B4J: New in ABMaterial 3.50: Drag and Drop about anything

It may have been a bit silent the last few weeks around ABMaterial, but behind the scenes I have been working nights and weekends on maybe the biggest new feature since Chipmunk was introduced: Drag & Drop!

In 3.50, it will be possible to drag ABMContainers (and hence about anything in it) from one cell to another.

Let’s watch a video demonstration first:

Pretty cool hè!

How it works in B4J:
I explain the basics here, the DragDrop demo project included in the ABMaterial 3.50 download will show all tricks shown in the demo video.

1. Page_ParseEvent() gets a little bit of extra code to sync the moves made in the browser with our server

...
If SubExists(Me, eventName) Then
     Params.Remove("eventname")
     Params.Remove("eventparams")
     ' BEGIN NEW DRAGDROP
     If eventName = "page_dropped" Then
       page.ProcessDroppedEvent(Params)
     End If
     ' END NEW DRAGDROP
     Select Case Params.Size
     ...

2. Next we define a ‘DRAG’ group:

' name, minimum height of a cell
page.DragDropCreateGroup("DRAG", 150)

3. We add cells to this ‘DRAG’ group we want to drag & drop between. The last ‘null’ parameter can be any ABMComponent you want to use a title of the cell (e.g. the COLUMN X ABMLabel in the demo).

page.DragDropAddZone("DRAG", "DRAGCELL1", page.Cell(3,1),null)
page.DragDropAddZone("DRAG", "DRAGCELL2", page.Cell(3,2),null)
page.DragDropAddZone("DRAG", "DRAGCELL3", page.Cell(3,3),null)

4. We add our draggable ABMContainers to the cells. Note: they MUST be added with AddArrayComponent!

Here we also enable them to be draggable with cont.EnableDragDropZone().  There is also a shortcut method to enable/disable all ‘Zones/Cells’ in a group with cont.EnableDragDropAllZonesFromGroup() in one go.

page.Cell(3,1).AddArrayComponent(CreateCard("1", True, True, True, "I may be dragged everywhere", "../images/list1.jpg"), "Cards")
...

Sub CreateCard(ID As String, AllowInCell1 As Boolean, AllowInCell2 As Boolean, AllowInCell3 As Boolean, Title As String, image As String) As ABMContainer
  Dim cont As ABMContainer
  cont.Initialize(page, ID, "")
  cont.AddRows(1,True,"").AddCells12(1, "")
  cont.BuildGrid

  cont.IsTextSelectable = False

  If AllowInCell1 Then
    ' can be dragged to zone 1 of 'DRAG'
    cont.EnableDragDropZone("DRAG","DRAGCELL1",True)
  End If
  If AllowInCell2 Then
    ' can be dragged to zone 2 of 'DRAG'
    cont.EnableDragDropZone("DRAG","DRAGCELL2",True)
  End If
  If AllowInCell3 Then
    ' can be dragged to zone 3 of 'DRAG'
    cont.EnableDragDropZone("DRAG","DRAGCELL3",True)
  End If
  cont.EnableDragDropZone("DRAG","DRAGCELL4",True) ' for the sidebar

  Dim card As ABMCard
  card.InitializeAsCard(page, "card", "MY CARD", Title, ABM.CARD_SMALL, "")
  card.Image = image
  card.AddAction("Press me")

  ' add the card to the page
  cont.Cell(1,1).AddComponent(card)
  Return cont
End Sub

5. There are three events you will receive (all on Page level):

Sub Page_DragStart(component As String, source As String)
  Log("Drag start: " & component)
End Sub

Sub Page_DragCancelled(component As String, source As String)
  Log("Drag cancelled: " & component)
End Sub

' there are four parameters: component, source , target, before
Sub Page_Dropped(Params As Map)
  Log("Dropped: " & Params.Get("component"))
End Sub

And this is basically it! Very simple without having to write any HTML, CSS, PHP or Javascript. All done in pure B4J!

I’m finishing up ABMaterial 3.50, ABMonitor (an upcoming article on this for B4J and B4A soon on the blog) and ABTreeTableView now and early next week I think I may be able to release it to the donators.

Cheers,

Alwaysbusy

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