How to get ISelectionService outside of UI-Thread - eclipse

I am trying to find the currently selected Project/File and all ways I found so far are using the ISelectionService. The way I found to get an instance of it is:
ISelectionService selectionService = PlatformUI.getWorkbench()
.getActiveWorkbenchWindow().getActivePage();
But unfortunatly .getActiveWorkbenchWindow() returns null since I am not inside the UI-Thread. Is there any good way to get the ISelectionService from outside the UI-Thread?

You can use:
Display.getDefault().synchExec(runnable);
to run a Runnable in the UI thread where you can get the selection service.
However most UI code expects to be run in the UI thread so you may need to use syncExec or asyncExec for anything that is to do with the UI.

Most likely you are following the wrong appraoch. You should obtain the selected project or file before you run the non-UI/background thread.
If your background thread is triggered by a user interaction and should operate on the selected resource (project/file) the selection may well have changed when the thread reaches the point where it queries the selection.
Instead, evaluate the selection on the UI thread and pass the extracted resource as a parameter to your background thread.
For example (simplified code):
// on the UI thread:
IResource resource = ( IResource )getSelectionService().getSelection().getFirstElement();
new Thread( new Runnable() {
public void run() {
resource.copy( ... ); /// or whatever should be done with the resource
}
} ).start();

Related

Background Process as NSOperation or Thread to monitor and update File

I want to check if a pdf file is changed or not, and if is changed i want to update the corresponding view. I don't know if it's more suitable to use a background process as a Thread or as an NSOperation to do this task. The Apple Documentation says: "Examples of tasks that lend themselves well to NSOperation include network requests, image resizing, text processing, or any other repeatable, structured, long-running task that produces associated state or data.But simply wrapping computation into an object doesn’t do much without a little oversight".
Also, if I understood correctly from the documentation, a Thread once started can't be stopped during his execution while an NSOperation could be paused or stopped and also they could rely on dependency to wait the completion of another task.
The workflow of this task should be more or less this diagram:
Task workflow
I managed to get the handler working after the notification of type .write has been sent. If i monitor for example a *.txt file everything works as expected and i receive only one notification. But i am monitoring a pdf file which is generated from terminal by pdflatex and thus i receive with '.write' nearly 15 notification. If i change to '.attrib' i get 3 notification. I need the handler to be called only once, not 15 or 3 times. Do you have any idea how can i do it or is not possible with a Dispatch Source? Maybe there is a way to execute a dispatchWorkItem only once?
I have tried to implement it like this(This is inside a FileMonitor class):
func startMonitoring()
{
....
let fileSystemRepresentation = fileManager.fileSystemRepresentation(withPath: fileStringURL)
let fileDescriptor = open(fileSystemRepresentation, O_EVTONLY)
let newfileMonitorSource = DispatchSource.makeFileSystemObjectSource(fileDescriptor: fileDescriptor,
eventMask: .attrib,
queue: queue)
newfileMonitorSource.setEventHandler(handler:
{
self.queue.async
{
print(" \n received first write event, removing handler..." )
self.newfileMonitorSource.setEventHandler(handler: nil)
self.test()
}
})
self.fileMonitorSource = newfileMonitorSource
fileMonitorSource!.resume()
}
func test()
{
fileMonitorSource?.cancel()
print(" restart monitoring ")
startMonitoring()
}
I have tried to reassign the handler in test(), but it's not working(if a regenerate the pdf file, what is inside the new handler it's not executed) and to me, doing in this way, it seems a bit boilerplate code. I have also tried the following things:
suspend the DispatchSource in the setEventHandler of startMonitoring() (passing nil), but then when i am resuming it, i get the remaining .write events.
cancel the DispatchSource object and recall the startMonitoring() as you can see in the code above, but in this way i create and destroy the DispatchSource object everytime i receive an event, which i don't like because the cancel() function shoul be called in my case only when the user decide to disable this feauture i am implementing.
I will try to write better how the workflow of the app should be so you can have an more clear idea of what i am doing:
When the app starts, a functions sets the default value of some checkboxes of the window preference. The user can modify this checkboxes. So when the user open a pdf file, the idea is to launch in a background thread the following task:
I create a new queue call it A and launch asynch an infinite while where i check the value of the UserDefault checkboxe (that i use to reload and update the pdf file) and two things could happen
if the user set the value to off and the pdf document has been loaded there could be two situations:
if there is no current monitoring of the file (when the app starts): continue to check the checkboxe value
if there is currently a monitoring of the file: stop it
if the user set value to on and the pdf document has been loaded in this background thread (the same queue A) i will create a class Monitor (that could be a subclass of NSThread or a class that uses DispatchSourceFileSystemObject like above), then i will call startMonitoring() that will check the date or .write events and when there is a change it will call the handler. Basically this handler should recall the main thread (the main queue) and check if the file can be loaded or is corrupted and if so update the view.
Note: The infinite while loop(that should be running in the background), that check the UserDefault related to the feature i am implementing it's launched when the user open the pdf file.
Because of the problem above (multiple handlers calls), i should use the cancel() function when the user set checkboxe to off, and not create/destroy the DispatchSource object everytime i receive a .write event.

