一个多月以来，我正在尝试使用WiFi-Direct在两个android设备之间发送字符串，但是我仍在努力了解自己在做什么错。
我到处都是论坛，但他们通常没有提供有关如何实现我想要的目标的详细信息。
我还浏览了android开发者网站上的这两个指南：
我正在使用一项活动-ActivityConnection-在这里我根据用户先前选择发送还是接收字符串来切换视图的可见性。
在discoverPeers()的客户端上，立即查找任何启用了WiFi Direct的设备，并将其显示在ListView上。一旦用户选择了设备并按下发送按钮，连接即完成，字符串被发送。
在服务器端，使用我的AsyncServerTask类立即启动了服务器。在那里，它等待客户端连接并检索其发送的字符串。
我的主要问题是，在选择设备并点击发送按钮后，服务器端什么也没收到。 我的第二个问题是，有时找不到设备，并且列表视图保持空白。
我想念什么吗？还是做错了什么？
这是我当前的代码。 我自由地摆脱了我认为与上下文无关的任何内容，以使其更易于阅读。
ActivityConnection
public class ActivityConnection extends AppCompatActivity implements NewPeersListener {
public static final String CONNECTION_ACTOR = "actor";
public static final String SEND_INFO = "send";
public static final String RECEIVE_INFO = "receive";
ListView listViewDevices;
private IntentFilter intentFilter;
private WifiP2pManager manager;
private WifiP2pManager.Channel channel;
private WiFiDirectBroadcastReceiver receiver;
public List <WifiP2pDevice> listDevices;
private WifiP2pDevice selectedDevice;
@Override
public void onCreate (Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
confirm.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
connectToSelectedDevice();
}
});
Intent intent = this.getIntent();
String actor = intent.getStringExtra(CONNECTION_ACTOR);
this.intentFilter = new IntentFilter();
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
this.manager = (WifiP2pManager) this.getSystemService(Context.WIFI_P2P_SERVICE);
this.channel = this.manager.initialize(this, this.getMainLooper(), null);
this.receiver = new WiFiDirectBroadcastReceiver(this.manager, this.channel, this);
this.listDevices = new ArrayList <> ();
if (actor.equals(SEND_INFO)) {
DeviceAdapter adapter = new DeviceAdapter(ActivityConnection.this, R.layout.device_item, this.listDevices);
this.listViewDevices.setAdapter(adapter);
this.listViewDevices.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectedDevice = listDevices.get(position);
}
});
this.discoverPeers();
}
else if (actor.equals(RECEIVE_INFO)) {
new ServerAsyncTask(this).execute();
}
}
@Override
protected void onResume() {
super.onResume();
this.receiver = new WiFiDirectBroadcastReceiver(this.manager, this.channel, this);
this.registerReceiver(this.receiver, this.intentFilter);
}
@Override
protected void onPause() {
super.onPause();
this.unregisterReceiver(this.receiver);
}
public void resultReceived (String result) {
Toast.makeText(ActivityConnection.this, "Received! :)", Toast.LENGTH_SHORT).show();
}
private void discoverPeers () {
manager.discoverPeers(channel, new WifiP2pManager.ActionListener() {
@Override
public void onSuccess() {
// The discovery process succeeded
}
@Override
public void onFailure(int reason) {
// The discovery process DID NOT succeed
Toast.makeText(ActivityConnection.this, "Discovery process DID NOT succeed. Please verify that WiFi-Direct is active.", Toast.LENGTH_LONG).show();
}
});
}
private void connectToSelectedDevice () {
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = this.selectedDevice.deviceAddress;
this.manager.connect(this.channel, config, new WifiP2pManager.ActionListener() {
@Override
public void onSuccess() {
// Send string
Intent serviceIntent = new Intent(ActivityConnection.this, TransferService.class);
serviceIntent.setAction(TransferService.ACTION_SEND_STRING);
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, getMacAddress());
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_PORT, 8090);
startService(serviceIntent);
onBackPressed();
}
@Override
public void onFailure(int reason) {
Toast.makeText(ActivityConnection.this, "Connection failed. Try again.", Toast.LENGTH_SHORT).show();
}
});
}
@NonNull
private String getMacAddress () {
try {
List <NetworkInterface> all = Collections.list(NetworkInterface.getNetworkInterfaces());
for (NetworkInterface nif : all) {
if (!nif.getName().equalsIgnoreCase("wlan0")) continue;
byte[] macBytes = nif.getHardwareAddress();
if (macBytes == null) {
return "";
}
StringBuilder result = new StringBuilder();
for (byte b : macBytes) {
result.append(String.format("%02X:",b));
}
if (result.length() > 0) {
result.deleteCharAt(result.length() - 1);
}
return result.toString();
}
} catch (Exception e) {
}
return "02:00:00:00:00:00";
}
@Override
public void newPeers (WifiP2pDeviceList wifiP2pDeviceList) {
this.listDevices = new ArrayList <> (wifiP2pDeviceList.getDeviceList());
DeviceAdapter adapter = new DeviceAdapter(ActivityConnection.this, R.layout.device_item, this.listDevices);
this.listViewDevices.setAdapter(adapter);
}
}
WiFiDirectBroadcastReceiver
public class WiFiDirectBroadcastReceiver extends BroadcastReceiver {
private WifiP2pManager manager;
private WifiP2pManager.Channel channel;
private ActivityConnection activity;
private List <NewPeersListener> listeners;
public WiFiDirectBroadcastReceiver(WifiP2pManager manager, WifiP2pManager.Channel channel, ActivityConnection activity) {
super();
this.manager = manager;
this.channel = channel;
this.activity = activity;
this.listeners = new ArrayList <> ();
this.listeners.add(activity);
}
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
// Wi-Fi P2P is enabled
} else {
// Wi-Fi P2P is not enabled
Toast.makeText(this.activity, "Please turn on WiFi-Direct (or WiFi-P2P).", Toast.LENGTH_SHORT).show();
}
} else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {
// Request available peers from the wifi p2p manager.
