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Mastering Android Game Development
Mastering Android Game Development

Mastering Android Game Development: Master game development with the Android SDK to develop highly interactive and amazing games

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Mastering Android Game Development

Chapter 2. Managing User Input

In this chapter, we will learn how to handle user input in a generic way and later expand it to be either a virtual joystick, sensors, or an external controller.

To get a visual feedback of the input, we will be placing a spaceship on the screen and moving it around. We will also make it fire some bullets. This will also help you understand the interaction between the game objects and the game engine.

We will extend the generic InputController class to make the simplest keypad controller possible to understand how the class fits in the existing architecture and how the input is processed and read inside the game objects.

Once we get the basic keypad working, we will implement a virtual joystick, which is a much better way of handling user input.

Managing physical controllers is also important for the game we are writing, so we will see how to detect them and handle different options.

Finally, we will talk a bit about using sensors as controls. They are...

The InputController base class

It does not matter how we want to control the game; it can always be abstracted as a two-axis joystick and a button to fire. For other games this could be different, but you should always be able to extract basic actions from the user and create an InputController that handles them. The InputController we are building is useful for any game that uses directional control.

Note

Input controllers are quite specific to each type of game.

We are going to consider a normalized horizontal and vertical axis as an input (going from -1 to 1). In the case of a controller that does not have a range, we will just set it to the maximum. This will allow us to handle user input with precision when the type of input allows us to, as is the case with virtual and real joysticks as well as with sensors.

The InputController base class

The coordinate system of a phone screen

Just as a reminder, the coordinates on a computer screen have [0,0] in the top-left corner and go positive towards to the right and down. The...

The most basic virtual keypad

The simplest we can go is to build a simple keypad in the shape of a cross on the left-hand side of the screen and a fire button on its right-hand side. For this layout, we are going to create a new file under the layout folder and call it view_keypad.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_gravity="bottom"
  android:padding="@dimen/keypad_size"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">

  <Button
    android:id="@+id/keypad_up"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/keypad_left"
    android:layout_width="@dimen/keypad_size"
    android:layout_height="@dimen/keypad_size" />

  <Button
    android:id="@+id/keypad_down"
    android:layout_below=...

Creating a virtual joystick

We are going to improve the user input and we are going to do it by creating a virtual joystick.

A virtual joystick measures the distance from the touch position to its center and uses this information to set the values on the two axes. It behaves as a traditional analog joystick.

Since it is virtual, we are not constrained to have it at a specific position on the screen, so we can place it anywhere the player touches it.

We cannot, however, take the entire screen for the virtual joystick. There needs to be a fire button too.

We have experienced the frustration of small touch targets, so we are going to make the fire button as big as we can. This means that we are going to use half the screen for the virtual joystick and half the screen for the fire button.

The layout that we are going to use will have two views that fill the screen, each of them covering half of the width. We will name this layout view_vjoystick.xml:

<?xml version="1.0" encoding=&quot...

Physical controllers

Time to move into a type of controller that hardcore gamers love: physical ones.

There are a few devices that have a controller included as a part of their hardware. Some notable examples are XPeria Play—one of the pioneer phones that had a sliding gamepad—and Nvidia Shield, the latest in this category.

XPeria Play was one of the first devices with an integrated gamepad:

Physical controllers

Nvidia Shield is one of the most powerful Android devices with a gamepad:

Physical controllers

On the other hand, there are many brands that build game controllers for smartphones and they have been fairly popular among traditional gamers. All of them are Bluetooth controllers that can be connected to your phone or tablet. Some of them are designed to make your phone fit into it like Gametel (another pioneer) and most of the MOGA models.

Physical controllers

MOGA controller with an adjustable strip to hold your phone

There are also a few Android-powered devices that use controllers as the main input source. Here, we are talking about...

Sensors and InputControllers

Sensors are a common way to control games on smartphones. They work fine when the only controls in the game are left and right (like a car racing game). If you plan to also move up and down, you need to ask the player to do a calibration at the beginning of the game to make it usable. Note that, when you are using only one axis, such calibration is not necessary.

In addition to this, the up and down movement tends to interfere with the sensorLandscape orientation. So, the use of sensors is not a very good idea for YASS.

Note

Sensors are good controls only in certain cases.

You also have to consider that, while sensors are a replacement for directions, you still need to place the action buttons on the screen—in our case, the fire button.

We are not going to use sensors for YASS but, if you want to make a game that uses them, we will cover the basics.

You need to register a listener for the accelerometer and another one for the magnetic field. You should only...

The InputController base class


It does not matter how we want to control the game; it can always be abstracted as a two-axis joystick and a button to fire. For other games this could be different, but you should always be able to extract basic actions from the user and create an InputController that handles them. The InputController we are building is useful for any game that uses directional control.

Note

Input controllers are quite specific to each type of game.

We are going to consider a normalized horizontal and vertical axis as an input (going from -1 to 1). In the case of a controller that does not have a range, we will just set it to the maximum. This will allow us to handle user input with precision when the type of input allows us to, as is the case with virtual and real joysticks as well as with sensors.

The coordinate system of a phone screen

Just as a reminder, the coordinates on a computer screen have [0,0] in the top-left corner and go positive towards to the right and down. The...

