I am writing a small experimental desktop application. Basically it has the options to display a list of recipes and detailed information about a single recipe.
To accomplish that i implemented a class called RecipeContext that stores a ObservableList<Recipe> that i bind to a TableView, so the view gets automatically updated if i add to, or remove from the collection.
I want something similar for the single recipe, an Observable where i simply have to change the contained recipe and have the view automatically update to display the new recipe information.
To make this a bit more clear, i want something like this:
SingleObservable<Recipe> detailedRecipe = new SingleObservable<>(new Recipe("A"));
detailedInformationController.bindRecipeObservable(detailedRecipe);
// Recipe A is displayed
detailedRecipe.set(new Recipe("B"));
// View is notified about the change and displays Recipe B
Is there a class that does that?
SimpleObjectProperty will do what you want.
SimpleObjectProperty<Recipe> detailedRecipe = new SimpleObjectProperty<>(new Recipe("A"));
...
detailedRecipe.set(new Recipe("B"));
http://docs.oracle.com/javase/8/javafx/api/javafx/beans/property/SimpleObjectProperty.html
Related
I have a query that is observed on viewWillAppear on View Controller A
let query = FIRDatabase.database().reference().child("tags").
queryOrdered(byChild: "users/uid").queryEqual(toValue: userId)
In the same view controller, in viewDidDisappear I remove this observer.
So let's say I push into another view controller from View Controller A.
When I come back to View Controller A, the observer returns a snapshot, even though my data on the backend hasn't changed.
I only want a snapshot returning if there's been some actual change to my database. How do I solve this problem? Thanks.
One answer is to simply let the observer do it's job and update your data in the background.
So if the user is on controllerA the observer updates a datasource (an array) so then the UI is updated from that array.
When the user switches to controllerB, the observer can still update the array, but don't update the UI in controllerA since there's no need to.
When the user switches back to A you'll have current data available so just reload the tableView (assuming iOS here) from the array.
This solution reduces the 'polling' nature and let's Firebase do the heavy lifting to notify your app when it needs to. You're just reloading the tableViews from an array when that controller becomes active.
Edit
The idea here is to add the observer once - perhaps when the view loads the first time only (viewDidLoad) or maybe in your app delegate. Once you add the observer it will update your dataSource arrays when data changes so when you move from view to view the only action needed will be to reload the tableView from the updated array.
There are times when you may want to remove an observer but it doesn't sound like you need to do that from your question. So - attach the observers once and let them update the dataSource arrays as the data changes. Reload your tableViews when switching views.
You have put the query in viewWillAppear, which means every time you come to viewController A, this query will be executed irrespective of you have removed the observer or not.
Try putting the same query in viewDidLoad which means, the query will be called once and don't remove the observer anywhere. Now the query would be called only when data gets changed in firebase.
I have a problem I want to use the list and when I click on a component of the list it take me to another form (make an action) meaning if I click on an item from the list depending on the selected index it takes me to another form.
Is this in a GUI builder app or manual app?
For GUI builder use the action event callback for the list see: http://www.codenameone.com/how-do-i---handle-eventsnavigation-in-the-gui-builder--populate-the-form-from-code.html
Then get the index/selected item using:
int index = list.getSelectedIndex();
Object value = list.getSelectedItem();
Then you can show the form you want using:
showForm("FormName", null);
In handcoded apps you can get the selected item/index in exactly the same way then do something like:
form.show();
To show a specific form.
I am new to Qt.
I have the following situation.
Can someone suggest me how to tackle it.Thanks
I have a custom made model which i should populate in the backend.ie when the program starts there is no guarantee there will be elements in the model.But these elements may be added later in the backend.So if i add a new element in the data structure in the model how do i let the view know the change.And this is an insertion and not a change in the data.
Also if i want the view i display to be sorted how should i notify the view
To update any connected views of an insertion, call beginInsertRows(const QModelIndex& parent, int first, int last) before you modify the model, and endInsertRows() after. Read the docs.
To sort views you need to use a QAbstractProxyModel, it is highly configurable so read the docs before asking more specific questions about it.
I want to display quite a bit of demographic data for a certain pin when someone touches on it, so providing a pop-up isn't going to cut it. I figured once the pin is touched I will just stick a tableviewController onto the NavigationController and the table view will have access to the object and display the single objects information, with one item per row and 1 section.
Anyway I'm having a hard time figuring out MKMapViewDelegates methods as it appears none of them do what I need and/or allow me to return a tableview or push that view onto the navigation controller.
I played around with:
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation;
But that requires a MKAnnotationView be returned and I really just need this method to work by showing the user a table view of all the data. I was hoping for something simple like a userDidTouchPin method....
Anyone have any ideas how to accomplish what I am trying to do?
If you want to do something when the user selects the pin (and not a button on its callout), then implement the mapView:didSelectAnnotationView: delegate method and present or push your detail view controller there.
The selected annotation object is available as the annotation property of the view parameter:
- (void)mapView:(MKMapView *)mapView
didSelectAnnotationView:(MKAnnotationView *)view
{
YourDetailViewController *dvc = [[YourDetailViewController alloc] init...
dvc.annotation = view.annotation;
//present or push here
[dvc release];
}
You might need to check which type of annotation was selected (eg. if MKUserLocation was selected do nothing, etc) and you might need to cast the view.annotation to your own annotation class to easily access any custom properties you may have.
I made a model with EMF, representing the settings of a device, and a RCP GUI. In the GUI I have a list to select different devices of the type of the model (Master).
The model has a List of Objects of a small class which should be displayed in a table (Detail).
The tableItems itself need to be edited so I have a small GUI part with checkboxes etc. to change the settings. Here the tableitem is master and all fields shown in the GUI are details.
Observable for the List of devices:
IObservableValue selection = ViewersObservables.observeSingleSelection(availableDevicesList);
Table:
IObservableList list = EMFObservables.observeDetailList(Realm.getDefault(), selection,DevicePackage.Literals.LIST);
TableViewer tableViewer = new TableViewer(parent, SWT.SINGLE | SWT.FULL_SELECTION);
tableViewer.setInput(list);
IObservableValue tableSelection = ViewersObservables.observeSingleSelection(tableViewer);
Editing:
Spinner field1 = new Spinner(parent, SWT.BORDER);
dbc.bindValue(SWTObservables.observeSelection(field1), EMFObservables.observeDetailValue(Realm.getDefault(), tableSelection, DevicePackage.Literals.Value1));
When changing the device selection the tableitems get replaced. But the tableSelection seems to have a problem with this. Sometimes it still contains values of a a tableitem from a different device and sometimes it just contains null.
I also have a button which gets enabled/disabled according the validation status of all fields. When the tableSelection puts null into these fields the validation does not work and the button is disabled until a entry in the table is selected.
I tried to manually set the selection empty with a listener on the list and:
tableViewer.setSelection(StructuredSelection.EMPTY, true);
but this does not do the full job. At least all "old" values are replaced but the null problem still occurs.
All I need is to set the tableSelection to an empty state as after the launch of the application, when no tableitem was selected yet.
I found the solution by myself. The problem was actually the spinner itself. It threw a nullpointer when the selection was empty and there was no value.
I solved it by giving it a custom converter (from int to int...) where I return a default value if the source is null.
Now the validation works fine and my button's enable state is set correct.