MVVM, wait cursor while opening "slow" page

I have MVVM application with multiple pages. My all pages have ReadCommand() bound with:
<i:Interaction.Triggers>
<i:EventTrigger EventName="Loaded">
<i:InvokeCommandAction Command="{Binding ReadCommand}" CommandParameter="{Binding}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
This is my Read() command in ViewModel:
private void Read(object parameter)
{
HwDevice Device = new HwDevice();
this.Alarms = Device.Alarms; // this is slow (reading data from RS232 device)
Device.Dispose();
}
One page has slow data source and my application is frozen when this page is being loaded (about 5 seconds).
I want to set wait cursor on whole window, but I don't know how to do it in MVVM (Im MVVM newbie). Do I have to pass window reference by command parameter and set Wait cursor in command? If I should - how can I do it in XAML?
The problem is that the thread where you are going to execute your operation, is the same where your UI live. It's here that the BackgroundWorker come in handy.
BackgroundWorker bw = new BackgroundWorker();
bw.RunWorkerAsync += bw_DoWork;
bw.ProgressChanged += bw_ProgressChanged;
bw.RunWorkerCompleted += bw_WorkDone
The previous part was the declaration. Now you need to implement the events, but first modify Read method
private void Read(object parameter)
{
bw.RunWorkerAsync(parameter);
// put your logic here
}
private void bw_DoWork(object sender, DoWorkEventArgs e)
{
object parameter = e.Argument;
}
Now that the logic is placed on another thread, you can use the progressChanged method to do various stuff. Like showing a progress bar to report the status, or simply enable or disable your wait cursor.
EDIT: You don't need to pass the bw to the UI. If you are using MVVM (like you should and you are doing) you can use bindings and event at your advantage, or implement an interface like this one. The point of the whole thing is that the UI is just "informed" that something on the background is going on, avoiding to freeze the main thread. You just need to decide how to display it. So it can be either using a wait cursor, or implementing a progress bar.

EditorExit event handler called recursively

The below portion of my code caused recursive call on onEditorExit method. If I remove setData call, then no recursion occur.
What can be the workaround?
myGrid.addEditorExitHandler(new EditorExitHandler() {
public void onEditorExit(EditorExitEvent event) {
GWT.log("Hello");
myGrid.setData(new ListGridRecord());
}
});
Now check the console output -
Console Screenshot
It won't work because each time you call setData() the editor will fire an editorExit event in an infinite loop (not recursively). By the way, calling setData() in the way you are doing will replace all your records in the ListGrid with one new empty record. This seems like a disconcerting user experience.
It looks like you want to create and start editing a new record when you tab out of the last one. In order to do that in a ListGrid, you use:
grid.setListEndEditAction(RowEndEditAction.NEXT);
That's all you need to do in order to get it working.

