Mouse events II (with <em>GGMouseTouchListener

Mouse events II (with GGMouseTouchListener)

Different to the methods of GGMouseListener (mouse.getX(), mouse.getY()), which return the grid coordinates of the mouse click, the methods of GGMouseTouchListener return the actor which the mouse hits or touches. This comes in handy when working with small celled or pixel grids. In this example, Nemo can be moved smoothly around the whole window. It does not jump from cell to cell, as in the examples of the GGMouseListener.

The GGMouseTouchListener is registered with addMouseTouchListener(). Only events which are needed in this application are defined. In our examples l Press, lDrag and lRelease.

Example 1: The actor Nemo can be grabbed at any position of the Sprite and moved to any position inside the grid. The cell size is set to one (pixel grid).

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// JGameEx22.java

import ch.aplu.jgamegrid.*;
import java.awt.*;

public class JGameEx22 extends GameGrid implements GGMouseTouchListener
{
  private Point hotSpot;

  public JGameEx22()
  {
    super(300, 300, 1, false);
    setTitle("Drag Nemo!");
    Actor nemo = new Actor("sprites/nemo.gif");
    nemo.addMouseTouchListener(this,
      GGMouse.lPress | GGMouse.lDrag | GGMouse.lRelease);
    addActor(nemo, new Location(150, 150));
    show();
  }

  public void mouseTouched(Actor actor, GGMouse mouse, Point spot)
  {
    switch (mouse.getEvent())
    {
      case GGMouse.lPress:
        hotSpot = spot;
        break;
      case GGMouse.lDrag:
        if (hotSpot == null)  // Pressed outside sprite
          hotSpot = spot;
        Location loc =
          new Location(mouse.getX() - hotSpot.x, mouse.getY() - hotSpot.y);
        actor.setLocation(loc);
        refresh();
        break;
      case GGMouse.lRelease:
        hotSpot = null;
        break;
    }
  }

  public static void main(String[] args)
  {
    new JGameEx22();
  }
}

Explaining the program code:

addMouseTouchListener(this, GGMouse.lPress \| GGMouse.lDrag \| GGMouse.lRelease	registers the MouseTouchListener with the left mouse click, drag and release. Since the application implements a GGMouseTouchListener, its reference is set as a parameter (this)
mouseTouched(Actor actor, GGMouse mouse, Point spot)	a callbackmethod, which returns an event if the mouse touches an actor's Sprite
Location loc = new Location(mouse.getX() - hotSpot.x, mouse.getY() - hotSpot.y); actor.setLocation(loc);	moves the actor to its new position

Example 2: Sometimes its useful to smoothly move an object and finally setting it down exactly in a grid cell. In this example, randomly set pearls have to be moved into a one row.

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// JGameEx22a.java

import ch.aplu.jgamegrid.*;
import java.awt.*;

public class JGameEx22a extends GameGrid
  implements GGMouseTouchListener, GGMouseListener
{
  private Point hotSpot = null;
  private Actor nemo = new Actor("sprites/nemo.gif");

  public JGameEx22a()
  {
    super(300, 300, 1, false);
    setTitle("Drag Nemo!");
    nemo.addMouseTouchListener(this, GGMouse.lPress | GGMouse.lRelease);
    addMouseListener(this, GGMouse.lDrag);
    addActor(nemo, new Location(150, 150));
    show();
  }

  public boolean mouseEvent(GGMouse mouse)
  {
    if (hotSpot == null)
      return false;
    Location loc =
      new Location(mouse.getX() - hotSpot.x, mouse.getY() - hotSpot.y);
    nemo.setLocation(loc);
    refresh();
    return false;
  }

  public void mouseTouched(Actor actor, GGMouse mouse, Point spot)
  {
    switch (mouse.getEvent())
    {
      case GGMouse.lPress:
        hotSpot = spot;
        break;
      case GGMouse.lRelease:
        hotSpot = null;
        break;
    }
  }

  public static void main(String[] args)
  {
    new JGameEx22a();
  }
}

Explaining the program code:

addMouseTouchListener(this, GGMouse.lPress \| GGMouse.lDrag \| GGMouse.lRelease)	registers the MouseTouchListener with the left mouse click, drag and release. Since the application implements a GGMouseTouchListener, its reference is set as a parameter (this)
case GGMouse.lPress: draggedPearl = actor	the method lPress of the GGMouseTouchListener returns the actor which is selected with the mouse. The selected pearl is called draggedPearl. This step is important, because it allows the player to set several pearls into the same location. The top one can then be removed again if necessary
if (draggedPearl != null)	actions only happen when a pearl is selected. Since the click outside a pearl does not return anything, it is necessary to start this query before the next action
Point mousePos = new Point(mouse.getX(), mouse.getY()); draggedPearl.setPixelLocation(mousePos);	follows the mouse cursor and moves the selected pearl
case GGMouse.lRelease: draggedPearl.setLocationOffset(new Point(0, 0)); draggedPearl = null;	after releasing the pearl, it is set exactly in the middle of the cell. The variable draggedPearl is set to null. This allows a new pearl to be selected

Example 3: clicking on a match, it is removed. The click can be made on any part of the match

As in the other examples, the advantages of the GGMouseTouchListener are used. Not the grid cells define the interactive parts, but its Sprites.

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// JGameEx25.java

import ch.aplu.jgamegrid.*;
import java.awt.*;

public class JGameEx25 extends GameGrid implements GGMouseTouchListener
{

  private int nbMatches = 20;

  public JGameEx25()
  {
    super(600, 120, 1, false);
    setTitle("Remove matches");
    for (int i = 0; i < nbMatches; i++)
    {
      Actor match = new Actor("sprites/match.gif");
      addActor(match, new Location(12 + 30 * i, 60));
      match.addMouseTouchListener(this, GGMouse.lPress);
    }
    show();
    doRun();
  }

  public void mouseTouched(Actor actor, GGMouse mouse, Point pix)
  {
    actor.removeSelf();
    nbMatches--;
    setTitle("Remove matches. " + nbMatches + " matches remaining.");
  }


  public static void main(String[] args)
  {
    new JGameEx25();
  }
}

Explaining the program code:

addActor(match, new Location(12 + 30 * i, 60)) match.addMouseTouchListener(this, GGMouse.lPress)	positions the matches in the pixel grid. Registers the MouseTouchListener for each match
void mouseTouched() actor.removeSelf()	callbackmethod of the MouseTouchListeners. The touched match is removed
nbMatches--	number of matches left is shown in the title bar

GameGrid: Game programming with Java	Deutsch
Research project PHBern

GameGrid: Game programming with Java

Mouse events II (with GGMouseTouchListener)