AssetManager: NullPointerException vs isLoaded => true ~ unload() called twice

Please ensure you have given all the following requested information in your report.

Issue details

when AssetManager try to unload same resource twice it will fail on NullPointerException, here:

		// get the asset and its type
		Class type = assetTypes.get(fileName);
		if (type == null) throw new GdxRuntimeException("Asset not loaded: " + fileName);

		RefCountedContainer assetRef = assets.get(type).get(fileName); // <<< NullPointerException

		// if it is reference counted, decrement ref count and check if we can really get rid of it.
		assetRef.decRefCount();

• on 1st attempt, when resource is loaded: assetManager.isLoaded(resourceName) will return true; and then assetManager.unload(resourceName); is OK!

but

• on 2nd attemt, resource is already unloaded and: somehow assetManager.isLoaded(resourceName) returns TRUE instead of false! so mine code will call again: assetManager.unload(resourceName) ~ because it says its loaded, so: next pass is failing on NullPointerException: “RefCountedContainer assetRef = assets.get(type).get(fileName);” where first get(type) is positive - but second one get(fileName) will return null!

Reproduction steps/code

v1.9.10:

1. assetManager.load(any TextureAtlas);
2. ask for isLoaded(textureAtlasName) => true;
3. so unload(TextureAtlasName); => OK
4. ask again for isLoaded(textureAtlasName) => false; <<< OK
5. so unload(TextureAtlasName); => GdxRuntimeException("Asset not loaded: " + fileName); <<< OK

v1.9.11-SNAPSHOT ~ 2020-03-01

1. assetManager.load(any TextureAtlas);
2. ask for isLoaded(textureAtlasName) => true;
3. so unload(TextureAtlasName); => OK
4. ask again for isLoaded(textureAtlasName) => true; <<< BUG
5. so unload(TextureAtlasName); => NullPointerException <<< BUG

Version of LibGDX and/or relevant dependencies

1.9.11-SNAPSHOT (v.1.9.10 is ok)

Stacktrace

| 2020/03/01 21:09:46.103 |  ERROR  | Current screen: com.sjet.gula.graphics.screens.singleplayer.SingleplayerGameScreen                                                                               [ WorldOfClonesGame.java:343 ]
| 2020/03/01 21:09:46.104 |  ERROR  | Application detected fatal exception!                                                                                                                            [ WorldOfClonesGame.java:344 ]
Exception:java.lang.NullPointerException
com.badlogic.gdx.assets.AssetManager.unload(AssetManager.java:237)
com.sjet.gula.resources.dynamic.DynamicResourcesManager.unloadGroupTextures(DynamicResourcesManager.java:579)
com.sjet.gula.resources.dynamic.DynamicResourcesManager.unloadGroup(DynamicResourcesManager.java:553)
com.sjet.gula.resources.ResourcesManager.unloadGroup(ResourcesManager.java:361)
com.sjet.gula.graphics.screens.ScreenBase.unloadScreenResources(ScreenBase.java:252)
com.sjet.gula.graphics.screens.ScreenBase.hide(ScreenBase.java:168)
com.sjet.gula.graphics.screens.GameScreenBase.hide(GameScreenBase.java:686)
com.badlogic.gdx.Game.setScreen(Game.java:58)
com.sjet.gula.WorldOfClonesGame.setScreen(WorldOfClonesGame.java:389)
com.sjet.gula.graphics.screens.GameScreenBase.redirectToNextScreen(GameScreenBase.java:458)
com.sjet.gula.graphics.screens.GameScreenBase.onUserAnswered(GameScreenBase.java:640)
com.sjet.gula.graphics.ui.items.dialogs.YesOrNoDialog.fireUserAnswered(YesOrNoDialog.java:59)
com.sjet.gula.graphics.ui.items.dialogs.YesOrNoDialog$1.changed(YesOrNoDialog.java:156)
com.badlogic.gdx.scenes.scene2d.utils.ChangeListener.handle(ChangeListener.java:28)
com.badlogic.gdx.scenes.scene2d.Actor.notify(Actor.java:189)
com.badlogic.gdx.scenes.scene2d.Actor.fire(Actor.java:153)
com.badlogic.gdx.scenes.scene2d.ui.Button.setChecked(Button.java:132)
com.badlogic.gdx.scenes.scene2d.ui.Button$1.clicked(Button.java:95)
com.badlogic.gdx.scenes.scene2d.utils.ClickListener.touchUp(ClickListener.java:89)
com.badlogic.gdx.scenes.scene2d.InputListener.handle(InputListener.java:60)
com.badlogic.gdx.scenes.scene2d.Stage.touchUp(Stage.java:353)
com.badlogic.gdx.InputMultiplexer.touchUp(InputMultiplexer.java:124)
com.badlogic.gdx.backends.lwjgl.LwjglInput.processEvents(LwjglInput.java:360)
com.badlogic.gdx.backends.lwjgl.GulaDesktopLWJGLApp.mainLoop(GulaDesktopLWJGLApp.java:121)
com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:128)
[__RETURN_CODE__] 2
Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Asset not loaded: graphics/units/bellis/attack.png
	at com.badlogic.gdx.assets.AssetManager.unload(AssetManager.java:232)
	at com.badlogic.gdx.assets.AssetManager.clear(AssetManager.java:725)
	at com.badlogic.gdx.assets.AssetManager.dispose(AssetManager.java:693)
	at com.sjet.gula.resources.ResourcesManager.dispose(ResourcesManager.java:179)
	at com.sjet.gula.WorldOfClonesGame.dispose(WorldOfClonesGame.java:411)
	at com.badlogic.gdx.backends.lwjgl.GulaDesktopLWJGLApp.mainLoop(GulaDesktopLWJGLApp.java:162)
	at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:128)

