Pane和Group之间的区别 [英] Difference between Pane and Group

问题描述

我的问题很简单：在JavaFX中， Pane 和组之间有什么区别？我没有任何区别。

My question is simple : in JavaFX, what is the difference between a Pane and a Group ? I can't make any difference.

推荐答案

组不是可调整大小（意味着其大小不受场景图中其父级管理），并且具有其子节点边界的并集。 （换句话说， Group 的局部边界将是包含所有子节点边界的最小矩形）。如果它大于它在父母中分配的空间，它将被剪裁。

A Group is not resizable (meaning that its size is not managed by its parent in the scene graph), and takes on the union of the bounds of its child nodes. (So, in other words, the local bounds of a Group will be the smallest rectangle containing the bounds of all the child nodes). If it is larger than the space it is allocated in its parent, it will be clipped.

相比之下， Pane 是可调整大小的，因此它的大小由其父级设置，这基本上决定了它的界限。

By contrast, a Pane is resizable, so its size is set by its parent, which essentially determine its bounds.

这是一个快速演示。 组位于顶部， Pane 位于下方。两者都包含一个固定的蓝色方块（100,100）和一个绿色方块，通过按左/右箭头键移动。请注意，在开头，蓝色方块如何出现在组的左上角，因为组的本地边界从其所有子节点的最左上角开始（即组的本地边界从<$延伸） c $ c>（100,100）正确和向下）。当您将绿色矩形移出屏幕时，该组会调整其边界以尽可能合并更改，而窗格保持固定。

Here is a quick demo. The Group is on top and the Pane below. Both contain a fixed blue square at (100,100) and a green square which is moved by pressing the left/right arrow keys. Note how at the beginning, the blue square appears in the top left corner of the group, because the local bounds of the group start at the top-leftmost point of all its child nodes (i.e. the local bounds of the group extend from (100, 100) right and down). As you move the green rectangles "off screen", the group adjusts its bounds to incorporate the changes, wherever possible, whereas the pane remains fixed.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.Pane;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class GroupVsPaneDemo extends Application {

    @Override
    public void start(Stage primaryStage) {
        Pane pane = new Pane();
        Group group = new Group();

        VBox.setVgrow(group, Priority.NEVER);
        VBox.setVgrow(pane, Priority.NEVER);

        VBox vbox = new VBox(group, pane);


        Rectangle rect1 = new Rectangle(100, 100, 100, 100);
        Rectangle rect2 = new Rectangle(100, 100, 100, 100);
        Rectangle rect3 = new Rectangle(200, 200, 100, 100);
        Rectangle rect4 = new Rectangle(200, 200, 100, 100);
        rect1.setFill(Color.BLUE);
        rect2.setFill(Color.BLUE);
        rect3.setFill(Color.GREEN);
        rect4.setFill(Color.GREEN);

        group.getChildren().addAll(rect1, rect3);
        pane.getChildren().addAll(rect2, rect4);

        Scene scene = new Scene(vbox, 800, 800);
        scene.addEventHandler(KeyEvent.KEY_PRESSED, e -> {
            double deltaX ;
            switch(e.getCode()) {
                case LEFT:
                    deltaX = -10 ;
                    break ;
                case RIGHT:
                    deltaX = 10 ;
                    break ;
                default:
                    deltaX = 0 ;
            }
            rect3.setX(rect3.getX() + deltaX);
            rect4.setX(rect4.getX() + deltaX);
        });

        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

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