libgdx: Dispose Screen on Demand - libgdx

Question

Say I have a splash screen. This screen is loaded only at the beginning of the game, and afterwards I don't use it.
Is it possible to dispose this screen on demand?
I tried to dispose it right after setting the screen after the splash, and also tried to call dispose() on the hide() method.
Both of the tries rendered in an exception.
How can I dispose this screen on demand? I have there pretty heavy textures, and wanted to free the memory as soon as possible.
Example:
// SplashScreen class
class SplashScreen implements Screen {
private boolean renderingEnabled = true;
private Object lock = new Object();
#Override
public void render(float delta) {
synchronized(lock) {
if (!renderingEnabled) {
return;
}
spriteBatch.begin();
// here render the animations
spriteBatch.end();
}
}
#Override
public void dispose() {
synchronized(lock) {
renderingEnabled = false;
// here come the disposing of SpriteBatch and TextureAtlas
atlas.dispose();
atlas = null;
spriteBatch.dispose();
spriteBatch = null;
}
}
}
// The usage
game.setScreen(splashScreen);
...
// now when the splash screen animation is finished, I am calling the following from the controller:
splashScreen.dispose();
game.setScreen(mainMenuScreen);
I get the following exception:
FATAL EXCEPTION: GLThread 398
java.lang.NullPointerException
at mypackage.SplashScreen.render(SplashScreen.java:85)
at com.badlogic.gdx.Game.render(Game.java:46)
at mypackage.Game.render(MyGame.java:33)
at com.badlogic.gdx.backends.android.AndroidGraphics.onDrawFrame(AndroidGraphics.java:414)
at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1522)
at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)
And when I have the following dispose pattern (disposing after showing the mainMenuScreen)
// The usage
game.setScreen(splashScreen);
...
// now when the splash screen animation is finished, I am calling the following from the controller:
game.setScreen(mainMenuScreen);
splashScreen.dispose();
I get the same exception.
The exception is on spriteBatch.end() row inside the render method. The spriteBatch member turns to be null. Really confusing, since I have mutual exclusive lock on the render and the dispose methods.

Answer 1

What I figured out, is that LibGDX works in one thread.
What happens is the following. When the game.setScreen(mainMenuScreen) is called, and the program is in the middle of the render method of the splash screen, the thread is interrupted, and the code for setting the mainMenuScreen is executed (in the Game class), and then going back to continue the render method of the splash screen. Weird, right? After setting the new screen still to render the old screen?
Anyways, what I did is the following:
As part of the Game.setScreen(Screen screen) method, the Screen.hide() method is called on the old screen.
So what I did, I introduced a flag, hideCalled and set it to true in the hide() event inside the splash screen.
Inside the render method of the splash screen I check this flag at the beginning and at the end of the method. If the flag is true - I dispose the screen.

Answer 2

I was just thinking about AssetManager, maybe it would help you with this problem in a cleaner way.
Take a look here.
I see it loads assets asynchronously so maybe this problem that you described would not be happening again.
And just for some knowledge sharing, I changed screens with another approach:
I used actions attached to an image, and these actions are executed in the order they are added. First i created an action which loads the images, then, when this first action was finished, i added another action which switches the screen.
Here is my code:
#Override
public void show() {
stage.addActor(splashImage);
splashImage.addAction(Actions.sequence(Actions.alpha(0), Actions.run(new Runnable() {
#Override
public void run() {
Assets.load();
}
}), Actions.fadeIn(0.5f), Actions.delay(1), Actions.fadeOut(0.5f), Actions.run(new Runnable() {
#Override
public void run() {
Utils.changeGameScreen(new GameScreen());
// ((Game) Gdx.app.getApplicationListener()).setScreen(new
// GameScreen());
}
})));
}