I have a HttpConnection thread class. when ı stop httpConnection, I show this messeage.
how should ı stop httpConnection??
Blackberry Output Console:
RuntimeException
blocking operation not permitted on event dispatch thread
net_rim_cldc-10
EventThreadCheck
throwException
0x3434
net_rim_cldc_io_tcp
Protocol
<private>
0x18B8
net_rim_cldc_io_tcp
Protocol
outputStreamClosed
0xB2D
net_rim_cldc_io_tcp
TcpOutputStream
close
0x40BF
net_rim_os-2
ClientProtocol
close
0x154E
CepVizyon-2
Http
cancel
0x174F
CepVizyon-2
Camera
cancel
0x6E7
CepVizyon
ViewCam
close
0xE79
net_rim_cldc-7
Screen
onClose
0x5DAC
net_rim_cldc-7
Screen
keyCharUnhandled
0x5C58
net_rim_cldc-9
MainScreen
keyCharUnhandled
0x23D7
net_rim_cldc-7
Screen
dispatchKeyEvent
0x51DB
net_rim_cldc-7
Screen
processKeyEvent
0x718D
net_rim_cldc-7
UiEngineImpl
processMessage
0x9E3C
net_rim_cldc-4
Application
processNextMessage
0x1073
net_rim_cldc-4
Application
enterEventDispatcher
0x775
CepVizyon-2
CepVizyonMain
main
0x1175
parts of My Connection class:
public abstract class Http extends Thread{
protected HttpConnection httpConnection;
HttpConnectionFactory factory;
protected static Base64 base64;
private boolean cancel = false;
/** bağlantının yapılcağı adres */
protected String url = "";
/** paremetre olarak gönderilecek data */
protected String queryString = "";
...
public void cancel() {
try {
if (httpConnection != null)
httpConnection.close();
if(factory!=null)
factory.cancel();
} catch (IOException ex) {
}
cancel = true;
}
part of my screen class:
public void close() {
super.close();
StaticVar.ActiveCam.cancel();
// CameraListScreen screen = new CameraListScreen();
// UiApplication.getUiApplication().pushScreen(screen);
//
}
and part of Camera Class/*ActiveCam's cancel is here/:
// finishes connection.
public void cancel() {
setConnected(false);
if (mjpeghttp != null) {
mjpeghttp.cancel();
//mjpeghttp.interrupt();
//mjpeghttp = null;
}
}
It looks like your HttpConnection is accessed from a background (non UI) thread which is good. However your UI calls close() directly which may block. You should consider spawning another thread to do the close().
You must work with screen only from event thread
//safely (recommended)
Application.getApplication().invokeLater(new Runnable() {
public void run() {
//your code here
}
});
or
//fast
synchronized(Application.getEventLock()) {
//your code here
}
Related
I am attempting to close a stream coming from an http request using Retrofit and rxjava, either because it timedOut, or because I need to change details that went into the request. Both appear to work perfectly, as when I cancel subscription I get the doOnCancel debug message and when doOnNext is completed I get the doOnTerminate message. I also do not receive inputLines from multiple threads. However, my thread count rises every single time either of the above actions happen. It appears that responsebody.close is not releasing their resources and therefore the thread is not dying (I also have gotten error messages along the lines of "OKHTTP leaked. did you close youre responseBody?")
Does anyone have any suggestions?
public boolean closeSubscription() {
flowableAlive = false;
subscription.cancel();
return true;
}
public void subscribeToFlowable() {
streamFlowable.observeOn(Schedulers.newThread()).subscribeOn(Schedulers.newThread())
.doOnTerminate(() -> log.debug("TERMINATED")).doOnCancel(() -> log.debug("FLOWABLE CANCELED"))
.subscribe(new Subscriber<ResponseBody>() {
#Override
public void onSubscribe(Subscription s) {
subscription = s;
subscription.request(Long.MAX_VALUE);
}
#Override
public void onNext(ResponseBody responseBody) {
log.debug("onNext called");
String inputLine;
try (InputStream inputStream = responseBody.byteStream()) {
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
while (flowableAlive && ((inputLine = br.readLine()) != null)) {
log.debug("stream receive input line for thread " + name);
log.debug(inputLine);
}
} catch (IOException e) {
log.debug("error occurred");
log.debug(e.getMessage());
}
}
#Override
public void onError(Throwable t) {
log.debug("error");
flowableAlive = false;
}
#Override
public void onComplete() {
log.debug("completed");
closeSubscription();
flowableAlive = false;
}
});
}
The result of subscribe() is Disposable object. You should store it as a filed and call Disposable.dispose() on it later as shown here:
https://proandroiddev.com/disposing-on-android-the-right-way-97bd55cbf970
Tour OkHttp call will be interrupted properly because dispose() interrupts thread on which the call runs and OkHttp checks regularly if Thread was interrupted to stop transfer when that happened - it's called cooperative cancelling/interruption.
