问题
I am making my first Socket.io based android application. The socket sends and receives data from a web service. There are a number of screens in the application for different features. How do i use the same socket connection in these different activities.
I have tried setting and storing the Socket Object in the Application class and it appears to work well but when the application goes into the background and left there for some time the application is killed and the socket object is then NULL causing the aoo to crash with a null pointer exception.
public class MyApplication extends Application {
private Socket mSocket;
private final String TAG = "Application Class";
public Socket getSocket() {
return mSocket;
}
public Socket createSocket() {
try {
Manager manager = new Manager(new URI("http://0.0.0.0"));
} catch (URISyntaxException URIse) {
URIse.printStackTrace();
}
return mSocket;
}
}
Access the socket in the activities
MyApplication app;
app = (MyApplication ) getApplication();
app.getSocket;
回答1:
You can create a singleton manager class for socket. It will allow you to keep single socket connection accessible to entire app. See following code and change it according to your requirement
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Handler;
import android.os.Looper;
import android.os.PowerManager;
import android.util.Log;
import com.myapp.app.ui.adapter.OnSocketConnectionListener;
import java.util.ArrayList;
import java.util.List;
import io.socket.client.IO;
import io.socket.client.Socket;
import io.socket.emitter.Emitter;
/**
* Created by penguin on 6/30/2016.
* <p/>
* SocketManager manages socket and internet connection.
* It also provide listeners for connection status
*/
public class SocketManager {
/**
* The constant STATE_CONNECTING.
*/
public static final int STATE_CONNECTING = 1;
/**
* The constant STATE_CONNECTED.
*/
public static final int STATE_CONNECTED = 2;
/**
* The constant STATE_DISCONNECTED.
*/
public static final int STATE_DISCONNECTED = 3;
/**
* The constant CONNECTING.
*/
public static final String CONNECTING = "Connecting";
/**
* The constant CONNECTED.
*/
public static final String CONNECTED = "Connected";
/**
* The constant DISCONNECTED.
*/
public static final String DISCONNECTED = "Disconnected";
private static SocketManager instance;
private SocketManager() {
}
/**
* Gets instance.
*
* @return the instance
*/
public synchronized static SocketManager getInstance() {
if (instance == null) {
instance = new SocketManager();
}
return instance;
}
/**
* The constant TAG.
*/
public static final String TAG = SocketManager.class.getSimpleName();
private Socket socket;
private List<OnSocketConnectionListener> onSocketConnectionListenerList;
/**
* Connect socket.
*
* @param token the token
* @param userId the user id
* @param host the host
* @param port the port
*/
public void connectSocket(String token,String userId, String host, String port) {
try {
if(socket==null){
String serverAddress = host+":"+port;
IO.Options opts = new IO.Options();
opts.forceNew = true;
opts.reconnection = true;
opts.reconnectionAttempts=5;
opts.secure = true;
opts.query = "token=" + token + "&" + "user_id=" + userId;
socket = IO.socket(serverAddress, opts);
socket.on(Socket.EVENT_CONNECT, new Emitter.Listener() {
@Override
public void call(Object... args) {
fireSocketStatus(SocketManager.STATE_CONNECTED);
Log.i(TAG, "socket connected");
}
}).on(Socket.EVENT_RECONNECTING, new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.e(TAG, "Socket reconnecting");
fireSocketStatus(SocketManager.STATE_CONNECTING);
}
}).on(Socket.EVENT_RECONNECT_FAILED, new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.e(TAG, "Socket reconnection failed");
// fireSocketStatusIntent(SocketManager.STATE_DISCONNECTED);
}
}).on(Socket.EVENT_RECONNECT_ERROR, new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.e(TAG, "Socket reconnection error");
// fireSocketStatus(SocketManager.STATE_DISCONNECTED);
}
}).on(Socket.EVENT_CONNECT_ERROR, new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.e(TAG, "Socket connect error");
fireSocketStatus(SocketManager.STATE_DISCONNECTED);
socket.disconnect();
}
}).on(Socket.EVENT_DISCONNECT, new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.e(TAG, "Socket disconnect event");
fireSocketStatus(SocketManager.STATE_DISCONNECTED);
}
}).on(Socket.EVENT_ERROR, new Emitter.Listener() {
@Override
public void call(Object... args) {
try {
final String error = (String) args[0];
Log.e(TAG + " error EVENT_ERROR ", error);
if (error.contains("Unauthorized") && !socket.connected()) {
if (onSocketConnectionListenerList != null) {
for (final OnSocketConnectionListener listener : onSocketConnectionListenerList) {
new Handler(Looper.getMainLooper())
.post(new Runnable() {
@Override
public void run() {
listener.onSocketEventFailed();
}
});
}
}
}
} catch (Exception e) {
Log.e(TAG, e.getMessage() != null ? e.getMessage() : "");
}
}
}).on("Error", new Emitter.Listener() {
@Override
public void call(Object... args) {
Log.d(TAG, " Error");
}
});
socket.connect();
}else if(!socket.connected()){
socket.connect();
}
} catch (Exception e) {
e.printStackTrace();
}
}
private int lastState = -1;
/**
* Fire socket status intent.
