i have created an application.In that i have created a button.After clicking on the button a process get's started.Now when i press the close('X') button of the application,the application closes.I want all this to happen on a click of a button i.e When i click the button for the first time it should start the process & as soon as click the same button again the process should get closed.
Here it is. Comments are inside code.
using System.Diagnostics;
/// <summary>
/// Process started by our app
/// </summary>
Process process;
private void button1_Click(object sender, EventArgs e)
{
// Haven't been started yet or user closed it
if (process == null || process.HasExited)
{
// Do open
try
{
process = Process.Start("notepad.exe");
}
catch (Exception ex)
{
// Inform user about error
}
}
// It is started
else
{
// many a thing can go wrong here.
// Even something as simple as user closing the app himself
try
{
// Send app instruction to close itself
if (!process.CloseMainWindow())
{
// Unable to comply - has to be put to death
// Merciful people might give it a few retries
// before execution
process.Kill();
}
}
catch (Exception ex)
{
// Inform user about error
}
finally
{
// So the cycle of life can start again
process = null;
}
}
}
You can use flags that stores a true value if the application is already running i.e. if the button is pressed for the first time. Then use a simple if condition to call the respective function.
Related
I am developing an app in Xamarin.Forms, before I was trying to make a master detail page to become my MainPage when I logged in to my app, this I have already achieved. Now I have the problem that when I use the button behind the phone my app is miimiza and goes to the background which is the behavior I hope, but when I return to my app does not continue showing my master detail page, but returns to my LginPage.
It is as if my app was running twice or at least there were two instances of LoginPage existing at the same time, this is because in my LoginPage I trigger some DisplayAlert according to some messages that my page is listening through the MessaginCenter and they are they shoot twice.
Can someone tell me how I can return the same to my app on the master detail page and not restart in the strange way described?
LoginView.xaml.cs:
public partial class LogonView : ContentPage
{
LogonViewModel contexto = new LogonViewModel();
public LogonView ()
{
InitializeComponent ();
BindingContext = contexto;
MessagingCenter.Subscribe<LogonViewModel>(this, "ErrorCredentials", async (sender) =>
{
await DisplayAlert("Error", "Email or password is incorrect.", "Ok");
}
);
}
protected override void OnDisappearing()
{
base.OnDisappearing();
MessagingCenter.Unsubscribe<LogonViewModel>(this, "ErrorCredentials");
}
}
Part of my ViewModel:
if (Loged)
{
App.token = token;
Application.Current.MainPage = new RootView();
}
else
{
MessagingCenter.Send(this, "ErrorCredentials");
}
Thanks.
I hope this is in Android. All you can do is, you can override the backbuttonpressed method in MainActivity for not closing on back button pressed of the entry page. like below, you can add some conditions as well.
public override void OnBackPressed()
{
Page currentPage = Xamarin.Forms.Application.Current.MainPage.Navigation.NavigationStack.LastOrDefault();
if (currentPage != null)
{
if (currentPage.GetType().Name == "HomePage" || currentPage.GetType().Name == "LoginPage")
{
return;
}
}
base.OnBackPressed();
}
When you press the Home button, the application is paused and the
current state is saved, and finally the application is frozen in
whatever state it is. After this, when you start the app, it is
resumed from the last point it was saved with.
However, when you use the Back button, you keep traversing back in
the activity stack, closing one activity after another. in the end,
when you close the first activity that you opened, your application
exits. This is why whenever you close your application like this, it
gets restarted when you open it again.
Answer taken from this answer. The original question asks about the native Android platform, but it still applies here.
It means you have to Use Setting Plugin or save data in Application properties.
You have to add below code in App.xaml.cs file:
if (SettingClass.UserName == null)
MainPage = new LoginPage();
else
MainPage = new MasterDetailPage();
For Setting Plugin you can refer this link.
I am performing a long running operation and showing message dialog as "fetching details" and closing the same once the operation is performed.
try{
MessageDialog dialog = new MessageDialog(Display.getDefault().getActiveShell(), "Information", null, "Fetching Details...", MessageDialog.NONE , new String[] {}, -1);
dialog.setBlockOnOpen(false);
dialog.open();
//Schedule long Running operations
} finally{
dialog.close()
}
If the operation takes more time, dialog is showing not responding (Title changes to "Information (Not Responding)").
How can avoid the not responding status ?
You must not run long operations in the UI thread. Doing so will block the thread until they finish and the UI will become unresponsive.
Run your operations in a background thread, or an Eclipse Job or even a Java 8 CompleteableFuture.
Use the Display asyncExec in your background code to update the UI as required.
