我再次遇到了我的应用程序的问题。我使用NSDAPI 来发现和连接服务，并使用数组adapter来获取有关服务的数据，例如 IP 地址和服务名称，并将其打印在应用程序屏幕上。到目前为止，我在显示服务名称时没有任何问题，但我不能不显示服务的 IP 地址。但是，当我将它记录到日志时，我可以打印 IP 地址，如果我打开应用程序而不是 IP 地址，它会显示文本“null”。
有人对此有任何建议或经验吗？
这是 MainActivity.java
public class MainActivity extends AppCompatActivity {
private String SERVICE_TYPE = "_printer._tcp."; // change to normal
private InetAddress hostAddress;
private int hostPort;
private NsdManager mNsdManager;
ArrayList<NsdServiceInfo> services;
private NsdServiceInfoAdapter mAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Getting toolbar by id
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
services = new ArrayList<>();
mAdapter = new NsdServiceInfoAdapter(this, R.id.TextView_serviceName, services);
ListView listView = findViewById(R.id.ListViewServices);
listView.setAdapter(mAdapter); // we add custom adapter to the listview to display data from adapter.
//disabling default title text
getSupportActionBar().setDisplayShowTitleEnabled(false);
//NSD stuff
mNsdManager = (NsdManager) getSystemService(Context.NSD_SERVICE);
mNsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
Object serviceObj = adapterView.getItemAtPosition(i);
NsdServiceInfo selectedService = (NsdServiceInfo) serviceObj;
//mNsdManager.stopServiceDiscovery(mDiscoveryListener);
//mNsdManager.resolveService(selectedService, mResolveListener);
}
});
}
NsdManager.DiscoveryListener mDiscoveryListener = new NsdManager.DiscoveryListener() {
@Override
public void onStartDiscoveryFailed(String serviceType, int errorCode) {
Log.e("TAG", "DiscoveryFailed: Error code: " + errorCode);
mNsdManager.stopServiceDiscovery(this);
}
@Override
public void onStopDiscoveryFailed(String serviceType, int errorCode) {
Log.e("TAG", "Discovery failed : Error code: " + errorCode);
}
@Override
public void onDiscoveryStarted(String regType) {
Log.d("TAG", "Service discovery started");
}
@Override
public void onDiscoveryStopped(String serviceType) {
Log.i("TAG", "Discovery stopped: " + serviceType);
}
@Override
public void onServiceFound(final NsdServiceInfo serviceInfo) {
Log.d("TAG", "Service discovery success : " + serviceInfo);
Log.d("TAG", "Host = " + serviceInfo.getServiceName());
Log.d("TAG", "Port = " + serviceInfo.getPort());
services.add(serviceInfo);
NsdManager.ResolveListener mResolveListener2 = new NsdManager.ResolveListener() {
@Override
public void onResolveFailed(NsdServiceInfo nsdServiceInfo, int errorCode) {
Log.e("TAG", "Resolved failed " + errorCode);
Log.e("TAG", "Service = " + nsdServiceInfo);
}
@Override
public void onServiceResolved(NsdServiceInfo nsdServiceInfo) {
Log.d("TAG", "bbz" + nsdServiceInfo);
Log.d("TAG", "Resolve Succeeded " + nsdServiceInfo);
if (nsdServiceInfo.getServiceType().equals(SERVICE_TYPE)) {
Log.d("TAG", "Same IP");
return;
}
hostPort = nsdServiceInfo.getPort();
hostAddress = nsdServiceInfo.getHost();
Log.d("hello", String.valueOf(hostAddress));
runOnUiThread(new Runnable() {
@Override
public void run() {
mAdapter.notifyDataSetChanged();
}
});
}
};
mNsdManager.resolveService(serviceInfo, mResolveListener2);
}
@Override
public void onServiceLost(NsdServiceInfo nsdServiceInfo) {
Log.d("TAG", "Service lost " + nsdServiceInfo);
NsdServiceInfo serviceToRemove = new NsdServiceInfo();
for (NsdServiceInfo currentService : services) {
if (currentService.getHost() == nsdServiceInfo.getHost() && currentService.getPort() == currentService.getPort() && currentService.getServiceName() == currentService.getServiceName()) {
serviceToRemove = currentService;
}
}
if (serviceToRemove != null) {
services.remove(serviceToRemove);
runOnUiThread(new Runnable() {
@Override
public void run() {
mAdapter.notifyDataSetChanged();
}
});
}
Log.d("TAG", "Xd" + services);
}
};
这是我的ArrayAdapter课
//Creating new custom NsdServiceInfoAdapter which extends ArrayAdapter
public class NsdServiceInfoAdapter extends ArrayAdapter<NsdServiceInfo> {
private Context mContext;
private ArrayList<NsdServiceInfo> services;
//Creating new constructor with parameters such as this class(context), layout id (list item layout Id) and data model.
public NsdServiceInfoAdapter(@NonNull Context context, int layoutId, ArrayList<NsdServiceInfo> list) {
super(context, layoutId, list);
mContext = context;
services = list;
}
@NonNull
@Override
// Creating method get(), which is called when listItem needs to be populated with data.
//Get a View that displays the data at the specified position in the data set.
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
View listItem = convertView;
//Checking if view is empty then we inflate our list layout.
if (listItem == null)
listItem = LayoutInflater.from(mContext).inflate(R.layout.list_item, parent, false);
//Getting data's position in the data set.
NsdServiceInfo currentService = (NsdServiceInfo) services.get(position);
//We asign the the view to the item layout as a TextView
TextView t = listItem.findViewById(R.id.TextView_serviceName);
//We set text as a services name.
t.setText(String.valueOf(currentService.getHost()));
//t.setText(currentService.getServiceName());
Log.d("tag", "service name" + currentService.getServiceName());
return listItem;
}
}
这是日志
这是我的应用程序屏幕
