LoadImage Android Studio

I already checked this forum with loadimage and I haven’t been able to add images to my project yet.
I have the assets folder add to the project where I have put my images but when I call them it keeps showing an error.

Attempt to invoke interface method ‘android.content.res.AssetManager processing.core.PSurface.getAssets ()’ on a null object reference

I have tried AssetManager but I have not succeeded, I have not been able to return a String which is the parameter that receives loadImage ()

Help me please

public void settings () {
size (500, 700);
asteroid = loadImage (“asteroid.png”);
background = loadImage (“background.png”);
nave2 = loadImage (“nave2.png”);
noStroke ();