I am developing an android app with node.js running on the backend. In the android app, I have multiple activities. I am opening a socket connection using Socket.io from the first activity. But the problem is that I don't know how to use that connection over multiple activities. I don't know how to implement this using Service. It would be great if you could answer with some code reference.
Thanks in Advance
socket.io has a chat app example implemented in android link below:
https://github.com/nkzawa/socket.io-android-chat
any way, for using socket.io in android, i think best way is using it inside a service something like this:
public class ChatService extends Service {
public void connectSocket() {
try {
IO.Options options = new IO.Options();
socket = IO.socket("http://192.168.1.1:8080", options);
socket.on(Socket.EVENT_CONNECT, new Emitter.Listener() {
#Override
public void call(Object... args) {
}
}).on(Socket.EVENT_DISCONNECT, new Emitter.Listener() {
#Override
public void call(Object... args) {
}
}).on("error", new Emitter.Listener() {
#Override
public void call(Object... args) {
}
});
socket.connect();
} catch (Exception ignored) {
}
}
#Override
public void onDestroy() {
socket.disconnect();
super.onDestroy();
}
}
Related
I have to make a chat for a Xamarin Forms (PCL) application. I'm using the NuGet package SocketIoClientDotNet for socket.
At first I could not connect at all. After many researches on internet I found this open issue on Github, so I downgraded the library but also all the dependencies:
EngineIOClient.Net V0.9.22
SocketIOClientDotNet V0.9.13
WebSocket4Net V0.14.1.0
It was better, the connection seemed to work but I encountered a new issue: the connection is very instable and it's difficult for me to test anything cause of that. One time it can connect multiple times, one time it not connect at all, it's very annoying...
My code is very simple:
Common Code:
ISocketIO interface:
public interface ISocketIO
{
void Connect(string url);
void On(string eventString, Action<object> action);
}
MsgService class:
readonly string EVENT_CONNECT = "connect";
public MsgService(ISocketIO socket)
{
Socket = socket;
if (Socket != null)
{
Socket.On(EVENT_CONNECT, () =>
{
(code here...)
});
}
}
public void Connect()
{
if (Socket != null)
{
Socket.Connect("chat_url_here");
}
}
App class:
public partial class App : Application
{
public static MsgService MsgService;
public App(ISocketIO socket)
{
InitializeComponent();
Language = Language.FRENCH;
MsgService = new MsgService(socket);
MsgService.Connect();
MainPage = new NavigationPage(new MainPage());
}
...
}
iOS code (same for Android):
Class SocketIO
[assembly: Xamarin.Forms.Dependency(typeof(SocketIO))]
namespace MeetYou.iOS
{
public class SocketIO : ISocketIO
{
Socket _socket;
public void Connect(string url)
{
IO.Options opt = new IO.Options
{
Path = "path_here"
};
_socket = IO.Socket(url, opt);
_socket.Connect();
}
}
}
AppDelegate:
[Register("AppDelegate")]
public class AppDelegate : Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
public override bool FinishedLaunching(UIApplication uiApplication, NSDictionary launchOptions)
{
Xamarin.Forms.Forms.Init();
LoadApplication(new App(new SocketIO()));
return base.FinishedLaunching(uiApplication, launchOptions);
}
}
Maybe I'm doing something wrong of maybe it exists an other plugin I could use instead this one.
Have you tried running this without this line?
_socket.Connect();
I managed to make my example work in my application only using the
_socket = IO.Socket("wss://" + HostUrl + "/");
I get the fact that it might take more than 10 lines of code (hopefully not more than 50), but I was wondering if you could help me anyway.
I'm trying to update one user's UI thread at runtime, based on another user's input. I've created a basic project which implements three predefined users (jim, tom and threeskin). I'd like to send a message from jim to tom and have it appear as a new Label object in tom's UI, without threeskin ever knowing about it, even though they're all logged in. Oh, and jim shouldn't have to refresh his page. The label should just spawn on screen out of it's own accord.
