1 page.title=Creating P2P Connections with Wi-Fi 2 3 trainingnavtop=true 4 5 @jd:body 6 7 <div id="tb-wrapper"> 8 <div id="tb"> 9 <h2>This lesson teaches you how to</h2> 10 <ol> 11 <li><a href="#permissions">Set Up Application Permissions</a></li> 12 <li><a href="#receiver">Set Up the Broadcast Receiver and Peer-to-Peer 13 Manager</a></li> 14 <li><a href="#discover">Initiate Peer Discovery</a></li> 15 <li><a href="#fetch">Fetch the List of Peers</a></li> 16 <li><a href="#connect">Connect to a Peer</a></li> 17 </ol> 18 <h2>You should also read</h2> 19 <ul> 20 <li><a href="{@docRoot}guide/topics/connectivity/wifip2p.html">Wi-Fi Peer-to-Peer</a></li> 21 </ul> 22 </div> 23 </div> 24 25 <p>The Wi-Fi peer-to-peer (P2P) APIs allow applications to connect to nearby devices without 26 needing to connect to a network or hotspot (Android's Wi-Fi P2P framework complies with the 27 <a href="http://www.wi-fi.org/discover-and-learn/wi-fi-direct" 28 class="external-link">Wi-Fi Direct™</a> certification program). 29 Wi-Fi P2P allows your application to quickly 30 find and interact with nearby devices, at a range beyond the capabilities of Bluetooth. 31 </p> 32 <p> 33 This lesson shows you how to find and connect to nearby devices using Wi-Fi P2P. 34 </p> 35 <h2 id="permissions">Set Up Application Permissions</h2> 36 <p>In order to use Wi-Fi P2P, add the {@link 37 android.Manifest.permission#CHANGE_WIFI_STATE}, {@link 38 android.Manifest.permission#ACCESS_WIFI_STATE}, 39 and {@link android.Manifest.permission#INTERNET} 40 permissions to your manifest. Wi-Fi P2P doesn't require an internet connection, 41 but it does use standard Java sockets, which require the {@link 42 android.Manifest.permission#INTERNET} permission. 43 So you need the following permissions to use Wi-Fi P2P.</p> 44 45 <pre> 46 <manifest xmlns:android="http://schemas.android.com/apk/res/android" 47 package="com.example.android.nsdchat" 48 ... 49 50 <uses-permission 51 android:required="true" 52 android:name="android.permission.ACCESS_WIFI_STATE"/> 53 <uses-permission 54 android:required="true" 55 android:name="android.permission.CHANGE_WIFI_STATE"/> 56 <uses-permission 57 android:required="true" 58 android:name="android.permission.INTERNET"/> 59 ... 60 </pre> 61 62 <h2 id="receiver">Set Up a Broadcast Receiver and Peer-to-Peer Manager</h2> 63 <p>To use Wi-Fi P2P, you need to listen for broadcast intents that tell your 64 application when certain events have occurred. In your application, instantiate 65 an {@link 66 android.content.IntentFilter} and set it to listen for the following:</p> 67 <dl> 68 <dt>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_STATE_CHANGED_ACTION}</dt> 69 <dd>Indicates whether Wi-Fi P2P is enabled</dd> 70 <dt>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_PEERS_CHANGED_ACTION}</dt> 71 <dd>Indicates that the available peer list has changed.</dd> 72 <dt>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_CONNECTION_CHANGED_ACTION}</dt> 73 <dd>Indicates the state of Wi-Fi P2P connectivity has changed.</dd> 74 <dt>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_THIS_DEVICE_CHANGED_ACTION}</dt> 75 <dd>Indicates this device's configuration details have changed.</dd> 76 <pre> 77 private final IntentFilter intentFilter = new IntentFilter(); 78 ... 79 @Override 80 public void onCreate(Bundle savedInstanceState) { 81 super.onCreate(savedInstanceState); 82 setContentView(R.layout.main); 83 84 // Indicates a change in the Wi-Fi P2P status. 85 intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION); 86 87 // Indicates a change in the list of available peers. 88 intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION); 89 90 // Indicates the state of Wi-Fi P2P connectivity has changed. 91 intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION); 92 93 // Indicates this device's details have changed. 94 intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION); 95 96 ... 97 } 98 </pre> 99 100 <p>At the end of the {@link android.app.Activity#onCreate onCreate()} method, get an instance of the {@link 101 android.net.wifi.p2p.WifiP2pManager}, and call its {@link 102 android.net.wifi.p2p.WifiP2pManager#initialize(Context, Looper, WifiP2pManager.ChannelListener) initialize()} 103 method. This method returns a {@link 104 android.net.wifi.p2p.WifiP2pManager.Channel} object, which you'll use later to 105 connect your app to the Wi-Fi P2P framework.</p> 106 107 <pre> 108 @Override 109 110 Channel mChannel; 111 112 public void onCreate(Bundle savedInstanceState) { 113 .... 114 mManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE); 115 mChannel = mManager.initialize(this, getMainLooper(), null); 116 } 117 </pre> 118 <p>Now create a new {@link 119 android.content.BroadcastReceiver} class that you'll use to listen for changes 120 to the System's Wi-Fi P2P state. In the {@link 121 android.content.BroadcastReceiver#onReceive(Context, Intent) onReceive()} 122 method, add a condition to handle each P2P state change listed above.