Null Pointer Exception when using unProject in Libgdx

Question

I have a smasher game project and having problem when the game switches from MainMenuScreen to MainGameScreen, because of camera.unproject.

Texture img;
Array<Rectangle> listBalloon;
long lastSpawnTime;
OrthographicCamera camera;

BalloonPopper game;

public MainGameScreen(BalloonPopper game) {
this.game = game;
listBalloon = new Array<Rectangle>();
spawnBalloon();
}

@Override
public void show() {
img = new Texture("testBalloon.png");
}

@Override
public void render(float delta) {
ScreenUtils.clear(1, 0, 0, 1);

game.batch.begin();
for(Rectangle blns: listBalloon) {
game.batch.draw(img, blns.x, blns.y, blns.width,blns.height);
}
game.batch.end();

if(TimeUtils.nanoTime() - lastSpawnTime > 1000000000) spawnBalloon();

for(Iterator<Rectangle> iter = listBalloon.iterator(); iter.hasNext();) {
Rectangle blns = iter.next();
blns.y += 200 * Gdx.graphics.getDeltaTime();
if(blns.y > 720) iter.remove();
if(Gdx.input.isTouched()) {
Vector3 blnXY = new Vector3();
blnXY.set(Gdx.input.getX(), Gdx.input.getY(), 0);
camera.unproject(blnXY);
if(blns.contains(blnXY.x, blnXY.y)) {
iter.remove();
}
}
}
}

public void spawnBalloon() {
Rectangle bln = new Rectangle();
bln.x = MathUtils.random(0, 480 - 64);
bln.y = -20;
bln.width = 64;
bln.height = 128;
listBalloon.add(bln);
lastSpawnTime = TimeUtils.nanoTime();
}

In for(Iterator<Rectangle> iter = listBalloon.iterator(); iter.hasNext();) in render(), if I remove the camera.unproject, the program will move to MainGameScreen with no problem. However, sometimes clicking the spawned texture won't remove them and i have to click like a bit above of the texture so it can be removed. So the only thing i know to make it precisely find the location when clicking, is by adding camera.unproject. But yeah the problem is the null pointer exc

Answer 1

Hello M.O.HONOR

I am not familiar with libgdx but I know Nullpointerexeptions ;)

The best is to use debug mode in your ide and run the code step by step to see which variable returns null.

Did you initialize camera?

OrthographicCamera camera;
//default value: null

camera.anyMethod() will throw a Nullpointerexeption.

Answer 2

perhaps it is better to ask here

https://libgdx.com/community/discord/