问题描述
任务说明： 我打算构建一个应用程序，它可以使用 NSD android 在我的网络中发现 ESP32 提供的服务，所以我实现了下面的代码 代码：
import android.net.DhcpInfo;
import android.net.nsd.NsdManager;
import android.net.nsd.NsdManager.discoveryListener;
import android.util.Log;
import android.net.nsd.NsdServiceInfo;
import android.text.format.Formatter;
import java.net.NetworkInterface;
import java.net.socketException;
import java.util.Enumeration;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.net.InetAddress;
import java.io.IOException;
import java.net.UnkNownHostException;
//import android.app.Activity;
import java.lang.reflect.Method;
public class MusicList extends org.qtproject.qt5.android.bindings.QtActivity {
public static String getWifiName(Context context) throws IOException {
WifiManager manager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
final DhcpInfo dhcp = manager.getDhcpInfo();
InetAddress localhost = null;
//byte[] localHostIp = InetAddress.getLocalHost().getAddress();
//String string = new String(localHostIp);
//InetAddress in= null;
//in = InetAddress.getByName(Formatter.formatIpAddress(dhcp.gateway));
if (manager.isWifiEnabled()) {
WifiInfo wifiInfo = manager.getConnectionInfo();
if (wifiInfo != null) {
DetailedState state = WifiInfo.getDetailedStateOf(wifiInfo.getSupplicantState());
if (state == DetailedState.CONNECTED || state == DetailedState.OBTAINING_IPADDR) {
System.out.println(Formatter.formatIpAddress(dhcp.gateway));
System.out.println(Formatter.formatIpAddress(dhcp.netmask));
return wifiInfo.getSSID()+"/"+Formatter.formatIpAddress(dhcp.gateway)+"/"+Formatter.formatIpAddress(dhcp.netmask);
}
}
}
else {
manager.setWifiEnabled(true);
}
return null;
}
public void initializediscoveryListener() {
// Instantiate a new discoveryListener
discoveryListener = new NsdManager.discoveryListener() {
// Called as soon as service discovery begins.
@Override
public void ondiscoveryStarted(String regType) {
Log.d(TAG,"Service discovery started");
}
@Override
public void onServiceFound(NsdServiceInfo service) {
// A service was found! Do something with it.
Log.d(TAG,"Service discovery success" + service);
if (!service.getServiceType().equals(SERVICE_TYPE)) {
// Service type is the string containing the protocol and
// transport layer for this service.
Log.d(TAG,"UnkNown Service Type: " + service.getServiceType());
} else if (service.getServiceName().equals(serviceName)) {
// The name of the service tells the user what they'd be
// connecting to. It Could be "Bob's Chat App".
Log.d(TAG,"Same machine: " + serviceName);
} else if (service.getServiceName().contains("NsdChat")){
nsdManager.resolveService(service,resolveListener);
}
}
@Override
public void onServiceLost(NsdServiceInfo service) {
// When the network service is no longer available.
// Internal bookkeeping code goes here.
Log.e(TAG,"service lost: " + service);
}
@Override
public void ondiscoveryStopped(String serviceType) {
Log.i(TAG,"discovery stopped: " + serviceType);
}
@Override
public void onStartdiscoveryFailed(String serviceType,int errorCode) {
Log.e(TAG,"discovery Failed: Error code:" + errorCode);
nsdManager.stopServicediscovery(this);
}
@Override
public void onStopdiscoveryFailed(String serviceType,"discovery Failed: Error code:" + errorCode);
nsdManager.stopServicediscovery(this);
}
};
}
public void discoverServices(){
nsdManager = Context.getSystemService(Context.NSD_SERVICE);
nsdManager.discoverServices("_http._tcp.",NsdManager.PROTOCOL_DNS_SD,discoveryListener);
}
}
但我收到以下错误：
D:\ProgQt\build-app-Android_for_armeabi_v7a_arm64_v8a_x86_x86_64_Clang_Qt_5_15_0_for_android-debug\android-build\src\org\qtproject\example\musiclist\MusicList.java:127：错误：找不到符号 discoveryListener = new NsdManager.discoveryListener() { ^
^
你能帮忙吗？
解决方法
你忘记输入变量的类型了。如果应该是
您在使用 nsdManager 时也会遇到同样的问题。在您的最后一个函数中，因为您使用了 discoveryListener 而不定义它。当您从某处复制粘贴此代码时，您是否忘记复制粘贴类的实例变量？
,总是在同一条路上，我遇到了这个问题
:\ProgQt\build-app-Android_for_armeabi_v7a_arm64_v8a_x86_x86_64_Clang_Qt_5_15_0_for_Android-Debug\android-build\src\org\qtproject\example\musiclist\MusicList.java:188: error: not a static discovery context variable nsdManager.discoverServices("_http._tcp.",NsdManager.PROTOCOL_DNS_SD,discoveryListener);
public void initializeDiscoveryListener() {
// Instantiate a new DiscoveryListener
discoveryListener = new NsdManager.DiscoveryListener() {
// Called as soon as service discovery begins.
@Override
public void onDiscoveryStarted(String regType) {
Log.d(TAG,"Service discovery started");
}
@Override
public void onServiceFound(NsdServiceInfo service) {
// A service was found! Do something with it.
Log.d(TAG,"Service discovery success" + service);
if (!service.getServiceType().equals(SERVICE_TYPE)) {
// Service type is the string containing the protocol and
// transport layer for this service.
Log.d(TAG,"Unknown Service Type: " + service.getServiceType());
} else if (service.getServiceName().equals(serviceName)) {
// The name of the service tells the user what they'd be
// connecting to. It could be "Bob's Chat App".
Log.d(TAG,"Same machine: " + serviceName);
} else if (service.getServiceName().contains("NsdChat")){
// nsdManager.resolveService(service,resolveListener);
}
}
@Override
public void onServiceLost(NsdServiceInfo service) {
// When the network service is no longer available.
// Internal bookkeeping code goes here.
Log.e(TAG,"service lost: " + service);
}
@Override
public void onDiscoveryStopped(String serviceType) {
Log.i(TAG,"Discovery stopped: " + serviceType);
}
@Override
public void onStartDiscoveryFailed(String serviceType,int errorCode) {
Log.e(TAG,"Discovery failed: Error code:" + errorCode);
nsdManager.stopServiceDiscovery(this);
}
@Override
public void onStopDiscoveryFailed(String serviceType,"Discovery failed: Error code:" + errorCode);
nsdManager.stopServiceDiscovery(this);
}
};
}
public static void discover(){
System.out.println("discoverServices");
nsdManager.discoverServices("_http._tcp.",discoveryListener);
}
//nsdManager = (NsdManager)c.getSystemService(Context.NSD_SERVICE);
}