[Android] Use the ViewHolder design pattern for the FolderBrowserAdap…

…ter. In directories with a lot of files, this should be noticeably smoother in terms of scrolling. Also fixed the case where the subtitle text might disappear.

Source/Android/src/org/dolphinemu/dolphinemu/folderbrowser/FolderBrowserAdapter.java

@@ -27,9 +27,21 @@
  */
 public final class FolderBrowserAdapter extends ArrayAdapter<FolderBrowserItem>
 {
+	// ViewHolder which is used to hold onto
+	// items within a listview. This is done
+	// so that findViewById is not needed to
+	// be excessively called over and over.
+	private static final class ViewHolder
+	{
+		TextView title;
+		TextView subtitle;
+		ImageView icon;
+	}
+
 	private final Context context;
 	private final int id;
 	private final List<FolderBrowserItem> items;
+	private ViewHolder viewHolder;
 
 	/**
 	 * Constructor
@@ -60,42 +72,50 @@ public View getView(int position, View convertView, ViewGroup parent)
 		{
 			LayoutInflater vi = LayoutInflater.from(context);
 			convertView = vi.inflate(id, parent, false);
+
+			// Initialize the ViewHolder and store it.
+			viewHolder = new ViewHolder();
+			viewHolder.title    = (TextView)  convertView.findViewById(R.id.ListItemTitle);
+			viewHolder.subtitle = (TextView)  convertView.findViewById(R.id.ListItemSubTitle);
+			viewHolder.icon     = (ImageView) convertView.findViewById(R.id.ListItemIcon);
+			convertView.setTag(viewHolder);
+		}
+		else // Can recover the holder.
+		{
+			viewHolder = (ViewHolder) convertView.getTag();
 		}
 
 		final FolderBrowserItem item = items.get(position);
 		if (item != null)
 		{
-			ImageView icon    = (ImageView) convertView.findViewById(R.id.ListItemIcon);
-			TextView title    = (TextView) convertView.findViewById(R.id.ListItemTitle);
-			TextView subtitle = (TextView) convertView.findViewById(R.id.ListItemSubTitle);
-
-			if(title != null)
+			if (viewHolder.title != null)
 			{
-				title.setText(item.getName());
+				viewHolder.title.setText(item.getName());
 			}
 
-			if(subtitle != null)
+			if (viewHolder.subtitle != null)
 			{
 				// Remove the subtitle for all folders, except for the parent directory folder.
 				if (item.isDirectory() && !item.getSubtitle().equals(context.getString(R.string.parent_directory)))
 				{
-					subtitle.setVisibility(View.GONE);
+					viewHolder.subtitle.setVisibility(View.GONE);
 				}
 				else
 				{
-					subtitle.setText(item.getSubtitle());
+					viewHolder.subtitle.setVisibility(View.VISIBLE);
+					viewHolder.subtitle.setText(item.getSubtitle());
 				}
 			}
 
-			if (icon != null)
+			if (viewHolder.icon != null)
 			{
 				if (item.isDirectory())
 				{
-					icon.setImageResource(R.drawable.ic_menu_folder);
+					viewHolder.icon.setImageResource(R.drawable.ic_menu_folder);
 				}
 				else
 				{
-					icon.setImageResource(R.drawable.ic_menu_file);
+					viewHolder.icon.setImageResource(R.drawable.ic_menu_file);
 				}
 			}
 		}