本課程的第一課“使用網絡服務發現”向您介紹了如何發現連接到本地網絡的服務。然而，使用 WLAN 點對點 (P2P) 服務發現可讓您在未連接到網絡的情況下直接發現附近設備的服務。您還可以廣播您的設備上運行的服務。使用這些功能，即使沒有可用的本地網絡或熱點，也可以在應用之間進行通信。

雖然這組 API 在用途方面與上一課程中介紹的網絡服務發現 API 相似，但在代碼中實現它們的方式卻截然不同。本課程向您介紹了如何使用 WLAN 點對點發現其他設備提供的服務，并假定您已熟悉 WLAN 點對點 API。

設置清單

如需使用 WLAN 點對點，請在清單中添加

package="com.example.android.nsdchat"

...

android:required="true"

android:name="android.permission.ACCESS_WIFI_STATE"/>

android:required="true"

android:name="android.permission.CHANGE_WIFI_STATE"/>

android:required="true"

android:name="android.permission.ACCESS_FINE_LOCATION"/>

android:required="true"

android:name="android.permission.INTERNET"/>

...

除了上面的權限外，以下 API 還需要啟用位置信息模式：

添加本地服務

如果您要提供本地服務，則需要注冊它以支持服務發現。注冊本地服務后，框架會自動響應來自對等設備的服務發現請求。

如需創建本地服務，請執行以下步驟：

用您的服務相關信息填充該對象。

調用

Kotlin

private fun startRegistration() {

// Create a string map containing information about your service.

val record: Map = mapOf(

"listenport" to SERVER_PORT.toString(),

"buddyname" to "John Doe${(Math.random() * 1000).toInt()}",

"available" to "visible"

)

// Service information. Pass it an instance name, service type

// _protocol._transportlayer , and the map containing

// information other devices will want once they connect to this one.

val serviceInfo =

WifiP2pDnsSdServiceInfo.newInstance("_test", "_presence._tcp", record)

// Add the local service, sending the service info, network channel,

// and listener that will be used to indicate success or failure of

// the request.

manager.addLocalService(channel, serviceInfo, object : WifiP2pManager.ActionListener {

override fun onSuccess() {

// Command successful! Code isn't necessarily needed here,

// Unless you want to update the UI or add logging statements.

}

override fun onFailure(arg0: Int) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

}

})

}Java

private void startRegistration() {

// Create a string map containing information about your service.

Map record = new HashMap();

record.put("listenport", String.valueOf(SERVER_PORT));

record.put("buddyname", "John Doe" + (int) (Math.random() * 1000));

record.put("available", "visible");

// Service information. Pass it an instance name, service type

// _protocol._transportlayer , and the map containing

// information other devices will want once they connect to this one.

WifiP2pDnsSdServiceInfo serviceInfo =

WifiP2pDnsSdServiceInfo.newInstance("_test", "_presence._tcp", record);

// Add the local service, sending the service info, network channel,

// and listener that will be used to indicate success or failure of

// the request.

manager.addLocalService(channel, serviceInfo, new ActionListener() {

@Override

public void onSuccess() {

// Command successful! Code isn't necessarily needed here,

// Unless you want to update the UI or add logging statements.

}

@Override

public void onFailure(int arg0) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

}

});

}

發現附近的服務

Android 使用回調方法向應用通知可用服務，因此首先要設置這些方法。創建

Kotlin

private val buddies = mutableMapOf()

...

private fun discoverService() {

/* Callback includes:

* fullDomain: full domain name: e.g "printer._ipp._tcp.local."

* record: TXT record dta as a map of key/value pairs.

* device: The device running the advertised service.

*/

val txtListener = DnsSdTxtRecordListener { fullDomain, record, device ->

Log.d(TAG, "DnsSdTxtRecord available -$record")

record["buddyname"]?.also {

buddies[device.deviceAddress] = it

}

}

}Java

final HashMap buddies = new HashMap();

...

private void discoverService() {

DnsSdTxtRecordListener txtListener = new DnsSdTxtRecordListener() {

@Override

/* Callback includes:

* fullDomain: full domain name: e.g "printer._ipp._tcp.local."

