTLINE, color=B),
            icon_padding=padding.only(top=20, bottom=10),
            actions_alignment=MainAxisAlignment.END
        )

        return d

    def close_dialog(d):

        global dialog5
        page.close(dialog5)
    
    def GO(view): # For other type of routing, page buttons etc

        print(view)

        page.views.append(view)
        page.update()

    def BACK(): # For routing with "back" Android button

        global dialog5

        if page.views[-1].route == "/1": # Open a exit dialog instead of exit directly (Destroy())

            page.open(dialog5)

        else: # Return to main page if you are not in there

            page.views.append(page_1_view())

    def Destroy():

        page.window.destroy()

   def page_1_view():

        return View(
                        route="/1"
                    )
   #....

    def page_x_view():

        return View(
                        route="/x"
                    )
    
    #....

    dialog5 = Dialog("Exit.","Want to exit?",[TextButton("No", on_click=lambda_:close_dialog(dialog5)),TextButton("yes",on_click=lambda_: Destroy())])

    page.window.prevent_close = False # Necesary
    page.on_view_pop = lambda _: BACK() # For routing with "back" Android button
    page.views.clear()
    page.views.append(page_1_view())
    page.views.append(page_1_view()) # Necesary

I can't send more because it's a professional project. Try to integrate it to make sense in the context of your app.

[SIRGPrice]

In my case if I press the android button it always returns to the main screen wherever it is. If you are already in the main one, launch a dialogue that tells you if you want to leave the app. You can change BACK () to go wherever you want. If you want to go back to the previous view, you'll just need to remove the current view from your page.views with page.views.pop (). All of the above works only once you make the apk, in the flet test app it does not work.

[GreenDringo42]

Está funcionando, muchas gracias bro!

[SIRGPrice]

Un placer tio, si necesitas algo pregunta en el discord de flet que todos los días entro, y la gente ayuda mucho.Saludos!