通过 Wi-Fi 直连创建点对点连接

Wi-Fi 直连（也称为点对点或点对点）可让您的应用快速查找附近的设备并与其互动 蓝牙功能的范围之内。

通过 Wi-Fi Direct (P2P) API，应用无需 需要连接到网络或热点。 如果您的应用设计为安全、近距离网络的一部分，则 Wi-Fi 与传统的 Wi-Fi 临时相比，直连是更加合适的选项 可能出于以下原因：

• Wi-Fi 直连支持 WPA2 加密。（某些临时网络仅支持 WEP 加密）。
• 设备可以广播其提供的服务，这有助于其他 设备更容易发现合适的对等设备。
• 在确定哪台设备应成为该网络的群组所有者时， Wi-Fi 直连检查每台设备的电源管理、界面和服务 功能并利用这些信息选择可以处理 服务器职责。
• Android 不支持 Wi-Fi 临时模式。

本课介绍了如何使用 WLAN 点对点连接查找并连接到附近的设备。

设置应用权限

要使用 Wi-Fi 直连，请将 ACCESS_FINE_LOCATION, CHANGE_WIFI_STATE, ACCESS_WIFI_STATE 和 INTERNET 权限。 如果您的应用以 Android 13（API 级别 33）或更高版本为目标平台，也请添加 NEARBY_WIFI_DEVICES 权限。无线局域网 直接上传不需要互联网连接，但使用标准 Java 套接字，这需要 INTERNET 权限。因此，您需要以下权限才能使用 Wi-Fi 直连：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android.nsdchat"
    ...
    <!-- If your app targets Android 13 (API level 33)
         or higher, you must declare the NEARBY_WIFI_DEVICES permission. -->
        <uses-permission android:name="android.permission.NEARBY_WIFI_DEVICES"
        <!-- If your app derives location information from Wi-Fi APIs,
             don't include the "usesPermissionFlags" attribute. -->
        android:usesPermissionFlags="neverForLocation" />
        
    <uses-permission
        android:required="true"
        android:name="android.permission.ACCESS_FINE_LOCATION"
        <!-- If any feature in your app relies on precise location information,
             don't include the "maxSdkVersion" attribute. -->
        android:maxSdkVersion="32" />
    <uses-permission
        android:required="true"
        android:name="android.permission.ACCESS_WIFI_STATE"/>
    <uses-permission
        android:required="true"
        android:name="android.permission.CHANGE_WIFI_STATE"/>
    <uses-permission
        android:required="true"
        android:name="android.permission.INTERNET"/>
    ...

除上述权限外，以下 API 还要求启用位置信息模式：

• discoverPeers
• discoverServices
• requestPeers

设置广播接收器和对等连接管理器

要使用 Wi-Fi 直连，您需要监听告知 并在发生特定事件时触发应用在您的应用中，实例化 IntentFilter，并将其设置为监听以下内容：

WIFI_P2P_STATE_CHANGED_ACTION

用于指示是否启用 Wi-Fi 直连

WIFI_P2P_PEERS_CHANGED_ACTION

表示可用的类似应用列表已更改。

WIFI_P2P_CONNECTION_CHANGED_ACTION

指示 Wi-Fi 直连连接的状态已更改。起始内容 对于 Android 10，这不是固定的。如果您的应用依赖于接收这些 在注册时广播，因为此类广播是固定的，请使用适当的 get 方法获取信息。

WIFI_P2P_THIS_DEVICE_CHANGED_ACTION

指示此设备的配置详细信息已更改。起始内容 对于 Android 10，这不是固定的。如果您的应用依赖于接收这些 在注册时广播，因为此类广播是固定的，请使用适当的 get 方法获取信息。

Kotlin

private val intentFilter = IntentFilter()
...
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.main)

    // Indicates a change in the Wi-Fi Direct status.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION)

    // Indicates a change in the list of available peers.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION)

    // Indicates the state of Wi-Fi Direct connectivity has changed.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION)

    // Indicates this device's details have changed.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION)
    ...
}

Java

private final IntentFilter intentFilter = new IntentFilter();
...
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    // Indicates a change in the Wi-Fi Direct status.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);

    // Indicates a change in the list of available peers.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);

    // Indicates the state of Wi-Fi Direct connectivity has changed.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);

    // Indicates this device's details have changed.
    intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
    ...
}

在 onCreate() 方法结束时，获取 WifiP2pManager 的实例，并调用其 initialize() 方法。此方法会返回一个 WifiP2pManager.Channel 对象，稍后您将使用该对象 将应用连接到 Wi-Fi Direct 框架。

Kotlin

private lateinit var channel: WifiP2pManager.Channel
private lateinit var manager: WifiP2pManager

override fun onCreate(savedInstanceState: Bundle?) {
    ...
    manager = getSystemService(Context.WIFI_P2P_SERVICE) as WifiP2pManager
    channel = manager.initialize(this, mainLooper, null)
}

