What is meant by the word "Node" within context of JavaFx/FXML? If I search for this question, all I find are people using the term discussing something else, but no explanation. For example, this answer to the question: How do I open the JavaFX FileChooser from a controller class?:
For any node in your scene (for example, the root node; but any node
you have injected with #FXML will do), do
chooser.showOpenDialog(node.getScene().getWindow());
What would the node be, and how for that matter would I "inject it with #FXML"?
Before you understand what a Node is, it is also important to first of all understand what a Scene Graph is in JavaFX.
JavaFX applications consist of a Stage and a Scene or several scenes. The stage being the top-level container of your application. The Scene(s) on the other hand, contains all the content (User Interface elements) of your application (if your application has only one "page") or the content of one of the "pages" of your application, and exists in/on a stage. (To be clear here, by page I mean what the user interacts with, for instance, a login page.)
The Scene Graph is a graphical illustration of how all the stuff in your scene are laid out. This graph is represented in the form of a tree data structure.
A Node is an item in the scene graph.
I think this image explains this clearly.
Example of a Node is a Control, which is anything that can be manipulated by the user E.g., TextField, Button, TextArea
Photo Credit
A Node is the abstract superclass of the graphical elements the scenegraph are "made of".
Some examples of classes inheriting from Node:
TextField
AnchorPane
Canvas
Group
VBox
Button
Label
...
Injecting a Node with the FXMLLoader id done this way:
Create a field in the controller associated with the fxml with a appropriate type (i.e. any type the element you want to inject can be assigned to). This field must be accessible by the FXMLLoader which means it has to be public or annotated with the #FXML annotation.
Add the id attribute from the fxml namespace (most likely using the prefix fx) to the element in the fxml file that should be injected. The value of that attribute is the name of the field in the controller.
Example
fxml
....
<TextField fx:id="myTextField" ....>
....
Controller
....
#FXML
private TextField myTextField;
....
The FXMLLoader uses this information to assign the object it creates for that fxml element to the field before the controller's initialize method is called.
A full example/extendend tutorial including injection can be can be found here: https://docs.oracle.com/javase/8/javafx/fxml-tutorial/fxml_tutorial_intermediate.htm#JFXMG153
This is an old question, but it is answered abstractly. "What is a node?" and "in order to understand what is a node you must first understand what is a scene-graph". A node is the highest level abstract class from which nearly all that is graphically displayed in a GUI, is derived. Its super class is Object. In the image displayed by Ojonugwa Ochalifu there is one stage that contains one scene which contains several nodes that contain other nodes. The image shown of a GUI begs the question "How is this created?".
For general understanding here are the JavaDocs for Stage, Scene, and EventTarget.
In javafx doc Stage https://docs.oracle.com/javase/8/javafx/api/javafx/stage/Stage.html
and Scene https://docs.oracle.com/javase/8/javafx/api/javafx/scene/Scene.html
Both Stage and Scene inherit the same interface, EventTarget as well as Pane, and Control and a long list of classes. https://docs.oracle.com/javase/8/javafx/api/javafx/event/EventTarget.html
I also recommend looking at the source code for classes that you are using. It will help provide insight into the behavior of classes that inherit from node. For example, JavaFX documentation mentions that a bug could exist when displaying an Image. Ensuring that this bug does not occur in a UI requires thorough testing. Other insight such as how to access the graph with multi-threaded techniques requires understanding the "how" and "What" a class uses.
The Scene-Graph is contained by the Stage and is comprised of any subclass of node. Some nodes such as Panes may have children. A child is still a node. Children are contained in a structure which may contain other nodes that may also have children. Thus the graph is much like a multi-dimensional array or non-binary tree. It's also important to understand that: The Scene-Graph is a Non-Directional Graph meaning that a child can access its parent; a child can have only one parent; but can have an unlimited number of children. The getParent() method provides access to a nodes parent.
Image of scene-graph
Note that essentially the graph structure is a multi-dimensional array. Or in other words, an array that may contain either other arrays of items that inherit from Node, or Nodes such as ImageViews, Buttons, etc. Array like Nodes are Panes, Canvas's etc... which may contain other nodes.
This is important to understand when it comes to test automation & reliably assuring that a UI is displaying what it should show.
A good book to get started with JavaFX is "Learn JavaFX 8" by Kishori Sharan. https://www.amazon.com/Learn-JavaFX-Building-Experience-Interfaces/dp/148421143X/ref=asc_df_148421143X/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4584413736126928&psc=1
Related
How can I show a static component in Vaadin 14? Every time I update the page, I get the error.
