android – 如何通知wifi网络状态变化？

我正在编写一个通过wifi连接到telnet服务器的应用程序.我有一个管理套接字连接的服务.一切正常,但是当手机休眠时,它会断开wifi无线电,导致套接字连接中断(并抛出SocketException).

我觉得我应该能够设置一个广播接收器,当wifi网络连接丢失时调用onResume()方法,这将允许我优雅地关闭套接字,并在网络立即重新打开它重新连接.但我在文档或搜索中找不到类似的东西.

服务代码在这里,如果你需要它,感谢您的帮助,我真的很感激！

package com.wingedvictorydesign.LightfactoryRemote;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteCallbackList;
import android.os.RemoteException;
import android.text.Editable;
import android.util.Log;
import android.widget.Toast;
import android.os.Debug;

/**
 * @author Max
 */
public class TelnetService extends Service {

    private final int DISCONNECTED = 0;
    private final int CONNECTED = 1;
    // place notifications in the notification bar
    NotificationManager mNM;
    protected InputStream in;
    protected OutputStream out;
    protected Socket socket;
    // the socket timeout,to prevent blocking if the server connection is lost.
    protected final int SO_TIMEOUT = 250;
    // holds the incoming stream from socket until it is ready to be read.
    BufferedReader inputBuffer;
    final RemoteCallbackList<TelnetServiceCallback> mCallbacks =
            new RemoteCallbackList<TelnetServiceCallback>();

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("LightfactoryRemote","TelnetService onCreate()");
        mNM = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
    }// end onCreate()

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("LightfactoryRemote","TelnetService onDestroy()");
        // Cancel the persistent notification,if it hasn't been already.
        mNM.cancel(R.string.telnet_service_connected);
    }// end onDestroy()

    @Override
    public IBinder onBind(Intent intent) {
        Log.d("LightfactoryRemote","TelnetService onBind()");
        return mBinder;
    }

    @Override
    public boolean onUnbind(Intent intent) {
        super.onUnbind(intent);
        Log.d("LightfactoryRemote","TelnetService onUnBind()");
        return true;
    }

    @Override
    public void onStart(Intent intent,int startId) {
        super.onStart(intent,startId);
        Log.d("TelnetService","TelnetService onStart()");
    }

    private final TelnetServiceInterface.Stub mBinder =
            new TelnetServiceInterface.Stub() {

        public void registerCallback(TelnetServiceCallback cb) {
            if (cb != null) mCallbacks.register(cb);
        }

        public void unregisterCallback(TelnetServiceCallback cb) {
            if (cb != null) mCallbacks.unregister(cb);
        }

        public String connectToTelnet(String Host,int Port)
                throws RemoteException {
            // android.os.Debug.waitForDebugger();
            String hostInfo = null;
            try {
                socket = new java.net.Socket();
                socket.setSoTimeout(SO_TIMEOUT);
                socket.connect(new InetSocketAddress(Host,Port),10000); //setup
                // the port with a timeout of 10sec.
                out = socket.getOutputStream();
                /*
                 * in is wrapped in a reader,then in a Buffered reader. This is
                 * supposedly better for performance,and allows us to read a
                 * line at a time using the readLine() method.
                 */
                inputBuffer = new BufferedReader(new InputStreamReader(
                    socket.getInputStream()));
            } catch (java.io.IOException e) {
                Log.d("TelnetService.java","Connection failed! " + e);
                /*
                 * if the connection fails,return null for serverResponse,* which will be handled appropriately on the client side.
                 */
                return hostInfo;
            }
            // now that the command has been sent,read the response.
            hostInfo = readBuffer();
            Log.d("TelnetService.java",hostInfo);
            // notify the user that we are connected
            showNotification(CONNECTED,Host,Port);
            return hostInfo;
        }// end connectToTelnet

