Issue 4485 - Clear cache directory

src/org/adblockplus/sbrowser/contentblocker/engine/Engine.java

Index: src/org/adblockplus/sbrowser/contentblocker/engine/Engine.java
===================================================================
--- a/src/org/adblockplus/sbrowser/contentblocker/engine/Engine.java
+++ b/src/org/adblockplus/sbrowser/contentblocker/engine/Engine.java
@@ -251,16 +251,26 @@ public final class Engine
     {
       Log.d(TAG, "Writing filters...");
       final File filterFile = this.subscriptions.createAndWriteFile();
 
       final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this.serviceContext);
       final String key = this.serviceContext.getString(R.string.key_cached_filter_path);
       prefs.edit().putString(key, filterFile.getAbsolutePath()).commit();
 
+      Log.d(TAG, "Cleaning up cache...");
+      final File dummyFile = getDummyFilterFile(this.serviceContext);
+      for (final File file : getFilterCacheDir(this.serviceContext).listFiles())

[anton, 2016/09/30 06:17:15]

listFiles() can return `null` is getFilterCacheDir() does not exist. If you're
sure the directory exists, then it's ok, Otherwise check for null.
BTW, if something like that is used anywhere else i'd prefer to move it to
`FileUtils` helper class or smth like that. Not too important though

[diegocarloslima, 2016/09/30 14:35:47]

The directory should exists in order for the previous line to succeed: 'final
File filterFile = this.subscriptions.createAndWriteFile()', but it won't hurt to
add a null check here since the cache cleaning is sort of an optional step, so
it shouldn't ever raise an Exception.

About the FileUtils: There are some other IO logic across the project that can
be moved to a helper class too, but that refactoring should be done in a
separate issue. 

+      {
+        if (!file.equals(dummyFile) && !file.equals(filterFile))
+        {
+          Log.d(TAG, "Deleting file:" + file);
+          file.delete();
+        }
+      }
     }
     catch (IOException e)
     {
       Log.e(TAG, "Failed to write filters", e);
     }
     finally
     {
       this.unlock();