Android Question b4xImageView and Invalidate

[bocker77]

I am trying to place numerous bitmaps on a b4xImageView using a touch event from an underlying panel. You use to be able to this, I believe, by invalidating an imageview after each placement. In the AI when doing a search on the web it states that you can invalidate a b4xImageView.

B4XImageView1.Bitmap = xui.LoadBitmap(File.DirAssets, "image.png")
B4XImageView1.Invalidate ' Force redraw

But b4xImageView does support an "Invalidate". Also I didn't find any hit in the forum.

How do I go about doing this?

Thanks

 

[zed]

B4XImageView is not designed to display multiple overlapping bitmaps.
It displays only one bitmap at a time, and disabling the ImageView does not force a "repaint" with multiple images as was possible in the past.

The solution would be to create a bitmap “canvas”, draw all your images on it, then assign the result to your B4XImageView.

Sub Process_Globals
    Private xui As XUI
End Sub

Sub Globals
    Private iv As B4XImageView
    Private pnl As Panel
    Private baseBitmap As B4XBitmap
End Sub

Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("main")

    ' Base bitmap (for example a background image)
    baseBitmap = xui.LoadBitmap(File.DirAssets, "backround.png")

    iv.Bitmap = baseBitmap
End Sub

Sub pnl_Touch (Action As Int, X As Float, Y As Float)
    If Action = pnl.ACTION_DOWN Then
        AddImage(X, Y)
    End If
End Sub

Sub AddImage(X As Float, Y As Float)
    Dim bmp As B4XBitmap = xui.LoadBitmap(File.DirAssets, "icone.png")

    ' Create a temporary canvas
    Dim c As B4XCanvas
    Dim newBmp As B4XBitmap = xui.CreateBitmap(baseBitmap.Width, baseBitmap.Height)
    c.Initialize(newBmp)

    ' Draw base image
    c.DrawBitmap(baseBitmap, 0, 0, baseBitmap.Width, baseBitmap.Height)

    ' Draw the new image
    c.DrawBitmap(bmp, X - bmp.Width/2, Y - bmp.Height/2, bmp.Width, bmp.Height)

    c.Invalidate

    ' Update the base bitmap
    baseBitmap = newBmp

    ' Show result
    iv.Bitmap = baseBitmap
End Sub

untested code