Chapter 2

Simple Starfish Collector

Added sharky as suggested in summary

Chapter Notes

The Life Cycle of a Video Game

• Startup: Any files needed are loaded, game objects are created, and values are initialized.
• The game loop: Repeats continuously while the game is running.
  • Process Input: Checks user action.
  • Update: Perform tasks that involve the state of the game world and entities
  • Render: Draw all graphics on the screen.
• Shutdown: Removing images or data from memory, saving player data or the game state, signalling the computer to stop monitoring hardware devices for user inpu, and closing any windows that were created by the game.

New Imports

import com.badlogic.gdx.ApplicationListener - An ApplicationListener is called when the Application is created, resumed, rendering, paused or destroyed. All methods are called in a thread that has the OpenGL context current. You can thus safely create and manipulate graphics resources.

The ApplicationListener interface follows the standard Android activity life-cycle and is emulated on the desktop accordingly.

import com.badlogic.gdx.Input.Keys - Input polling of keyboard states

import com.badlogic.gdx.math.Rectangle - Encapsulates a 2D rectangle defined by its corner point in the bottom left and its extents in x (width) and y (height).

import com.badlogic.gdx.scenes.scene2d.Actor - An actor has a position, rectangular size, origin, scale, rotation, Z index, and color. The position corresponds to the unrotated, unscaled bottom left corner of the actor. The position is relative to the actor's parent. The origin is relative to the position and is used for scale and rotation.

An actor has a list of in progress actions that are applied to the actor (often over time). These are generally used to change the presentation of the actor (moving it, resizing it, etc). See act(float), Action, and its many subclasses.

import com.badlogic.gdx.scenes.scene2d.Stage - A 2D scene graph containing hierarchies of actors. Stage handles the viewport and distributes input events.

A stage must receive input events so it can distribute them to actors. This is typically done by passing the stage to Gdx.input.setInputProcessor.

Interfaces

An interface is a kind of contract that classes promise to do. The methods are only declared; they do not contain any actual code. All that is required is the signature of the method: the name, the input, the output and any modifiers, such as public. When implementing an interface you must write methods for eveything declared in the interface.

Abstract Classes

When programming you would want to reduce redundant code by refactoring repeated features in a base class and then extending that class. An abstract class is like an interface but the methods may also be written.

Diagram of the game's inheritance