if (this.manager != null) {
this.manager.requestPeers(this.channel, new WifiP2pManager.PeerListListener() {
@Override
public void onPeersAvailable(WifiP2pDeviceList peers) {
for (NewPeersListener listener : listeners) {
listener.newPeers(peers);
}
}
});
}
} else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {
// Respond to new connection or disconnections
} else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
// Respond to this device's wifi state changing
}
}
}
ServerAsyncTask（服务器）
public class ServerAsyncTask extends AsyncTask<Void, Void, String> {
private ServerSocket serverSocket;
private Socket clientSocket;
private DataInputStream stream;
private WeakReference <Context> contextWeakReference;
ServerAsyncTask (Context context) {
this.contextWeakReference = new WeakReference <> (context);
}
@Override
protected String doInBackground (Void... params) {
try {
this.serverSocket = new ServerSocket(8090);
this.clientSocket = this.serverSocket.accept();
this.stream = new DataInputStream(this.clientSocket.getInputStream());
String received = this.stream.readUTF();
this.serverSocket.close();
return received;
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
return null;
} finally {
if (this.stream != null) {
try {
this.stream.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
if (this.clientSocket != null) {
try {
this.clientSocket.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
if (this.serverSocket != null) {
try {
this.serverSocket.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
}
}
/*
* (non-Javadoc)
* @see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
@Override
protected void onPostExecute (String result) {
super.onPostExecute(result);
((ActivityConnection) this.contextWeakReference.get()).resultReceived(result);
}
}
TransferService（客户端）
public class TransferService extends IntentService {
public static final String TAG = "WIFI_DIRECT";
private static final int SOCKET_TIMEOUT = 5000;
public static final String ACTION_SEND_STRING = "sendString";
public static final String EXTRAS_GROUP_OWNER_ADDRESS = "go_host";
public static final String EXTRAS_GROUP_OWNER_PORT = "go_port";
public TransferService (String name) {
super(name);
}
public TransferService () {
super("TransferService");
}
@Override
protected void onHandleIntent (Intent intent) {
Context context = getApplicationContext();
if (intent.getAction().equals(ACTION_SEND_STRING)) {
String toSend = "string to send";
String host = intent.getExtras().getString(EXTRAS_GROUP_OWNER_ADDRESS);
int port = intent.getExtras().getInt(EXTRAS_GROUP_OWNER_PORT);
Socket socket = null;
DataOutputStream stream = null;
try {
// Create a client socket with the host, port, and timeout information.
socket = new Socket();
socket.bind(null);
socket.connect((new InetSocketAddress(host, port)), SOCKET_TIMEOUT);
Log.d(TAG, "Client connected socket - " + socket.isConnected());
// Send string
stream = new DataOutputStream(socket.getOutputStream());
stream.writeUTF(toSend);
stream.close();
Toast.makeText(context, "Sent! :)", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Log.e(TAG, Objects.requireNonNull(e.getMessage()));
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
if (socket.isConnected()) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
}
}
答案 0 :(得分：1)
在ActivityConnetion类中，我提供的是MAC地址而不是IP地址。我不知道为什么我没看到这个，也不知道为什么我首先看到了。因此，我环顾了这个论坛，并了解了如何获取WiFi-Direct的群组所有者的IP地址：Wifi Direct Group Owner Address。
要使代码运行，我进入了ActivityConnetion类，删除了getMacAddress()方法并替换了这一行：
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, getMacAddress());
有这行：
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, "192.168.49.1");
由于组所有者的IP始终相同，因此可以直接将其写下来。由于这样做会在IP更改时停止工作，因此建议您改为查找组所有者的IP。上面的链接显示了操作方法。