        /**
         * Tests for a currently active connection. Three cases must be
         * distinguished. 1. A connection attempt has not been made. Return
         * false. 2. A connection attempt has been made,and socket is
         * initialized,but no connection is active. isConnected() returns
         * false. 3. A connection is active. isConnected() returns true.
         */
        public boolean areYouThere() {
            if (socket != null) {
                boolean connectStatus = socket.isConnected();
                return connectStatus;
            } else {
                return false;
            }
        }// end areYouThere

        public void disconnect() {
            try {
                if (inputBuffer != null) {
                    inputBuffer.close();
                }
                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {}
            // Cancel the persistent notification.
            mNM.cancel(R.string.telnet_service_connected);
        }// end disconnect()

        /**
         * send the string to the telnet server,and return the response from
         * server If the connection is lost,an IOException results,so return
         * null to be handled appropriately on the client-side.
         * 
         * @throws RemoteException
         */
        public String sendToTelnet(String toTelnet) throws RemoteException {
            if (out == null) {
                /*
                 * if out is still null,no connection has been made. Throw
                 * RemoteException to be handled on the client side.
                 */
                throw new RemoteException();
            } else {
                byte arr[];
                arr = (toTelnet + "\r" + "\n").getBytes();
                try {
                    out.write(arr);
                    // now that the command has been sent,read the response.
                    String serverResponse = readBuffer();
                    return serverResponse;
                } catch (IOException e) {
                    /*
                     * if a connection was made,but then lost,we end up here.
                     * throw a Remoteexception for handling by the client.
                     */
                    Log.d("TelnetService","IO exception" + e);
                    disconnect();
                    throw new RemoteException();
                }
            }// end else
        }// end sendToTelnet
    };// end ConnectService.Stub class

    public String readBuffer() {
        StringBuilder serverResponse = new StringBuilder();
        int character;
        try {
            // keep reading new lines into line until there are none left.
            while (inputBuffer.ready()) {
                /*
                 * as each character is read,append it to serverResponse,* throwing away the carriage returns (which read as glyphs),* and the ">" prompt symbols.
                 */
                character = inputBuffer.read();
                if ((character != 13) && (character != 62)) {
                    serverResponse.append((char) character);
                }
            }
        }// end try
        catch (SocketTimeoutException e) {
            Log.d("TelnetService read()","SocketTimeoutException");
        } catch (IOException e) {
            Log.d("TelnetService read()","read() IO exception" + e);
        }
        return serverResponse.toString();
    }

    /**
     * Show a notification while this service is running.
     */
    private void showNotification(int event,String Host,int Port) {
        // In this sample,we'll use the same text for the ticker and the
        // expanded notification
        CharSequence notificationText = "Connected to " + Host + " : " + Port;
        // Set the icon,scrolling text and timestamp
        Notification notification = new Notification(
            R.drawable.notbar_connected,notificationText,System.currentTimeMillis());
        // set the notification not to clear when the user hits
        // "Clear All Notifications"
        notification.flags |= Notification.FLAG_NO_CLEAR;
        // The PendingIntent to launch our activity if the user selects this
        // notification
        PendingIntent contentIntent = PendingIntent.getActivity(this,new Intent(this,LightfactoryRemote.class),0);
        // Set the info for the views that show in the notification panel.
        notification.setLatestEventInfo(this,getText(R.string.telnet_service_connected),contentIntent);
        // Send the notification.
        // We use a string id because it is a unique number. We use it later to
        // cancel.
        mNM.notify(R.string.telnet_service_connected,notification);
    }// end showNotification()
} // end TelnetConnection

解决方法

为ConnectivityManager.CONNECTIVITY_ACTION注册BroadcastReceiver.在onReceive处理程序中,您可以调用NetworkInfo info =(NetworkInfo)intent.getParcelableExtra(ConnectivityManager.EXTRA_NETWORK_INFO),然后调用info.getType()并检查ConnectivityManager.TYPE_WIFI并执行您想要的操作.