Using unProject correctly in Java Libgdx

Using unProject correctly in Java Libgdx

I'm really new to actually making games in java with libgdx. And right now
i'm not trying to make a button clickable and something is going to
happen. But it isn't working, it seems like i need to use the unproject
but i can't figur out how. Help appreciated. Here is the code:
Texture playButtonImage;
SpriteBatch batch;
ClickListener clickListener;
Rectangle playButtonRectangle;
Vector2 touchPos;
OrthographicCamera camera;
@Override
public void show() {
playButtonImage = new Texture(Gdx.files.internal("PlayButton.png"));
camera = new OrthographicCamera();
camera.setToOrtho(false, 800, 480);
batch = new SpriteBatch();
playButtonRectangle = new Rectangle();
playButtonRectangle.x = 400;
playButtonRectangle.y = 250;
playButtonRectangle.width = 128;
playButtonRectangle.height = 64;
}
@Override
public void render(float delta) {
Gdx.gl.glClearColor(0, 0, 0.2f, 1);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
camera.update();
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(playButtonImage, playButtonRectangle.x,
playButtonRectangle.y);
batch.end();
if (Gdx.input.isTouched()) {
Vector2 touchPos = new Vector2();
touchPos.set(Gdx.input.getX(), Gdx.input.getY());
if (playButtonRectangle.contains(touchPos)) {
batch.begin();
batch.draw(playButtonImage, 1, 1);
batch.end();
}
}
}