Java

Channel channel;
WifiP2pManager manager;

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    manager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
    channel = manager.initialize(this, getMainLooper(), null);
}

现在，创建一个新的 BroadcastReceiver 类，您将使用该类监听更改 设为系统的 Wi-Fi 状态。在onReceive()中 方法，添加一个条件来处理上面列出的每个状态变化。

Kotlin

override fun onReceive(context: Context, intent: Intent) {
    when(intent.action) {
        WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION -> {
            // Determine if Wi-Fi Direct mode is enabled or not, alert
            // the Activity.
            val state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1)
            activity.isWifiP2pEnabled = state == WifiP2pManager.WIFI_P2P_STATE_ENABLED
        }
        WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION -> {

            // The peer list has changed! We should probably do something about
            // that.

        }
        WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION -> {

            // Connection state changed! We should probably do something about
            // that.

        }
        WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION -> {
            (activity.supportFragmentManager.findFragmentById(R.id.frag_list) as DeviceListFragment)
                    .apply {
                        updateThisDevice(
                                intent.getParcelableExtra(
                                        WifiP2pManager.EXTRA_WIFI_P2P_DEVICE) as WifiP2pDevice
                        )
                    }
        }
    }
}

Java

@Override
public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
        // Determine if Wi-Fi Direct mode is enabled or not, alert
        // the Activity.
        int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
        if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
            activity.setIsWifiP2pEnabled(true);
        } else {
            activity.setIsWifiP2pEnabled(false);
        }
    } else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {

        // The peer list has changed! We should probably do something about
        // that.

    } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {

        // Connection state changed! We should probably do something about
        // that.

    } else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
        DeviceListFragment fragment = (DeviceListFragment) activity.getFragmentManager()
                .findFragmentById(R.id.frag_list);
        fragment.updateThisDevice((WifiP2pDevice) intent.getParcelableExtra(
                WifiP2pManager.EXTRA_WIFI_P2P_DEVICE));

    }
}

最后，添加代码，以便在发生以下情况时注册 intent 过滤器和广播接收器： 您的主 activity 处于活跃状态，并在该 activity 暂停时取消注册这些 activity。 建议这样做的最佳地点是onResume() onPause() 方法。

Kotlin

/** register the BroadcastReceiver with the intent values to be matched  */
public override fun onResume() {
    super.onResume()
    receiver = WiFiDirectBroadcastReceiver(manager, channel, this)
    registerReceiver(receiver, intentFilter)
}

public override fun onPause() {
    super.onPause()
    unregisterReceiver(receiver)
}

Java

/** register the BroadcastReceiver with the intent values to be matched */
@Override
public void onResume() {
    super.onResume();
    receiver = new WiFiDirectBroadcastReceiver(manager, channel, this);
    registerReceiver(receiver, intentFilter);
}

@Override
public void onPause() {
    super.onPause();
    unregisterReceiver(receiver);
}

启动对等设备发现

如需使用 Wi-Fi 点对点连接开始搜索附近的设备，请调用 discoverPeers()。此方法将 以下参数：

• 您获得的WifiP2pManager.Channel 您在初始化点对点 mManager 时收到的响应
• 包含方法的 WifiP2pManager.ActionListener 实现 成功和失败的发现进行调用。

Kotlin

manager.discoverPeers(channel, object : WifiP2pManager.ActionListener {

    override fun onSuccess() {
        // Code for when the discovery initiation is successful goes here.
        // No services have actually been discovered yet, so this method
        // can often be left blank. Code for peer discovery goes in the
        // onReceive method, detailed below.
    }

    override fun onFailure(reasonCode: Int) {
        // Code for when the discovery initiation fails goes here.
        // Alert the user that something went wrong.
    }
})

Java

manager.discoverPeers(channel, new WifiP2pManager.ActionListener() {

    @Override
    public void onSuccess() {
        // Code for when the discovery initiation is successful goes here.
        // No services have actually been discovered yet, so this method
        // can often be left blank. Code for peer discovery goes in the
        // onReceive method, detailed below.
    }

    @Override
    public void onFailure(int reasonCode) {
        // Code for when the discovery initiation fails goes here.
        // Alert the user that something went wrong.
    }
});

请记住，这仅启动对等设备发现。通过 discoverPeers() 方法会启动发现过程，然后 会立即返回结果。如果对等设备发现进程处于 通过在提供的操作监听器中调用方法成功启动。 此外，在启动连接或点对点组被启动之前，发现一直处于活跃状态 。

获取对等设备列表

现在编写获取并处理对等设备列表的代码。第一页 实现 WifiP2pManager.PeerListListener 接口，提供有关 Wi-Fi 直连的对等设备的信息 。此信息还让您的应用可以确定同伴加入或加入的时间 离开网络。以下代码段展示了这些操作 与类似应用相关：

