I want to check internet connection in Broadcast Receiver; And set result (A boolean flag) to a global variable, to use it on whole application, in if conditions; That if internet is disconnected, set a status imageview in main activity, to red image, and if connected, set it to green.
I followed this topic. But there is no getApplication() in Broadcast Receiver; And iI should use getApplicationContext() instead.
On another side, this topic:
when writing code in a broadcast receiver, which is not a context but
is given a context in its onReceive method, you can only call
getApplicationContext(). Which also means that you are not guaranteed
to have access to your application in a BroadcastReceiver.
What are the concerns?
How can I access to my application class in broadcast Receiver?
Is there better solution to check internet connection, set global variable and change my status imageview?
You can access your Application class in BroadCastReceiver by using its context,
#Override
public void onReceive(final Context context, Intent intent) {
MyApplication mApplication = ((MyApplication)context.getApplicationContext());
}
Maybe it will help somebody. If using own application class:
public class App extends Application {
private static App sInstance;
public static App get() {
return sInstance;
}
#Override
public void onCreate() {
sInstance = this;
super.onCreate();
}
}
Then you can use App.get() in your broadcast receiver.
According to onCreate() docs it will be called before receiver calls.
Called when the application is starting, before any activity, service, or receiver objects (excluding content providers) have been created.
Related
What seems to be just common practice could be the wrong thing to do in Service Fabric. I suspect the below code where stateManager is saved as local cache could cause a potential issue when the 'Startup' class is instantiated within the return statement of 'CreateServiceReplicaListeners()' method in 'SomeService' stateful service.
The situation that can happen is when the state manager is somehow re-instantiated. I need more explanation as to whether the below practice is the right thing to do or not. If not, what could be the best practice instead?
internal class SomeService : StatefulService
{
protected override IEnumerable<ServiceReplicaListener> CreateServiceReplicaListeners()
{
return new[]{
new ServiceReplicaListener(
initParams =>
new OwinCommunicationListener("SomeService", new Startup(this.StateManager), initParams))
};
}
}
}
public class Startup : IOwinAppBuilder
{
private readonly IReliableStateManager stateManager;
public Startup(IReliableStateManager stateManager)
{
this.stateManager = stateManager;
}
public void Configuration(IAppBuilder appBuilder)
{
// other initialization codes..
...
...
UnityConfig.RegisterComponents(config, this.stateManager);
appBuilder.UseWebApi(config);
}
}
Whenever a Stateful Service change roles it triggers a IStatefulServiceReplica.ChangeRoleAsync(ReplicaRole newRole, CancellationToken cancellationToken).
ChangeRoleAsync(..) ensure that the new role uses the correct communications doing the following:
Call CloseCommunicationListenersAsync(CancellationToken cancellationToken) to close any listeners open
Call OpenCommunicationListenersAsync(newRole, cancellationToken) for Primary or ActiveSecondary roles
The method OpenCommunicationListenersAsync() will call CreateServiceReplicaListeners() to get the listeners and call CreateCommunicationListener(serviceContext) for each returned listener to open the related endpoints.
Change of Roles is very common to happen during upgrades and Load Balancing, so this is a very common event.
In Summary,
Every time a Change of Role happens, CreateServiceReplicaListeners() will be called, ChangeRole does not shutdown the service, so it might have side effects, for example if you register dependencies in a DI container, you might face duplicate registrations.
I am in the process of converting a home grown logging system to NLog and am wondering if there is a way to add an event to a Logger or otherwise support a mechanism where when I log a message I can get a callback with the final formatted message and the LogLevel. I currently use something like this to send server messages back to a connected client.
Thx
This is an MCVE of what I was talking about in the comments. Create a target that accepts some callback functions:
[Target("MyFirst")]
public sealed class MyFirstTarget : TargetWithLayout
{
private readonly Action<string>[] _callbacks;
public MyFirstTarget(params Action<string>[] callbacks)
{
_callbacks = callbacks;
}
protected override void Write(LogEventInfo logEvent)
{
foreach (var callback in _callbacks)
{
callback(logEvent.FormattedMessage);
}
}
}
Configure NLog to use the target. I do this programmatically since the callbacks are passed in the constructor. You can also configure the target in the NLog.config, but your target will need to be a singleton then so you can register the callbacks in code.
class Program
{
public static void Main()
{
LogManager.Configuration.AddTarget("MyFirst", new MyFirstTarget(s => Debug.WriteLine(s)));
var logger = LogManager.GetCurrentClassLogger();
logger.Debug("test");
}
}
With no other NLog configuration (copy this code into an empty project and add the NLog nuget package), this will emit a message to your debug window.
