B4J Question customlistview's memory is not released

[xulihang]

I use customlistview to load tens of thousands of items with lazy load.

The layout has two textareas.

​

Load with empty pane:

Sub readWorkFile(filename As String,filesegments As List,fillUI As Boolean,root As String)
   ......
        Dim segmentsList As List
        segmentsList=sourceFileMap.Get(innerFilename)
        filesegments.AddAll(segmentsList)
        If fillUI Then
            For Each bitext As List In segmentsList
                createEmptyPane(bitext)
            Next
        End If
    Next
End Sub

When visible range changed, fill the pane

Public Sub fillPane(FirstIndex As Int, LastIndex As Int)
    If segments.Size=0 Then
        Return
    End If
    Dim ExtraSize As Int
    ExtraSize=15
    For i = Max(0,FirstIndex-ExtraSize*2) To Min(Main.editorLV.Size - 1,LastIndex+ExtraSize*2)
        Dim segmentPane As Pane
        segmentPane=Main.editorLV.GetPanel(i)
        If i > FirstIndex - ExtraSize And i < LastIndex + ExtraSize Then
            'visible+
            segmentPane.Enabled=True
            If segmentPane.NumberOfNodes = 0 Then
                Dim bitext As List
                bitext=segments.Get(i)
                addTextAreaToSegmentPane(segmentPane,bitext.Get(0),bitext.Get(1))
            End If
        Else
            'not visible
            segmentPane.Enabled=False
            If segmentPane.NumberOfNodes > 0 Then
                segmentPane.RemoveAllNodes '<--- remove the layout
            End If
        End If
    Next
End Sub

When I call clv.clear, the memory is not released.

Is this because the customlistview is a global variable?

 

[Harris]

Don't see where you called clv - clear?
This should empty the xCLV list view where you can add newest items...

 

[xulihang]

Don't see where you called clv - clear?
This should empty the xCLV list view where you can add newest items...

This is called in a closeProject sub.

Public Sub closeProject
    ......
        tmTableView.ClearSelection
        tmTableView.Items.Clear
        projectTreeTableView.ClearSelection
        projectTreeTableView.Root.Children.Clear
        editorLV.Clear ' this is the customlistview
        termLV.Items.Clear
        MainForm.Title="BasicCAT"
End Sub

I expect the memory usage to go down after this "closing" sub. Normally, the clv will not load that many items. It will be around 700MB when loading 700 items.

 

[Harris]

closeProject

Did not see where this was ever called...

 

[xulihang]

Did not see where this was ever called...

It is done manually by the user using the menubar.

 

[Harris]

So if never called by your user, will the clv just grow and grow?

 

[xulihang]

It will grow when more items are loaded. And I am asking why the memory still is not released when I call clv.clear.

 

[keirS]

I don't think you understand how the garbage collector works. The GC does not necessarily release any heap space back to the OS. To see what the JVM is doing in terms of free heap space within the process you should use JConsole.

 

[Harris]

I call clv.clear

or when your USER calls clv.clear???

Seems you leave this up to them? Just reaching out here...

 

[xulihang]

or when your USER calls clv.clear???

It is a text editor which reads text files to clv. When the user open a new file, the clv will be cleared. And when a project is closed, it will be cleared, too.

 

[xulihang]

I don't think you understand how the garbage collector works......

Jconsole seems a professional tool. I am not familiar with java. I may need to learn more before optimizing this B4J program.

 

[Harris]

I may need to learn more before optimizing this B4J program.

perhaps... Good Luck!

 

[xulihang]

As loading too many items will cause large memory usage, I think the easiest way for me is to use pagination. Load 50 items for each page and the heap space will not grow.

I loaded the same number of items with a c++ ATL program and it only costs 45MB, amazing. I use autoit to inspect it and find these items belong to one control. Maybe it is part of the secret.

 

[Harris]

I think the easiest way for me is to use pagination

That makes sense...

For example, my latest android app does this with images from the Camera (or selected) folder.
The xCLV loads the 10 most recent images for the user to select (and send).
The pager will allow to load the next 10 images, and so on.
Images are scaled down in size to dramatically reduce memory use.

 

[xulihang]

I think the easiest way for me is to use pagination.

The user experience of using pagination is not good. So I am trying use listview with lazy loading. It uses less memory. We can add anything to a listview while customlistview can only add panes.

 

[Erel]

Can you upload a project that shows the memory issue? Did the process eventually crash?

 

[xulihang]

Can you upload a project that shows the memory issue? Did the process eventually crash?

It will show out of memory if loading too much as it will load all the items and customlistview with lazyloading still has to add an empty pane which costs memory. I have solved this using listview with lazyloading.

 

[Harris]

I think Erel was implying that it (CLV) shouldn't do this - unless your (many) images are not scaled and excessively large (2 - 8 meg let's say).
Lazy Loading was designed (I believe) to re-cycle views and prevent OOM situations. A small example may help him uncover where it - or your use of - went sideways...

Thanks

 

[Erel]

Creating 50k empty items when the app starts is too much. It will be slow. Empty items still hold a panel. A different approach will work. You can create more items as the user scrolls the list.

Another point to consider is whether a 50k items list will be convenient for the user to scroll.

 

[xulihang]

Because it is a text editor, I want users can scroll to any position they want. Loading more when the scrollbar reaches end is not convenient.