播放器可以移出屏幕吗？

Question

So, I'm creating a simple 2D video game. I noticed recently that the player can move off the screen, so I added this code:

if (newX <= SIZE * TagsCanvas.SCALE) {
            newX = SIZE * TagsCanvas.SCALE;
        } else if (newX >= TagsCanvas.CANVAS_WIDTH - (SIZE * TagsCanvas.SCALE) - getAABB().getRadX()) {
            newX = TagsCanvas.CANVAS_WIDTH - (SIZE * TagsCanvas.SCALE) - getAABB().getRadX();
        }

        if (newY <= SIZE * TagsCanvas.SCALE) {
            newY = SIZE * TagsCanvas.SCALE;
        } else if (newY >= TagsCanvas.CANVAS_HEIGHT - (SIZE * TagsCanvas.SCALE) - getAABB().getRadY()) {
            newY = TagsCanvas.CANVAS_HEIGHT - (SIZE * TagsCanvas.SCALE) - getAABB().getRadY();
        }

TagsCanvas.CANVAS_WIDTH is the width of the canvas object. Height is the height of the canvas object. Size is the size of the player, and scale is the scale of the game (At the moment it's 2). getAABB().getRadX() returns the radius from the center of the player to the edge (The 'player' is a square box).

Now, the x works fine, but the Y part doesn't. It'll block the player from moving up off the map (The first statement), but it will let the player go about 20 points too far down. Any help would be appreciated!

Answer 1

What you can do is have it wraparound by using the Modulo operator (ie remainder after integer division).

Say you want to move 5 units: Have a method:

public void move(int amt){
 pos = (pos + amt) % TagsCanvas.CANVAS_WIDTH.
}

The Modulo operator makes sure that the value will never be equal to or greater than TagsCanvas.CANVAS_WIDTH.