I have a test project with Room database. Using Asynctask I can successfully insert an object with some test data into the database. I'm trying to learn RxJava and replace Asynctask with RxJava's observer, but it doesn't work. I have read alot of documentation and watched tutorials, but I don't think I quite get it. Here's the relevant code:
Here I set my Room object with the data from my List:
for(ObjectForArray item: listToDatabase) {
myRoomEntity.setName( item.getName() );
Log.d( "TAG", myRoomEntity.getName() );
}
Then I try to use RxJava Observable to insert data into the database. This was originally and successfully done using Asynctask:
Observable<MyRoomEntity> myRX = Observable
.just(myRoomEntity)
.subscribeOn( Schedulers.io() )
.observeOn( AndroidSchedulers.mainThread() );
myRX.subscribe( new Observer<MyRoomEntity>() {
#Override
public void onSubscribe(Disposable d) {
Log.d("TAG ONSUBSCRIBE", d.toString());
try {
myViewModel.insertDatabase( myRoomEntity );
Log.d( "TAG", "Populating database Success" );
}catch(Error error) {
Log.d( "TAG", error.toString() );
}
}
The OnNext, OnError and OnComplete are empty.
When I run the project it crashes with the error:
Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
I'm obviously using RxJava wrong since the point is to do asynchronous tasks away from the main thread.
i have use RX java in replace of Asyntask as it has been deprecated in android 9
there are multiple replacements that android provides like Executors, threads, Listenable Futures , Coroutines 🔥, so you are looking how to implement this with rxjava and how RX Java java helps your to migrate just add these dependencies first in gradle
implementation "io.reactivex.rxjava2:rxjava:2.2.20"
implementation "io.reactivex.rxjava2:rxandroid:2.1.1"
once you import lets start working with RX java i will let you know where you can put background task, pre execute, on post execute like asynctask
lets start codding with Rx java first , i have comment in the method that will help you to put the code
Observable.fromCallable(new Callable<Boolean>() {
#Override
public Boolean call() throws Exception {
/// here is your background task
return true;
}
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<Boolean>() {
#Override
public void onSubscribe(Disposable d) {
//// pre execute here is my progress dialog
showProgressDialog(getString(R.string.scanning));
}
#Override
public void onNext(Boolean aBoolean) {
//// here is on sucess you can do anystuff here like
if (aBoolean){
/// if its value true you can go ahead with this
}
}
#Override
public void onError(Throwable e) {
/// this helps you to go if there is any error show dialog whatever you wants here
Log.e("error of kind",e.getMessage() );
}
#Override
public void onComplete() {
/// when your task done means post execute
}
});
once its done lets start working with implementation
Observable.fromCallable(new Callable<Boolean>() {
#Override
public Boolean call() throws Exception {
/// here is your background task
uribitmap = getScannedBitmap(original, points);
uri = Utils.getUri(getActivity(), uribitmap);
scanner.onScanFinish(uri);
return true;
}
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<Boolean>() {
#Override
public void onSubscribe(Disposable d) {
//// pre execute here is my progress dialog
showProgressDialog(getString(R.string.scanning));
}
#Override
public void onNext(Boolean aBoolean) {
//// here is on sucess you can do anystuff here like
if (aBoolean){
/// if its value true you can go ahead with this
}
}
#Override
public void onError(Throwable e) {
/// this helps you to go if there is any error show dialog whatever you wants here
Log.e("error of kind",e.getMessage() );
}
#Override
public void onComplete() {
/// when your task done means post execute
uribitmap.recycle();
dismissDialog();
}
});
now i will do this with executors :
/// pre execute you can trigger to progress dialog
showProgressDialog(getString(R.string.scanning));
ExecutorService executors = Executors.newSingleThreadExecutor();
executors.execute(new Runnable() {
#Override
public void run() {
//// do background heavy task here
final Bitmap uribitmap = getScannedBitmap(original, points);
uri = Utils.getUri(getActivity(), uribitmap);
scanner.onScanFinish(uri);
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
//// Ui thread work like
uribitmap.recycle();
dismissDialog();
}
});
}
});
You are getting this error because you are trying to insert an Object on the main (UI) thread.
