i wrote a small application, which among other things makes a REST call to a JIRA REST API do download issues. I have a progress bar indicating the progress of the download. However, actually i need to make two REST calls. The first one needs to finished before the second one starts. Between them i need to update the UI.
Below is some example code:
// Loads the dialog from the fxml file and shows it
#FXML
public void showProgressDialog() {
mainApp.showDownloadProgressDialog();
}
// Retrieves some meta information
public void firstDownload() {
Task<Void> task = new Task<Void>() {
#Override
public Void call() {
// do something
}
};
new Thread(task).start();
}
// Do some UI update
// Retrieves the actual issues
public void secondDownload() {
Task<Void> task = new Task<Void>() {
#Override
public Void call() {
for (int i = 0; i < limit; i++) {
// so something
updateProgress((double) i / (double) limit, max);
}
}
};
new Thread(task).start();
}
// Do some UI update
How can i ensure that all functionality shown above is executed in exactly this order?
Thanks for any help!
You could use a EcecutorService with a single thread to control the scheduling:
ExecutorService service = Executors.newSingleThreadExecutor();
service.submit(task1);
service.submit(task2);
// shutdown after last submitted task
service.shutdown();
Related
I'm making a program which sends some data to the Matlab and receives output from matlab. To do that, I used matlabcontrol library.
Problem
After I click Java FX application button to submit data, matlabcontrol opens Matlab for further calculations. But when java opens the matlab, Java FX application stuck with wait cursor.Then starts to work again after Matlab finishes the process of calculation.
What I did
public void runner()
{
Platform.runLater(new Runnable()
{
#Override
public void run()
{
firstFunc();
}
});
Platform.runLater(new Runnable()
{
#Override
public void run()
{
secondFunc();
}
});
}
public void firstFunc()
{
// This function controls UI while Matlab does it's calculations
double progress = 0.2;
progressLabel.setText(progress*100+"% Completed");
progressBar.setProgress(progress);
}
public void secondFunc()
{
// This method creates matlab connection and handle matlab
firstClass mainFunc = new firstClass(pathSelected);
mainFunc.func();
}
So I used Platform runLater to run two methods separately. But still my program stuck with wait cursor when Matlab starts to functioning.
I also used threads to run these functions in parallel. But had the same issue. How can I correct this. Any help?
Update
As described in this question, I did use service and task with countdownlatch. But still didn't get what I wanted. In there,
Service<Void> service = new Service<Void>() {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
//Background work
final CountDownLatch latch = new CountDownLatch(1);
Platform.runLater(new Runnable() {
#Override
public void run() {
try{
//FX Stuff done here
firstFunc();
}finally{
latch.countDown();
}
}
});
latch.await();
//Keep with the background work
// I added matlab calling function here.
secondFunc();
return null;
}
};
}
};
service.start();
latch await and let background work to carry on. But in my case, my FX application shows a progress bar. So it should always update while background task happens. In here, it finishes FX task and moves to background task. I didn't get what I wanted. please help.
I had to use Service, Task and CountDownLatch to accomplish this task as I mentioned in Question Update part.
Also, I had to run another task inside the firstFunc, where I did update the progress. Like in this answer.
I'd like to effectively "poll" on a JavaFX TableView so that if a job is created in the database by another user the current user would pick it up (let's say every 5 seconds).
I have tried using Timer;
new Timer().schedule(new TimerTask() {
#Override
public void run() {
try {
newI(connection, finalQuery, adminID);
} catch (SQLException e) {
e.printStackTrace();
}
}
}, 0, 5000);
However this gets the following error: Exception in thread "Timer-0" java.lang.IllegalStateException: This operation is permitted on the event thread only; currentThread = Timer-0 which I assume means that it is not supported in JavaFX? How am I able to periodically update the TableView in JavaFX?
You can use a ScehduleService- something like this...
private class MyTimerService extends ScheduledService<Collection<MyDTO>> {
#Override
protected Task<Collection<MyDTO>> createTask() {
return new Task<Collection<MyDTO>>() {
#Override
protected Collection<MyDTO> call() throws ClientProtocolException, IOException {
//Do your work here to build the collection (or what ever DTO).
return yourCollection;
}
};
}
}
//Instead of time in your code above, set up your schedule and repeat period.
service = new MyTimerService () ;
//How long the repeat is
service.setPeriod(Duration.seconds(5));
//How long the initial wait is
service.setDelay(Duration.seconds(5));
service.setOnSucceeded(event -> Platform.runLater(() -> {
//where items are the details in your table
items = service.getValue();
}));
//start the service
service.start();
I'm working on a Minecraft Bukkit plugin, I know how to handle events and everything, but I'm not sure how to do this. I haven't actually written the code yet so here's a basic example of what I want to do:
public void playerDead() {
runCommand(commandHere)
//Wait 2 minutes.
runCommand(otherCommandHere
}
I just need the part to wait two minutes. Everything else is covered.
EDIT2: Seems I need to reset the delay to the beginning if someone else dies while it's going. Any suggestions?
Since I see you want to perform your action after the player has died. Then for sure you don't want to halt the main Thread with Thread.sleep(x);
What you can do is create a cooldown for the player that passed away.
public Map<String, Long> cooldown = new HashMap<String, Long>();
Long time = cooldown.get(player.getName());
if(time - System.currentTimeMillis() > 10*1000)
cooldown.put(player.getName(), System.currentTimeMillis());
else
int remains = (int)Math.floor(10 - System.currentTimeMillis());
Code reference here.
Or you can create your task to run like this:
Bukkit.getScheduler().scheduleSyncDelayedTask(plugin, new Runnable()
{
public void playerDied()
{
// Your code here.