</p> 123 124 <pre> 125 126 @Override 127 public void onReceive(Context context, Intent intent) { 128 String action = intent.getAction(); 129 if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) { 130 // Determine if Wifi P2P mode is enabled or not, alert 131 // the Activity. 132 int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1); 133 if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) { 134 activity.setIsWifiP2pEnabled(true); 135 } else { 136 activity.setIsWifiP2pEnabled(false); 137 } 138 } else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) { 139 140 // The peer list has changed! We should probably do something about 141 // that. 142 143 } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) { 144 145 // Connection state changed! We should probably do something about 146 // that. 147 148 } else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) { 149 DeviceListFragment fragment = (DeviceListFragment) activity.getFragmentManager() 150 .findFragmentById(R.id.frag_list); 151 fragment.updateThisDevice((WifiP2pDevice) intent.getParcelableExtra( 152 WifiP2pManager.EXTRA_WIFI_P2P_DEVICE)); 153 154 } 155 } 156 </pre> 157 158 <p>Finally, add code to register the intent filter and broadcast receiver when 159 your main activity is active, and unregister them when the activity is paused. 160 The best place to do this is the {@link android.app.Activity#onResume()} and 161 {@link android.app.Activity#onPause()} methods. 162 163 <pre> 164 /** register the BroadcastReceiver with the intent values to be matched */ 165 @Override 166 public void onResume() { 167 super.onResume(); 168 receiver = new WiFiDirectBroadcastReceiver(mManager, mChannel, this); 169 registerReceiver(receiver, intentFilter); 170 } 171 172 @Override 173 public void onPause() { 174 super.onPause(); 175 unregisterReceiver(receiver); 176 } 177 </pre> 178 179 180 <h2 id="discover">Initiate Peer Discovery</h2> 181 <p>To start searching for nearby devices with Wi-Fi P2P, call {@link 182 android.net.wifi.p2p.WifiP2pManager#discoverPeers(WifiP2pManager.Channel, 183 WifiP2pManager.ActionListener) discoverPeers()}. This method takes the 184 following arguments:</p> 185 <ul> 186 <li>The {@link android.net.wifi.p2p.WifiP2pManager.Channel} you 187 received back when you initialized the peer-to-peer mManager</li> 188 <li>An implementation of {@link android.net.wifi.p2p.WifiP2pManager.ActionListener} with methods 189 the system invokes for successful and unsuccessful discovery.</li> 190 </ul> 191 192 <pre> 193 mManager.discoverPeers(mChannel, new WifiP2pManager.ActionListener() { 194 195 @Override 196 public void onSuccess() { 197 // Code for when the discovery initiation is successful goes here. 198 // No services have actually been discovered yet, so this method 199 // can often be left blank. Code for peer discovery goes in the 200 // onReceive method, detailed below. 201 } 202 203 @Override 204 public void onFailure(int reasonCode) { 205 // Code for when the discovery initiation fails goes here. 206 // Alert the user that something went wrong. 207 } 208 }); 209 </pre> 210 211 <p>Keep in mind that this only <em>initiates</em> peer discovery. The 212 {@link android.net.wifi.p2p.WifiP2pManager#discoverPeers(WifiP2pManager.Channel, 213 WifiP2pManager.ActionListener) discoverPeers()} method starts the discovery process and then 214 immediately returns. The system notifies you if the peer discovery process is 215 successfully initiated by calling methods in the provided action listener. 216 Also, discovery will remain active until a connection is initiated or a P2P group is 217 formed.</p> 218 219 <h2 id="fetch">Fetch the List of Peers</h2> 220 <p>Now write the code that fetches and processes the list of peers. First 221 implement the {@link android.net.wifi.p2p.WifiP2pManager.PeerListListener} 222 interface, which provides information about the peers that Wi-Fi P2P has 223 detected. The following code snippet illustrates this.</p> 224 225 <pre> 226 private List<WifiP2pDevice> peers = new ArrayList<WifiP2pDevice>(); 227 ... 228 229 private PeerListListener peerListListener = new PeerListListener() { 230 @Override 231 public void onPeersAvailable(WifiP2pDeviceList peerList) { 232 233 // Out with the old, in with the new. 234 peers.clear(); 235 peers.addAll(peerList.getDeviceList()); 236 237 // If an AdapterView is backed by this data, notify it 238 // of the change. For instance, if you have a ListView of available 239 // peers, trigger an update. 