Handle Window close event

I'm trying to handle the event when the close button of a Window is clicked:
// View Code
#Override
public void attachWindowListener(WindowListener listener) {
window.addWindowListener(listener);
}
// Presenter code
view.attachWindowListener(new WindowListener(){
public void windowHide(WindowEvent we) {
GWT.log("Window Event - Processing fields");
processFields();
}
});
However, the windowHide function seems to be not executed since I can't see the log I placed there.
How to properly handle that event?
How about
Window.addCloseHandler(
new CloseHandler<Window>()
{
public void onClose( CloseEvent<Window> windowCloseEvent )
{
// Do your worst here
}
} );
I usually put this in onModuleLoad() in my EntryPoint class.
Cheers,
Based on the information provided I would guess that either a.) the events you think are firing do not fire for the Window component (even if it seems like they should) or b.) the events are firing but in a different order than you expect.
For example, it's possible that a BrowserEvent or some other event is firing first as the window is being closed and the Window object's WindowEvent never fires. According to the API docs for GXT 2.x, the WindowEvent will fire on hide and deactivate but it does not specify that it fires on close. The GXT 3.0.x API doc is less clear on this point but I would assume the same behavior. Unfortunately Sencha does not provide good documentation on what events fire for a given component and in what order.
With that said, I have had some luck working through similar issues to this by using a debug class which outputs all the events on a component to which it is attached. This may shed some light on which events are firing and their order of execution, and you may find an optimal event to which you can attach your processFields() method.
For a good example of a debugger class, see this answer from a related post: https://stackoverflow.com/a/2891746/460638. It also includes an example of how to attach the debugger to your component.
API Doc for Window, GXT 2.x: http://dev.sencha.com/deploy/gxt-2.2.5/docs/api/com/extjs/gxt/ui/client/widget/Window.html
API Doc for Window, GXT 3.0.x: http://dev.sencha.com/deploy/gxt-3.0.0/javadoc/gxt/com/sencha/gxt/widget/core/client/Window.html
This worked:
window.addListener(Events.Hide, new Listener<ComponentEvent>() {
#Override
public void handleEvent(ComponentEvent be) {
// Do stuff
}
});

pause viewmodel process for user input

I've been looking at a view examples of the typical "raise dialog from viewmodel" problem, noting 3 main solutions:
use attached behaviors
use a mediator pattern
use a service
I'm getting a bit bogged down though and struggling to find a solution that easily fits into my problem space - which is a very simple file copy problem:
My viewmodel is processing a loop (copying a list of files)
When a file already exists at the destination I need to raise a modal dialog to get confirmation to replace
The vm needs to wait for and receive confirmation before continuing
The "modal dialog" is actually not a new window but a hidden overlay in my MainWindow, as per http://www.codeproject.com/KB/WPF/wpfmodaldialog.aspx (thanks Ronald!)
I'm mostly there but the biggest struggles I have are:
- how to pause the loop in the viewmodel while it waits for input
- how to get input back to the viewmodel within the loop so it can carry on
So far I'm leaning towards the service solution because it seems a direct method call with a return that the vm must wait for. However, it does mean the service needs to tie directly to the view in order to make an element visible?
If anyone can post some simple code that deals directly with this problem I (and the net) would be very happy! Thanks!
For example, you have a service called IDialogService with the following interface:
public interface IDialogService
{
bool ConfirmAction(string title, string confirmationText);
}
As you mentioned, in order for the service to be able to show the actual dialog it needs to have a reference to the view that will show the actual overlay element. But instead of directly referencing the view I prefer to reference it via an interface. Lets call it ICanShowDialog and it will have the following members:
public interface ICanShowDialog
{
void ShowDialog(object dialogContent);
void HideDialog();
}
This interface will be implemented by your view that owns the dialog overlay (e.g. your main window).
Now the interesting part: suspending the code execution while the dialog is shown. First of all, I would recommend you not to use overlay elements but use usual windows if possible. Then you will not have that problem. You can style the dialog window so it will look just like the overlay element.
Anyway, if you still want to use overlay elements then you can do the following trick to suspend the code execution:
Here is pseudo code of the ConfirmAction method of the IDialogService inteface:
public bool ConfirmAction(string title, string confirmationText)
{
ConfirmationDialogView dialogView = new ConfirmationDialogView(title, confirmationText);
DialogShower.ShowDialog(dialogView); // DialogShower is of type ICanShowDialog
while (!dialogView.ResultAvailable)
{
DispatcherUtils.DoEvents();
}
DialogShower.HideDialog();
return dialogView.Result;
}
Here is the code of DispatcherUtils.DoEvents() (that was taken from here: http://dedjo.blogspot.com/2007/08/how-to-doevents-in-wpf.html):
public static class DispatcherUtils
{
public static void DoEvents()
{
DispatcherFrame f = new DispatcherFrame();
Dispatcher.CurrentDispatcher.BeginInvoke(
DispatcherPriority.Background,
(SendOrPostCallback)delegate(object arg) {
DispatcherFrame fr = arg as DispatcherFrame;
fr.Continue=True;
}, f);
Dispatcher.PushFrame(frame);
}
}
But I must warn you. Using DoEvents can result in some subtle bugs caused by inner dispatcher loops.
As an alternative to suspending the code execution while a dialog is shown you can use callbacks:
public interface IDialogService
{
void ConfirmAction(string title, string confirmationText, Action<bool> dialogResultCallback);
}
But it will not be so convenient to use.