You should do something like this:
Observable.fromCallable(() -> myViewModel.insertDatabase( myRoomEntity ))
.subscribeOn( Schedulers.io() )
.observeOn( AndroidSchedulers.mainThread() );
And then use an Observer to subscribe to the Observable.
Please try restructuring your code like this:
Completable.fromAction(() -> myViewModel.insertDatabase(myRoomEntity))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(() -> Log.d("TAG", "Populating database Success"),
throwable -> Log.d("TAG", throwable.toString()))
Considerations:
If your myRoomEntity is not available before this whole construct gets subscribed, make sure you use defer http://reactivex.io/documentation/operators/defer.html
Your subscribe section handlers are operating on "main", that's why you were receiving a crash.
If possible, avoid unnecessary just calls
I read much about the JavaFX GUI Model, Plattform->RunLater and Threads, but I still do not figure out how to get this right. I had a JavaFX GUI which on a button click executed a process and updated a Progress Bar and Label. This was running well with Threading and Platform, but I had to Change this to an Observer Model.
I invoke a Progress Tracker in a Singleton Model, which gets updated by the class executing the process and is Observable. I implemented an Observer as well which should update the two UI Elements.
GUI Controller with Button Event
private void createKeyPressed(ActionEvent event) {
// Make Progressbar visible
pbKeyProgress.visibleProperty().set(true);
if (!Check.keyFileExistant() || cbKeyOverwrite.selectedProperty().get()) {
ProgressTracker.getTracker().addObserver(new ProgressObserver(pbKeyProgress, lblKeyProgress));
Creator.createKey(cbKeyLength.getValue());
} else {
}
}
Progress Observer
public class ProgressObserver implements Observer {
private final ProgressBar progressBar;
private final Label statusLabel;
public ProgressObserver(ProgressBar progressBar, Label statusLabel) {
this.progressBar = progressBar;
this.statusLabel = statusLabel;
}
#Override
public void update(Observable o, Object o1) {
Platform.runLater(() -> {
System.out.println("Tracker set to "+ProgressTracker.getProgress() + " " + ProgressTracker.getStatus());
progressBar.setProgress(ProgressTracker.getProgress());
statusLabel.setText(ProgressTracker.getStatus());
});
}
}
Progress Tracker
public synchronized void setTracker(int currentStep, String currentStatus) {
checkInstance();
instance.step = currentStep;
instance.status = currentStatus;
instance.notifyObservers();
System.out.println(instance.countObservers());
}
Creator
public static void createKey(String length) {
Task<Void> task;
task = new Task<Void>() {
#Override
public Void call() throws Exception {
initTracker(0,"Start");
doStuff();
ProgressTracker.getTracker().setTracker(1,"First");
doStuff();
ProgressTracker.getTracker().setTracker(2,"Second");
// and so on
return null;
}
};
new Thread(task)
.start();
}
The Print within the ProgressTracker gets executed. However, if I add a print within the update of the Observer nothing will be printed. If I check within the Progresstracker, the Observer Count is 1.
Why does the Observer not get notified or execute anything, even if the Notify is called? Did I get the Threading and Execution Modell wrong?
The Progress Bar and the Label will also stay on their initial values.
Don't reinvent the wheel. The JavaFX Properties Pattern is a ready-made implementation of the Observable pattern: there is no need to implement it yourself. Additionally, Task already defines methods for updating various properties, which can be called from any thread but will schedule the actual updates on the FX Application Thread. See updateProgress() and updateMessage(), for example.
So you can do, for example:
public static Task<Void> createKey(String length) {
Task<Void> task;
task = new Task<Void>() {
final int totalSteps = ... ;
#Override
public Void call() throws Exception {
updateProgress(0, totalSteps);
updateMessage("Start");
doStuff();
updateProgress(1, totalSteps);
updateMessage("First");
doStuff();
updateProgress(2, totalSteps);
updateMessage("Second");
// and so on
return null;
}
};
new Thread(task)
.start();
return task ;
}
and
private void createKeyPressed(ActionEvent event) {
// Make Progressbar visible
pbKeyProgress.visibleProperty().set(true);
if (!Check.keyFileExistant() || cbKeyOverwrite.selectedProperty().get()) {
Task<Void> task = Creator.createKey(cbKeyLength.getValue());
pbKeyProgress.progressProperty().bind(task.progressProperty());
lblKeyProgress.textProperty().bind(task.messageProperty());
} else {
}
}
I want to perform some long running operation (e.g. listening to some event raised by OS) on the background thread. Most of the times, operation will run continuously without any problem. But in certain rare conditions, OS level API sends some error code and I need to raise exception from background thread which has to be propagated to the main thread to show it to the user of my WinFrom application.
