如何在AnimationTimer循环JavaFX中创建对象生成器

Question

I'm making simple spaceship game on JavaFX. I have class SpaceShip and i want to make random objects from this class in my main game loop on random starting position(in interval of 5 seconds for example). I try to use Timer schedule() method for the task. The problem is that i can't get clear image of the spaceship, it disappears and show in other point because of the constantly looping. Can someone help me with advice how to handle with this.

My game loop:

 new AnimationTimer() { @Override public void handle(long currentNanoTime) { double t = (currentNanoTime - startNanoTime) / 1000000000.0; double xMoving = ((100 * t) % (canvas.getWidth() + 100)); double x = 232 + 128 * Math.cos(t); double y = 232 + 128 * Math.sin(t); //background image clears canvas gc.drawImage(space, 0, 0); gc.drawImage(earth, x, y); gc.drawImage(sun, 196, 196); // draw UFO gc.drawImage(ufo.getFrame(t), 100, 25); //draw spaceShip SpaceShip.generate(new SpaceShip(spaceShipImageArr, 0.100, gc, t, xMoving - 100, (randomNum + 150))); //timer schedule Timer timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { SpaceShip.generate(new SpaceShip(spaceShipImageArr, 0.100, gc, t, xMoving - 100, (randomNum + 230))); } }, 5000); } }.start(); 

And the SpaceShip class:

package objectClasses;

import javafx.scene.canvas.GraphicsContext;
import javafx.scene.image.Image;


public class SpaceShip{

private final GraphicsContext gc;
private final double frame;
private final double y;
private final double x;
private AnimatedImage object;

public SpaceShip(Image[] arr, double duration, GraphicsContext gc, double frame, double x, double y) {
    object = new AnimatedImage();
    this.object.frames = arr;
    this.object.duration = duration;
    this.gc = gc;
    this.frame = frame;
    this.y = y;
    this.x = x;
}

private void drawShip() {
    this.gc.drawImage(this.object.getFrame(frame), x, y);
}

public static void generate(SpaceShip spaceShip) {
    spaceShip.drawShip();
}

}

Answer 1

This is the culprit.

SpaceShip.generate(new SpaceShip(spaceShipImageArr, 0.100, gc, t, xMoving - 100, (randomNum + 150)));

Basically, in each frame you create a new instance of SpaceShip . The blinking images are caused by space ships being created over and over again. That won't work.

You need to create these objects outside the game loop and store their references:

SpaceShip mySpaceShip = new SpaceShip(spaceShipImageArr, 0.100, gc, t, xMoving - 100, (randomNum + 150));

In the game loop you just update the position of your actors (that part is missing) and keep drawing them at new positions.

SpaceShip.generate(mySpaceShip);

Side note: you can remove the generate method altogether, make drawShip public, rename it to draw and simply call mySpaceShip.draw() - it will be more evident what's the role of your methods. It's perfectly acceptable for an object to draw itself.