How to detect Back Button?

[ahwong]

Many android phones including my Samsung Note have a Back Button.

What is the method used to detect this button? I want a sub routine to be called when user presses that button...

Thanks

 

[Omar]

Many android phones including my Samsung Note have a Back Button.

What is the method used to detect this button? I want a sub routine to be called when user presses that button...

Thanks

Sub Activity_KeyPress (KeyCode As Int) As Boolean

If KeyCode = KeyCodes.KEYCODE_BACK Then

'Perform your functions here

End If

End Sub

 

[Gianni M]

Sub Activity_KeyPress (KeyCode As Int) As Boolean 'return true if you want to consume the event
If KeyCode = KeyCodes.KEYCODE_BACK Then
If Msgbox2("Do you want to close?", "", "Yes", "Cancel", "No", Null) = DialogResponse.POSITIVE Then
' Return False
ExitApplication 'App is exiting
Else
Return True
End If
End If
End Sub

 

[Pitu]

Hi everyone... I'm new and this is my first post.

How can I take control of the "Back Button" in order to decide to kill or stay in the app?

I saw the implementation of the "Sub Activity_KeyPress (KeyCode As Int) As Boolean" sub (previous post), but whatever I decide inside this sub, then it always goes to the "Activity_Pause" sub and the activity gets destroyed!

I saw many apps showing a modal asking you if you really want to quit or not after pressing the "Back Button", and I would like to implement the same thing in my app: I the user chosse NO, the app should remain foreground, otherwise --> ExitApplication!

Thanks in advance.

 

[Erel]

Please post your Activity_Press code.

 

[ac9ts]

The way I do it. It may not be the best but it does the job. This one will exit if you press back twice within a few seconds, not the "Are you sure" scheme but you can always modify.

Sub Globals

Dim closeCounter As Int                    ' For double click exit routine
Dim closeTimer As Long

end sub

Sub Activity_KeyPress (KeyCode As Int) As Boolean

    Select KeyCode
        Case KeyCodes.KEYCODE_BACK
                                                          
            closeCounter = closeCounter + 1                    ' Handle the user exit request
  
            ' First time so start the counter
  
            If closeCounter = 1 Then                  
                closeTimer = DateTime.Now
                ToastMessageShow("Press Back again to exit", False)
            End If
  
            ' Second time but not within 3 seconds, reset to "First time"
  
            If closeCounter = 2 AND DateTime.Now > closeTimer + 3000 Then
                closeCounter = 1
                closeTimer = DateTime.Now
                ToastMessageShow("Press Back again to exit", False)
            End If
  
            ' Two tries within 3 seconds, we're done
  
            If closeCounter = 2 Then
                closeCounter = 0
                Activity.Finish
            End If

            Return True
        Case Else
            Return False
    End Select
  
End Sub

 

[Pitu]

Please post your Activity_Press code.

Hi Erel... reviewing my code I found that I have used the "Return False" twice (...already fixed and now seems it is working fine...)

Sub Activity_KeyPress (KeyCode As Int) As Boolean
    If KeyCode = KeyCodes.KEYCODE_BACK Then
        If Msgbox2("Are you sure to exit?", "", "Yes", "", "No", Null) = DialogResponse.POSITIVE Then
            Return False
            ExitApplication '...or whatever other previous killing actions.
        Else
            Return True
        End If
    End If
End Sub

What I don't understand is what's the meaning of returning True/False within "Sub Activity_KeyPress"and how does this affect "Activity_Pause"... since I can't put a breakpoint within "Activity_Pause" I am not sure wich one of these two subs is fired first... I guess "Activity_KeyPress".

Thanks in advance

 

[Erel]

By returning True from this sub you are telling the OS that you have already handled the back key event and that the OS doesn't need to do anything with it. If the back key event is not handle the default action is applied (which is to call Activity.Finish).

 

[Pitu]

Thanks! ...clear, short and simple explanation

 

[Harish Kumar Arya]

But the IDE underlines sub name with error "not all code paths return a value (Warning #2)", and "ExitApplication" with "Unreachable code detected (Warning #1).
What does this mean?

 

[ac9ts]

If you are referring to Pitu's example, I'm guessing it is because the only key press that will return a boolean value is KeyCodes.KEYCODE_BACK

Add a default return value for the other presses:

Sub Activity_KeyPress (KeyCode As Int) As Boolean
    If KeyCode = KeyCodes.KEYCODE_BACK Then
        If Msgbox2("Are you sure to exit?", "", "Yes", "", "No", Null) = DialogResponse.POSITIVE Then
            Return False
            ExitApplication '...or whatever other previous killing actions.
        Else
            Return True
        End If
    Else
        Return False    ' Handle the other presses in the OS
    End If
End Sub

 

[Sgardy]

Sub Activity_KeyPress (KeyCode As Int) As Boolean
If KeyCode = KeyCodes.KEYCODE_BACK Then
If Msgbox2("Are you sure to exit?", "", "Yes", "", "No", Null) = DialogResponse.POSITIVE Then
Return False
ExitApplication 'THIS CODE WILL BE NEVER EXECUTED JUST RETURN FALSE AND THE ACTIVITY WILL STAY ALIVE
Else
Return True
End If
Else
Return False ' Handle the other presses in the OS
End If
End Sub

Just to avoid confusion any additional code must be inserted before RETURN.

 

[xor83]

Sub Activity_KeyPress (KeyCode As Int) As Boolean

Select KeyCode
Case KeyCodes.KEYCODE_BACK

closeCounter = closeCounter + 1 ' Handle the user exit request

' First time so start the counter

If closeCounter = 1 Then
closeTimer = DateTime.Now
ToastMessageShow("Press Back again to exit", False)
End If

' Second time but not within 3 seconds, reset to "First time"

If closeCounter = 2 AND DateTime.Now > closeTimer + 3000 Then
closeCounter = 1
closeTimer = DateTime.Now
ToastMessageShow("Press Back again to exit", False)
End If

' Two tries within 3 seconds, we're done

If closeCounter = 2 Then
closeCounter = 0
Activity.Finish
End If

Return True
Case Else
Return False
End Select

End Sub

I used the above code but my activity reloads once and i have to click back again to close the activity, why this is happening?

 

[Erel]

This is an old thread. Please start a new thread and explain what you are trying to do.