To say that I'd appreciate some help would be the understatement of the decade.
public class User {
public String nume;
public User(String nume) {
super();
this.nume = nume;
}
}
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
public class Engine implements ServletContextListener {
public static ArrayList<User>userbase;
public void contextDestroyed(ServletContextEvent arg0) { }
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("This code is running at startup");
userbase =new ArrayList<User>();
userbase.add(new User("jim"));userbase.add(new User("tom"));userbase.add(new User("threeskin"));
}
}
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
public class InfigeUI extends UI {
User us3r;
#WebServlet(value = "/*", asyncSupported = true)
#VaadinServletConfiguration(productionMode = false, ui = InfigeUI.class)
public static class Servlet extends VaadinServlet {}
protected void init(VaadinRequest request) {
VerticalLayout everything=new VerticalLayout();
setContent(everything);
if (us3r==null){everything.addComponent(auth());}else{everything.addComponent(main());}
}
ComponentContainer auth(){
final VerticalLayout layout = new VerticalLayout();
layout.setMargin(true);
TextField userField=new TextField();
Button login = new Button("Log in");
login.addClickListener(new Button.ClickListener() {
public void buttonClick(ClickEvent event) {
us3r=login(userField.getValue());
if (us3r!=null){
saveValue(InfigeUI.this, us3r);
layout.removeAllComponents();
layout.addComponent(main());
}else{Notification.show("I only know jim, tom and threeskin. Which one are you?");}}
});
layout.addComponent(userField);
layout.addComponent(login);
return layout;
}
User login(String nume){
for (int i=0;i<Engine.userbase.size();i++){
if (nume.equals(Engine.userbase.get(i).nume)){return Engine.userbase.get(i);}
}
return null;
}
static void saveValue(InfigeUI ui,User value){
ui.us3r=value;
ui.getSession().setAttribute("something", value);
VaadinService.getCurrentRequest().getWrappedSession().setAttribute("something", value);
}
ComponentContainer main(){
VerticalLayout vl=new VerticalLayout();
Label label=new Label("This is the post-login screen");
String name=new String(us3r.nume);
Label eticheta=new Label(name);
TextField to=new TextField("Send to");
TextField message=new TextField("Message");
Button sendNow=new Button("Send now!");
vl.addComponent(eticheta);
vl.addComponent(label);
vl.addComponent(eticheta);
vl.addComponent(to);
vl.addComponent(message);
vl.addComponent(sendNow);
return vl ;
}
}
Basically you want three things
UI updates for a user which does no action himself, or in other words a message sent from the server to the browser. To enable this, you need to annotate the UI class using #Push. Otherwise, the update will only be shown when the user does something which causes a server visit, e.g. clicks a button
Some way of sending messages between UI instances (there is one UI instance per user). You can use some message bus implementation for this (CDI, Spring, ...) or you can make a simple on using a static field (static fields are shared between all users). See e.g. https://github.com/Artur-/SimpleChat for one way of doing it. It's also a good idea here to avoid all *.getCurrent methods as they in many cases will refer to another UI than you think (e.g. sender when you are in the receiver code), and you will do something else than you intend.
Safely update a UI when a message arrives. This is done using UI.access, also visible in the chat example.
First of all you need to enable the server push on your project help
based on Vaadin Documentation.
However, below code example will give what you want:
Create an Broadcast Listener Interface:
public interface BroadcastListener {
public void receiveBroadcast(final String message);
}
The Broadcaster Class:
public class Broadcaster {
private static final List<BroadcastListener> listeners = new CopyOnWriteArrayList<BroadcastListener>();
public static void register(BroadcastListener listener) {
listeners.add(listener);
}
public static void unregister(BroadcastListener listener) {
listeners.remove(listener);
}
public static void broadcast(final String message) {
for (BroadcastListener listener : listeners) {
listener.receiveBroadcast(message);
}
}
}
Your UI with Push Enalbed (via Annotation):
#Push
public class BroadcasterUI extends UI implements BroadcastListener {
#Override
protected void init(VaadinRequest request) {
final VerticalLayout layout = new VerticalLayout();
layout.setMargin(true);
setContent(layout);
final TextArea message = new TextArea("",
"The system is going down for maintenance in 10 minutes");
layout.addComponent(message);
final Button button = new Button("Broadcast");
layout.addComponent(button);
button.addClickListener(new Button.ClickListener() {
#Override
public void buttonClick(ClickEvent event) {
Broadcaster.broadcast(message.getValue());
}
});
// Register broadcast listener
Broadcaster.register(this);
}
#Override
public void detach() {
Broadcaster.unregister(this);
super.detach();
}
#Override
public void receiveBroadcast(final String message) {
access(new Runnable() {
#Override
public void run() {
Notification n = new Notification("Message received",
message, Type.TRAY_NOTIFICATION);
n.show(getPage());
}
});
}
you can find the full link here.