Another alternative is to use ProgressMonitorDialog:
ProgressMonitorDialog dialog = new ProgressMonitorDialog(shell);
try {
dialog.run(true, true, new IRunnableWithProgress() {
#Override
public void run(IProgressMonitor monitor) {
monitor.beginTask("Task name", IProgressMonitor.UNKNOWN);
try {
// TODO your long running code
// TODO check monitor.isCanceled() as often as possible
}
finally {
monitor.done();
}
}
});
}
... catch exceptions
I'm using the CellTree for the very first time and slowly getting a hang of it.
Right now I'm struggling how to display a progress icon (just like when opening a tree node) beside the "Show more" text when clicking on it.
Any ideas?
I guess it is a common problem that users are clicking on "Shore more" multiple times if they do not get any visual feedback - which leads to multiple server calls and a bunch of duplicated nodes (in my case).
Any time you send a call off to the server, you know that you are making the call. Likewise, you will get a call back into your code, whether it succeeded or failed.
For the sake of this example, I'm assuming you are using something like GWT-RPC (since the question doesn't specify):
// field to track if we're loading
private boolean isLoading = false
//...
// inside a method which needs to load data:
if (isLoading) {
return;//don't attempt to load again
}
isLoading = true;
//just before we start the call, show the loading indicator
loadingIndicator.flash();//or whatever you'd like to make it do
//then start the request
service.getMyData(param1, param2, new AsyncCallback<MyData> () {
public void onSuccess(MyData response) {
//loading was successful, so stop the loading marker
isLoading = false;
loadingIndicator.success();
//do something with the data
//...
}
public void onFailure(Throwable ex) {
//loading stopped, but it was an error, tell the user
isLoading = false;
loadingIndicator.error();
}
});
I'm implementing a document editor with JavaFX8 and e(fx)clipse and want to user to be informed when the export (write to disc) is ongoing. I'm using the main (GUI) Thread for this as I want to block the gui during this operation (which takes 2-3 seconds). During this operation I want to show a small popup to inform the user that the export is ongoing, nothing fancy.
#FXML
public void export() {
Dialog dialog = new Dialog();
dialog.setContentText("exporting ...");
dialog.show();
// some lenghty methods come here, ~equivalent to Thread.sleep(3000);
dialog.hide();
}
When I press the corresponding Button which invokes the export method, I get somehow two dialogs, one of them NOT closing and remaining open after the method has finished.
Does somebody has an idea what's happening here? I'm really interested in a simple solution, I don't need to have a progress bar etc..
Another possibility would be to show a wait-cursor before the operation starts and switching back to the default cursor after that. Unfortunately, this does also not seem to work. I understand that the UI is blocked during the "lengthty" operation, but I don't udnerstand why I cant change the UI before and after that operation....
Your example isn't very complete - however I would recommend using one of two approaches. However, you aren't putting the long process on a background thread which will FREEZE your app. You want to offload that process.
1) Use the ControlsFX Dialog which has a Progess Alert. Tie your work to either a Task or a Service and provide that to the alert. This will pop the alert up while the thread is active, and will automatically close it when done. If you have intermediary progress values, it can be used to update the progress bar.
Or if you don't want to use this dialog, you could do something like this:
Alert progressAlert = displayProgressDialog(message, stage);
Executors.newSingleThreadExecutor().execute(() -> {
try {
//Do you work here....
Platform.runLater(() ->forcefullyHideDialog(progressAlert));
} catch (Exception e) {
//Do what ever handling you need here....
Platform.runLater(() ->forcefullyHideDialog(progressAlert));
}
});
private Alert displayProgressDialog(String message, Stage stage) {
Alert progressAlert = new Alert(AlertType.NONE);
final ProgressBar progressBar = new ProgressBar();
progressBar.setMaxWidth(Double.MAX_VALUE);
progressBar.setPrefHeight(30);
final Label progressLabel = new Label(message);
progressAlert.setTitle("Please wait....");
progressAlert.setGraphic(progressBar);
progressAlert.setHeaderText("This will take a moment...");
VBox vbox = new VBox(20, progressLabel, progressBar);
vbox.setMaxWidth(Double.MAX_VALUE);
vbox.setPrefSize(300, 100);
progressAlert.getDialogPane().setContent(vbox);
progressAlert.initModality(Modality.WINDOW_MODAL);
progressAlert.initOwner(stage);
progressAlert.show();
return progressAlert;
}
private void forcefullyHideDialog(javafx.scene.control.Dialog<?> dialog) {
// for the dialog to be able to hide, we need a cancel button,
// so lets put one in now and then immediately call hide, and then
// remove the button again (if necessary).
