Move file list navigation to background (multi-threaded)

An xml view will never not exist, but it may be empty. Check the appropriate condition to avoid a crash.

Fix some error checking for file list clearing

shell/android-studio/app/src/main/java/com/reicast/emulator/FileBrowser.java

@@ -279,8 +279,8 @@ public class FileBrowser extends Fragment {
 		@Override
 		protected void onPostExecute(List<File> items) {
 			if (items != null && !items.isEmpty()) {
-				final LinearLayout list = (LinearLayout) getActivity().findViewById(R.id.game_list);
+				LinearLayout list = (LinearLayout) getActivity().findViewById(R.id.game_list);
-				if (list != null) {
+				if (list.getChildCount() > 0) {
 					list.removeAllViews();
 				}
 
@@ -298,7 +298,8 @@ public class FileBrowser extends Fragment {
 	
 	private void browseStorage(boolean images) {
 		if (images) {
-			navigate(new File(home_directory));
+			(new navigate()).executeOnExecutor(
+					AsyncTask.THREAD_POOL_EXECUTOR, new File(home_directory));
 		} else {
 			if (game_directory.equals(sdcard.getAbsolutePath())) {
 				HashSet<String> extStorage = FileBrowser.getExternalMounts();
@@ -307,26 +308,15 @@ public class FileBrowser extends Fragment {
 						String sdCardPath = sd.next().replace("mnt/media_rw", "storage");
 						if (!sdCardPath.equals(sdcard.getAbsolutePath())) {
 							if (new File(sdCardPath).canRead()) {
-								navigate(new File(sdCardPath));
+								(new navigate()).execute(new File(sdCardPath));
 								return;
 							}
 						}
 					}
 				}
 			}
-			navigate(new File(game_directory));
+			(new navigate()).executeOnExecutor(
-		}
+					AsyncTask.THREAD_POOL_EXECUTOR, new File(game_directory));
-	}
-
-	private static final class DirSort implements Comparator<File> {
-
-		@Override
-		public int compare(File filea, File fileb) {
-
-			return ((filea.isFile() ? "a" : "b") + filea.getName().toLowerCase(
-					Locale.getDefault()))
-					.compareTo((fileb.isFile() ? "a" : "b")
-							+ fileb.getName().toLowerCase(Locale.getDefault()));
 		}
 	}
 
@@ -429,20 +419,40 @@ public class FileBrowser extends Fragment {
 					}
 				});
 		list.addView(childview);
-		xmlParser.execute(game.getName());
+		xmlParser.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, game.getName());
 	}
 
-	void navigate(final File root_sd) {
+	private final class navigate extends AsyncTask<File, Integer, List<File>> {
-		LinearLayout v = (LinearLayout) getActivity().findViewById(R.id.game_list);
+
-		v.removeAllViews();
+		private LinearLayout listView;
+		private String heading;
+		private File parent;
+
+		private final class DirSort implements Comparator<File> {
+			@Override
+			public int compare(File filea, File fileb) {
+				return ((filea.isFile() ? "a" : "b") + filea.getName().toLowerCase(
+						Locale.getDefault()))
+						.compareTo((fileb.isFile() ? "a" : "b")
+								+ fileb.getName().toLowerCase(Locale.getDefault()));
+			}
+		}
+
+		@Override
+		protected void onPreExecute() {
+			listView = (LinearLayout) getActivity().findViewById(R.id.game_list);
+			if (listView.getChildCount() > 0)
+				listView.removeAllViews();
+		}
+
+		@Override
+		protected List<File> doInBackground(File... paths) {
+			heading = paths[0].getAbsolutePath();
 
 			ArrayList<File> list = new ArrayList<File>();
 
-		final String heading = root_sd.getAbsolutePath();
+			File flist[] = paths[0].listFiles();
-		createListHeader(heading, v, false);
+			parent = paths[0].getParentFile();
-
-		File flist[] = root_sd.listFiles();
-		File parent = root_sd.getParentFile();
 
 			list.add(null);
 
@@ -454,7 +464,13 @@ public class FileBrowser extends Fragment {
 				Arrays.sort(flist, new DirSort());
 				Collections.addAll(list, flist);
 			}
+			return list;
+		}
 
+		@Override
+		protected void onPostExecute(List<File> list) {
+			if (list != null && !list.isEmpty()) {
+				createListHeader(heading, listView, false);
 				for (final File file : list) {
 					if (file != null && !file.isDirectory() && !file.getAbsolutePath().equals("/data"))
 						continue;
@@ -482,7 +498,8 @@ public class FileBrowser extends Fragment {
 							new OnClickListener() {
 								public void onClick(View view) {
 									if (file != null && file.isDirectory()) {
-								navigate(file);
+										(new navigate()).executeOnExecutor(
+												AsyncTask.THREAD_POOL_EXECUTOR, file);
 										ScrollView sv = (ScrollView) getActivity()
 												.findViewById(R.id.game_scroller);
 										sv.scrollTo(0, 0);
@@ -525,9 +542,11 @@ public class FileBrowser extends Fragment {
 
 								}
 							});
-			v.addView(childview);
+					listView.addView(childview);
+				}
+				listView.invalidate();
+			}
 		}
-		v.invalidate();
 	}
 	
 	private boolean DataDirectoryBIOS() {