}
}, <delay in ticks>);
Get a reference to your plugin and pass it as the parameter plugin. Or if you are lazy just write it inside the plugin and pass it this.
You should use the BukkitScheduler provided by Bukkit.
You have to save the BukkitTask object returned by the Scheduler.runTaskLater(...) method to use it later.
Every time playerDead() is called, you can reset the delay by cancelling and restarting the task.
BukkitTask task;
public void playerDead() {
// Command here
if (task != null) {
task.cancel();
}
task = getServer().getScheduler().runTaskLater(Plugin, new Task(), 2400L);
}
public class Task extends BukkitRunnable {
#Override
public void run() {
// Other command here
task = null;
}
}
You may try like this:
new Timer().schedule(new TimerTask() {
#Override
public void run() {
runCommand(commandHere);
}
}, 120000);
I am wanting to execute a task at a regular interval from my JavaFX application. The task pulls data from a remote stream.
While I know I could use a Timer as suggested below:
JavaFX periodic background task
I believe this should be able to be done using the JavaFX Service object. There's mention in the Javadoc about specifying a custom executor (ScheduledThreadPoolExecutor comes to mind here), but how would one specify the period and delay? Ideally, this would use the Service's usual start, reset, restart, and state bindings...
public class MyFirstLineService extends Service<String> {
private StringProperty url = new SimpleStringProperty(this, "url");
public final void setUrl(String value) { url.set(value); }
public final String getUrl() { return url.get(); }
public final StringProperty urlProperty() { return url; }
public MyFirstLineService() {
setExecutor(new ScheduledThreadPoolExecutor());
}
protected Task createTask() {
final String _url = getUrl();
return new Task<String>() {
protected String call() throws Exception {
URL u = new URL(_url);
BufferedReader in = new BufferedReader(
new InputStreamReader(u.openStream()));
String result = in.readLine();
in.close();
return result;
}
};
}
}
A ScheduledService was requested in the JavaFX issue tracker - RT18702.
The tracker includes source for a preliminary implementation which has not been incorporated in the 2.2 branch. If needed, you could take a look at that source and see if it helps improve on your solution.
I have found a way to do this, building on the comments from sarcan above...
One can create a Timeline object, normally used to animate UI elements, as a timer that operates on the FX Application Thread. Using this its possible to restart the Service object, which then performs the long-running operation on a background thread, yet preserves property access and updates via the FX Application Thread bindings.
Ex:
final MyFirstLineService svc = new MyFirstLineService();
final Duration oneFrameAmt = Duration.seconds(5);
final KeyFrame oneFrame = new KeyFrame(oneFrameAmt,
new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent evt) {
svc.restart();
}
});
Timeline timer = TimelineBuilder.create()
.cycleCount(Animation.INDEFINITE)
.keyFrames(oneFrame)
.build();
timer.playFromStart();
Run into the same problem. An example with ScheduledThreadPoolExecutor could be:
ScheduledExecutorService executor = Executors.newScheduledThreadPool(5);
Service s = new Service(){
#Override
protected Task<String> createTask() {
return new Task<String>() {
#Override
protected String call() throws Exception {
// code...
}
};
}
}
// created tasks shall be run in thread pool
s.setExecutor(executor);
// start the service the first time
s.start();
// restart the service every 5 seconds
s.scheduleWithFixedDelay(new Runnable() {
#Override
public void run() {
// need runLater here since trigger needs to be in the javaFX thread
Platform.runLater(new Runnable() {
#Override
public void run() {
checker.restart();
}
});
}
}, 0, 5, TimeUnit.SECONDS);
}
Could be solved with a Timer but then you lost the JavaFX data binding capability (as you already mentioned). Looking forward to Java8!
I have two buttons and when the user click the first one it will start a thread to update the UI, and when the user click the second one the app will set a boolean variable for the first thread to not allow it to update the thread and then it will start the second one. This is my Runnable :
class MyRunnable implements Runnable {
boolean isUpdateEnabled = true;
#Override
public void run() {
// Retrieve list from Internet. takes about 10 sec to complete.
if (isUpdateEnabled) {
runOnUiThread(new Runnable() {
public void run() {
System.out.print("Update UI");
}
});
}
}
void enableUpdate(boolean enable) {
isUpdateEnabled = enable;
}
}
but since the thread will take a time to complete, if the user press the first button again can i check if the first thread is alive and then enable it to update the thread while guarantee that the code inside if (isUpdateEnabled) will execute if or what the right way to do it?
...
// on button click
if(thread.isAlive())
runnable.enableUpdate(true);
...
I suppose you will need to do two things here :
Synchnorize access to isEnableUpdate, because two different threads are accessing it.
You may want to break your code in public void run into smaller chunks, and check the isEnableUpdate variable every once in a while when you finish some logical piece of work or something like that.
Sample :
class MyRunnable implements Runnable
{
boolean isUpdateEnabled = true;
Object myUpdateLockObj = new Object();
#Override
public void run() {
// Retrieve list from Internet. takes about 10 sec to complete.
if (isUpdateEnabled) {
runOnUiThread(new Runnable() {
public void run() {
lock(myUpdateLockObj)
{
if (!isUpdateEnabled) return;
}
//do work in parts
System.out.print("Update");
lock(myUpdateLockObj)
{
if (!isUpdateEnabled) return;
}
// do work in parts
System.out.print(" UI");
}
});
}
}
void enableUpdate(boolean enable)
{
synhronized(myUpdateLockObj)
{
isUpdateEnabled = enable;
}
}
}