1
Session 3.1
Getting Player Input
Using a Gamepad
Chapter 3.1: Getting Player Input Using a Gamepad
2
Session Overview
 Introduce the gamepad device
 Show how a C# object can be used to represent the
state of a gamepad
 Find out how to use the properties of the
GamePadState object in a program
 Create a Mood Light that is controlled by the
gamepad
 Discover how to use logical operators OR and AND
 Create our first XNA multiplayer game
Chapter 3.1: Getting Player Input Using a Gamepad
A User-Controlled Mood Light
 We are going to make a Mood Light that is
controlled by the user
 They will press the buttons on the gamepad to
control the brightness and color of the screen
background
 The user can select any color that they want
 This can also serve as the basis of a game
 To do this we need to know how XNA games get
input from the player
3
Chapter 3.1: Getting Player Input Using a Gamepad
The Xbox Gamepad
 The gamepad is a very
complex device
 It is connected to the host
either by USB or a wireless
connection
 It can be used with a
Windows PC or an Xbox
 You can obtain a wireless
adapter for the Windows
PC
4
Chapter 3.1: Getting Player Input Using a Gamepad
The Zune Buttons
 The Zune buttons work in the
same way as the buttons on
a gamepad
 The same XNA program can
work with a gamepad or a
Zune
 However, the Zune doesn’t
provide all the buttons that a
gamepad does
5
Chapter 3.1: Getting Player Input Using a Gamepad
6
Software and Objects
 We know that C# programs are made up of objects
that bring together data and behaviors
 A game has Game World data and draw and update
methods
 The state of a gamepad can be represented by a C#
object called a GamePadState object
 This contains the information about the state of the
gamepad at a particular instant
 The GamePadState object also provides properties
you can use to read this status information
Chapter 3.1: Getting Player Input Using a Gamepad
7
The GamePadState object
 A GamePadState object
contains information about all
the input devices the gamepad
has
Buttons
 We are going to consider just
the buttons and the DPad at the
moment
DPad
 When the Red button (B) is
pressed we want the
redIntensity value of the
background color to increase
GamePadState
Chapter 3.1: Getting Player Input Using a Gamepad
8
Creating a GamePadState Variable
GamePadState pad1;
 The game will use a variable to hold the state of the
gamepad
 It will then test the values of the buttons in this
variable so that the gamepad can be used to control
the game
 The variable must be declared like any other
variable in the game program
 It has been given the identifier pad1
Chapter 3.1: Getting Player Input Using a Gamepad
9
The pad1 Variable
 Each time that update is called, the pad1 variable
is set with the state of the gamepad for player 1
 Code in the update method will use this variable
 Should the pad1 variable be a local variable or a
member of the Game1 class?
 Member variables are shared between all the
methods in a class
 Local variables are just used inside the body of a
method and discarded when no longer required
Chapter 3.1: Getting Player Input Using a Gamepad
10
Using Local Variables
 The variable pad1 should be local to the update
method
 We don’t want to retain the value of gamepad
states from previous calls of update
 No other methods need to use the value of pad1
 Deciding which variables should be local and which
should be members is part of the program design
process
Chapter 3.1: Getting Player Input Using a Gamepad
11
Setting the pad1 Variable
GamePadState pad1 = GamePad.GetState (PlayerIndex.One) ;
 We can set the value of pad1 when we declare it
 The XNA Framework provides a class called
GamePad that exposes a getState method
 The getState method is told which gamepad to
get the state of
 We don’t need to know how getState works, just
how to call it and what the type of the result is
Chapter 3.1: Getting Player Input Using a Gamepad
12
GamePadState Properties
 A property is member of a class
that represents some data in
the class
 They can be set up to be read or
Buttons
written, or both
 The GamePadState properties
can only be read
DPad
 Each of the properties can
contain several values
GamePadState
Chapter 3.1: Getting Player Input Using a Gamepad
13
Game Update Behavior
if (pad1.Buttons.B == ButtonState.Pressed) redIntensity++;
 This condition tests the state of the B (Red) button
 If the button is Pressed the condition adds 1 to the
value of redIntensity
 If the button is held down successive calls of
update will cause the redIntensity to increase
 The equality operator is used because we are
comparing the state of Buttons.B with the value
ButtonState.Pressed
Chapter 3.1: Getting Player Input Using a Gamepad
14
Game Update Behavior
GamePadState pad1 = GamePad.GetState(PlayerIndex.One);
if (pad1.Buttons.B == ButtonState.Pressed) redIntensity++;
 This is the code that allows a game to control the
red intensity using button B on a gamepad
 Create a local variable called pad1 that contains the
state of the gamepad for player 1
 Get the state of button B out of the Buttons in the
pad, and if the button is pressed, increase the value
of redIntensity.
Chapter 3.1: Getting Player Input Using a Gamepad
1. User-Controlled Red Light
 This version of Mood
Light uses the code
above to control the
redIntensity value
 When the Red button is
pressed the screen
redIntensity value
gets larger
15
Chapter 3.1: Getting Player Input Using a Gamepad
16
Controlling Green and Blue
GamePadState pad1 = GamePad.GetState(PlayerIndex.One);
if (pad1.Buttons.B == ButtonState.Pressed) redIntensity++;
if (pad1.Buttons.A == ButtonState.Pressed) greenIntensity++;
if (pad1.Buttons.X == ButtonState.Pressed) blueIntensity++;
 The same code construction can be used to control
the green and blue intensity values
 Note that we don’t need to get a new
GamePadState value each time, the program can
just read different properties from the same pad1
value
Chapter 3.1: Getting Player Input Using a Gamepad