Kotlin

private val peers = mutableListOf<WifiP2pDevice>()
...

private val peerListListener = WifiP2pManager.PeerListListener { peerList ->
    val refreshedPeers = peerList.deviceList
    if (refreshedPeers != peers) {
        peers.clear()
        peers.addAll(refreshedPeers)

        // If an AdapterView is backed by this data, notify it
        // of the change. For instance, if you have a ListView of
        // available peers, trigger an update.
        (listAdapter as WiFiPeerListAdapter).notifyDataSetChanged()

        // Perform any other updates needed based on the new list of
        // peers connected to the Wi-Fi P2P network.
    }

    if (peers.isEmpty()) {
        Log.d(TAG, "No devices found")
        return@PeerListListener
    }
}

Java

private List<WifiP2pDevice> peers = new ArrayList<WifiP2pDevice>();
...

private PeerListListener peerListListener = new PeerListListener() {
    @Override
    public void onPeersAvailable(WifiP2pDeviceList peerList) {

        List<WifiP2pDevice> refreshedPeers = peerList.getDeviceList();
        if (!refreshedPeers.equals(peers)) {
            peers.clear();
            peers.addAll(refreshedPeers);

            // If an AdapterView is backed by this data, notify it
            // of the change. For instance, if you have a ListView of
            // available peers, trigger an update.
            ((WiFiPeerListAdapter) getListAdapter()).notifyDataSetChanged();

            // Perform any other updates needed based on the new list of
            // peers connected to the Wi-Fi P2P network.
        }

        if (peers.size() == 0) {
            Log.d(WiFiDirectActivity.TAG, "No devices found");
            return;
        }
    }
}

现在，修改广播接收器的 onReceive() 方法，以便在收到具有 WIFI_P2P_PEERS_CHANGED_ACTION 操作的 intent 时调用 requestPeers()。您 因此需要以某种方式将此监听器传入接收器。一种方法是发送 作为广播接收器构造函数的参数。

Kotlin

fun onReceive(context: Context, intent: Intent) {
    when (intent.action) {
        ...
        WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION -> {

            // Request available peers from the wifi p2p manager. This is an
            // asynchronous call and the calling activity is notified with a
            // callback on PeerListListener.onPeersAvailable()
            mManager?.requestPeers(channel, peerListListener)
            Log.d(TAG, "P2P peers changed")


        }
        ...
    }
}

Java

public void onReceive(Context context, Intent intent) {
    ...
    else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {

        // Request available peers from the wifi p2p manager. This is an
        // asynchronous call and the calling activity is notified with a
        // callback on PeerListListener.onPeersAvailable()
        if (mManager != null) {
            mManager.requestPeers(channel, peerListListener);
        }
        Log.d(WiFiDirectActivity.TAG, "P2P peers changed");
    }...
}

现在，一个包含 WIFI_P2P_PEERS_CHANGED_ACTION intent 操作的 intent 触发对更新后的对等列表的请求。

连接到对等设备

如需连接到对等节点，请创建一个新的 WifiP2pConfig 对象，并将数据从 WifiP2pDevice，表示您要 连接。然后，调用 connect() 方法。

Kotlin

override fun connect() {
    // Picking the first device found on the network.
    val device = peers[0]

    val config = WifiP2pConfig().apply {
        deviceAddress = device.deviceAddress
        wps.setup = WpsInfo.PBC
    }

    manager.connect(channel, config, object : WifiP2pManager.ActionListener {

        override fun onSuccess() {
            // WiFiDirectBroadcastReceiver notifies us. Ignore for now.
        }

        override fun onFailure(reason: Int) {
            Toast.makeText(
                    this@WiFiDirectActivity,
                    "Connect failed. Retry.",
                    Toast.LENGTH_SHORT
            ).show()
        }
    })
}

Java

@Override
public void connect() {
    // Picking the first device found on the network.
    WifiP2pDevice device = peers.get(0);

    WifiP2pConfig config = new WifiP2pConfig();
    config.deviceAddress = device.deviceAddress;
    config.wps.setup = WpsInfo.PBC;

    manager.connect(channel, config, new ActionListener() {

        @Override
        public void onSuccess() {
            // WiFiDirectBroadcastReceiver notifies us. Ignore for now.
        }

        @Override
        public void onFailure(int reason) {
            Toast.makeText(WiFiDirectActivity.this, "Connect failed. Retry.",
                    Toast.LENGTH_SHORT).show();
        }
    });
}

如果群组中的每台设备都支持 Wi-Fi 直连，您就不需要 在连接时明确要求输入群组密码。允许设备 不支持 Wi-Fi 直连功能加入群组，但您需要 通过调用 requestGroupInfo()，以 如以下代码段所示：

