Example mouse-driven map input processor for libgdx

MapInputProcessor.java

package mygame;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Input.Buttons;
import com.badlogic.gdx.InputAdapter;
import com.badlogic.gdx.Screen;
import com.badlogic.gdx.graphics.OrthographicCamera;

/**
 * A simple input processor which supports dragging the view by clicking and holding the left mouse button,
 * as well as scrolling with the mouse wheel.
 * <p>
 * Example usage:
 * <p>
 * In {@link Screen#show()} or {@link ApplicationListener#create()}
 * <pre>
 * mapInputProc = new MapInputProcessor();
 * Gdx.input.setInputProcessor(mapInputProc);
 * </pre>
 * In {@link Screen#render()} or {@link ApplicationListener#render()}, assuming the usage of an {@link OrthographicCamera}
 * <pre>
 * camera.viewportWidth = Gdx.graphics.getWidth() * mapInputProc.scale;
 * camera.viewportHeight = Gdx.graphics.getHeight() * mapInputProc.scale;
 * camera.position.x = mapInputProc.offsetX;
 * camera.position.y = mapInputProc.offsetY;
 * camera.update();
 * </pre>
 */
public class MapInputProcessor extends InputAdapter {
	private static final float MIN_SCALE = 0.01f;
	private static final float MAX_SCALE = 10.0f;
	
	private boolean mouseDown = false;
	public float scale = 1.0f;
	public float offsetX = 0.0f;
	public float offsetY = 0.0f;
	private int lastX;
	private int lastY;

	@Override public boolean touchDown(int screenX, int screenY, int pointer, int button) {
		if( button == Buttons.LEFT ) {
			mouseDown = true;
			lastX = screenX;
			lastY = screenY;
		}
		return false;
	}

	@Override public boolean touchUp(int screenX, int screenY, int pointer, int button) {
		if( button == Buttons.LEFT ) {
			mouseDown = false;
		}
		return false;
	}

	@Override public boolean touchDragged(int screenX, int screenY, int pointer) {
		if( mouseDown ) {
			offsetX -= (screenX - lastX) * scale;
			offsetY += (screenY - lastY) * scale;
			lastX = screenX;
			lastY = screenY;
		}
		return false;
	}

	@Override public boolean scrolled(int amount) {
		updateScale(scale * (1.0f + amount/10.0f));
		return false;
	}
	
	public void updateScale(float newScale) {
		if( newScale > MAX_SCALE ) { newScale = MAX_SCALE; }
		if( newScale < MIN_SCALE ) { newScale = MIN_SCALE; }
		scale = newScale;
	}
}