I have a BlackBerry App that has a Listener for the Send Button implemented in the CheckIn Screen. Data is sent through a web service. If the data is sent successfully, a confirmation message of "OK" is received. I am trying to switch screens in my BlackBerry App depending on the response received.
FieldChangeListener sendBtnListener = new FieldChangeListener() {
public void fieldChanged(Field field, int context)
{
try {
String alertMsg=sendTextCheckIn();
if(alertMsg.equals("OK"))
{
UiApplication.getUiApplication().invokeLater( new Runnable()
{
public void run ()
{
UiApplication.getUiApplication().pushScreen(new MyScreen());
}
} );
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
However, the above is throwing an App Error 104: IllegalStateException. Can anyone please guide on how to switch screens between a BlackBerry App.
EDIT: I can switch to any other screen but I CAN NOT switch to MyScreen. NOTE: MyScreen is the main (first) screen of the App. The above method sendTextCheckIn() calls another method that is placed inside MyScreen. Has this got anything to do with the error? Please advice.
The 'fieldChanged' event is already running on the UI event thread, so you shouldn't need to do the invokeLater call within it, just call pushScreen directly.
You mention that your problem with IllegalStateException only happens for MyScreen. That makes it sound like something specific with the implementation of MyScreen. Start narrowing down the problem - look at what happens in the constructor of MyScreen, and any events that might get called before the screen is visible. Some of that code is what is causing the problem.
Wrap everything that could possibly raise in exception in try/catch.
Don't do e.printStackTrace() - that won't give you much.
Instead do something like System.err.println ("KABOOM in method abc() - " + e); - seems like more effort, but trust me, that becomes INVALUABLE when debugging issues like this.
Catch Exception, unless you have a VERY good reason to catch a specific a subtype - otherwise you WILL end up with unexpected, and uncaught exceptions, which you will hunt for DAYS.
Related
I've built a simple app that talks over UDP, to an endpoint at an IP the user specifies. It uses System.Net.Sockets.UdpClient, which works pretty well on Android - I'm able to send and receive packets fairly consistently. With one glaring exception... Exceptions. It seems to completely evade try/catch; my guess is the underlying implementation errors so hard that errors cannot be caught. For example:
UdpClient Udp { get; protected set; }
Udp.Connect("192.168.1.254"); // Any bad IP
try
{
int bytesSent = await udp.SendAsync(bytes, bytes.Length);
}
catch(Exception ex)
{
return null;
}
When testing on an actual Android device, any UDP traffic sent to a bad IP consistently destroys the application.
The behavior gets crazier. For example, if I put the call out on a background thread, with a nested try/catch, like this:
Task.Run(ping).ConfigureAwait(false);
protected async Task ping()
{
try
{
await checkIp();
}
catch(Exception ex)
{
}
}
Then there are some scenarios where I actually can get an Exception - but only in the outer catch! The throw occurs on the SendAsync call inside the inner try, but the inner catch misses it, landing only in the outer catch. The exception is a System.Net.Sockets.SocketException with type ConnectionRefused. Depending on how exactly I step through it, sometimes that gets caught there, sometimes not at all; when it's not at all, the app just implodes.
Is this expected behavior? Is Xamarin UdpClient just not supposed to be used? Bug? Better approach than SendAsync? Other?
I am developing an app using Xamarin.Forms to re-use as much code as possible.
Specifically, I have a static class that manages all the POST/GET requests to my Azure Web Server.
Everything single call works fantastically except for one call - this one:
public async static Task<Models.UserParkPosition> GetUserParkPositionForCurrentUserAsync()
{
var body = new JArray { App.User.Id };
var test = await AzureMobileServiceClient.Instance.MobileService.InvokeApiAsync<JArray, Models.UserParkPosition>(ConnectionsAPI, body, HttpMethod.Get, null);
return test;
}
The method above is called when the user presses a button - specifically like this:
private async Task OnGoingToTheParkClicked(object sender, EventArgs e)
{
bool success = false;
var already = await viewModel.AlreadyHavePendingRequestAsync());
Console.WriteLine("TEST");
throw new Exception();
}
When the debugger hits the "var test" line mentioned, above.... nothing happens. The code doesn't deadlock, the UI is still responsive, but the code never returns. I never see the "TEST" word and the exception is not even thrown... what happens??
All my other APIs are called in the same way, and are working correctly.
OTHER INFO:
- Same code works on UWP and Android
- The GET request arrives at the webservice, which responds in a timely fashion (< 1 sec)
Thanks to anyone who might help or even point me in the right direction!
Found the issue - InvokeApiAsync throws an exception which is not catched anywhere from any calling thread. It somehow just disappears without causing any error nor device log, nor crash. Weird, but that's how the world goes.
I try to handle a Summernote Keyup event with this:
myEditor.addSummernoteKeyUpHandler(new SummernoteKeyUpHandler() {
#Override
public void onSummernoteKeyUp(final SummernoteKeyUpEvent event) {
// TODO Auto-generated method stub
log.fine("hello");
}
});
I get a UmbrellaException which is IMHO a class cast exception.
