iOS Question how to make a degraded panel to transparent?

SetGradientBackground(Panel2, Array As Int(0xFF000000,Colors.Transparent), "TOP_BOTTOM")

public Sub SetGradientBackground(pnl As B4XView, Clrs() As Int, Orientation As String)
    Dim bc As BitmapCreator
    bc.Initialize(pnl.Width / xui.Scale, pnl.Height / xui.Scale)
    bc.FillGradient(Clrs, bc.TargetRect, Orientation)
    Dim iv As ImageView
    iv.Initialize("")
    Dim xiv As B4XView = iv
    pnl.AddView(xiv, 0, 0, pnl.Width, pnl.Height)
    xiv.SendToBack
    bc.SetBitmapToImageView(bc.Bitmap, xiv)
End Sub