Button.java

package fi.hbp.angr.screens;


import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Camera;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.BitmapFont.TextBounds;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.Vector3;

/**
 * Menu screen button class.
 */
public class Button {
    /**
     * Screen camera.
     *
     * Camera reference is needed for project between screen and openGL world.
     */
    private final Camera camera;
    /** Font for drawing this button. */
    private BitmapFont font;
    /** Action class that will be called if this button is touched. */
    private final ButtonAction action;
    /**  ID of this button. */
    private final int id;

    /** Test vector used for bounds calculation. */
    private final Vector3 t1 = new Vector3();
    /** Test vector used for bounds calculation. */
    private final Vector3 t2 = new Vector3();

    /** Button text. */
    private String text;

    /**
     * UI Button Action Interface.
     */
    public interface ButtonAction {
        /**
         * Button action method that is called once if any
         * button is pressed.
         * @param id button id.
         */
        void buttonAction(int id);
    }

    /**
     * Constructor for UI button.
     * @param camera camera object used for projection.
     * @param font font that is used to draw this button.
     * @param action action that is called if button is touched.
     * @param id button identifier that is passed to the button action handler.
     */
    public Button(Camera camera, BitmapFont font, ButtonAction action, int id) {
        this(camera, font, action, "Default", id);
    }

    /**
     * Constructor for UI button.
     * @param camera camera object used for projection.
     * @param font font that is used to draw this button.
     * @param action action that is called if button is touched.
     * @param text button text.
     * @param id button identifier that is passed to the button action handler.
     */
    public Button(Camera camera, BitmapFont font, ButtonAction action, String text, int id) {
        this.camera = camera;
        this.font = font;
        this.action = action;
        this.text = text;
        this.id = id;
    }

    /**
     * Draw this button with temporary text.
     * @param batch sprite batch to be used.
     * @param text current button text. (This doesn't update the internal button text.)
     * @param x coordinate.
     * @param y coordinate.
     */
    public void draw(SpriteBatch batch, String text, float x, float y) {
        TextBounds bnd = font.draw(batch, text, x, y);

        t1.set(x, y, 0f);
        float y2 = y - font.getLineHeight();
        t2.set(x + bnd.width, y2, 0f);

        camera.project(t1);
        camera.project(t2);

        t1.y = (float)(Gdx.graphics.getHeight()) - t1.y;
        t2.y = (float)(Gdx.graphics.getHeight()) - t2.y;

        if(justTouched((int)t1.x, (int)t1.y, (int)t2.x, (int)t2.y)) {
            action.buttonAction(id);
        }
    }

    /**
     * Draw this button.
     * @param batch sprite batch to be used.
     * @param x coordinate.
     * @param y coordinate.
     */
    public void draw(SpriteBatch batch, float x, float y) {
        draw(batch, this.text, x, y);
    }

    /**
     * Check if an area was just touched.
     * @param x1 border coordinate.
     * @param y1 border coordinate.
     * @param d2 border coordinate.
     * @param d2 border coordinate.
     * @return true if given area was just touched; otherwise false.
     */
    protected static boolean justTouched(int x1, int y1, int x2, int y2) {
        int tmp;

        if (x1 > x2) {
            tmp = x1;
            x1 = x2;
            x2 = tmp;
        }

        if (y1 > y2) {
            tmp = y1;
            y1 = y2;
            y2 = tmp;
        }

        if (Gdx.input.justTouched()) {
            int px = Gdx.input.getX();
            int py = Gdx.input.getY();

            if ((px >= x1 && px <= x2) && (py >= y1 && py <= y2)) {
                return true;
            }
        }

        return false;
    }

    /**
     * Set button text.
     * @param text new button text.
     */
    public void setText(String text) {
        this.text = text;
    }

    /**
     * Get button text.
     * @return current button text.
     */
    public String getText() {
        return this.text;
    }

    /**
     * Get ID of this button.
     * @return id of this button.
     */
    public int getID() {
        return id;
    }
}