I have the following problem:
I am trying to model a process using GWT, where i have a couple of views with a couple of submit buttons. And pressing button1 will create a server interaction and if everything was ok, the next view will be loaded. My problem is now that I get really nasty spaghetti code (just very highlevel to show you what i mean):
onClick {
AsyncCallback {
onSuccess {
load new view with another clickhandler and an asynccallback
}
}
}
Is there some way to create some kind of abstraction or something? Maybe a state pattern? How? Thanks a lot!
This is actually a very good question - and probably one without a definitive answer. It's a problem that applies to many frameworks, not just GWT, so I like your idea to look at this with some simplified code. I'll make this a little bit longer, to show what even just 4 very simple callbacks look like:
Nested callbacks
alice.call("a", new Callback() {
#Override
public void onSuccess() {
bob.call("b", new Callback() {
#Override
public void onSuccess() {
charlie.call("c", new Callback() {
#Override
public void onSuccess() {
daisy.call("d", new Callback() {
#Override
public void onSuccess() {
// finished
}
});
}
});
}
});
}
});
Named callbacks
You can use your IDE to refactor this easily into named callbacks (hint: Please read the callbacks from bottom to top!):
final Callback daisyCallback = new Callback() {
#Override
public void onSuccess() {
// finished
}
};
final Callback charlieCallback = new Callback() {
#Override
public void onSuccess() {
daisy.call("d", daisyCallback);
}
};
final Callback bobCallback = new Callback() {
#Override
public void onSuccess() {
charlie.call("c", charlieCallback);
}
};
final Callback aliceCallback = new Callback() {
#Override
public void onSuccess() {
bob.call("b", bobCallback);
}
};
alice.call("a", aliceCallback);
Problem: The control flow is not so immediately obvious anymore.
Still, an IDE can help by using "Search References" (Ctrl-G in Eclipse) or something similar.
Event Bus (or Observer/Publish-Subscribe pattern)
This is how the same calls look like with an event bus:
alice.call("a", new Callback() {
#Override
public void onSuccess() {
bus.fireEvent(BusEvent.ALICE_SUCCESSFUL_EVENT);
}
});
bus.addEventListener(BusEvent.ALICE_SUCCESSFUL_EVENT, new BusEventListener() {
#Override
public void onEvent(final BusEvent busEvent) {
bob.call("b", new Callback() {
#Override
public void onSuccess() {
bus.fireEvent(BusEvent.BOB_SUCCESSFUL_EVENT);
}
});
}
});
bus.addEventListener(BusEvent.BOB_SUCCESSFUL_EVENT, new BusEventListener() {
#Override
public void onEvent(final BusEvent busEvent) {
charlie.call("c", new Callback() {
#Override
public void onSuccess() {
bus.fireEvent(BusEvent.CHARLIE_SUCCESSFUL_EVENT);
}
});
}
});
bus.addEventListener(BusEvent.CHARLIE_SUCCESSFUL_EVENT, new BusEventListener() {
#Override
public void onEvent(final BusEvent busEvent) {
daisy.call("d", new Callback() {
#Override
public void onSuccess() {
bus.fireEvent(BusEvent.DAISY_SUCCESSFUL_EVENT);
}
});
}
});
bus.addEventListener(BusEvent.DAISY_SUCCESSFUL_EVENT, new BusEventListener() {
#Override
public void onEvent(final BusEvent busEvent) {
// finished
}
});
Under the right circumstances (when it's very clear what each event means, and
if you don't have too many), this pattern can make things very nice and clear.
But in other cases, it can make the control flow more confusing (and you easily get twice the lines of code).
It's harder to use your IDE to find out about the control flow.
The GWT History mechanism is a very positive example for where to use this technique reasonably.