*
* @param socketState the socket state
*/
public synchronized void fireSocketStatus(final int socketState) {
if(onSocketConnectionListenerList !=null && lastState!=socketState){
lastState = socketState;
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
for(OnSocketConnectionListener listener: onSocketConnectionListenerList){
listener.onSocketConnectionStateChange(socketState);
}
}
});
new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
@Override
public void run() {
lastState=-1;
}
},1000);
}
}
/**
* Fire internet status intent.
*
* @param socketState the socket state
*/
public synchronized void fireInternetStatusIntent(final int socketState) {
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
if(onSocketConnectionListenerList !=null){
for(OnSocketConnectionListener listener: onSocketConnectionListenerList){
listener.onInternetConnectionStateChange(socketState);
}
}
}
});
}
/**
* Gets socket.
*
* @return the socket
*/
public Socket getSocket() {
return socket;
}
/**
* Sets socket.
*
* @param socket the socket
*/
public void setSocket(Socket socket) {
this.socket = socket;
}
/**
* Destroy.
*/
public void destroy(){
if (socket != null) {
socket.off();
socket.disconnect();
socket.close();
socket=null;
}
}
/**
* Sets socket connection listener.
*
* @param onSocketConnectionListenerListener the on socket connection listener listener
*/
public void setSocketConnectionListener(OnSocketConnectionListener onSocketConnectionListenerListener) {
if(onSocketConnectionListenerList ==null){
onSocketConnectionListenerList = new ArrayList<>();
onSocketConnectionListenerList.add(onSocketConnectionListenerListener);
}else if(!onSocketConnectionListenerList.contains(onSocketConnectionListenerListener)){
onSocketConnectionListenerList.add(onSocketConnectionListenerListener);
}
}
/**
* Remove socket connection listener.
*
* @param onSocketConnectionListenerListener the on socket connection listener listener
*/
public void removeSocketConnectionListener(OnSocketConnectionListener onSocketConnectionListenerListener) {
if(onSocketConnectionListenerList !=null
&& onSocketConnectionListenerList.contains(onSocketConnectionListenerListener)){
onSocketConnectionListenerList.remove(onSocketConnectionListenerListener);
}
}
/**
* Remove all socket connection listener.
*/
public void removeAllSocketConnectionListener() {
if(onSocketConnectionListenerList !=null){
onSocketConnectionListenerList.clear();
}
}
/**
* The type Net receiver.
*/
public static class NetReceiver extends BroadcastReceiver {
/**
* The Tag.
*/
public final String TAG = NetReceiver.class.getSimpleName();
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager cm =
(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null &&
activeNetwork.isConnectedOrConnecting();
SocketManager.getInstance().fireInternetStatusIntent(
isConnected?SocketManager.STATE_CONNECTED:SocketManager.STATE_DISCONNECTED);
if (isConnected) {
if(SocketManager.getInstance().getSocket()!=null
&& !SocketManager.getInstance().getSocket().connected()){
SocketManager.getInstance().fireSocketStatus(SocketManager.STATE_CONNECTING);
}
PowerManager powerManager =
(PowerManager) context.getSystemService(Context.POWER_SERVICE);
boolean isScreenOn;
if (android.os.Build.VERSION.SDK_INT
>= android.os.Build.VERSION_CODES.KITKAT_WATCH) {
isScreenOn = powerManager.isInteractive();
}else{
//noinspection deprecation
isScreenOn = powerManager.isScreenOn();
}
if (isScreenOn && SocketManager.getInstance().getSocket() !=null) {
Log.d(TAG, "NetReceiver: Connecting Socket");
if(!SocketManager.getInstance().getSocket().connected()){
SocketManager.getInstance().getSocket().connect();
}
}
}else{
SocketManager.getInstance().fireSocketStatus(SocketManager.STATE_DISCONNECTED);
if(SocketManager.getInstance().getSocket() !=null){
Log.d(TAG, "NetReceiver: disconnecting socket");
SocketManager.getInstance().getSocket().disconnect();
}
}
}
}
}
Connecting socket
You can connecting/disconnect socket from any activity or background service
SocketManager.getInstance().connectSocket(user.getToken(), user.getUserId(),
getResources().getString(R.string.host), "8000");
Update
If in background your app is killed socket will also destroy. If you want socket to remain connected in background you have to make you own logic with background service which has nothing to do with socket.
implement OnSocketConnectionListener
public interface OnSocketConnectionListener {
void onSocketEventFailed();
void onSocketConnectionStateChange(int socketState);
void onInternetConnectionStateChange(int socketState);
}
来源：https://stackoverflow.com/questions/38095293/android-storing-socket-io-object-for-multiple-activities