Please select the affected platforms

• Android
• iOS (robovm)
• iOS (MOE)
• HTML/GWT
• Windows
• Linux
• MacOS

EXAMPLE ~ which fails (on 1.9.11-SNAPSHOT) and 1.9.10 is ok

(focus on part around: “if (Version.isLower(1, 9, 11))” else …

	private void unloadGroupAnimations(Array<String> resources)
	{
		if (resources == null)
		{
			return;
		}
		for (String resource : resources)
		{
			AnimationConfiguration animationConfig = configLoader.getAnimationConfiguration(resource);
			boolean isFreezed = freezeToUnloadResources.contains(animationConfig.getTextureAtlas());
			boolean isLoaded = assetManager.isLoaded(animationConfig.getTextureAtlas());
			logger.debug(
				"unload(animation)["
				+ (isFreezed ? "F" : "-")
				+ (isLoaded  ? "L" : "-")
				+ "]:"
				+ resource
			);
			isFreezed = false;
			if (!isFreezed && isLoaded)
			{
				if (animationConfig.getTextureAtlas() != null)
				{
					if (Version.isLower(1, 9, 11))
					{
						assetManager.unload(animationConfig.getTextureAtlas());
					}
					else
					{
						// because v1.9.10 is ok (~but contains AnimatedTile bug) and 1.9.11-SNAPSHOT has this
						// weird behavior...
						try
						{
							assetManager.unload(animationConfig.getTextureAtlas());
						}
						catch(Exception e)
						{
							// im just ignoring it...
							// it's because unload is async! and there isnt any callback, when its finished!
							// eg: unload:
							// - graphics/units/gribs/run_left.json
							// - graphics/units/gribs/run_right.json
							//
							// its using same TextureAtlas ~ "graphics/units/gribs/run.atlas" and
							// 1st unload() will create async task to unload it. and do it!
							// 2nd unload() will report, that resource is loaded(true) ~ so this will fail!
							//
							// its happening inside: AssetManager.unload(), at:
							// RefCountedContainer assetRef = assets.get(type).get(fileName);
System.out.println(e);
						}
					}
				}
				onUnloadListeners.onUnloadResourceAnimation(animationConfig);
			}
		}
	}

| 2020/03/01 21:30:25.568 |  DEBUG  | unload(animation)[-L]:graphics/units/gribs/die_left.json                                                                                                         [ Logger.java:142 ]
| 2020/03/01 21:30:25.568 |  DEBUG  | unload(animation)[-L]:graphics/units/gribs/die_right.json                                                                                                        [ Logger.java:142 ]
| 2020/03/01 21:30:25.569 |  DEBUG  | unload(animation)[-L]:graphics/units/gribs/run_left.json                                                                                                         [ Logger.java:142 ]
java.lang.NullPointerException
| 2020/03/01 21:32:22.823 |  DEBUG  | unload(animation)[-L]:graphics/units/gribs/run_right.json                                                                                                        [ Logger.java:142 ]
java.lang.NullPointerException
| 2020/03/01 21:32:33.615 |  DEBUG  | unload(animation)[-L]:graphics/units/kingofanimals/attack_left.json                                                                                              [ Logger.java:142 ]
| 2020/03/01 21:32:33.616 |  DEBUG  | unload(animation)[-L]:graphics/units/kingofanimals/attack_right.json                                                                                             [ Logger.java:142 ]
| 2020/03/01 21:32:33.618 |  DEBUG  | unload(animation)[-L]:graphics/units/kingofanimals/die_left.json                                                                                                 [ Logger.java:142 ]
| 2020/03/01 21:32:33.619 |  DEBUG  | unload(animation)[-L]:graphics/units/kingofanimals/die_right.json                                                                                                [ Logger.java:142 ]
| 2020/03/01 21:32:33.621 |  DEBUG  | unload(animation)[-L]:graphics/units/kingofanimals/run_left.json 

[tommyettinger]

I submitted a PR that might fix this, #5932 , above. The PR is meant to addresses a case where put() and remove() are called in a mixed order; that is probably what is happening here and would explain unexpected null results. If #5932 doesn’t fix this issue, it’s going to take more in-depth stepping through AssetManager to find where things go wrong.

[j3nda]

confirm #5932 fixes this problem