In WPF, there is a Closing event on <Window... tag, where we can hook up some dispose code in MainWindow_OnClosing.
But there is no such event in UWP app. The closing I guess is Unloaded, not even Unloading is there.
I just placed my disposing code there but still feel concerned. Is Unloaded event supposed for this type of work? Is there something I need to take note?
According to the MSDN, the Window class has a Closed event.
I'm mentioning this as you posted the Closing event of a window component, but keep in mind the remark of the event:
The Closed event occurs when a Window closes. However, Windows Store
apps typically use a single Window instance, and do not open and close
additional Window instances.
Now, when using the Frame navigation system of the main window with Pages, I advise you to use the OnNavigatedTo and OnNavigatedFrom events to manipulate all initialisation and dispose functionality of the class.
You may want to pay attention to the OnNavigationFrom as it is invoked immediately before the Page is unloaded and is no longer the current source of a parent Frame.
A really simple example:
Windows.ApplicationModel.Resources.ResourceLoader loader;
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
loader = new Windows.ApplicationModel.Resources.ResourceLoader();
var navigationPageContentFormat = loader.GetString("NavigationPageContent");
var navigationPageContentWhenEmpty = loader.GetString("NavigationPageContentWhenEmpty");
this.ParameterTextBlock.Text = String.Format(navigationPageContentFormat, e.Parameter?.ToString() ?? navigationPageContentWhenEmpty);
}
protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
loader = null;
}
Related
Nowadays, I am working on a java swing application using DJ NativeSwing as my embed browser to do something automatic work. The scenario of my application is that a user click start button and the embed browser auto click some position of the current page and then redirect to another one and then execute some other operations like click or something other. Now here is my solution. First, I will define a webbrowser class (extends JWebBrowser) and webbrowser listener class (implements WebBrowserListener), which represents a webbrowser and contains loadingProgressChanged, windowOpening and so on separately. Second, I define a thread class to do some logic computing and execute my browser operations as mentioned above by webbrowser.executeJavascript. At last, I add mouseListener for start and stop button to start or stop the task. When I open my application, the JFrame add the browser and its listener class. I click the start button, the browser works and will click the target position as I expected and then the page will redirect to another one. As we all know, js code can’t be executed until the page was loaded completely. So I set a global flag to check whether the page has loaded completely or not in loadingProgressChanged (code:if(e.getWebBrowser().getLoadingProgress() == 100)globalflag = true;) within webbrowser listener class. And in the thread class, I use code( while(globalflag == false){Thread.sleep(500);}) after first click to detect if the current page was loaded completely. However, when browser first click the target position and the page redirects successfully, I find that the current page has changed but blocked. After some debugging, I find it. In my thread class, browser will execute js code by webbrowser.executeJavascript("document.getElementById(‘target’).click();") to click the target position and then java code (while(globalflag == false){Thread.sleep(500);}) to detect if the current page was loaded completely and then execute some other java code. I find that the globalflag will never change and the current page’s loadingProgressChanged listener will never work because the java code (while(globalflag == false)). Because after I remove all java code after the first webbrowser.executeJavascript("document.getElementById(‘target’).click();"), the current page’s loadingProgressChanged listener works and the page was not blocked. With the DJ NativeSwing demo, I could execute my js in the loadingProgressChanged. However, I want to do a series of operations with my browser and also want to stop the task whenever need. So, I prefer to my solution for my demand rather than the provided one by demo. So, I wonder that after webbrowser.executeJavascript the DJ NativeSwing thread will wait my thread? And, in my software architecture, does anyone could have any suggestions? Thanks a lot. Any suggestion is appreciated!
PS.my application works fine with jdic-0.9.5, but it supports IE7 only.
I paste my code here to demonstrate my problem:
After I click the start button in JFrame, I will new a thread as follow
public class MyVisit implements Runnable{
private void doClick1(){
webbrowser.executeJavascript("document.getElementById('n').value='test'");
webbrowser.executeJavascript("document.getElementById('f').submit()");
}
public void run() {
globalFlag=false;
webbrowser.executeJavascript("document.getElementById(‘t’).click();") ;
while(!globalFlag){
Thread.sleep(500);
}
this.doClick1();
}
}
listener:
public class MyListener implements WebBrowserListener {
…
public void loadingProgressChanged(WebBrowserEvent e) {
if (e.getWebBrowser().getLoadingProgress() == 100) {
globalFlag=true;
}
}
}
DJ Native Swing enforces the Swing approach to threading: manipulate the components in the AWT Event Dispatch thread (a.k.a. UI thread). But also, do not block that thread, because listeners are triggered in that thread too.
So, you should not have a "while" loop in the UI thread, but should instead spawn a new thread. I hope your global variable is volatile, or AtomicBoolean or all accesses to it protected by synchronized block, otherwise you might have interesting threading side effects.