240 ((WiFiPeerListAdapter) getListAdapter()).notifyDataSetChanged(); 241 if (peers.size() == 0) { 242 Log.d(WiFiDirectActivity.TAG, "No devices found"); 243 return; 244 } 245 } 246 } 247 </pre> 248 249 <p>Now modify your broadcast receiver's {@link 250 android.content.BroadcastReceiver#onReceive(Context, Intent) onReceive()} 251 method to call {@link android.net.wifi.p2p.WifiP2pManager#requestPeers 252 requestPeers()} when an intent with the action {@link 253 android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_PEERS_CHANGED_ACTION} is received. You 254 need to pass this listener into the receiver somehow. One way is to send it 255 as an argument to the broadcast receiver's constructor. 256 </p> 257 258 <pre> 259 public void onReceive(Context context, Intent intent) { 260 ... 261 else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) { 262 263 // Request available peers from the wifi p2p manager. This is an 264 // asynchronous call and the calling activity is notified with a 265 // callback on PeerListListener.onPeersAvailable() 266 if (mManager != null) { 267 mManager.requestPeers(mChannel, peerListListener); 268 } 269 Log.d(WiFiDirectActivity.TAG, "P2P peers changed"); 270 }... 271 } 272 </pre> 273 274 <p>Now, an intent with the action {@link 275 android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_PEERS_CHANGED_ACTION} intent will 276 trigger a request for an updated peer list. </p> 277 278 <h2 id="connect">Connect to a Peer</h2> 279 <p>In order to connect to a peer, create a new {@link 280 android.net.wifi.p2p.WifiP2pConfig} object, and copy data into it from the 281 {@link android.net.wifi.p2p.WifiP2pDevice} representing the device you want to 282 connect to. Then call the {@link 283 android.net.wifi.p2p.WifiP2pManager#connect(WifiP2pManager.Channel, 284 WifiP2pConfig, WifiP2pManager.ActionListener) connect()} 285 method.</p> 286 287 <pre> 288 @Override 289 public void connect() { 290 // Picking the first device found on the network. 291 WifiP2pDevice device = peers.get(0); 292 293 WifiP2pConfig config = new WifiP2pConfig(); 294 config.deviceAddress = device.deviceAddress; 295 config.wps.setup = WpsInfo.PBC; 296 297 mManager.connect(mChannel, config, new ActionListener() { 298 299 @Override 300 public void onSuccess() { 301 // WiFiDirectBroadcastReceiver will notify us. Ignore for now. 302 } 303 304 @Override 305 public void onFailure(int reason) { 306 Toast.makeText(WiFiDirectActivity.this, "Connect failed. Retry.", 307 Toast.LENGTH_SHORT).show(); 308 } 309 }); 310 } 311 </pre> 312 313 <p>The {@link android.net.wifi.p2p.WifiP2pManager.ActionListener} implemented in 314 this snippet only notifies you when the <em>initiation</em> succeeds or fails. 315 To listen for <em>changes</em> in connection state, implement the {@link 316 android.net.wifi.p2p.WifiP2pManager.ConnectionInfoListener} interface. Its {@link 317 android.net.wifi.p2p.WifiP2pManager.ConnectionInfoListener#onConnectionInfoAvailable(WifiP2pInfo) 318 onConnectionInfoAvailable()} 319 callback will notify you when the state of the connection changes. In cases 320 where multiple devices are going to be connected to a single device (like a game with 321 3 or more players, or a chat app), one device will be designated the "group 322 owner".</p> 323 324 <pre> 325 @Override 326 public void onConnectionInfoAvailable(final WifiP2pInfo info) { 327 328 // InetAddress from WifiP2pInfo struct. 329 InetAddress groupOwnerAddress = info.groupOwnerAddress.getHostAddress()); 330 331 // After the group negotiation, we can determine the group owner. 332 if (info.groupFormed && info.isGroupOwner) { 333 // Do whatever tasks are specific to the group owner. 334 // One common case is creating a server thread and accepting 335 // incoming connections. 336 } else if (info.groupFormed) { 337 // The other device acts as the client. In this case, 338 // you'll want to create a client thread that connects to the group 339 // owner. 340 } 341 } 342 </pre> 343 344 <p>Now go back to the {@link 345 android.content.BroadcastReceiver#onReceive(Context, Intent) onReceive()} method of the broadcast receiver, and modify the section 346 that listens for a {@link 347 android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_CONNECTION_CHANGED_ACTION} intent. 348 When this intent is received, call {@link 349 android.net.wifi.p2p.WifiP2pManager#requestConnectionInfo(WifiP2pManager.Channel, 350 WifiP2pManager.ConnectionInfoListener) requestConnectionInfo()}. This is an 351 asynchronous call, so results will be received by the connection info listener 352 you provide as a parameter. 353 354 <pre> 355 ... 356 } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) { 357 358 if (mManager == null) { 359 return; 360 } 361 362 NetworkInfo networkInfo = (NetworkInfo) intent 363 .getParcelableExtra(WifiP2pManager.EXTRA_NETWORK_INFO); 364 365 if (networkInfo.isConnected()) { 366 367 // We are connected with the other device, request connection 368 // info to find group owner IP 369 370 mManager.requestConnectionInfo(mChannel, connectionListener); 371 } 372 ... 373 </pre> 374