DialogPane dialogPane = dialog.getDialogPane();
dialogPane.getButtonTypes().add(ButtonType.CANCEL);
dialog.hide();
dialogPane.getButtonTypes().remove(ButtonType.CANCEL);
}
I have a working ProgressMonitorDialog, but I want to make sure that I am setting it up correctly.
First the Code:
Method to create Dialog
public void startProgressBar() {
try {
new ProgressMonitorDialog(getShell()).run(true, true,
new ProgressBarThread());
}
catch (InvocationTargetException e) {
MessageDialog.openError(getShell(), "Error", e.getMessage());
}
catch (InterruptedException e) {
MessageDialog.openInformation(getShell(), "Cancelled", e.getMessage());
}
}
Class File
class ProgressBarThread implements IRunnableWithProgress {
private static final int TOTAL_TIME = 1000;
public ProgressBarThread() {
}
public void run(IProgressMonitor monitor) throws InvocationTargetException,InterruptedException {
monitor.beginTask("Creating PDF File(s): Please wait.....", IProgressMonitor.UNKNOWN);
for (int total = 0; total < TOTAL_TIME ; total++) {
Thread.sleep(total);
monitor.worked(total);
if (total == TOTAL_TIME / 2) monitor.subTask("Please be patient... Operation should finish soon.");
}
monitor.done();
}
}
Method that calls the ProgressBar and runs a Pdf file creation Operation
private void startSavePdfOperation() {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
startProgressBar();
}
});
saveOp = new AplotSaveOperation(appReg.getString("aplot.message.SAVETOPDF"), "PDF", session);
saveOp.addOperationListener(new MyOperationListener(this) {
public void endOperationImpl() {
java.io.File zipFile = null;
try {
AplotSaveResultsParser.SaveResult saveResults = saveOp.getSaveResults();
if (saveResults != null) {
ETC..... ETC......
Questions:
Being the ProgressMonitorDialog is a GUI, it needs to be executed in a
Display.getDefault().asyncExec?
If the ProgressMonitorDialog is running in a separate thread, how does it know to close when the operation is finsihed?
Is there any relationship between the progressbar and the operation?
I am correct in assuming that the for loop in the ProgressBarThread class is basically the timer that keeps the monitor open?
Is there a way to increase the speed of the ProgressMonitorDialog's indicator, also can you remove the cancel button?
This is what I am thinking is happening currently.
I am starting the progress bar just before I start the PDF Operation Listener
See startSavePdfOperation() Above
The progress bar is running as unknown, but using a for loop to keep the progress bar dialog open, while the operation is running on a thread in the background.
See Class ProgressBarThread above
When the PDF operation completes the listener operation class closes the base GUI dialog.
public void endOperation() {
try {
endOperationImpl();
}
finally {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
w.getShell().setCursor(new Cursor(Display.getCurrent(), SWT.CURSOR_ARROW));
w.recursiveSetEnabled(getShell(), true);
w.getShell().setEnabled(!getShell().getEnabled());
w.close();
}
});
}
}
I am not sure what is happening to the ProgressBarThread monitor?
Is this Possible?
When the PDF Operation starts, the ProgressMonitorDialog opens and starts the indicator. OK with keeping it unknown.
When the PDF Operation completes, the monitor closes, then the base Dialog
I am just wanting to open progress bar dialog that will inform the user that their request is working in the background.
As stated the above code works, but I am afraid by letting the closing of Base GUI, destroy my Progress Thread and Monitor is not good practice.
First of all, in your ProgressBarThread#run() you should use monitor.worked(1). You don't need to set the total worked but increment it by the amount of work done, since the last time it was called.
Q1. Yes it needs to be executed in the display thread
Q2. Normally the work that needs to be done is actually performed in the runnable that is passed to the progress monitor dialog so that you can accurately report the amount of progress made. So your operation (if it is a synchronous call) should be called from within ProgressBarThread#run() so that you call monitor.worked(1) only when one file processing is complete.
Q3. What kind of operation are you running, perhaps it already supports showing progress bar, and you just need to invoke the right API. Is it an IUndoableOperation?
Q4. As I said this approach is problematic because you can never accurately report the progress and close the dialog only when the operation is completed. But if this is the only choice you have, then you can just save the monitor reference somewhere so that it is accessible to the other thread. Once monitor.done() is called, your ProgressBarThread#run() should return, the dialog will close.
Q5. You can remove the cancel button by passing the correct parameter to ProgressMonitorDialog#run(..):
new ProgressMonitorDialog(getShell()).run(true, false, new ProgressBarThread());
For the rest of the questions I can better answer if I know what kind of operation (what API) you are using.