In before, I know sub thread cant call unity api which can only be called in unity main thread. but recently I wirte a demo. it works , I am confused. Could someone tell me the reseaon. I use unity in version 2019.4.
code just like this:
public void TestThread(){
Thread thread = new Thread( ()=>{
Thread.Sleep(3300);
TestUnityFun();
} );
thread.Start();
}
public void TestUnityFun()
{
if (testGameOB != null)
{
testGameOB.SetActive(!testGameOB.activeSelf);
}
}
Could someone tell me the reseaon. Thanks
This may cause crash in a low probability on android.
Related
My C# app has lots of forms to perform various tasks. To keep things simple, I have a static class FormsCollection where the instances of each of the other forms are kept, so that they are shown and hidden from one place.
Now i was getting that classic debug time "Cross-thread" error. I tried to fix it the following way:
public class FormsCollection : Control // inherited from Control only to be
// able to call "this.Invoke"
{
public delegate void ShowFormDelegate(Form form);
public static Main mainForm;
// and many other forms...
public void ShowForm(Form form)
{
if (form.InvokeRequired)
{
ShowFormDelegate delegateFunc = new ShowFormDelegate(ShowForm);
this.Invoke(delegateFunc, new object[] { form });
}
else
{
previousForm = currentForm;
currentForm.Hide();
currentForm = form;
currentForm.Show();
}
}
}
Inside the user/caller forms, i simply make an object of FormsCollection and call the ShowForm method (almost a 100 such calls):
FormsCollection f = new FormsCollection();
f.ShowForm(FormsCollection.mainForm);
And after all this ordeal, what i get is that the same error appears at the very same spot as before! What an irony! :)
What am i doing wrong? Please help me out....
I got extremely hard-to-find answer to this problem from this slightly irrelevant page. Following is the updated code for any struggling programmers looking for a work around to this problem:
public void Show(Form nextForm)
{
Thread thread = new Thread(
new ThreadStart(() =>
{
PreviousForm.BeginInvoke(
new Action(() =>
{
PreviousForm = CurrentForm;
CurrentForm = nextForm;
PreviousForm.Hide();
CurrentForm.Show();
}
));
}
));
thread.Start();
}
This seems to have resolved the cross-thread problem that i was facing despite several work-arounds. It is working as yet without raising any exceptions and I have tested almost all the scenarios of my app going back and forth from form to form.
I have a question about using external c++ library (irrKlang.dll) which is an audio playback engine. Now, the problem is that when I get a SoundStopped event out of it, and do an action in the main form, all kinds of stack related errors arise. Let me show the code:
namespace WindowsFormsApplication4
{
public class IsoundFinished : ISoundStopEventReceiver
{
public delegate void OnSoundStoppedEventHandler(object source, EventArgs e);
public event OnSoundStoppedEventHandler IStopped;
public void OnSoundStopped(ISound iSound, StopEventCause reason, object userData)
{
if (reason.ToString() == "SoundFinishedPlaying")
IStopped?.Invoke(this, EventArgs.Empty);
}
}
}
That is an extended class for me to do custom actions (for example - if sound finished, raise the event...) I am creating an instance of it, for the event action to get exposed in my main Form1 class:
IsoundFinished iStopReceiver = new IsoundFinished();
Now in my main form, I have this line in my Form1() method, just under my InitializeComponent():
iStopReceiver.IStopped += new soundFinished.OnSoundStoppedEventHandler(OnStopped);
It's for subscribing to the event handler. And finally - my OnStopped() method which is supposed to do stuff when the song ends it's playback - it's on the same Form1:
private void OnStopped(object sender, EventArgs e)
{
if (InvokeRequired)
{
Invoke(new Action<object, EventArgs>(OnStopped), sender, e);
return;
}
btnStop1.PerformClick();
}
My Stop1 button method is (for those who work with the IrrKlang) ISound.Stop(); and few more lines of code, dealing with the display of playlist and so on. Although I have invoked it from the main UI thread - which should provide me with some degree of thread misalignment protection, all kinds of errors appear, mostly
Cannot evaluate expression because a native frame is on the top of the call stack.
Of course, if I do it without event handler, ISound.Stop(); drops the sound from the engine, like it should. I know something wrong is happening with the threads, but I can't figure out what's going on. If someone would give me few tips, I'd appreciate that a lot.
Well it seems I've solved it myself ! It's all about understanding how the threads are working in Visual C#. The problem was this : I was actually PAUSING the background thread where my audioengine was triggering the event - so 'till I performed an action after INVOKE in the main UI thread, background thread was paused along with the whole irrKlang engine. It was unable to purge itself properly, so it's call stack got clogged!
Using BEGININVOKE solved the problem, as it doesn't PAUSE the background task. It lets it run instead. Diagram on this answer gave me much needed piece of info I was looking for.
Maybe someone will need this answer too, glad I helped myself :P
private void OnStopped(object sender, EventArgs e)
{
if (InvokeRequired)
{
BeginInvoke(new Action<object, EventArgs>(OnStopped), sender, e);
return;
}
btnStop1.PerformClick();
}
I have a problem while working with JavaFX and Threads. Basically I have two options: working with Tasks or Platform.runLater. As I understand Platform.runLater should be used for simple/short tasks, and Task for the longer ones. However, I cannot use any of them.
When I call Thread, it has to pop up a captcha dialog in a middle of task. While using Task, it ignores my request to show new dialog... It does not let me to create a new stage.
On the other hand, when I use Platform.runLater, it lets me show a dialog, however, the program's main window freezes until the pop up dialog is showed.
I need any kind of solution for this. If anyone knows how to deal with this or had some similar experience and found a solution I am looking forward to hearing from you!
