Detect user input in render() or using InputProcessor in libgdx - libgdx

Question

I am new to libgdx and I wonder if you should use the render() method to get user input or if you should use the InputProcessor.

Answer 1

That depends on the use-case. Why do you need it and does that need to be done event driven or continuous?
For example, if you want to move a sprite on the screen while a certain key is pressed, then that's a continuous action:
#Override public void render() {
if (Gdx.input.isKeyPressed(Input.Keys.SPACE))
sprite.translateX(speed * Gdx.graphics.getDeltaTime());
...
}
However, if you for example want to change the color when the user presses a certain key, then that's an event:
#Override public void create() {
Gdx.input.setInputProcessor(new InputAdapter() {
#Override public boolean keyUp (int keycode) {
if (keycode == Input.Keys.SPACE)
sprite.setColor(Color.RED);
}
});
...
}
Note that polling is a convenience method built on top of events, it is very easy to that yourself. Like so:
private boolean moving;
#Override public void create() {
Gdx.input.setInputProcessor(new InputAdapter() {
#Override public boolean keyDown (int keycode) {
if (keycode == Input.Keys.SPACE)
moving = true;
}
#Override public boolean keyUp (int keycode) {
if (keycode == Input.Keys.SPACE)
moving = false;
}
});
...
}
#Override public void render() {
if (moving)
sprite.translateX(speed * Gdx.graphics.getDeltaTime());
...
}
This often allows you to write more clean and use-case specific code, like so:
private float speed;
#Override public void create() {
Gdx.input.setInputProcessor(new InputAdapter() {
#Override public boolean keyDown (int keycode) {
switch (keycode) {
case Input.Keys.LEFT: speed -= 10f; break;
case Input.Keys.RIGHT: speed += 10f; break;
}
}
#Override public boolean keyUp (int keycode) {
switch (keycode) {
case Input.Keys.LEFT: speed += 10f; break;
case Input.Keys.RIGHT: speed -= 10f; break;
}
}
});
...
}
#Override public void render() {
sprite.translateX(speed * Gdx.graphics.getDeltaTime());
...
}
With this in mind, it can in many cases be better to use event driven input handling. However, if you find yourself using a lot of boolean flags, then you might as well use the builtin input polling.

Answer 2

You should use InputProcessor for user input.
if you want to write anonymously then in show method you should write:-
Gdx.input.setInputProcessor(new InputProcessor() {
#Override
public boolean touchUp(int arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean touchDragged(int arg0, int arg1, int arg2) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean touchDown(int arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean scrolled(int arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean mouseMoved(int arg0, int arg1) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean keyUp(int arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean keyTyped(char arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean keyDown(int arg0) {
// TODO Auto-generated method stub
return false;
}
});
or you can implement input processor and register instance in setInputProcessor.
Example:-
public class InputTest implements InputProcessor {
#Override
public boolean keyDown(int arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean keyTyped(char arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean keyUp(int arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean mouseMoved(int arg0, int arg1) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean scrolled(int arg0) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean touchDown(int arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean touchDragged(int arg0, int arg1, int arg2) {
// TODO Auto-generated method stub
return false;
}
#Override
public boolean touchUp(int arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
return false;
}
}
in show method of your screen class you should write:-
public void show() {
Gdx.input.setInputProcessor(new InputTest());
}
in my suggestion these two are the best way to take user input if you are not using stage.
Hope this will work for you.