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Moving figures

Example 1: The fish should swim back and forth and thereby always look ahead. If the fish is in a border cell, he has to turn his direction of movement by 180° and thereby mirror his sprite image.

With the method setHorzMirror(), an image can be mirrored.
setHorzMirror(true): the image is mirrored
setHorzMirror(false): the image is not mirrored

Since we have to distinguish in this example if the fish is top right or top left, we use method getX() in order to check the border cells. This indicates the x coordinate of the current cell.

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Download sources (AndroidEx2.zip)

// AndroidEx2.java

package app.ex2;

import ch.aplu.android.*;

public class AndroidEx2 extends GameGrid
{
  public AndroidEx2()
  {
    super(8, 8, 0, RED);
  }

  public void main()
  {
    Fish nemo = new Fish();
    addActor(nemo, new Location(1, 1));
    doRun();
  }
}

class Fish extends Actor
{
  public Fish()
  {
    super("nemo");
  }

  public void act()
  {
    move();
    if (getX() == 7)
    {
      turn(180);
      setHorzMirror(true);
    }
    if (getX() == 0)
    {
      turn(180);
      setHorzMirror(false);
    }
  }
}

Explanations to the program code:

getX()	Gives back the current cell coordinate of the actor
setHorzMirror(true)	Mirrors the sprite image horizontally
setHorzMirror(false)	The sprite image is not mirrored (default)

Example 2: Pass through the cells of the grid/ use background image

The fish starts at cell (0, 0) and moves from cell to cell. If it reaches the cell with the x-coordinate 7, it turns around by 90°. If it's still at 7 in the next step, it has to turn around again. On the left edge, it has to turn around by 270°.

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App installieren auf Smartphone oder Tablet

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Download sources (AndroidEx3.zip)

// AndroidEx3.java

package app.ex3;

import ch.aplu.android.*;

public class AndroidEx3 extends GameGrid
{
  public AndroidEx3()
  {
    super(8, 8, cellZoom(60), RED, "reef", false);
  }

  public void main()
  {
    Fish nemo = new Fish();
    addActor(nemo, new Location(0, 0));
    doRun();
  }
}

class Fish extends Actor
{
  public Fish()
  {
    super("nemo");
  }

  public void act()
  {
    move();
    if (getX() == 7)
    {
      turn(90);
      setHorzMirror(true);
    }
    if (getX() == 0)
    {
      turn(270);
      setHorzMirror(false);
    }
  }
}

Explanations to the program code:

super(8, 8, 40, Color.RED, "reef", true)

As background image, we use reef.gif. Since the image has to the size of 320x320 pixel, it is better to use a fix cell size. With bigger displays (e.g. with tablets), the whole game window, including the background image is enlarged.

Example 3: Move figure on an arc/ Rotatable sprites

So that the car moves on an arc, there has to be a rotation by a small angle with every step (turn(2.5)). In order to turn the sprite image before every step into the moving direction, there is entered the parameter true when the car is initialized.

super(true,"redcar")

The parameter true causes the direction of the sprites to be calculated and updated continuously. The speed of the car can be changed by using the volume control of the phone.

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App installieren auf Smartphone oder Tablet

Download sources (AndroidEx4.zip)

// AndroidEx4.java

package app.ex4;

import ch.aplu.android.*;

public class AndroidEx4 extends GameGrid
{
  public AndroidEx4()
  {
    super(300, 300, 1, 0, true);
  }

  public void main()
  {
    RedCar car = new RedCar();
    addActor(car, new Location(150, 20));
    doRun();
  }
}

class RedCar extends Actor
{
  public RedCar()
  {
    super(true,"redcar");
  }

  public void act()
  {
    move();
    turn(2.5);
  }
}

Explanations to the program code:

super(300, 300, 1, 0, true)	Pixel resolution without grid with activated navigation
super(true,"redcar")	Rotatable sprite

Game apps for smartphones and tablets	Deutsch
Research project PHBern

Game apps for smartphones and tablets

Moving figures