IImageSource 介面的 IsEmpty 方法

// 自訂影像來源的範例實作，用於維護影像檔案佇列
public class ImageSourceCallback : FREngine.IImageSource
{
   public ImageSourceCallback( string imageFilesDirectory )
   {
       imageFiles = ImageSourceHelper.LoadFilesNames( imageFilesDirectory );
       nextFileIndex = 0;
   }
   public bool IsEmpty()
   {
       return nextFileIndex >= imageFiles.Length;
   }
   public FREngine.IFileAdapter GetNextImageFile()
   {
       if( !IsEmpty() ) {
           return new FileAdapterCallback( imageFiles[nextFileIndex++] );
       }
       return null;
   }
   public FREngine.IImageDocument GetNextImageDocument()
   {
       ...
   }
   private string[] imageFiles;
   private int nextFileIndex;
}
public class FileAdapterCallback : FREngine.IFileAdapter
{
    ...
}
public class ImageSourceHelper
{
    ...
}