I had decided to use BackgroundWorker for this. But .NET 4.0 provides Task class of the Task Parallel Library which is a better option as per various blogs on the TPL.
In my application, I have to kick off the background task before actual form is shown. Since actual code is quite complex, I have written some sample code simulating real time problem:
public static Task task;
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
ThreadTest tt = new ThreadTest();
task = new Task(() => tt.PerformTask("hi"));
task.Start();
try
{
task.Wait();
}
catch (AggregateException aggregateException)
{
// Handle exception here.
}
Application.Run(new Form1());
}
In this code, I never see the main form simply because background task keeps running without exception and task.Wait() call makes the current thread waiting until background task finishes!
Can I use TPL's Task for such scenarios where main thread should not wait until background task is finished but at the same time, it should get exception details whenever exception is raised from the background task?
In above code, one of the solutions could be to move the task creation code at some later stage. But my question is more academic in this case.
Yes you can. Please see the code below.
The program code is:
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
Task longRunningTask = new Task((state) =>
{
LongRunningWork.DoWork( cancellationTokenSource.Token);
},cancellationTokenSource.Token,TaskCreationOptions.LongRunning);
var newForm = new Form1(cancellationTokenSource);
new Thread((state) =>
{
longRunningTask.Start();
try
{
longRunningTask.Wait();
}
catch (AggregateException exception)
{
Action<Exception> showError = (ex) => MessageBox.Show(state as Form, ex.Message);
var mainForm = state as Form;
if (mainForm != null)
{
mainForm.BeginInvoke(showError, exception.InnerException);
}
}
}).Start(newForm);
Application.Run(newForm);
And the code for the long running task is:
public class LongRunningWork
{
public static void DoWork( CancellationToken cancellationToken)
{
int iterationCount = 0;
//While the
while (!cancellationToken.IsCancellationRequested &&iterationCount <5)
{
//Mimic that we do some long jobs here
Thread.Sleep(1000);
iterationCount++;
//The jobs may throw the exception on the specific condition
if (iterationCount ==5)
{
throw new InvalidOperationException("Invalid action");
}
}
//cancel the task
cancellationToken.ThrowIfCancellationRequested();
}
}
Finally, the code for the Form1 which includes a exit button, whose function is to terminate the program on clicking.
public partial class Form1 : Form
{
private CancellationTokenSource _cancellationTokenSource;
public Form1()
{
InitializeComponent();
}
public Form1(CancellationTokenSource cancellationTokenSource):this()
{
_cancellationTokenSource = cancellationTokenSource;
}
private void exitBtn_Click(object sender, EventArgs e)
{
//Cancel out the task
if (_cancellationTokenSource != null)
{
_cancellationTokenSource.Cancel();
}
//Exit the program
Application.Exit();
}
}
Start your long running operation from the form itself rather than before the form is created. Remember that Application.Run() starts a message loop on the current thread, but that means you can use that message loop to poll your task from the Timer class.
class Form1 : Form
{
private Timer PollingTimer;
private Task BackgroundTask;
public Form1()
{
InitializeComponent();
// Begin the background task.
ThreadTest tt = new ThreadTest();
this.BackgroundTask = new Task(() => tt.PerformTask("hi"));
this.BackgroundTask.Start();
// Monitor the task's status by polling it regularly.
this.PollingTimer = new Timer();
this.PollingTimer.Interval = 1000; // In milliseconds.
this.PollingTimer.Tick += timerCallback;
this.PollingTimer.Start();
}
private timerCallback(object sender, EventArgs e)
{
if (this.BackgroundTask.IsFaulted)
{
// Exception information is in BackgroundTask.Exception.
}
}
}
If you dislike polling (which I do), you'll need to catch the exception from your task and marshall it back to your UI thread. The best way to do that is simply not catch the exception in the task itself and provide a continuation method which will only execute on error.
class Form1 : Form
{
private Task BackgroundTask;
public Form1()
{
InitializeComponent();
// Capture the UI thread context.
// (Note, it may be safer to run this in the Form.Load event than the constructor.
var uiContext = TaskScheduler.FromCurrentSynchronizationContext();
// Begin the background task.
