How to move a sprite with the keyboard keys using libGDX?

Question

i have just started using java and libgdx and have this code, very simply it prints a sprite onto the screen. This works perfectly, and i learnt a lot from it.

Answer 1

My preferred method is to use an InputController which stores all the standard keys ready for checking.

import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.math.Vector2;

public class KeyboardController  implements InputProcessor {
    public boolean left,right,up,down;
    public boolean isMouse1Down, isMouse2Down,isMouse3Down;
    public boolean isDragged;
    public Vector2 mouseLocation = new Vector2(0,0);

    @Override
    public boolean keyDown(int keycode) {
        boolean keyProcessed = false;
        switch (keycode) // switch code base on the variable keycode
        {
            case Keys.LEFT:     // if keycode is the same as Keys.LEFT a.k.a 21
                left = true;    // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.RIGHT:    // if keycode is the same as Keys.LEFT a.k.a 22
                right = true;   // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.UP:       // if keycode is the same as Keys.LEFT a.k.a 19
                up = true;      // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.DOWN:     // if keycode is the same as Keys.LEFT a.k.a 20
                down = true;    // do this
                keyProcessed = true;    // we have reacted to a keypress
        }
        return keyProcessed;    //  return our peyProcessed flag
    }
    @Override
    public boolean keyUp(int keycode) {
        boolean keyProcessed = false;
        switch (keycode) // switch code base on the variable keycode
        {
            case Keys.LEFT:     // if keycode is the same as Keys.LEFT a.k.a 21
                left = false;   // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.RIGHT:    // if keycode is the same as Keys.LEFT a.k.a 22
                right = false;  // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.UP:       // if keycode is the same as Keys.LEFT a.k.a 19
                up = false;     // do this
                keyProcessed = true;    // we have reacted to a keypress 
                break;
            case Keys.DOWN:     // if keycode is the same as Keys.LEFT a.k.a 20
                down = false;   // do this
                keyProcessed = true;    // we have reacted to a keypress
        }
        return keyProcessed;    //  return our peyProcessed flag
    }
    @Override
    public boolean keyTyped(char character) {
        return false;
    }
    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        if(button == 0){
            isMouse1Down = true;
        }else if(button == 1){
            isMouse2Down = true;
        }else if(button == 2){
            isMouse3Down = true;
        }
        mouseLocation.x = screenX;
        mouseLocation.y = screenY;
        return false;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        isDragged = false;
        //System.out.println(button);
        if(button == 0){
            isMouse1Down = false;
        }else if(button == 1){
            isMouse2Down = false;
        }else if(button == 2){
            isMouse3Down = false;
        }
        mouseLocation.x = screenX;
        mouseLocation.y = screenY;
        return false;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        isDragged = true;
        mouseLocation.x = screenX;
        mouseLocation.y = screenY;
        return false;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        mouseLocation.x = screenX;
        mouseLocation.y = screenY;
        return false;
    }
    @Override
    public boolean scrolled(int amount) {
        return false;
    }
}

Then all I need to do is make the KeyboardController in the create method of your game with

controller = new KeyboardController();

Then tell GDX to use it to listen for events

Gdx.input.setInputProcessor(controller);

Finally if I want to check if a key is pressed I can go

if(controller.left){
    player.x -= 1;
}