I have a requirement in JavaFX 2 to display the notifications on the header. These notifications are populated in the database through an external system.
When a new notification is inserted in the database, my JavaFX application should listen to the same and refresh the header.
One solution I can think about is to implement a timeline that triggers the code to retrieve the latest notification status once every fixed time period, may be once every 2 mins.
Other than this, is there any other way to achieve this? Any hints on this would be highly appreciated.
You can create a new Task that would be listening (or checking) for changes in your database. This Task would be running in a different Thread as not to block your UI. Once a change occurs, it can then update your UI.
Your code could look like this :
//... initialize your variables.
task = new DatabaseWatcher();
executor = Executors.newSingleThreadExecutor();
executor.execute(task);
And your DatabaseWatcher :
public class DatabaseWatcher extends Task<Object> {
public DatabaseWatcher() {
//initialize here
}
#Override
protected Object call() throws Exception {
//Get data from database
//if new update :
updateUI();
return null;
}
private void updateUI() {
Platform.runLater(new Runnable() {
#Override
public void run() {
//Set your new values in your UI
//Call the method in your UI to update values.
}
});
}
}
This should get you started on the right path.
See Also
Multiple FXML with Controllers, share object, more specifically this answer
javafx, update ui from another thread
Concurrency in JavaFX
Related
i am making cron job like loop to do something using new thread.
when module stop, this thread keeps running, so when i deployed updated module, i'm afraid it will make duplicate thread doing similar task
#Component(immediate = true, service = ExportImportLifecycleListener.class)
public class StaticUtils extends Utils{
private StaticUtils() {}
private static class SingletonHelper{
private static final StaticUtils INSTANCE = new StaticUtils();
}
public static StaticUtils getInstance() {
return SingletonHelper.INSTANCE;
}
}
public class Utils extends BaseExportImportLifecycleListener{
public Utils() {
startTask();
}
protected Boolean CRON_START = true;
private void startTask() {
new Thread(new Runnable() {
public void run() {
while (CRON_START) {
System.out.println("test naon bae lah ");
}
}
}).start();
}
#Deactivate
protected void deactivate() {
CRON_START = false;
System.out.println(
"cron stop lah woooooooooooooooooy");
}
}
i'm using liferay 7
I have populated task that i store from db, so this thread is checking is there a task that it must do, then if it exist execute it.
I'm quite new in osgi and liferay. i've try to use scheduler and failed and also exportimportlifecycle listener but dont really get it yet
think again: Do you really need something to run all the time in the background, or do you just need some asynchronous processing in the background, when triggered? It might be better to start a background task as a one-off, that automatically terminates
Liferay provides an internal MessageBus, that you can utilize to listen to events and implement background processing, without the need for a custom thread
You're in the OSGi world, so you can utilize #Activate, #Modified, #Deactivate (from org.osgi.service.component.annotations) or use a org.osgi.framework.BundleActivator.
But, in general, it's preferable if you don't start your own thread
Having an huge customers profile page if two or more users start using same page and start editing big change will happen in my database so planing to implement Threads concept where only one user can use that customer page
i'm aware about threads concept but confused how to implement it
hope i need to use Singleton class as well
Any suggestion or Logic's will be helpful
I'm using Struts,Hibernate frame work
You may use application context to store a flag variable. Action will use its value to allow only one simultaneous execution.
public class TestAction extends ActionSupport implements ApplicationAware {
private static final String APP_BUSY_KEY = "APP_BUSY";
Map<String, Object> map;
#Override
public void setApplication(Map<String, Object> map) {
this.map = map;
}
#Override
public String execute() throws Exception {
if (map.containsKey(APP_BUSY_KEY)) {
return ERROR;
} else {
map.put(APP_BUSY_KEY, "1");
try {
// action logic here
} finally {
map.remove(APP_BUSY_KEY);
}
return SUCCESS;
}
}
}
If you plan to implement similar logic for two requests (lock after displaying values and release lock after submitting new values) then logic will be more complex and you will also need to handle lock release after timeout.
I have an update database operation, that has an activity, which keeps updating the percentage and it runs inside an AsyncTask.
