Adding Dynamic Entities

Before adding Hanny, lets start by adding her enemy, the evil swordfish. Since this fish will be based on the image sprites/swordfish.png and he will swim around, we will be using a DynamicSpriteEntity.

Add the `Swordfish`

Edit Create a new class called Swordfish that extends DynamicSpriteEntity in package com.github.hanyaeger.tutorial.entities. Since the image of the swordfish is already of the correct size, we don't need to set its size through the constructor, which can now look like:

public Swordfish(Coordinate2D location){
    super("sprites/swordfish.png", location);
}

Notice how we call super(String, Coordinate2D) and pass the url and
location to the constructor of the super class.

Animate the `Swordfish`

Since the swordfish is a DynamicSpriteEntity, we can let it move around the scene. To do this, we will need to set both the direction and speed. The direction will be an angle in degrees, where 0 denotes upwards. For convenience, Yaeger supplies a method to set both values at once. For the trivial directions (up, left, right and down) Yaeger provides an Enumeration called Direction, which can also be passed to the method.

Edit Add the following method-call to the constructor of Swordfish, just after the call to super:

setMotion(2, 270d);

Edit Now use the setupEntities() from GameLevel to add Swordfish.

Run Run the game again. You should now see a swordfish that swims from right to left and then disappears of the screen.

Make the swordfish swim in circles

Now we would like to add behaviour that notifies us when the swordfish has left the scene. That way we can place him to the right of the scene, and make him reappear and continue his path.

As seen before, adding behaviour is being done by implementing the correct interface. For this case, Yaeger supplies the interface SceneBorderCrossingWatcher.

Edit Let Swordfish implement the interface SceneBorderCrossingWatcher and implement the event handler in the following way:

@Override
public void notifyBoundaryCrossing(SceneBorder border){
    setAnchorLocationX(getSceneWidth());
}

Run Run the game again and see what happens. To also change the y-coordinate at which the swordfish reappears, you can add the following method-call: setAnchorLocationY(new Random().nextInt((int) getSceneHeight()- 81)); to the handler.

Use the build-in debugger to see what is happening

Yaeger contains a simple debugger that displays how much memory is used by the game and how many Entities are currently part of the game. When a game doesn't work as expected, you can use this debugger to get some inside information.

Run Run the game with the commandline argument --showDebug. Setting these options can usually be done from the Run Configuration within your IDE, as explained below.

See if you can relate the stated numbers to what you expect from your game. To disable the Debugger window, just remove the commandline argument from the Run Configuration.