Delphi Bitmap in Thread

Question

This is my code that tries not to block the app in Android while loading one or more images.

Every so often freezes or does not load properly.

If anyone knows a way to do what I need would be grateful.

This is my procedure:

uses

  System.IOUtils,
  System.Threading,
  System.SyncObjs,

  FMX.Surfaces,

  MyTasks;

procedure TForm1.Button1Click(Sender: TObject);
begin

  AniIndicator1.Enabled := True;
  AniIndicator1.Visible := True;
  Button1.Enabled := False;

  TTask.Run(

    procedure
    var
      VBitmapSurface: TBitmapSurface;
      VFiles: TStringDynArray;
      VFilesIndexes: TArray<NativeInt>;
      VFile: String;
      VIndex: Integer;
      VBitmapData: TBitmapData;
      VMapped: Boolean;
      VCriticalSection: TCriticalSection;
    begin
      VCriticalSection := TCriticalSection.Create;
      VCriticalSection.Acquire;

      VFiles := SearchFiles( [ TPath.GetPicturesPath, TPath.GetCameraPath, TPath.GetSharedPicturesPath, TPath.GetSharedCameraPath ], [ '*.jpg', '*.jpeg' ] ).Value;
      VFilesIndexes := Randomizer( Length( VFiles ) ).Value;
      VFile := VFiles[ VFilesIndexes[ 0 ] ];

      VBitmapSurface := TBitmapSurface.Create;
      try
        if TBitmapCodecManager.LoadFromFile( VFile, VBitmapSurface ) then
        begin
          VMapped := False;
          TThread.Synchronize( nil,
            procedure
            begin
              Image1.Bitmap.SetSize( VBitmapSurface.Width, VBitmapSurface.Height );
              VMapped := Image1.Bitmap.Map( TMapAccess.Write, VBitmapData );
            end
          );
          if VMapped then
          try
            if VBitmapData.Pitch = VBitmapSurface.Pitch then
              Move( VBitmapSurface.Bits^, VBitmapData.Data^, VBitmapSurface.Pitch * VBitmapData.Height )
            else
              for VIndex := 0 to VBitmapSurface.Height - 1 do
                Move( VBitmapSurface.Scanline[ VIndex ]^, Pointer( NativeInt( VBitmapData.Data ) + VIndex * VBitmapData.Pitch )^, VBitmapData.Width * VBitmapSurface.BytesPerPixel );
          finally
            TThread.Synchronize( nil,
              procedure
              begin
                Image1.Bitmap.Unmap( VBitmapData );
              end
            );
          end;

        end;
      finally
        VBitmapSurface.DisposeOf;
      end;

      VCriticalSection.Release;
      VCriticalSection.DisposeOf;

      TThread.Synchronize( nil,
        procedure
        begin
          AniIndicator1.Enabled := False;
          AniIndicator1.Visible := False;
          Button1.Enabled := True;
        end
      );

    end

  );

end;

Answer 1

Unfortunately FMX bitmaps are not thread safe, you can only use them in the main thread (or in a synchronised portion of another thread).