This is the call stack
I identified the following spot where te cast failes:
#HasNoSideEffects
static native boolean canCast(Object src, JavaScriptObject dstId) /*-{
if (#com.google.gwt.lang.Cast::instanceOfString(*)(src)) {
return !!#com.google.gwt.lang.Cast::stringCastMap[dstId];
} else if (src.#java.lang.Object::castableTypeMap) {
return !!src.#java.lang.Object::castableTypeMap[dstId]; //<-- this returns false!!!
} else if (#com.google.gwt.lang.Cast::instanceOfDouble(*)(src)) {
return !!#com.google.gwt.lang.Cast::doubleCastMap[dstId];
} else if (#com.google.gwt.lang.Cast::instanceOfBoolean(*)(src)) {
return !!#com.google.gwt.lang.Cast::booleanCastMap[dstId];
}
return false;
}-*/;
dstId contains:
Any help greatly appreciated!
I tested this with a small demo which actually works. But in my large application, I get this exception and I don't see why.
Do you have any idea whats wrong here?
Best regards
Hannes
As Andrei suggested I set the style to DETAILED. I use Eclipse as a development environment. I decided to clean build the system (which I had done before). Now the problem has simply vanished !! Furthermore, I use SDBG (see: https://sdbg.github.io/) to debug my GWT application. This works pretty well (even without -style DETAILED). Now the very very strange thing remains. I can set breakpoints for my application and they all work well, except setting a breakpoint within the event handling method. I use a logger to print some text to the console, so I see that the event handler for summernote is actually called but the debugger will not stop. I checked whether the breakpoint is listed in the tab "Breakpoints" and it is and it is checked. I don't get it. Perhaps I have to rebuild all again.
But to keep long things short:
The solution to the problem is probably to really issue a clean build and then hope for the best.
Is there way to handle situation when message is not delivered to server? Dolphin log infors about situation clearly, but I'would like to catch it from code. I was looking for some method like: onError to override like onFinished:
clientDolphin.send(message, new OnFinishedHandlerAdapter() {
#Override
public void onFinished(List<ClientPresentationModel> presentationModels) {
// Do something useful
}
}
});
, but there is nothing like that. Also wrapping send call in try/catch does not work(not suprising since send is not blocking its caller code).
I thing there is definitely some easy way to get informed about undelivered message, but I cant see it.
Thaks, in advace, for answers!
You can assign an onException handler to the ClientConnector - and you are actually supposed to do so. The exception handler will get the exception object passed in that happened in the asynchronous send action.
Below is the default handler that even tells you, what you should do ;-)
Closure onException = { Throwable up ->
def out = new StringWriter()
up.printStackTrace(new PrintWriter(out))
log.severe("onException reached, rethrowing in UI Thread, consider setting ClientConnector.onException\n${out.buffer}")
uiThreadHandler.executeInsideUiThread { throw up } // not sure whether this is a good default
}
I am using this example:
Android - Setting a Timeout for an AsyncTask?
in the following way:
al.setOnClickListener(new OnClickListener(){
public void onClick(View w)
{
final AlogLoader loader = new AlogLoader();
loader.execute();
Handler handler = new Handler();
handler.postDelayed(new Runnable()
{
public void run()
{
if(loader.getStatus() == AsyncTask.Status.RUNNING)
{
loader.cancel(true);
}
}
}, 1);
}
});
I set it to "1" because I wanted to see if I can stop it practically before it even starts - to see if my handler is working - in reality I would probably set it to 15000 (15 seconds).
However what happens is confusing:
Running the application, causes my onPreExecute() to draw a loading screen, which doesn't ever exit, so the user just sees a loading screen perpetually.
Running it in the debugger with the breakpoint at loader.cancel(true) -> Causes the debugger to stop at that line, which is expected because its only allowed to run for 1 millisecond. However, when I hit the resume button in the debugger after that - my onPostExecute() is called... How is that possible?
Clearly, I'm very new to timing out asynctasks - after some research, I found the example above and it seemed to make the most sense to me, definitely more then
loader.get(15000, TimeUnit.MILLISECONDS);, since that blocks the UI Thread.
Any help is appreciated...even an explanation on the process..
Okay,
So I essentially solved my problem but I am still confused... Don't know if that's all good.
I was unclear on how loader.cancel(true) actually works. Based on the API level (read this question : AsyncTask.onCancelled() not being called after cancel(true)) you need to have an onCancelled() or onCancelled(params) method, or both in your AsyncTask.
I did not have this, so this explains why I saw a loading screen forever. Okay Good.
Yet, it doesn't explain how in the debugger, I managed to still call the onPostExecute(), because according to Android API's, onPostExecute is never called once cancel(true) has been called...
The answer is:
Add this to your AsyncTask-
#Override
protected void onCancelled()
{
Toast.makeText(FriendsActivity.this,"Blah- reason", Toast.LENGTH_LONG).show();
loadingScreen.dismiss();
}