Android Question Graphic Lib for B4A Beginner

[artsoft]

Hi all!

I am looking for a graphic library in order to have the possibility to create flickerfree graphics (lines, (filled) rectangles, circles etc.). It must be possible to create these graphical elements while touching the activity with my finger. While moving the finger the graphic should be changed a little bit, but flickerfree (double buffer?).

Is there already such a library?
Thx in advance.

Regards
ARTsoft

 

[Erel]

The standard canvas creates flicker free graphics.

 

[artsoft]

Thx for the quick response!
Perfect!

Is there any library which capsulates all graphical commands?
Or must i use the B4A commands collection for the canvas?

Best regards
ARTsoft

 

[Erel]

There are several related libraries, though I recommend you to start with Canvas.

This library provides more features if you need: https://www.b4x.com/android/forum/threads/14638/#content

 

[artsoft]

Thanks a lot. I will try this lib.

At this moment i am playing with the canvas of a panel.

Perhaps you can help me: How to invalidate or clean a canvas.

Status:

I have 1 activity with 1 panel (panel size = activity size)
I get the canvas from this panel.
I draw a line to this canvas at the y position.
I increase the y pos by 10.
I draw a line again. But before i want to clear the canvas.

So the app should show always only 1 line moving to the bottom of the screen.

Background color of the panel is green - RGB(0.255.0)
Line color is red - RGB (255,0,0)

i use "DoEvents" in the loop to can react on click events in order to can terminate the app with a click.

But i see only a red background built by drawing only red lines.

Perhaps you can help or anybody here.

Thx again in advance.

Regards
ARTsoft

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    'Activity.LoadLayout("Layout1")

    Dim i As Int
    Dim y As Int

    Activity.LoadLayout("main")

    If (FirstTime = True) Then
  
        cv.Initialize(Panel1)
  
    End If

    y = 0

    Do While (y < Activity.Height)
  
        cv.DrawLine(0, y, Activity.Width, y, Colors.RGB(255,0,0), 10)

        y = y + 10
  
        If (y >= Activity.Height) Then
  
            y = 0
  
        End If
      
        For i = 1 To 100
            DoEvents
        Next

        Panel1.Invalidate
  
    Loop

End Sub

 

[artsoft]

Update:

No i have a red line moving to the bottom ...

But the Panel background should be green. Now it is black .... Why?!

Sub Activity_Create(FirstTime As Boolean)

    Dim i As Int
    Dim y As Int
    Dim areaRect As Rect

    Activity.LoadLayout("main")

    ' ------------------------------------------------------------------------------

    If (FirstTime = True) Then
        cv.Initialize(Panel1)
        areaRect.Initialize(0,0,Panel1.Width, Panel1.Height)
    End If

    ' ------------------------------------------------------------------------------

    y = 0

    Do While (y < Panel1.Height)
   
        cv.drawRect(areaRect, Colors.Transparent, True, 0)
        cv.DrawLine(0, y, Panel1.Width, y, Colors.RGB(255,0,0), 10)

        y = y + 10
   
        If (y >= Panel1.Height) Then
            y = 0
        End If

        Panel1.Invalidate

        DoEvents

    Loop

End Sub

 

[DonManfred]

But the Panel background should be green.

Then paint a green background first. See the documentation of the canvas object.
Especially DrawRect. Set the filled parameter to true

 

[klaus]

You could use a routine like this:

Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("main")
    Panel1.Color = Colors.RGB(0, 255,0)

    cv.Initialize(Panel1)
    y = -10
    Do While (y < Activity.Height)
        cv.DrawLine(0, y, Activity.Width, y, Colors.RGB(0, 255,0), 10)
        y = y + 10
        cv.DrawLine(0, y, Activity.Width, y, Colors.RGB(255,0,0), 10)
        If (y >= Activity.Height) Then
            y = 0
        End If

        DoEvents
    
        Panel1.Invalidate
    Loop
End Sub

To erase the previous line you could draw it again with the panel background color.

What is this supposed to do?

For i = 1 To 100
    DoEvents
Next

If you want to control the speed you should use a Timer.

 

[Erel]

The first step is to remove the DoEvents call and use a Timer as Klaus wrote.