17
Controlling Yellow Intensity Using the Y Button
if (pad1.Buttons.Y == ButtonState.Pressed)
{
redIntensity++;
greenIntensity++;
}
 The gamepad has a Yellow button (Y)
 We can increase the yellow intensity by increasing
both red and green when this button is pressed
 To achieve this, the two update statements must
be placed in a block after the condition
Chapter 3.1: Getting Player Input Using a Gamepad
2. User-Controlled Light
 This version of Mood
Light uses all the
gamepad buttons to
control the background
color
18
Chapter 3.1: Getting Player Input Using a Gamepad
Adding Zune Support Using the DPad
 The Zune does not have all of
the buttons on the gamepad
 However it does have a DPad
which can be pressed in one of
four directions
 We could make a “Mood
Flashlight” by using the DPad to
control the colors
 Then the program would work
on the Zune as well
19
Chapter 3.1: Getting Player Input Using a Gamepad
20
Controlling Red Using the DPad.Right Value
if (pad1.DPad.Right == ButtonState.Pressed) redIntensity++;
 The GamePadState type contains a DPad property
which gives the states of the Left, Right, Up, and
Down positions of the DPad
 These are used in exactly the same way as the
colored buttons on the gamepad
 If any button state is equal to the value
ButtonState.Pressed it means that the
direction is selected on the gamepad
Chapter 3.1: Getting Player Input Using a Gamepad
Combining Tests Using Logical OR
 We want to make the red light brighter if button B
(Red) is pressed or Right is pressed on the DPad
 We can do this by having two separate if
statements
 However, it would be neater to be able to use a
single condition:
“If Button B is pressed OR DPad Right is pressed
increase the value of redIntensity”
 C# provides a logical operator to allow this
 We must use the logical OR operator
21
Chapter 3.1: Getting Player Input Using a Gamepad
22
The Logical OR operator
if (pad1.DPad.Right == ButtonState.Pressed ||
pad1.Buttons.B == ButtonState.Pressed)
{
redIntensity++;
}
 The logical OR operator is two vertical bars - ||
 It works between Boolean values (i.e. true or false)
 If either of the values on each side are true, the
result it gives is true
 The above code increases redIntensity if either
button is pressed
Chapter 3.1: Getting Player Input Using a Gamepad
23
Logical OR Test
if (true || false ) redIntensity++;
if (true || true ) redIntensity++;
if (false|| false ) redIntensity++;
 Logical OR works between any two conditions that
return a Boolean result
 We can use it between the values true and false
 Although this might result in compiler warnings
 Which of the above statements would increase the
value of redIntensity?
Chapter 3.1: Getting Player Input Using a Gamepad
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Logical OR Test
if (true || false ) redIntensity++; // increases
if (true || true ) redIntensity++; // increases
if (false || false ) redIntensity++; // doesn’t increase
 The OR operator returns true if either of the
conditions on each side of the operator is true
 Therefore it only returns false if both the conditions
are false
Chapter 3.1: Getting Player Input Using a Gamepad
25
Logical AND
 There is also a logical AND operator
 We could use this to make the program reset all the
colors to 0 if both triggers are pressed on the
gamepad
 This makes it harder to reset the colors by mistake
 The logical AND condition only works out to true if
the conditions on both sides are true
 The logical AND operator is the character sequence
&&
Chapter 3.1: Getting Player Input Using a Gamepad
Logical AND Value Reset
if (pad1.Buttons.LeftShoulder == ButtonState.Pressed &&
pad1.Buttons.RightShoulder == ButtonState.Pressed)
{
redIntensity = 0;
greenIntensity = 0;
blueIntensity = 0;
}
 The program can test the values of the shoulder
buttons on the controller
 If both of them are pressed the block of code is
performed
 This resets the intensity values to 0
26
Chapter 3.1: Getting Player Input Using a Gamepad
3. Fully Functional Light
 This version of the Mood
Light will work on Zune,
Windows PC or Xbox
 It also provides the reset
behavior with the
shoulder buttons
27
Chapter 3.1: Getting Player Input Using a Gamepad
28
Game Idea – Color Nerve
 You can use this program as the basis of a game:
 Players take turns to press any buttons they like on
the gamepad (but they must change the color on the
screen)
 If the screen flashes from bright to dark (i.e. an
intensity value wraps around) during a turn that player
is out
 The game continues until one player is left to become
the winner
 Press the shoulder buttons to reset for the next game
Chapter 3.1: Getting Player Input Using a Gamepad
29
Summary

The XNA Framework uses the type
GamePadState to represent the state of a
gamepad in a game

The GamePad class, which is part of XNA, provides
a getState method that can be used to get the
GamePadState value for the selected player

The GamePadState type exposes properties that
can be read to get the state of the gamepad

These states can be combined using logical
operators to allow more complicated behaviors to
be created in a program
Chapter 3.1: Getting Player Input Using a Gamepad
30
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
31
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
32
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
33
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
34
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by||in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
35
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.
Chapter 3.1: Getting Player Input Using a Gamepad
36
True/False Revision Quiz
 An XNA program can control the state of the buttons
on a gamepad.
 The GamePadState type holds information about
the state of a gamepad.
 Objects can expose information by means of
properties.
 An XNA program can only connect to one gamepad.
 The Zune has a full set of colored buttons.
 The AND operator is represented by|| in a program.