Inside doInBackground() I call the controller that updates the database and keep updating the percentage on the activity, however, if I press home button or back button, the operation is cancelled. What u suggest me to do?
I was trying to start a Service inside doInBackground() so it would run in background, but it looks like its not working.
My code looks like this:
public class UpdateDatabaseAsyncTask extends AsyncTask<Void, Integer, Integer>
{
#Override
public void onPreExecute()
{
mCustomProgressBar.startAnimation();
}
#Override
public Integer doInBackground(Void... params)
{
return mController.updateDatabase();
}
#Override
public void onPostExecute(Integer result)
{
mCustomProgressBar.stopAnimation();
// finish the activity
}
#Override
public void onProgressUpdate(Integer... value)
{
updatePercentageValue(value[0]);
}
public void callPublishProgress(Integer value)
{
publishProgress(value);
}
}
And inside the controller I call the method callPublishProgress(value) passing the current percentage value, so it will publishProgress(value) in the UI.
I was debugging, and I pressed the home/back button, and it just stopped running the worker thread.
Another solution I tried, was starting a Service to run in background no matter the user press home/back button or not, so I thought, and the Service would make a call to the controller method that does the work, and it would call the callPublishProgress(value) to update the percentage value on the UI anyways.
However, what was happening is, the code reach doInBackground() and start the service, but it goes to onPostExecute() immediately, it just didn't wait the service to finish(of course!). So it gives a NullPointerException. I thought of making a loop inside doInBackground() with a flag set in the Service, so it would leave this loop while the service hasn't been finished (I was using an IntentService), but it didn't work anyways.
I thought of using a Timer too. But I don't know.
I was reading the articles in documentation about Threads, etc. And it suggests using AsyncTask, just as I was trying to do. It also talks about runOnUiThread(Runnable).
Anyways what I need is to make an operation in background(probably using an IntentService), so no matter if the user press the home button, it will keep running, but it must update the percentage on the UI, and when the user leave the screen and back to it, it shows the current percentage value updated in the screen.
What is the best solution for my case?
Thanks.
public class MyServce extends Service{
public static final String BROADCAST_ACTION = "com.myapp";
Intent intent;
private final Handler handler = new Handler();
#Override
public void onCreate()
{
super.onCreate();
intent = new Intent(BROADCAST_ACTION);
}
#Override
public void onStart(Intent intent, int startId) {
handler.removeCallbacks(sendUpdatesToUI);
handler.postDelayed(sendUpdatesToUI, 1000); // 1 second
}
private Runnable sendUpdatesToUI = new Runnable() {
public void run() {
DoYourWorking();
handler.postDelayed(this, 1000); // 1 seconds
}
private void DoYourWorking() {
........
........
intent.putExtra("key", progress);
sendBroadcast(intent);
}
};
#Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
#Override
public void onDestroy() {
super.onDestroy();
handler.removeCallbacks(sendUpdatesToUI);
}
Now in your Activity register broadcast to service
private BroadcastReceiver brodcast = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
//intent.getWhatever
// update your progress
//progressbar.setProgress
}
register broadcast
registerReceiver(brodcast, new IntentFilter(MyService.BROADCAST_ACTION));
This worked for me. I started a background service on a thread that just fetches the values and updates an object in a singleton.
In the view controller, I start a timer that keeps updating the view by fetching data from the object in singleton.
I had a little problem understanding your entire question text, so I'm not sure if you have tried this. But this is what worked. Also, the service was started with START_STICKY
Use an IntentService (which is a Service on a thread of its own), and Handler to pass the data back to the Activity.
Questions about threads are in no shortage, I know, but I can't seem to find a "full" example of a thread doing http work and then coming back to update the UI.
I basically call a few web services upon app launch. I obviously don't want to freeze the UI so I would want to use a separate thread, right? I have found a bunch of examples online on how to get a new thread to perform some task. But I haven't yet found one that shows how to actually update the UI when the thread's task is done.
How do I know when the web service thread is done? Is there a callback method? Can I access the UI from this callback method if one exists.