In this case, startStopYOLO, cameras, darknet, configuration, weights, thresholds, realTimeCameraImage, layout are all static
// Content
if(layout == null) {
layout = new VerticalLayout();
layout.add(new FormLayout(startStopYOLO, cameras, darknet, configuration, weights, thresholds));
layout.add(realTimeCameraImage);
layout.setAlignItems(Alignment.CENTER);
}
setContent(layout); // Here I get the error:
The error is:
Can't move a node from one state tree to another. If this is intentional, first remove the node from its current state tree by calling removeFromTree
So I need to clean up the content first. How can I do that in Vaadin 14?
The error already states the problem to some extend: Can't move a node from one state tree to another
Or rather: you can not share elements over different UIs. So no
static, no singletons, ... - you have to create fresh elements.
Elements becoming part of the scene graph for one UI (the state tree
from the error message) once they get attached. At this point the
Vaadin internals make sure, the element is not already attached to
a different UI (root) (it's OK to move elements inside one UI, which
also works by adding it to a different parent of the same UI).
If you have shared state over e.g. the server, you will have to create
elements for each UI and then sync this state with #Push and
UI.access or alike.
I don't know if I miss something, but I cannot manage to achieve that, I have the same label twice or more on the same view. I don't really want to duplicate it just use the same label with the same text/tooltip/style.
A simple example:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.control.Label?>
<AnchorPane xmlns="http://javafx.com/javafx"
xmlns:fx="http://javafx.com/fxml"
fx:controller="stackoverflow.dummy.Controller">
<Label fx:id="myLabel"/>
<!--<Label fx:id="myLabel"/>--> ofc this doesn't work.
<!--<Label fx:id="myLabel"/>-->
</AnchorPane>
If I try with <fx:reference> it appears only once, if I try with <fx:copy> it says I need a copy constructor, so I think I simply miss some easy solution. It should exist.
Note:
I don't really want want to duplicate the code like: myLabel1, myLabel2, ..., since all of them are having the same text/tooltip/style.
I also know I can create a separate .fxml file where I build the label and use it via <fx:include> but I would prefer solving it in the same .fxml since it is a really simple thing I think it doesn't worth creating a new .fxml only for this.
Problem
It is not possible to add the same Label multiple times to the scene graph. This is documented by Node (emphasis mine):
A node may occur at most once anywhere in the scene graph. Specifically, a node must appear no more than once in all of the following: as the root node of a Scene, the children ObservableList of a Parent, or as the clip of a Node.
The scene graph must not have cycles. A cycle would exist if a node is an ancestor of itself in the tree, considering the Group content ObservableList, Parent children ObservableList, and Node clip relationships mentioned above.
If a program adds a child node to a Parent (including Group, Region, etc) and that node is already a child of a different Parent or the root of a Scene, the node is automatically (and silently) removed from its former parent. If a program attempts to modify the scene graph in any other way that violates the above rules, an exception is thrown, the modification attempt is ignored and the scene graph is restored to its previous state.
The emphasized part explains why the Label only appears once when using <fx:reference>.
Solution
The only solution to your problem is to duplicate the Label. There are at least two options you can use to accomplish this.
Use <fx:copy>
One way to do this by using <fx:copy> (emphasis mine):
The <fx:copy> element creates a copy of an existing element. Like <fx:reference>, it is used with the fx:id attribute or a script variable. The element's "source" attribute specifies the name of the object that will be copied. The source type must define a copy constructor that will be used to construct the copy from the source value.
At the moment, no JavaFX platform classes provide such a copy constructor, so this element is provided primarily for use by application developers. This may change in a future release.
As stated in the documentation, using <fx:copy> requires the class to have a copy constructor. The documentation also states that none of the core JavaFX classes provide copy constructors. This means you'll have to subclass Label and provide the needed constructor, as shown in funkyjelly's answer. To ensure the properties stay up-to-date you can bind the properties inside the constructor:
public class CopyableLabel extends Label {
public CopyableLabel(CopyableLabel label) {
// You only mentioned the text, tooltip, and style properties
// in your question. Bind more properties as needed.
textProperty().bind(label.textProperty());
tooltipProperty().bind(label.tooltipProperty());
styleProperty().bind(label.styleProperty());
}
}
That way you only need to inject the "master" Label and any updates to it will be propagated to all the copies. Using this design you must keep in mind that bound properties cannot be set directly; trying to set a bound property will result in exceptions. You might want to document the constructor will bind the properties, not just copy the values.
Use Expression Bindings
Another option is to bind the needed properties in the FXML file. You would still be creating multiple Labels but you would only need to inject the "master" Label, as before.