Divide and Conquer
In my experience, it's often a good idea to "divide and conquer" by mixing nesting and named callbacks:
final Callback charlieCallback = new Callback() {
#Override
public void onSuccess() {
daisy.call("d", new Callback() {
#Override
public void onSuccess() {
// finished
}
});
}
};
alice.call("a", new Callback() {
#Override
public void onSuccess() {
bob.call("b", new Callback() {
#Override
public void onSuccess() {
charlie.call("c", charlieCallback);
}
});
}
});
Depending on the situation, two nested callbacks are often still readable, and they reduce jumping around between methods when reading the code by 50%.
(I created a pastebin of my examples here, if you like to play around with them: http://pastebin.com/yNc9Cqtb)
Spaghetti code is a tricky problem in GWT as it is in Javascript, where much of your code is structured around asynchronous callbacks.
Some of the techniques to deal with it that are described in the answers to this question could apply.
The suggested approach to avoid coupling between widgets is to use EventBus. Read more details here https://developers.google.com/web-toolkit/articles/mvp-architecture#events
Hope it helps.
changeview(boolean first){
if(first)
{
firstView.setVisible(true);
secondView.setVisible(false);
}else{
firstView.setVisible(false);
secondView.setVisible(true);
}
}
onClick {
AsyncCallback {
onSuccess {
changeView(false);
}
}
}
Switch between views by above.
Use MVP from very beginning. Use Activities and Places. Your code will be clean.
I am using gwt 2.3 with gwtp framework.In this application I wan to maintain a session time of 5 mins.This means if current user is not doing up to 5 min and he comes after five min then on his first event/action on screen a he should be be logged out.
In gwt there is class named Timer which can be used in this issues.But I am not getting how to recognize action of user on the screen.I did google on it, & found the code for gwt-ext.Below is the code of gwt-ext
Ext.get(“pagePanel”).addListener(“click”, new EventCallback() {
#Override
public void execute(EventObject e) {
MessageBox.alert(“On Mouse Click”);
}
});
Ext.get(“pagePanel”).addListener(“keydown”, new EventCallback() {
#Override
public void execute(EventObject e) {
MessageBox.alert(“On Key Press Click”);
}
});
In above code tag in working properly so I am attaching link from where I got this code.here
Same type of code I am looking in gwt.If there any other better way to do this then please let me know. Thanks in advance
If action/event can be really everythin, I would solve it with a
NativePreviewHandler in the following way:
boolean expired;
final Timer logoutTimer = new Timer() {
#Override
public void run() {
expired = true;
}
};
NativePreviewHandler nph = new NativePreviewHandler() {
#Override
public void onPreviewNativeEvent(NativePreviewEvent event) {
if (!expired) {
logoutTimer.cancel();
logoutTimer.schedule(300000);
} else {
// do your logout stuff here
}
}
};
Event.addNativePreviewHandler(nph);
If the user shell be logged out without a new action after 5 minutes:
final Timer logoutTimer = new Timer() {
#Override
public void run() {
// do your logout stuff here
}
};
NativePreviewHandler nph = new NativePreviewHandler() {
#Override
public void onPreviewNativeEvent(NativePreviewEvent event) {
// Of course do this only when logged in:
logoutTimer.cancel();
logoutTimer.schedule(300000);
}
};
Event.addNativePreviewHandler(nph);
I want to build a simple idea plugin, which will detect the changes of a kind of file, then convert them to another format.
Current, I use such code to do this:
VirtualFileManager.getInstance().addVirtualFileListener(new VirtualFileAdapter() {
#Override
public void contentsChanged(VirtualFileEvent event) {
// do something
}
});
It works, but not efficient.
I found this article says:
The most efficient way to listen to VFS events is to implement the BulkFileListener interface and to subscribe with it to the VirtualFileManager.VFS_CHANGES topic.
But I can't find any example to implement it. How to do that?
I guess you'll have found the answer by now, but for others it seems to work like this
public class A implements ApplicationComponent, BulkFileListener {
private final MessageBusConnection connection;
public A() {
connection = ApplicationManager.getApplication().getMessageBus().connect();
}
public void initComponent() {
connection.subscribe(VirtualFileManager.VFS_CHANGES, this);
}
public void disposeComponent() {
connection.disconnect();
}
public void before(List<? extends VFileEvent> events) {
// ...
}
public void after(List<? extends VFileEvent> events) {
// ...
}
...
}