I'm currently working on a simple GWT project. One of the things I'd like to do is that when the page loads I can dynamically populate the contents of a ListBox based on certain criteria. I actually don't see any handlers for a ListBox to handle the initial render event but I see change handlers.
How does one populate a ListBox contents with data from the server side on pageload with GWT?
Right now I have a class that implements EntryPoint that has a
final ListBox fooList = new ListBox();
I also have a set of beans but I also have a class implementing RemoteService. Since I can't seem to get direct calls to my user defined packages directly in the EntryPoint (which makes sense) how do I populate that ListBox with server side content on initial page load? Right now I'm using a List but I figure if I cant get that to work I can get a DB call to work...
I've tried things in the EntryPoint like:
for (String name : FOOS) {
fooList.addItem(name, name);
}
However FOOS would derive from a server side data and the EntryPoint is supposed to be largerly limited to what can compile to JS! I can't get user defined classes to be recognized on that side as that string is the result of a set of user defined classes.
I also tried creating a method in the class implementing RemoteService that returns a ListBox. This also didn't compile when I tried to call this method. Perhaps I don't fully understand how to call methods in a RemoteService service implementing class.
I've searched a lot and I can't find anything that clearly explains the fundamentals on this. My background is much more ASP.NET and JSPs so perhaps I'm missing something.
I'm using GWT 2.6 is that is relevant.
The usual procedure is the following:
Create a bean class for the data you want to transmit between client and server. Let's call it MyBean.
Place MyBean in the shared package of your project.
This class has to implement either Serializable or IsSerializable, otherwise GWT will complain that it doesn't know how to transmit it.
Create your RemoteService that contains the method you want to use to transmit MyBean from/to the server.
Once you get your data on the client using an AsyncCallback and your RemoteService, fill the ListBox using your beans, e.g. by calling MyBean#getName() or MyBean#toString().
Success!
I based my example on the GWT sample project ( I named it example), just replace the classes and it should work :
public class Example implements EntryPoint {
/**
* Create a remote service proxy to talk to the server-side Greeting
* service.
*/
private final GreetingServiceAsync greetingService = GWT
.create(GreetingService.class);
/**
* This is the entry point method.
*/
public void onModuleLoad() {
final ListBox listBox = new ListBox();
RootPanel.get("sendButtonContainer").add(listBox);
greetingService.getSomeEntries(new AsyncCallback<String[]>() {
#Override
public void onSuccess(String[] result) {
for (int i = 0; i < result.length; i++) {
listBox.addItem(result[i]);
}
}
#Override
public void onFailure(Throwable caught) {
}
});
}
}
This is our EntryPoint, it creates a listbox and calls the server with a AsyncCallback to get some dynamic data. If the call is successfull (onSuccess), the data is written into the listbox.
The GreetingService interface define the synchronous methods, it is implemented in the GreetingServiceImpl class :
#RemoteServiceRelativePath("greet")
public interface GreetingService extends RemoteService {
String[] getSomeEntries() ;
}
The asynchronous counterpart is the GreetingServiceAsync interface, we used it before to call the server :
public interface GreetingServiceAsync {
void getSomeEntries(AsyncCallback<String[]> callback) ;
}
The GreetingServiceImpl class is located on the server. Here you could call for example a database:
#SuppressWarnings("serial")
public class GreetingServiceImpl extends RemoteServiceServlet implements
GreetingService {
#Override
public String[] getSomeEntries() {
String[] entries = { "Entry 1","Entry 2","Entry 3" };
return entries;
}
}
Now if you want to use some Bean/Pojo between the server and client, replace the String[] in each class/interface with the object name, put the class in the shared package and consider that it implements Serializable/IsSerializable.
I have searched all over the net for this but couldn't find any..I want to use a single smartfox client obj and its connection until the user logs out on its own..
I tried this approach..
public class SfsClient extends Application {
private SmartFox sfsClient = new SmartFox(true);
public SmartFox getSfsClient() {
return sfsClient;
}
public void setSfsClient(SmartFox sfsClient) {
this.sfsClient = sfsClient;
}
}
If i call the sfsclient.connect(h,p) method in the getsfsclient method...the various responses which i want in the different activities in my app..are all acquired in my main activity Extension Response handler..
Say for example..I have Class A as Main and Class B as other activity..
Response for the processes done in Class B should b acquired in Class B Extension Resp..but they are coming in the Extension Resp of Class A..plz help..Thanks in advance..
How to communicate user defined objects and user defined (checked) exceptions between Service and UI in JavaFX2?
The examples only show String being sent in to the Service as a property and array of observable Strings being sent back to the UI.
Properties seem to be defined only for simple types. StringProperty, IntegerProperty, DoubleProperty etc.