The most basic virtual keypad


The simplest we can go is to build a simple keypad in the shape of a cross on the left-hand side of the screen and a fire button on its right-hand side. For this layout, we are going to create a new file under the layout folder and call it view_keypad.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_gravity="bottom"
  android:padding="@dimen/keypad_size"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">

  <Button
    android:id="@+id/keypad_up"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/keypad_left"
    android:layout_width="@dimen/keypad_size"
    android:layout_height="@dimen/keypad_size" />

  <Button
    android:id="@+id/keypad_down"
    android:layout_below="@+id/keypad_left"
    android:layout_toRightOf="@+id/keypad_left"
    android:layout_width="@dimen/keypad_size"
    android:layout_height...
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Description

If you are an intermediate-level Android developer who wants to create highly interactive and amazing games with the Android SDK, then this book is for you.

Who is this book for?

If you are an intermediate-level Android developer who wants to create highly interactive and amazing games with the Android SDK, then this book is for you.

What you will learn

  • Understand the internals of a game engine and the reasoning behind each of the components
  • Decide when to use each of the different ways of drawing on Android
  • Handle user inputs, from virtual joysticks to gamepads
  • Implement collision detection using different techniques and discover how to optimize it for complex games
  • Use animations and particle systems to provide a rich experience
  • Create beautiful, responsive, and reusable UIs by taking advantage of the Android SDK
  • Integrate Google Play Services to provide achievements and leaderboards to the players
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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jun 30, 2015
Length: 372 pages
Edition : 1st
Language : English
ISBN-13 : 9781783551774
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Length: 372 pages
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Language : English
ISBN-13 : 9781783551774
Vendor :
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Languages :
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Android Game Programming By Example
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Mastering Android Game Development
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Table of Contents

12 Chapters
1. Setting Up the Project Chevron down icon Chevron up icon
2. Managing User Input Chevron down icon Chevron up icon
3. Into the Draw Thread Chevron down icon Chevron up icon
4. Collision Detection Chevron down icon Chevron up icon
5. Particle Systems Chevron down icon Chevron up icon
6. Sound FX and Music Chevron down icon Chevron up icon
7. Menus and Dialogs Chevron down icon Chevron up icon
8. The Animation Framework Chevron down icon Chevron up icon
9. Integrating Google Play Services Chevron down icon Chevron up icon
10. To the Big Screen Chevron down icon Chevron up icon
A. API Levels for Android Versions Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3
(7 Ratings)
5 star 57.1%
4 star 14.3%
3 star 28.6%
2 star 0%
1 star 0%
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Amazon Customer Jan 01, 2020
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is a great book. It is well organized and takes the reader from project set up through game development. The organization of the code is very good and the author shows how to build a game engine. The beauty of the game in the book is that it can be modified into another game by replacing the images and game logic, all within the framework the author provides. I have read the book 3 times and appreciated it more and more with each read. The last 3 chapters cover Android animation, Google Play Services, and Android TV. These chapters are extremely informative. I highly recommend this book!
Amazon Verified review Amazon
Amazon Customer Jul 20, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Just finished this and I have to admit to skimming a few parts. I will update when I get a chance to go back to it if necessary.I found coverage of the structure of the code is a big positive.This is so often overlooked and it is very different to a regular Java or even Android app.Wish it didn't cover XML animations and "is this the right tool" and had more of the absolutely excellent info like on screen game controllers and particle effects made really easy.Five stars for that.
Amazon Verified review Amazon
jamie Aug 07, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Really enjoyed this book, from setting up a project right down to integrating google play services this has been a real enjoyment! mastering android game development gave me and hopefully will give you that bit extra and then some! the collision detection in making games was a weak spot for me but is now more clearer thanks to the way it is placed in this book.Some past books i have read i skipped through a bit and this was not the case this time around, if you dedicate your time to this without skipping through sections then there is no reason you cant take away some valuable knowledge to aid you in your games development! remember the will to learn puts you on the path to succeed! i find the hands on approach the best possible way to learn and this is what this book does, practice makes perfect as the saying goes and i now have plenty more knowledge to help me.The book is wriiten well and easy to follow, again its the will to learn that will determine how you take the methods in this book and what you take away after the final chapter. A great book thank you
Amazon Verified review Amazon
Hugo Oct 14, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This is the book if you want to learn how to make an android game, the concepts shown by the author are everything I would like to be presented when I was beginning in game development, but this book doesn't stopped in concepts of game development, he shows the pros and cons if you want to make a game purely with Android SDK. I've always trying to make games using complete game engines and editors, avoiding lose my time, but Isn't that crazy thing create a simple game engine to make a simple mobile game, now I think this is even fast process because I already knew how to program in Java and how Android works, the first chapter opened my mind, but the book has ten chapters and as I was reading and applying the concepts in my game I saw that it was a good choice, the book goes deep, and you become able to make a full featured game, the concepts shown are simple, but complete in way that you can easily adapt and apply for that game you want to do, all the features that most of the engines shows as their advantages like sounds, particles, collision, etc., are proved that isn't too difficult to implement and sometimes is even easier. This book was made by a top class game developer, and he mastered the art of teach what he knows. At the end of this book I felt that I became a better game developer because now I know how the game really works under the hood, this is much powerful, this book teached me more than a regular course, but it was fun and fast.
Amazon Verified review Amazon
BizyWizard Jul 04, 2016
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
This a great book for advanced programmers. Even if you are beginning it is a good read but beginner's should give themselves time to digest the information.
Amazon Verified review Amazon
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