How to get a list of all image files for a slide show

Question

This code works, in the sense that it crawls the directories. However it gets an exception on all the sub directories, and fails to return any files. Is this a permissions issue, or is there something wrong in my code?

ES file manager shows the files, there are at least 3 folders with images in them.

Sub AddImagesToMap(Dir As String) As Map'crawl tree for images

Dim fn As String , i As Int

Dim CRList As List, Ext As String

Try

    CRlist.initialize

    CRList=File.ListFiles(Dir)

    For i = 0 To CRlist.Size-1'jpg,png and gif

        fn=CRList.Get(i)

         Select fn     'ignore some system folders

            Case "/dev"   

            Case "/proc"

            Case "/sys"

            Case "/system"

            Case Else

                If File.IsDirectory(Dir,CRList.Get(i)) Then

                    Log("Dir:"&fn)

                    AddImagesToMap(fn)

                Else

                    Log(fn)

                    Ext= common.FileExt(fn)

                    If ext.ToLowerCase="jpg" OR ext.ToLowerCase="png" OR ext.ToLowerCase="gif" Then

                        Imagelist.Put(fn, Dir)

                    End If

                End If
        End Select

    Next

Catch

    Log ("error:"&Dir)

End Try

End Sub

Fusseldieb · Answer 1 · 2015-04-20T05:23:01.857

I know that's a bit late, but I figured it out. Here's how I can get all files:

Sub AddImagesToMap(Dir As String) 'crawl tree for files
Dim fn As String , i As Int
Dim CRList As List
Try
    CRList.initialize
    CRList=File.ListFiles(Dir)

    For i = 0 To CRList.Size-1'jpg,png and gif
        fn=CRList.Get(i)
                If File.IsDirectory(Dir,CRList.Get(i)) Then
                    Log("Dir: "&fn)
                    AddImagesToMap(Dir & "/" & fn)
                Else
                        Log(fn & " - " & Dir)
                End If
    Next
Catch
    Log ("Error: "&Dir)
End Try
End Sub

Hope I helped a lot of people with the same question.

EDIT: Here's a better version of mine. Here I sort the file types:

Sub AddImagesToMap(Dir As String)
Dim fn As String , i As Int
Dim CRList As List, Ext As String
Try
    CRList.initialize
    CRList=File.ListFiles(Dir)

    For i = 0 To CRList.Size-1
        fn=CRList.Get(i)

                If File.IsDirectory(Dir,CRList.Get(i)) Then
                    AddImagesToMap(Dir & "/" & fn)
                Else

                If fn.Contains(".") Then
                Ext=fn.SubString(fn.LastIndexOf("."))
                End If

                Select Case Ext

                Case ".jpg"
                    Log(fn & " - " & Dir)

                Case ".png"
                    Log(fn & " - " & Dir)

                End Select

                End If
    Next
Catch
    Log ("Error: "&Dir)
End Try
End Sub

score 0 · Answer 2 · answered Oct 31 '11 at 05:01

I believe this will fix your problem: when looking to see if a directory has any files in it, it may be empty. I too used the File.ListFiles function. When a folder is empty it returns an uninitialized result, which if you try to use an uninitialized variable will cause an exception. Here's what I did:

f1 = File.ListFiles(x)
If f1.IsInitialized=False Then
    f1.Initialize
End If

By the way, when I was trying to understand the File.ListFiles functions this code you posted on B4A was the only example I could find. So thanks, and I hope this solves your problem.

score 0 · Answer 3 · answered Oct 31 '11 at 19:50

I use this to get my mp3 amd m4a music files from my music folder.

Sub Activity_Create(FirstTime As Boolean)
  ListView1.Initialize("ListView1")
  Dim GD As GradientDrawable
  GD.Initialize("TR_BL", Array As Int(Colors.Gray, Colors.LightGray))
  Activity.Background = GD
  ListView1.ScrollingBackgroundColor = Colors.Transparent
  Dim Bitmap1 As Bitmap
  Bitmap1.Initialize(File.DirAssets, "button.gif")

  ListView1.SingleLineLayout.ItemHeight = 50dip
    ListView1.SingleLineLayout.Label.TextSize = 20
    ListView1.SingleLineLayout.Label.TextColor = Colors.Blue
    ListView1.SingleLineLayout.Label.Gravity = Gravity.LEFT
  ListView1.FastScrollEnabled = True

  root=File.DirRootExternal
  filePath = root & "/music/"

  FindFolder(filePath,"")

  Activity.AddView(ListView1, 0, 0, 100%x, 100%y)

End Sub

Sub FindFolder(myPath As String, subfolder As String) As String
  Dim fileList As List
  Dim i As Int
  Dim p,f As String

  fileList = File.ListFiles(myPath)
  fileList.Sort(True)

  For i = 0 To fileList.Size-1
    p = myPath
    f = fileList.Get(i)

    If File.IsDirectory(p, f) Then
      p = p & "/" & f
      p = FindFolder(p, subfolder)  '<---recursive
    Else
      If f.EndsWith("m4a") OR f.EndsWith("mp3") Then
        album = p.SubString(p.LastIndexOf("/")+1) 'treat folders names as artist or album
        song = f.SubString2(0,f.LastIndexOf(".")) 'treat files as musc remoce extension name
        ListView1.AddSingleLine(album & " : " & song)
      End If
    End If
  Next

End Sub

How to get a list of all image files for a slide show

3 Answers3