fxcollect | simultaneous collection | Time Series Database library

I'm going to reply in Java, as I'm more familiar with it. The reasoning applies to kotlin too.

Bindings.createStringBinding(function, dependencies) creates a binding that is invalidated any time any of the dependencies are invalidated. Here "invalidated" means "changes from a valid state to an invalid state". The problem with your code is that you define the dependency as property.valueAt(index), which is a binding to which you have no other reference.

When you change either the index or the bean at that index in the list, then the binding becomes invalid. Since you never compute the value of that binding again, it never becomes valid again (i.e. it never holds, or has returned, a valid value). So subsequent changes will not change its validation state (it is simply still invalid; it cannot transition from valid to invalid).

Changing the code to

Always remember to initialize your variable folks:

As stated in the comments by @jewelsea, your model class (Apple) should contain only data; it should not contain UI fields such as ImageView. Any Node can only appear once in the scene graph, which is why you only see the ImageView in a single row in the table.

You should instead store either the path to the image, or the Image (which is only data) itself in the model class. The trade-off between these two choices is a compute-time versus memory consumption trade-off. If you store the path to the image, the image will need to be loaded each time a cell updates (e.g. during scrolling), which takes time. On the other hand, if you store the Image, then all images needed for the entire table will need to be stored in memory, whether or not they are displayed.

I would recommend storing the Image in the model class if your table only needs a small number of images. This may happen if the table only has a few rows, or if there are a small number of images and multiple rows show the same image. Note that Images can be shared by multiple ImageViews, so there is no need to load any single Image more than once.

Using Image in the model class would look like this:

A union of shapes will create a single shape. The elements which comprise the union shape cannot be styled independently.

As James_D suggests in comments, don't union the shapes, instead use a parent container such as Group or HBox.

The example below demonstrates using an HBox for the graphic which allows the graphic content to be managed by the layout pane rather than requiring a manual layout.

You can do something like this:

If anyone else comes across this issue,

There are many things to consider in this example. Frist, let me explain the errors which your are facing.

Firstly, on click of button or choosing the choice box, you are getting constructLoadException. This is because you are using the same Controller class for both the fxmls. And you are are expecting both the fxmls to share the same Controller instance. This will not be the case. With your code, each fxml will have its own instance of BookController. So in fxml1 controller, all the instance variables related to fxml2 will be null and vice versa.

So when you initiate the fxml2, a new instance of BookController is created and the initialize method is called. As there is no "box" node in fxml2, that variable will be null and obviously will throw NPE, which is causing the exception to load the fxml.

The second error of NPE is also same, this time you are expecting the fxml2 instance variable "label" in fxml1 controller.

Solution:

There are two ways to address this issue. It depends on whether you want to share the same Controller class or If you are ok to go with separate controller class for each fxml.

#1. Using same controller class

In this way, you need to do the below two changes.

• Remove the controller declaration in the exscene2 fxml.
• Change the initialize and switchScene methods as below. The main changes are we are setting the same controller instance manually to the fxml2 loader. And doing some checks in initialize method, to not re-add the items again.

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Your code doesn't work, because you call (and evaluate) getSelectedStudent() at the time the binding is created (i.e. when you initialize the model). As a consequence, you only bind to the displayName property of the student that is selected at that time. (If nothing is selected, you'll get a NullPointerException.) The binding will only change if that initially-selected student's display name changes; it won't change if the selection changes.

You need a binding that unbinds from the old selected student's display name, and binds to the new selected student's display name, when the selected student changes. One way to do this is:

It looks like you are using AnchorPane incorrectly. I would use VBox or BorderPane. This example uses VBox.