Currently I have a user defined object (not a simple type), that I want Task to operate upon and update with the output data it produced. I am sending it through the constructor of Service which passes it on through the constructor of Task. I wondered about the stricture that parameters must be passed in via properties.
Also if an exception is thrown during Task's operation, How would it be passed from Service to the UI? I see only a getException() method, no traditional throw/catch.
Properties http://docs.oracle.com/javafx/2/binding/jfxpub-binding.htm
Service and Task http://docs.oracle.com/javafx/2/threads/jfxpub-threads.htm
Service javadocs http://docs.oracle.com/javafx/2/api/javafx/concurrent/Service.html#getException()
"Because the Task is designed for use with JavaFX GUI applications, it
ensures that every change to its public properties, as well as change
notifications for state, errors, and for event handlers, all occur on
the main JavaFX application thread. Accessing these properties from a
background thread (including the call() method) will result in runtime
exceptions being raised.
It is strongly encouraged that all Tasks be initialized with immutable
state upon which the Task will operate. This should be done by
providing a Task constructor which takes the parameters necessary for
execution of the Task. Immutable state makes it easy and safe to use
from any thread and ensures correctness in the presence of multiple
threads."
But if my UI only touches the object after Task is done, then it should be ok, right?
Service has a signature Service<V> the <V> is a generic type parameter used to specify the type of the return object from the service's supplied task.
Let's say you want to define a service which returns a user defined object of type Foo, then you can do it like this:
class FooGenerator extends Service<Foo> {
protected Task createTask() {
return new Task<Foo>() {
protected Foo call() throws Exception {
return new Foo();
}
};
}
}
To use the service:
FooGenerator fooGenerator = new FooGenerator();
fooGenerator.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
#Override public void handle(WorkerStateEvent t) {
Foo myNewFoo = fooGenerator.getValue();
System.out.println(myNewFoo);
}
});
fooGenerator.start();
If you want to pass an input value into the service each time before you start or restart it, you have to be a little bit more careful. You can add the values you want to input to the service as settable members on the service. These setters can be called from the JavaFX application thread, before the service's start method is invoked. Then, when the service's task is created, pass the parameters through to the service's Task's constructor.
When doing this it is best to make all information passable back and forth between threads immutable. For the example below, a Foo object is passed as an input parameter to the service and a Foo object based on the input received as an output of the service. But the state of Foo itself is only initialized in it's constructor - the instances of Foo are immutable and cannot be changed once created and all of it's member variables are final and cannot change. This makes it much easier to reason about the program, as you never need worry that another thread might overwrite the state concurrently. It seems a little bit complicated, but it does make everything very safe.
class FooModifier extends Service<Foo> {
private Foo foo;
void setFoo(Foo foo) { this.foo = foo; }
#Override protected Task createTask() {
return new FooModifierTask(foo);
}
private class FooModifierTask extends Task<Foo> {
final private Foo fooInput;
FooModifierTask(Foo fooInput) { this.fooInput = fooInput; }
#Override protected Foo call() throws Exception {
Thread.currentThread().sleep(1000);
return new Foo(fooInput);
}
}
}
class Foo {
private final int answer;
Foo() { answer = random.nextInt(100); }
Foo(Foo input) { answer = input.getAnswer() + 42; }
public int getAnswer() { return answer; }
}
There is a further example of providing input to a Service in the Service javadoc.
To return a custom user exception from the service, just throw the user exception during the service's task call handler. For example:
class BadFooGenerator extends Service<Foo> {
#Override protected Task createTask() {
return new Task<Foo>() {
#Override protected Foo call() throws Exception {
Thread.currentThread().sleep(1000);
throw new BadFooException();
}
};
}
}
And the exception can be retrieved like this:
BadFooGenerator badFooGenerator = new BadFooGenerator();
badFooGenerator.setOnFailed(new EventHandler<WorkerStateEvent>() {
#Override public void handle(WorkerStateEvent t) {
Throwable ouch = badFooGenerator.getException();
System.out.println(ouch.getClass().getName() + " -> " + ouch.getMessage());
}
});
badFooGenerator.start();
I created a couple of executable samples you can use to try this out.
Properties seem to be defined only for simple types. StringProperty, IntegerProperty, DoubleProperty etc. Currently I have a user defined object (not a simple type), that I want Task to operate upon and update with the output data it produced
If you want a property that can be used for your own classes try SimpleObjectProperty where T could be Exception, or whatever you need.
Also if an exception is thrown during Task's operation, How would it be passed from Service to the UI?
You could set an EventHandler on the Task#onFailedProperty from the UI with the logic with what to do on failure.
But if my UI only touches the object after Task is done, then it should be ok, right?
If you call it from your UI you are sure to be on the javaFX thread so you will be OK. You can assert that you're on the javaFX thread by calling Platform.isFxApplicationThread().