B4J Question Undo/Redo by canvas.drawline with UndoManager

[Alexander Stolte]

Hello,

How can i save the state of my Canvas drawing for the Undo and Redo Button with the UndoManager?


i use this code for drawing:

Process_Globals
    Private pnl_back As B4XView
    Private cvs_back As B4XCanvas
End Sub

Sub AppStart (Form1 As Form, Args() As String)

cvs_back.Initialize(pnl_back)

End Sub

Sub pnl_back_Touch (Action As Int, X As Float, Y As Float)
    
    Select Action
        Case pnl_back.TOUCH_ACTION_DOWN
            x2 = X
            y2 = Y
        Case pnl_back.TOUCH_ACTION_MOVE
            cvs_back.DrawLine(X, Y, x2, y2, xui.Color_RGB(r,g,b), bright)
            x2 = X
            y2 = Y
            cvs_back.Invalidate
        
    End Select
End Sub

 

[Erel]

A solution that might be too wasteful but you should try is to convert the image to bytes and store the bytes in UndoManager: https://www.b4x.com/android/forum/threads/b4x-bytes-to-file.70111/#post-445167