* record: TXT record dta as a map of key/value pairs.

* device: The device running the advertised service.

*/

public void onDnsSdTxtRecordAvailable(

String fullDomain, Map record, WifiP2pDevice device) {

Log.d(TAG, "DnsSdTxtRecord available -" + record.toString());

buddies.put(device.deviceAddress, record.get("buddyname"));

}

};

}

如需獲取服務信息，請創建一個

Kotlin

private fun discoverService() {

...

val servListener = DnsSdServiceResponseListener { instanceName, registrationType, resourceType ->

// Update the device name with the human-friendly version from

// the DnsTxtRecord, assuming one arrived.

resourceType.deviceName = buddies[resourceType.deviceAddress] ?: resourceType.deviceName

// Add to the custom adapter defined specifically for showing

// wifi devices.

val fragment = fragmentManager

.findFragmentById(R.id.frag_peerlist) as WiFiDirectServicesList

(fragment.listAdapter as WiFiDevicesAdapter).apply {

add(resourceType)

notifyDataSetChanged()

}

Log.d(TAG, "onBonjourServiceAvailable $instanceName")

}

manager.setDnsSdResponseListeners(channel, servListener, txtListener)

...

}Java

private void discoverService() {

...

DnsSdServiceResponseListener servListener = new DnsSdServiceResponseListener() {

@Override

public void onDnsSdServiceAvailable(String instanceName, String registrationType,

WifiP2pDevice resourceType) {

// Update the device name with the human-friendly version from

// the DnsTxtRecord, assuming one arrived.

resourceType.deviceName = buddies

.containsKey(resourceType.deviceAddress) ? buddies

.get(resourceType.deviceAddress) : resourceType.deviceName;

// Add to the custom adapter defined specifically for showing

// wifi devices.

WiFiDirectServicesList fragment = (WiFiDirectServicesList) getFragmentManager()

.findFragmentById(R.id.frag_peerlist);

WiFiDevicesAdapter adapter = ((WiFiDevicesAdapter) fragment

.getListAdapter());

adapter.add(resourceType);

adapter.notifyDataSetChanged();

Log.d(TAG, "onBonjourServiceAvailable " + instanceName);

}

};

manager.setDnsSdResponseListeners(channel, servListener, txtListener);

...

}

現在，創建一個服務請求并調用

Kotlin

serviceRequest = WifiP2pDnsSdServiceRequest.newInstance()

manager.addServiceRequest(

channel,

serviceRequest,

object : WifiP2pManager.ActionListener {

override fun onSuccess() {

// Success!

}

override fun onFailure(code: Int) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

}

}

)Java

serviceRequest = WifiP2pDnsSdServiceRequest.newInstance();

manager.addServiceRequest(channel,

serviceRequest,

new ActionListener() {

@Override

public void onSuccess() {

// Success!

}

@Override

public void onFailure(int code) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

}

});

Kotlin

manager.discoverServices(

channel,

object : WifiP2pManager.ActionListener {

override fun onSuccess() {

// Success!

}

override fun onFailure(code: Int) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

when (code) {

WifiP2pManager.P2P_UNSUPPORTED -> {

Log.d(TAG, "P2P isn't supported on this device.")

}

}

}

}

)Java

manager.discoverServices(channel, new ActionListener() {

@Override

public void onSuccess() {

// Success!

}

@Override

public void onFailure(int code) {

// Command failed. Check for P2P_UNSUPPORTED, ERROR, or BUSY

if (code == WifiP2pManager.P2P_UNSUPPORTED) {

Log.d(TAG, "P2P isn't supported on this device.");

else if(...)

...

}

});

如果一切進展順利，您就大功告成了！如果遇到問題，請記住，您所進行的異步調用采用

運行該應用的設備不支持 WLAN 點對點。

系統太忙，無法處理請求。

由于出現內部錯誤，操作失敗。

總結

以上是生活随笔為你收集整理的android 点对点 通信,将 WLAN 直连（点对点）用于服务发现的全部內容，希望文章能夠幫你解決所遇到的問題。

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