This question already has answers here:
Invoke or BeginInvoke cannot be called on a control until the window handle has been created
(8 answers)
Closed 9 years ago.
I have a WinForm screen that is also a message consumer (using Rhino ESB). If I try to update anything on the screen when I receive a message, nothing happens. A call to Invoke gives me an error that the handle is not created. The form is definitely created though, I'm firing a message on button click on the form and the background process sends a message back. It's with this return message I want to update the UI.
THIS IS NOT A DUPLICATE QUESTION, NONE OF THE SUGGESTED SOLUTIONS WORK.
I believe the difference here may be because I'm using Rhino Service bus. Rhino may be constructing a separate instance of my form rather than the one I'm using. I think what I probably need to do is to have Rhino use my instance of the form as the consumer by passing my instance into the IoC container Rhino is using. Another alternative is to move the Consumer off to it's own class and inject my Form into the consumer, and put a public method on my Form for the Consumer to use. This may work fine with my app because this is the main form and will never be disposed unless the app is closed. This would become problematic on another form that may be instantiated multiple times. Perhaps I could have my form "observe" another static object that a separate Consumer class updates. Please give suggestions as to the best approach.
public partial class MainForm : Form, ConsumerOf<MoveJobCompletedEvent>
{
public void Consume(MoveJobCompletedEvent message)
{
// This does nothing!
txtLogs.Text = "\nJob completed!";
}
}
This throws an error:
this.BeginInvoke((MethodInvoker)delegate
{
txtLogs.Text += "\nJob job completed!";
});
ERROR: Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
It seems that you're consuming a JobCompleted event before the window handle is created. You could try the following:
public partial class MainForm : Form, ConsumerOf<MoveJobCompletedEvent>
{
public void Consume(MoveJobCompletedEvent message)
{
if (!this.HandleCreated)
return;
this.BeginInvoke((MethodInvoker)delegate
{
txtLogs.Text += "\nJob job completed!";
});
}
}
I'm trying to do a simple chat application on javafx
my actual problem is the thread to insert updates into a observablelist and set it on a listview
the code im using :
String message_reçu;
try {
out = new PrintWriter(socket.getOutputStream());
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while (true) {
message_reçu = in.readLine();
if (message_reçu != null) {
messagesReçus.add(message_reçu);
}
if (message_reçu.equals("QUIT")) {
break;
}
}
in.close();
out.close();
socket.close();
I did this inside of a runnable class and once the server fire a msg the thread insert the msg on the list and shows on the listview but the thread dies instead of keep the work
I did a search on it and every one says to use a runlater but I’m completely lost there I did declare a runlater but I’m not sure how to execute it so any help is welcome
Thanks
Other Answers
This question is largely a duplicate of the following questions, so also refer to the answers to those:
Usage of JavaFX Platform.runLater and access to UI from a different thread
Platform.runLater and Task in JavaFX
Solution
Your question is little more specific than those though, so I'll provide some extra info.
For your particular code you want to wrap the add call in Platform.runLater:
Platform.runLater(new Runnable() {
public void run() {
messagesReçus.add(message_reçu);
}
});
Everything else in your example stays as it is.
Background Information
JavaFX UI updates must be made on the JavaFX application thread or there is a high likelihood that your program will malfunction in unexpected ways.
The ListView control listens for changes to the ObservableList backing the ListView cell values. When that list changes, a UI update is immediately triggered on the thread the originally updated the list.
Once you wrap the list modifications in Platform.runLater, you ensure that the subsequently triggered UI update is performed on the JavaFX application thread rather than your user thread.
Hi noticed some code in our application when I first started Java programming. I had noticed it created a dialog from a separate thread, but never batted an eye lid as it 'seemed to work'. I then wrapped this method up through my code to display dialogs.
This is as follows:
public class DialogModalVisibleThread
extends Thread {
private JDialog jDialog;
public DialogModalVisibleThread(JDialog dialog, String dialogName) {
this.setName("Set " + dialogName + " Visable");
jDialog = dialog;
}
#Override
public void run() {
jDialog.setVisible(true);
jDialog.requestFocus();
}
}
Usage:
WarnUserDifferenceDialog dialog = new WarnUserDifferenceDialog( _tableDifferenceCache.size() );
DialogModalVisibleThread dmvt = new DialogModalVisibleThread( dialog, "Warn User About Report Diffs");
dmvt.start();
Now, as far as I am now aware, you should never create or modify swing components from a separate thread. All updates must be carried out on the Event Dispatch Thread. Surely this applies to the above code?
EDT on WikiPedia
However, the above code has worked.
But lately, there have been countless repaint issues. For example, click on a JButton which then calls DialogModalVisibleThread to display a dialog. It caused buttons alongside the clicked button not to redraw properly.
