I know did lots and lots of reading and they keep saying the same thing. A root node doesn't have any parent nodes but only have children nodes.
If I only have stage and a scene but zero node, would I still have a root node by default?
If I have two nodes, one is a circle and the other is a square, which one is a root node?
If I only have stage and a scene but zero node
This is impossible. There is no constructor for a Scene that doesn't take a root node parameter (and if you pass null, you simply get a NullPointerException). So if you have a scene, you necessarily have a root node.
If I have two nodes, one is a circle and the other is a square, which one is a root node?
Neither, since neither is an instance of Parent, and the root property of Scene is a Parent.
The only way to display any node is to either have it as the root of a scene, or to have it as a child of the root, or the child of a child of the root, etc.
So if the Circle and square (presumably a Rectangle) are both displayed, they must both be descendants of some root node.
Related
i'm struggling with a vertical box i added a transition to, it stays at the back of the other nodes like label and imageview. i tried using toFront() but it didn't work. also i tried using .setStyle("-fx-view-order: [number]") but i was lost a bit in what the numbers represent exactly is it the order of nodes ascending or descending.
#1
vb.setStyle("-fx-view-order: 0");
img.setStyle("-fx-view-order: 1");
didn't work
#2
vb.setStyle("-fx-view-order: 1");
img.setStyle("-fx-view-order: 0");
didn't work
The easiest way to get a Node to render on top is to move it to the end of the child node list for its parent Node.
Note the documentation for -fx-view-order mentions: "The parent traverses its children in decreasing viewOrder order." To me that means higher view order is behind (drawn first) relative to lower view order. However, this is all relative to the parent node, not the Scene. Give us a reproducible example of what you are doing.
Also, what version of JavaFX are you using? -fx-view-order was not in JavaFX 8 (JDK 8)
https://docs.oracle.com/javase/8/javafx/api/javafx/scene/doc-files/cssref.html#node
Suppose you have a block of code:
Pane pane = new Pane();
pane.getChildren().add(circle);
pane.getChildren().add(rectangle);
Scene scene = new Scene(pane, 400, 400);
Do you have to write pane.getChildren().add(===); every time you want to add something to the pane? Similarly, what is the difference in just writing ..
Pane pane = new Pane(circle, rectangle);
Scene scene = new Scene(pane, 400, 400);
As I have found that it does the exact same thing when I run the program and have the shapes display. Additionally, what is the different in writing with the use of Pane instead of:
Group root = new Group(circle, rectangle);
Scene scene = new Scene(root, 400, 400);
Any help would be greatly appreciated! I have been looking online and have not seemed to have found anything that truly answers all of my questions.
There's not really any difference between:
Pane pane = new Pane(node1, node2);
And:
Pane pane = new Pane();
pane.getChildren().add(node1);
pane.getChildren().add(node2);
Both approaches add the nodes the the children list of the layout. It's just that the first approach does this via the constructor; it's basically a shortcut for the second approach. However, the second approach can be used at any time so long as you have a reference to the layout.
Here are some differences between Pane and Group, though I can't promise this is an exhaustive list:
A Group will take into account any transforms or effects on its children when computing its layout bounds. This can have a profound affect on how your UI behaves when nodes are transformed (or have an effect applied on them). For instance, when you rotate a square the width and height grows and shrinks over time. If that square was in a Group then the Group's width and height would correspondingly grow and shrink; a Pane would not do this.
The Group class extends directly from Parent. The Pane class extends from Region (and Region extends from Parent). That means a Group has none of the styling options provided by Region (e.g. backgrounds, borders, etc.).
The Javadoc of Group also says:
Any transform, effect, or state applied to a Group will be applied to all children of that group.
I've never really experimented with this, so I'm not sure if this is truly different behavior than Pane.
Also, keep in mind that you'll typically want to use Pane or, more specifically, subclasses of Pane. This includes layouts such as BorderPane, VBox, and StackPane. Those layouts automatically manage their children to resize and position them according to the layout's rules. You can use nested layouts to achieve more complex designs. Personally, I've really only used Group if I want the behavior mentioned in point one above or if I'm using 3D shapes.
In graphics view m setting scene in that adding objects (by dropping ), i can move these items by mouse, when i moved one object on another object moved object should be transparent. how can i make it?
I don't believe you actually want full transparency since it will make it impossible to visually recognize the transparent object later on. Reduced opacity - yes.
As for your question: each item inside your scene has a bounding rectangle (or other type of bounding area). You can easily get it by calling boundingRect() of your item. The returned QRectF has (just like QRect) has the bool QRect::intersects(const QRect &rectangle) const function, which takes another rectangle and checks if a collision is present.
Whenever you move your mouse while dragging an item you need to iterate either through all or just a subset of all items in your scene (by subset I mean just the items in a specific region to increase the performance) and check for collision. If a collision is detected, you can alter either the item you are dragging or the item underneath it.
Of course to make sure that one item covers another one you also need to check the Z value. The easiest way to do that is if you keep all currently not being dragged items at the same Z level and then, whenever you drag one, increase it's Z level by one so that it is "above" the others.
In javafx BorderPane the tab traversal order is defined by the order of the children.
The problem is I have some Stage inheritance with a BorderPane on the base class, and BorderPane.setBottom() is called first.
This screws the tab order, since the bottom child is the first item on the children list.
I want to make the tab traversal on the BorderPane to be:
top
left
center
right
bottom
How could I archieve this?
This makes more sense than the set (setTop, setCenter, ...) order.
It seems it can't be done.
The solution was to add AnchorPanes inside the BorderPane areas and calling setTop, setCenter, ... in the desired tab traversal order.
In JavaFX, is there something similar to setLayout(); or setBounds();?
For example, I want to position a button to a position that I desire.
Everything on JavaFX scene graph is a Node. Each node has a X-coordinate and a Y-coordinate. But there are different ways to set/change position of a child component. It depends on the layout manager used to show the component on the scene graph.
There are layout managers, like Group, which do not compute child's default position and you can use layoutX and layoutY directly on them
There are other layout managers, like Region, which automatically compute child's default position using layoutX and inorder to adjust the locations of the components from their default positions you need to use translateX and translateY values.
From the docs :
If the node is managed and has a Region as its parent, then the layout region will set layoutX according to its own layout policy. If the node is unmanaged or parented by a Group, then the application may set layoutX directly to position it.
You should read up on the Node class (the long text at the beginning), and then especially relocate, setLayoutX (and Y) and setTranslateX (and Y).
In addition to what others already mentioned, if you could place your button (or any node for that matter) inside a StackPane, then you could make use of the StackPane's alignment property that takes javafx.geometry.Pos (the alignment of the child within the StackPane). For example in your case:
<StackPane>
<Button translateY="-15" translateX="15" StackPane.alignment="TOP_RIGHT"/>
</StackPane>