Edit: (Here is some code)
//The activate method is called whenever my application gains focus.
public void activate(){
DoSomething wsThread = new DoSomething();
wsThread.start();
}
public void wsCallBack()
{
myTabScreen.add(new ButtonField("Callback called"));
}
public class DoSomething extends Thread
{
public void run()
{
try
{
wsCallBack();
}
catch(Exception e)
{
}
}
}
Very simple. But it never creates the button.
Any ideas?
Thanks a lot.
You can set up a "callback" system to notify the UI when the threads complete. Have a class that extends Thread and pass to it a reference of the class that should be called at the end. If you have a list of such classes that needs to be notified create a Vector on the Thread implementation to hold them. Override the run function and after doing everything you need to do simply call a method on the UI class (iterating through the vector if needed). So your classes may look like:
public class commThread extends Thread{
MyUIClass callbackObj;
public commThread(MyUIClass myUiClass){
callbackObj = myUiClass;
}
public void run(){
//do stuff
callbackObj.callback();
}
}
and your UI class:
public MyUIClass{
public void callback(){
//refresh the UI
}
}
Of course if you have multiple threads running at the same time and calling the same UI object make sure to synchronize the callback method.
Hope this helps!
In a multi form .NetCF 3.5 application I'm trying create the forms in the background while the user is occupied with the previous form.
We're using Orientation Aware Control in the project
We use a wrapper class (FormController) (please let me know if I'm using the wrong terminology) to keep static references to the different forms in our application. Since we only want to create them once.
At the moment the Forms are created the first time they are used. But since this is a time consuming operation we'd like to do this in the background while the user
Application.Run(new FormController.StartUI());
class FormController{
private static object lockObj = new object();
private static bool secIsLoaded = false;
private static StartForm startForm = new StartForm();
private static SecForm m_SecForm;
static SecForm FormWorkOrderList
{
get
{
CreateSecForm();
return m_SecForm;
}
}
private static void StartUI(){
startForm.Show();
ThreadStart tsSecForm = CreateSecForm;
Thread trSecForm = new Thread(tsSecForm);
trSecForm.Priority = ThreadPriority.BelowNormal;
trSecForm.IsBackground = true;
trSecForm.Start();
return startForm;
}
private static void CreateSecForm()
{
Monitor.Enter(lockObj);
if(!secIsLoaded){
m_SecForm = new SecForm();
secIsLoaded = true;
}
Monitor.Exit(lockObj);
}
private static void GotoSecForm()
{
SecForm.Show();
StartForm.Hide();
}
When I call GotoSecForm() the program throws an excepton on SecForm.Show() with an exection with hResult: 2146233067 and no other valuable information.
The stacktrace of the exception is:
on Microsoft.AGL.Common.MISC.HandleAr(PAL_ERROR ar)
on System.Windows.Forms.Control.SuspendLayout()
on b..ctor(OrientationAwareControl control)
on Clarius.UI.OrientationAwareControl.ApplyResources(CultureInfo cultureInfo, Boolean skipThis)
on Clarius.UI.OrientationAwareControl.ApplyResources()
on Clarius.UI.OrientationAwareControl.OnLoad(EventArgs e)
on Clarius.UI.OrientationAwareControl.c(Object , EventArgs )
on System.Windows.Forms.Form.OnLoad(EventArgs e)
on System.Windows.Forms.Form._SetVisibleNotify(Boolean fVis)
on System.Windows.Forms.Control.set_Visible(Boolean value)
on System.Windows.Forms.Control.Show()
I'm quite qlueless about what's going wrong here. Can anyone help me out?
Or are there some better ways to load the forms in the background?
Let me know if any more information is needed.
You can't create forms (or safely do any manipulation of controls or forms) in background threads. They need to be created on the same thread that the message pump is running on - its just the way that Windows Forms work.
Creating the form itself shouldn't be in itself an expensive task. My advice would be to perform any expensive computations needed to display the form in a background thread, and then pass the result of those computations back to the main message pump in order to create and display the form itself.
(Half way through writing this I realised that this question is about windows mobile, however I'm 99% sure that the above still applies in this situation)