1page.title=Supporting Multiple Game Controllers 2trainingnavtop=true 3 4@jd:body 5 6<!-- This is the training bar --> 7<div id="tb-wrapper"> 8<div id="tb"> 9 10<h2>This lesson teaches you to</h2> 11<ol> 12 <li><a href="#map">Map Players to Controller Device IDs</a></li> 13 <li><a href="#detect">Process Multiple Controller Input</a></li> 14</ol> 15 16<h2>Try it out</h2> 17<div class="download-box"> 18 <a href="http://developer.android.com/shareables/training/ControllerSample.zip" 19class="button">Download the sample</a> 20 <p class="filename">ControllerSample.zip</p> 21</div> 22 23 24</div> 25</div> 26<p>While most games are designed to support a single user per Android device, 27it's also possible to support multiple users with game controllers that are 28connected simultaneously on the same Android device.</p> 29<p>This lesson covers some basic techniques for handling input in your single 30device multiplayer game from multiple connected controllers. This includes 31maintaining a mapping between player avatars and each controller device and 32processing controller input events appropriately. 33</p> 34 35<h2 id="map">Map Players to Controller Device IDs</h2> 36<p>When a game controller is connected to an Android device, the system 37assigns it an integer device ID. You can obtain the device IDs for connected 38game controllers by calling {@link android.view.InputDevice#getDeviceIds() InputDevice.getDeviceIds()}, as shown in <a href="controller-input.html#input">Verify a Game Controller is Connected</a>. You can then associate each 39device ID with a player in your game, and process game actions for each player separately. 40</p> 41<p class="note"><strong>Note: </strong>On devices running Android 4.1 (API 42level 16) and higher, you can obtain an input device’s descriptor using 43{@link android.view.InputDevice#getDescriptor()}, which returns a unique 44persistent string value for the input device. Unlike a device ID, the descriptor 45value won't change even if the input device is disconnected, reconnected, or 46reconfigured. 47</p> 48<p>The code snippet below shows how to use a {@link android.util.SparseArray} 49to associate a player's avatar with a specific controller. In this example, the 50{@code mShips} variable stores a collection of {@code Ship} objects. A new 51player avatar is created in-game when a new controller is attached by a user, 52and removed when its associated controller is removed. 53</p> 54<p>The {@code onInputDeviceAdded()} and {@code onInputDeviceRemoved()} callback 55methods are part of the abstraction layer introduced in 56<a href="{@docRoot}training/game-controllers/compatibility.html#status_callbacks}"> 57Supporting Controllers Across Android Versions</a>. By implementing these 58listener callbacks, your game can identify the game controller's device ID when a 59controller is added or removed. This detection is compatible with Android 2.3 60(API level 9) and higher. 61</p> 62 63<pre> 64private final SparseArray<Ship> mShips = new SparseArray<Ship>(); 65 66@Override 67public void onInputDeviceAdded(int deviceId) { 68 getShipForID(deviceId); 69} 70 71@Override 72public void onInputDeviceRemoved(int deviceId) { 73 removeShipForID(deviceId); 74} 75 76private Ship getShipForID(int shipID) { 77 Ship currentShip = mShips.get(shipID); 78 if ( null == currentShip ) { 79 currentShip = new Ship(); 80 mShips.append(shipID, currentShip); 81 } 82 return currentShip; 83} 84 85private void removeShipForID(int shipID) { 86 mShips.remove(shipID); 87} 88</pre> 89 90<h2 id="detect">Process Multiple Controller Input</h2> 91<p>Your game should execute the following loop to process 92input from multiple controllers: 93</p> 94<ol> 95<li>Detect whether an input event occurred.</li> 96<li>Identify the input source and its device ID.</li> 97<li>Based on the action indicated by the input event key code or axis value, 98 update the player avatar associated with that device ID.</li> 99<li>Render and update the user interface.</li> 100</ol> 101<p>{@link android.view.KeyEvent} and {@link android.view.MotionEvent} input 102events have device IDs associated with them. Your game can take advantage of 103this to determine which controller the input event came from, and update the 104player avatar associated with that controller. 105</p> 106<p>The following code snippet shows how you might get a player avatar reference 107corresponding to a game controller device ID, and update the game based on the 108user's button press on that controller. 109</p> 110<pre> 111@Override 112public boolean onKeyDown(int keyCode, KeyEvent event) { 113 if ((event.getSource() & InputDevice.SOURCE_GAMEPAD) 114 == InputDevice.SOURCE_GAMEPAD) { 115 int deviceId = event.getDeviceId(); 116 if (deviceId != -1) { 117 Ship currentShip = getShipForId(deviceId); 118 // Based on which key was pressed, update the player avatar 119 // (e.g. set the ship headings or fire lasers) 120 ... 121 return true; 122 } 123 } 124 return super.onKeyDown(keyCode, event); 125} 126</pre> 127<p class="note"><strong>Note: </strong>As a best practice, when a user's 128game controller disconnects, you should pause the game and ask if the user 129wants to reconnect. 130</p> 131