How create a respawn area in a tiled map

Question

I'm creating a RPG game, I need to create a monster respawn area like the Pokemon games where if I walk through the long grass areas a Pokemon can appear. I already created the battle scene, I've seen examples of tile collision with solid objects but I don't know how create a collision action with passable objects.

Answer 1

I suppose you could call it a collision, but it's more like an intersection. You can create a trigger zone that activates when the player enters it. A simple way of doing that would just create a list of these zones, then check to see if the player is inside them every frame or when the player moves. A zone is just two points, a min and a max. Then you can check when something is inside like so:

public boolean contains(float x, float z) {
    return (x >= minX && x < maxX &&
        z >= minZ && z < maxZ);
}

Answer 2

Finally i got how create the respawn zone, i create 2 arrays of tmxmap objects and extract is properties in the example i create wall(unwalkable zone) and isMonsterRespawn zone, where if the player collide with that zone certain action happens, in my example case the respawn zone change the color tile. There i can set an action that cant send my character to the battle scene with a randomly chance:

private void createUnwalkableObjects(TMXTiledMap map,final AnimatedSprite pl) {

 for(final TMXObjectGroup group: this.mTMXTiledMap.getTMXObjectGroups()) {

   if(group.getTMXObjectGroupProperties().containsTMXProperty("wall", "true")){
             // This is our "wall" layer. Create the boxes from it
   for(final TMXObject object : group.getTMXObjects()) {

                final Rectangle rect = new Rectangle(object.getX(), object.getY(),object.getWidth(), object.getHeight());
                rect.setVisible(false);
                final FixtureDef boxFixtureDef = PhysicsFactory.createFixtureDef(0, 0, 1f);
                PhysicsFactory.createBoxBody(this.mPhysicsWorld, rect, BodyType.StaticBody, boxFixtureDef);
                mScene.attachChild(rect);
             }
         }if(group.getTMXObjectGroupProperties().containsTMXProperty("IsMonsterSpawnArea", "true")){
             // This is our "wall" layer. Create the boxes from it
             for(final TMXObject object : group.getTMXObjects()) {
                final Rectangle rect = new Rectangle(object.getX(), object.getY(),object.getWidth(), object.getHeight());
    rect.setVisible(true);
    mScene.attachChild(rect);
    mScene.registerUpdateHandler(new IUpdateHandler() {
                    @Override
                    public void reset() {

}

                    @Override
                    public void onUpdate(final float pSecondsElapsed) {
                        if(pl.collidesWith(rect)){
//here the action when the player collides the zone
                            rect.setColor(1, 0, 1);}else{
                                rect.setColor(1, 0, 0);
                            }   
                        }

                });

             }
         }
     }

}