As puce says, you have to use Task or Service for the things that you need to do in background. And Platform.runLater to do things in the JavaFX Application thread from the background thread.
You have to synchronize them, and one of the ways to do that is using the class CountDownLatch.
Here is an example:
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
}finally{
latch.countDown();
}
}
});
latch.await();
//Keep with the background work
return null;
}
};
}
};
service.start();
Use a Worker (Task, Service) from the JavaFX Application thread if you want to do something in the background.
http://docs.oracle.com/javafx/2/api/javafx/concurrent/package-summary.html
Use Platform.runLater from a background thread if you want to do something on the JavaFX Application thread.
http://docs.oracle.com/javafx/2/api/javafx/application/Platform.html#runLater%28java.lang.Runnable%29
It's too late to answer but for those who have the error, here is the solution XD
You can use one Thread.
Use the lambda expression for the runnable in the thread and the runlater.
Thread t = new Thread(() -> {
//Here write all actions that you want execute on background
Platform.runLater(() -> {
//Here the actions that use the gui where is finished the actions on background.
});
});
t.start();
You can user directly this code
Don't forget you can't send non-final variable in thread .
you can send final variable in thread
//final String me="ddddd";
new Thread(new Runnable() {
#Override
public void run() {
// me = me + "eee";
//...Your code....
}
}).start();
Use in
your code
try/catch
I am developing a Java-ME Based Mobile Application. Now My Requirements are like whenever I am updating one of my RMS, I want my application to be stay in a Freeze kind of mode; which means no other action like clicking button or anything else should happen. My Method is already "Synchronized".
Kindly guide me regarding this question.
Thanks.
The best way to handle this is to "serialize" your tasks. You can do this with a message queue - a class that maintains a Vector of message objects (tasks) and runs code based on each message. The queue runs on a thread that processes each task (message) in series. You create a simple message class for the different tasks - read RMS etc. A message can be an Integer if you like that wraps a number. The operation of adding and retrieving messages is synchronized but the code than does the tasks is not and runs on a simple switch block. The benefit of serializing your tasks is you don't have to worry about concurrency. Here is some of the essential code from a class I use to do this.
class MessageQueue implements Runnable{
Vector messages;
Thread myThread;
volatile boolean stop;
public void start() {
stop=false;
myThread=new Thread(this);
myThread.start();
}
// add message to queue - this is public
public synchronized void addMessage(Message m) {
messages.addElement(m);
if(stop) {
start();
} else {
// wake the thread
notify();
}
}
// get next message from queue - used by this thread
private synchronized Message nextMessage() {
if(stop) return null;
if(messages.isEmpty()) {
return null;
} else {
Message m=(Message)messages.firstElement();
messages.removeElementAt(0);
return m;
}
}
public void run() {
while (!stop) {
// make thread wait for messages
if (messages.size() == 0) {
synchronized (this) {
try {
wait();
} catch (Exception e) {
}
}
}
if (stop) {
// catch a call to quit
return;
}
processMessage();
}
}
}
// all the tasks are in here
private void processMessage() {
Message m = nextMessage();
switch (m.getType()) {
case Message.TASK1:
// do stuff
break;
case Message.TASK2:
// do other stuff
break;
case Message.TASK3:
// do other other stuff
break;
default: //handle bad message
}
}
}
What you are asking is very code depended. Usually when you want to make some synchronic actions you just write them one after the other. in java it's more complected, since sometimes you "ask" the system to do something (like repaint() method). But since the RMS read/write operations are very quick (few millisecond) i don't see any need in freesing.
Could you please provide some more information about the need (time for RMS to respond)? does your code runs on system thread (main thread) or your own thread?
I want my application to be stay in a Freeze kind of mode; which means no other action like clicking button or anything else should happen.
First of all I would strongly advise against real freezing of UI - this could make a suicidal user experience for your application.
If you ever happened to sit in front of computer frozen because of some programming bug, you may understand why approach like this is strongly discouraged. As they describe it in MIDP threading tutorial, "user interface freezes, the device appears to be dead, and the user becomes frustrated..."
This tutorial by the way also suggests possibly the simplest solution for problems like you describe: displaying a wait screen. If you don't really have reasons to avoid this solution, just do as tutorial suggests.
To be on a safe side, consider serializing tasks as suggested in another answer. This will ensure that when RMS update starts, there are no other tasks pending.
I have a j2me midlet running on a cell phone. The code works fine, but the issue that comes up is that the program seems to be running more than one instance of itself. I have code at the beginning of the application inside the appStart() method that runs twice when the application starts. During the lifetime of the program, the code can be seen running twice when text is written to the screen.
The code looks like this:
public MyClass()
{
form = new Form("MyProgram");
cmdClose = new Command("EXIT", Command.EXIT, 1);
form.addCommand(cmdClose);
form.setCommandListener(this);
display = Display.getDisplay(this);
display.setCurrent(form);
}
public void startApp()
{
form.append("App starting\n");
// Rest of program
}
I have no idea why the code is being called twice.
I'm coding on the i290.
This is definitely a JVM bug. startApp() should be called only once at startup and can't be called again until pauseApp() is called or you call notifyPaused() yourself.
What I suggest is the following code:
private boolean midletStarted = false;
public void startApp() {
if (!midletStarted) {
midletStarted = true;
//Your code
}
}
This way you can track midlet state changes. But in fact it is better that you don't use this method at all and use constructor instead.
Oh, by the way, I don't think that there are some multiple instances or something like that, this is merely a JVM error.
Maybe you did something that made the runtime call pauseApp() and then when you set the focus to the app the runtime called startApp() again.
Put logging in pauseApp() and see what happens.