<VBox xmlns="http://javafx.com/javafx/" xmlns:fx="http://javafx.com/fxml/1">
<Label fx:id="master"/>
<Label text="${master.text}" tooltip="${master.tooltip}" style="${master.style}"/>
<Label text="${master.text}" tooltip="${master.tooltip}" style="${master.style}"/>
<Label text="${master.text}" tooltip="${master.tooltip}" style="${master.style}"/>
<!-- repeat as needed -->
</VBox>
This uses the expression binding capabilities of JavaFX FXML. This option may clutter the FXML file but it doesn't require you to create a subclass of Label.
"I don't really want want to duplicate the code like: myLabel1, myLabel2, ..., since all of them are having the same text/tooltip/style." What if you just create multiple references pointing to the same label object ?
Or extend Label to include a copy constructor :
public MyLabel(MyLabel aLabel) {
this.property1 = aLabel.property1;
this.property2 = aLabel.property2;
...
}
Then in FXML using copy:
<MyLabel fx:id="myLabel1"/>
<fx:copy source="myLabel1"/>
I'm developing a small GUI using JavaFX for an assignment. Having never used JavaFX before, most of what I've used or learned I've research myself. Most of my application runs smoothly, animations included.
I have a small user input section:
I'm trying to allow it to swipe left prior to loading the next scene, to give the user the impression of sequence. I achieved this using a ParallelTransition populated by TranslationTransitions in which I load all of these Nodes.
However, just slightly before it animates, it appears to align everything right.
I have a feeling this is something to do with the container (AnchorPane) in which I'm placing these objects, or some undefined attribute which I'm not setting. As I'm learning this all on the fly, it's a bit difficult to narrow down. Can anyone give me an idea as to what is causing this and how I can retain the alignment? Each Node moves in the following way:
translateTransition.setFromX(node.getLayoutX());
translateTransition.setToX(node.getLayoutX()-500.00);
If I've left out any pertinent information, please let me know!
So, my issue turned out to be the way I'm laying out my objects. Placing them in an arbitrary AnchorPane with only specific attributes to locate those items means that, upon animation, it will group those objects and animate them accordingly. It was the incorrect way to layout those nodes.
Instead, I've placed them in a VBox which has two advantages.
I can align the contents of that VBox centre, so I need not specify the exact layout attributes of the elements.
I can animate using the single VBox, as opposed to the all the elements in a ParallelTransition. As a result, a single TranslateTransition on the VBox node will suffice!
JAVA's abstraction is somehow brought out by allowing us to create a JFrame (and save it in its own .JAVA file) and populate it with different kinds of objects such as JPanels, JTextFields ... (saved in different files) if and when needed by using the remove(), add(), validate(), repaint() methods.
I'm trying to move my JAVA project to JAVA-FX due its great flexibility in design via JavaFX Scene Builder and css. Are there any equivalents to the above methods here (In JAVA-FX)? Is there a way I could create a Pane or a Label ... and save it in its own file as it waits to replace onother Pane with its own child Nodes (and saved in its own file) on the Stage later when it's called via an action, such as a button click?
Would really appreciate any help. Sample code enumerating the above could help also.
Thank you all in advance.
Your's trully, Complete JAVA-FX Newbie.
In a regular JavaFX application, there is only one primary stage and its one scene. Create your FXML file (optionally with its controller) containing any JavaFX node and load this file on button action using FXMLoader. Then you can use the loaded node as a root of scene;
scene.setRoot(MYNode) (though only Parent can be set as root)
or add it to subtree of root node as a child;
if you know the substructure: scene.getRoot().getChildren().get(3).getChildren().add(MYNode);
if you know the id: scene.lookup("myPane").getChildren().add(MYNode);
The same logic applies to another FXML file(s) being loaded in another action event.
I have created a Node (AnchorPane) in the JavaFX scene builder and was wondering how to clone it.
I saw Duplicate/Clone Node in JavaFX 2.0 but I need to clone the Node without re-loading the fxml.
Is there any way to achieve this in JavaFX 2?
You can place the component that needs to be duplicated in a separate .fxml file.
Then you can load the separate file as many times as needed adding the nodes to the appropriate root in the main scene.
Additionally you can edit an <fx:include source="..."/> element to the main .fxml file and include the separate .fxml file. You can then still work with it in the JavaFX Builder.
There is no such node duplication function in the JavaFX platform, you will need to write your own which introspects on the properties of the node you are interested in cloning and creates a new node with the required properties.
Using an fxml template for the node definition is probably the easiest way to do this for node's with static initialization properties - but then, as you state in your question, you don't want to use fxml for this, so you'll have to code your cloning logic in Java.