Add API I18NBundle#keys() (libgdx#7068)

CHANGES

@@ -28,6 +28,7 @@
 - LWJGL3 Fix: Stereo audio can now be played on mono output devices. This may also improve downmixing to stereo and upmixing to surround.
 - API Addition: Added CheckBox#getImageDrawable.
 - FIX: HexagonalTiledMapRenderer now displays maps with the correct stagger index.
+- API Addition: Added I18NBundle#keys() method.
 - TOOLS Features: Save mode can be changed in Flame particle 3D editor.
 
 [1.11.0]

gdx/src/com/badlogic/gdx/utils/I18NBundle.java

@@ -19,9 +19,11 @@
 import java.io.IOException;
 import java.io.Reader;
 import java.util.ArrayList;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.MissingResourceException;
+import java.util.Set;
 
 import com.badlogic.gdx.files.FileHandle;
 
@@ -440,6 +442,20 @@ public String get (String key) {
 		return result;
 	}
 
+	/** Gets a key set of loaded properties. Keys will be copied into a new set and returned.
+	 *
+	 * @return a key set of loaded properties. Never null, might be an empty set */
+	public Set<String> keys () {
+		Set<String> result = new LinkedHashSet<>();
+		ObjectMap.Keys<String> keys = properties.keys();
+		if (keys != null) {
+			for (String key : keys) {
+				result.add(key);
+			}
+		}
+		return result;
+	}
+
 	/** Gets the string with the specified key from this bundle or one of its parent after replacing the given arguments if they
 	 * occur.
 	 *