ThreadTest tt = new ThreadTest();
this.BackgroundTask = new Task(() => tt.PerformTask("hi"))
// Schedule a continuation to be executed after the task is completed.
.ContinueWith((t,arg) =>
{
// Exception information is in t.Exception
},null, null,
// Only execute the continuation if the task throws an exception.
TaskContinuationOptions.OnlyOnFaulted,
// Execute the continuation on the UI thread we captured above.
uiContext);
this.BackgroundTask.Start();
}
}
MSDN references for Task.ContinueWith() and TaskScheduler.FromCurrentSynchronizationContext().
And, if you have the luxury of .NET 4.5 with async and await:
class Form1 : Form
{
private Task BackgroundTask;
public Form1()
{
InitializeComponent();
}
private async void Form1_Load(object sender, EventArgs e)
{
ThreadTest tt = new ThreadTest();
try
{
// Move your Task creation and start logic into a method.
await tt.RunAsync();
}
catch (Exception ex)
{
// Really smart compiler writers make sure you're on the right thread
// and everything Just Works(tm).
}
}
}
I am developping a BlackBerry application which communicates with the server via HTTP requests(javax.microedition.io.HttpConnection). On device, user clicks some UI items, and device sends the requests to server, when the response comes, UI changes. Communication takes place under new thread, while UI thread pushes and pops ProgressDialogScreen.
The problem is sometimes, when response comes and ProgressDialogScreen is popped, UI does not change but after couple seconds UI changes. If you have requested in between when ProgressDialogScreen is popped and when new Screen is pushed, there comes the mess. First oldest new Screen is pushed, and the newest new Screen is pushed. And this situation can be observed like server responsing wrong requests. This problems occur on simulator and device.
The other problem is, sometimes two same response returns for one request. I was able to see these two problems on simulator at the logs, but i have not able to see this issue on device since i can not see the logs.
EDIT:
String utf8Response;
HttpConnection httpConn = null;
try{
httpConn = (HttpConnection) Connector.open(url);
httpConn.setRequestMethod(HttpConnection.GET);
httpConn.setRequestProperty("Content-Type", "text/html; charset=UTF8");
if(sessionIdCookie != null){
//may throw IOException, if the connection is in the connected state.
httpConn.setRequestProperty("Cookie", sessionIdCookie);
}
}catch (Exception e) {
//...
}
try{
httpConn.getResponseCode();
return httpConn;
}catch (IOException e) {
// ...
}
byte[] responseStr = new byte[(int)httpConn.getLength()];
DataInputStream strm = httpConn.openDataInputStream();
strm.readFully(responseStr);
try{
strm.close();
}catch (IOException e) {
// ....
}
utf8Response = new String(responseStr, "UTF-8");
If this code successfully run, this piece of code runs and new screen is pushed:
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Vector accounts = Parser.parse(utf8Response,Parser.ACCOUNTS);
if (accounts.size() == 0){
DialogBox.inform(Account.NO_DEPOSIT);
return;
}
currentScreen = new AccountListScreen(accounts);
changeScreen(null,currentScreen);
}
});
public void changeScreen(final AbstractScreen currentScreen,final AbstractScreen nextScreen) {
if (currentScreen != null)
UiApplication.getUiApplication().popScreen(currentScreen);
if (nextScreen != null)
UiApplication.getUiApplication().pushScreen(nextScreen);
}
EDITv2:
private static void progress(final Stoppable runThis, String text,boolean cancelable) {
progress = new ProgressBar(runThis, text,cancelable);
Thread threadToRun = new Thread() {
public void run() {
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
try{
UiApplication.getUiApplication().pushScreen(progress);
}catch(Exception e){
Logger.log(e);
}
}
});
try {
runThis.run();
} catch (Throwable t) {
t.printStackTrace();
}
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
try {
UiApplication.getUiApplication().popScreen(progress);
} catch (Exception e) { }
}
});
}
};
threadToRun.start();
}
By the way ProgressBar is extended from net.rim.device.api.ui.container.PopupScreen and Stoppable is extended from Runnable
I preferred to pop progress bar after new Screen is prepared and pushed. This way there will be no new request between request and response.
Why not do:
private static void progress(final Stoppable runThis, String text,boolean cancelable) {
progress = new ProgressBar(runThis, text,cancelable);
UiApplication.getUiApplication().pushScreen(progress);
[...]
Seems like you are parsing on the UI Thread. Please remove Vector accounts = Parser.parse(utf8Response,Parser.ACCOUNTS); from ui thread and do it in a separate thread.