Kotlin

manager.requestGroupInfo(channel) { group ->
    val groupPassword = group.passphrase
}

Java

manager.requestGroupInfo(channel, new GroupInfoListener() {
  @Override
  public void onGroupInfoAvailable(WifiP2pGroup group) {
      String groupPassword = group.getPassphrase();
  }
});

请注意，在以下代码中实现的 WifiP2pManager.ActionListener： connect() 方法仅会在调用 成功或失败如需监听连接状态的变化，请实现 WifiP2pManager.ConnectionInfoListener 接口。 其 onConnectionInfoAvailable() 回调会在 更改连接。在将多台设备连接到时 一台设备（例如有三个或更多玩家的游戏，或聊天应用）、一台设备 已被指定为“群组拥有者”。您可以将特定设备指定为 按照 创建群组部分。

Kotlin

private val connectionListener = WifiP2pManager.ConnectionInfoListener { info ->

    // String from WifiP2pInfo struct
    val groupOwnerAddress: String = info.groupOwnerAddress.hostAddress

    // After the group negotiation, we can determine the group owner
    // (server).
    if (info.groupFormed && info.isGroupOwner) {
        // Do whatever tasks are specific to the group owner.
        // One common case is creating a group owner thread and accepting
        // incoming connections.
    } else if (info.groupFormed) {
        // The other device acts as the peer (client). In this case,
        // you'll want to create a peer thread that connects
        // to the group owner.
    }
}

Java

@Override
public void onConnectionInfoAvailable(final WifiP2pInfo info) {

    // String from WifiP2pInfo struct
    String groupOwnerAddress = info.groupOwnerAddress.getHostAddress();

    // After the group negotiation, we can determine the group owner
    // (server).
    if (info.groupFormed && info.isGroupOwner) {
        // Do whatever tasks are specific to the group owner.
        // One common case is creating a group owner thread and accepting
        // incoming connections.
    } else if (info.groupFormed) {
        // The other device acts as the peer (client). In this case,
        // you'll want to create a peer thread that connects
        // to the group owner.
    }
}

现在，返回到广播接收器的 onReceive() 方法，并修改此部分 用于监听 WIFI_P2P_CONNECTION_CHANGED_ACTION intent 的操作。 收到此 intent 时，调用 requestConnectionInfo()。这是一个异步调用 这样，您作为 参数。

Kotlin

when (intent.action) {
    ...
    WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION -> {

        // Connection state changed! We should probably do something about
        // that.

        mManager?.let { manager ->

            val networkInfo: NetworkInfo? = intent
                    .getParcelableExtra(WifiP2pManager.EXTRA_NETWORK_INFO) as NetworkInfo

            if (networkInfo?.isConnected == true) {

                // We are connected with the other device, request connection
                // info to find group owner IP

                manager.requestConnectionInfo(channel, connectionListener)
            }
        }
    }
    ...
}

Java

    ...
    } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {

        if (manager == null) {
            return;
        }

        NetworkInfo networkInfo = (NetworkInfo) intent
                .getParcelableExtra(WifiP2pManager.EXTRA_NETWORK_INFO);

        if (networkInfo.isConnected()) {

            // We are connected with the other device, request connection
            // info to find group owner IP

            manager.requestConnectionInfo(channel, connectionListener);
        }
        ...

创建群组

如果您希望运行应用的设备充当某个应用的群组所有者 包含旧版设备（即不支持与 Wi-Fi 直连 - 具体步骤与 连接到同行部分，但需要创建新的 WifiP2pManager.ActionListener 使用 createGroup() 而非 connect()。调用 WifiP2pManager.ActionListener 相同，如以下代码段所示：

Kotlin

manager.createGroup(channel, object : WifiP2pManager.ActionListener {
    override fun onSuccess() {
        // Device is ready to accept incoming connections from peers.
    }

    override fun onFailure(reason: Int) {
        Toast.makeText(
                this@WiFiDirectActivity,
                "P2P group creation failed. Retry.",
                Toast.LENGTH_SHORT
        ).show()
    }
})

Java

manager.createGroup(channel, new WifiP2pManager.ActionListener() {
    @Override
    public void onSuccess() {
        // Device is ready to accept incoming connections from peers.
    }

    @Override
    public void onFailure(int reason) {
        Toast.makeText(WiFiDirectActivity.this, "P2P group creation failed. Retry.",
                Toast.LENGTH_SHORT).show();
    }
});

注意 ：如果网络中的所有设备都支持 Wi-Fi 直接，您可以在每台设备上使用 connect() 方法，因为 方法，然后创建群组并自动选择群组所有者。

创建群组后，您可以 requestGroupInfo()，用于检索对等项的详细信息 包括设备名称和连接状态。