The repaint problem is more frequent on my machine and not the other developers machine. The other developer has a laptop with his desktop extended onto a 21" monitor - the monitor being his main display. He is running Windows 7 with Java version 1.6.0_27.
I am running on a laptop with Windows 7 and Java version 1.6.0_24. I have 2 additional monitors with my desktop extended onto both.
In the meantime I am going to upgrade to Java 1.6 update 27.
I wondered if the above code could cause repaint problems or are there any other people out there with related paint issues?
Are there any easy ways to diagnose these problems?
Thanks
So, you're breaking a rule, having problems, and wondering if these problems could be cause by the fact that you broke the rule. The answer is Yes. Respect the rules!
To detect the violations, you might be interested by the following page: http://weblogs.java.net/blog/2006/02/16/debugging-swing-final-summary
The easiest way to check if your problems are being caused by breaking the rules is to fix them (You should fix them anyway :-)
Just use SwingWorker.invokeLater() from the thread you want to update to UI from to easily adhere to Swing's contract. Something like this should do the trick:
#Override
public void run() {
SwingUtilities.invokeLater(new Runnable() {
jDialog.setVisible(true);
jDialog.requestFocus();
}
});
}
EDIT: You should make the 'jDialog' variable final for this to work.
How can you make a background web request and then update the UI, but have all the code that does the web requesting/parsing in a separate class so you can use it in multiple places? I thought I could use the classes methods as event handlers for a BackgroundWorker class, like
APIHelper mHelper = new APIHelper("http://example.com?foo=bar");
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork +=new DoWorkEventHandler(mHelper.GetResponse);
bw.RunWorkerCompleted +=new RunWorkerCompletedEventHandler(mHelper.HandleResponse);
bw.RunWorkerAsync();
where APIHelper has the method
public void GetResponse(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker) sender;
WebRequest request = HttpWebRequest.Create(this.URL);
IAsyncResult result = (IAsyncResult)
request.BeginGetResponse(ResponseCallback, request);
}
but then I don't know how to access the worker thread from ResponseCallback and, anyway, HandleResponse gets called first (obviously). (I tried putting in result.AsyncWaitHandle.WaitOne(); but I get a NotSupportedException error.) Yet I can't work out how to make the web request call synchronously. I'm clearly trying to go about this the wrong way, but I have no idea what the right way is.
ETA:
My aim is to be able to go:
user clicks (a) button(s) (on various pages)
a "working" message is displayed on the UI thread (and then input is blocked)
in a background thread my APIHelper class makes the relevant API call, gets the response, and passes it back to the UI thread; I only seem to be able to do this by starting another thread and waiting for that to return, because there's no synchronous web requests
the UI thread updates with the returned message (and input continues as before)
I can do the first two bits, and if I have the response, I can do the last bits, but I can't work out how to do the middle bit. Hopefully that made it clearer!
It took me several tried before I found there is a Dispatcher.
During the BackgroundWorker's dowork and complete methods you can call:
this.Dispatcher.BeginInvoke(() =>
{
// UPDATE UI BITS
});
I think the Dispatcher is only available in the view. So I'm not sure if the methods can exist outside of the xaml.cs
Put whatever you want to update in your UI; when updating an ObservableCollection you must do the update of you items in the Dispatcher.BeginInvoke too
This link might be a good read too:
http://www.windowsphonegeek.com/articles/All-about-Splash-Screens-in-WP7-ndash-Creating-animated-Splash-Screen
Update to assist notes
This is just a rough idea mind you...
bw.DoWork +=new DoWorkEventHandler(DoWork);
bw.RunWorkerCompleted +=new RunWorkerCompletedEventHandler(Complete)
// At least I think the EA is DoWork....
public void DoWork(object sender, DoWorkEventArgs e)
{
mHelper.GetResponse();
this.Dispatcher.BeginInvoke(() =>
{
UIObject.Visibility Collapse.
});
// Wait and do work with response.
});
}
public void Complete(object sender, RunWorkerCompleteEventArgs e)
{
this.Dispatcher.BeginInvoke(() =>
{
UIObject.Visible ....
});
}
I'd put all this logic in a viewmodel that the viewmodel of each page inherits from.
Have the pages bind to properties on the viewmodel (such as ShowLoading, etc.) which the model updates appropriately. i.e. before making the webrequest and in the callback.
As you won't be running the viewmodel code in the UI thread you also wouldn't need to run in a separate BackgroundWorker and you'll be able to access the properties of the viewmodel without issue.
It might be useful if you use a helper class that I have developed for WebDownload purposes during WP7 development.
I'm using it in 2-3 WP7 apps and no problem so far. Give it a go to see if it helps. You can get the class from the my blog linked bellow:
http://www.manorey.net/mohblog/?p=17#content
[NOTE] When working with this class you don't need to run anything in a background worker or new thread; it handles it all asynchronously.