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java - 调整窗口大小时在场景中居中滚动窗格

问题描述

嗨，我有一个带有 GridPane 的 ScrollPane，因为它是孩子，

ScrollPane scroll = new ScrollPane(grid);
        Scene scene = new Scene(scroll);

有谁知道如何在调整窗口大小时使 ScrollPane 的项目在场景中居中？

标签： javajavafx

解决方案

ScrollPane如果我正确理解了这个问题，当内容小于视口时，您希望将内容居中。这并不像简单地使用将其子元素作为内容居中的布局那样简单。AScrollPane默认情况下，仅将其内容调整为所述内容的首选大小，但将内容与左上角对齐。这意味着当内容小于视口时，只占用左上角的空间；即使内容以自己的孩子为中心，内容的面积也不等于视口的面积，因此内容不在视口内居中。

ScrollPane如果有一个“对齐”属性来自定义这种行为，那就太好了。由于不存在这样的属性，您必须配置ScrollPane以填充其视口，同时还允许内容超出视口的尺寸。然后，您只需要使用一个将其子元素居中的布局，或者可以配置为这样做——<code>GridPane 就是这样一种布局。这是一个例子：

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class Main extends Application {

  @Override
  public void start(Stage primaryStage) {
    // create and populate GridPane
    GridPane gridPane = new GridPane();
    gridPane.setHgap(10);
    gridPane.setVgap(10);
    for (int row = 0; row < 10; row++) {
      for (int col = 0; col < 10; col++) {
        Rectangle rectangle = new Rectangle(50, 50, Color.TRANSPARENT);
        rectangle.setStroke(Color.BLACK);
        gridPane.add(rectangle, col, row);
      }
    }

    /*
     * From the property's Javadoc: "The alignment of the grid within
     * the gridpane's width and height".
     *
     * Using Pos.CENTER makes the GridPane center its grid when the GridPane
     * has extra horizontal and/or vertical space.
     */
    gridPane.setAlignment(Pos.CENTER);

    /*
     * Forces the dimensions of the GridPane to be at least the same
     * as its preferred size. This prevents the GridPane from shrinking
     * due to the fit-to-width/fit-to-height configuration of the
     * ScrollPane.
     */
    gridPane.setMinSize(Region.USE_PREF_SIZE, Region.USE_PREF_SIZE);

    ScrollPane scrollPane = new ScrollPane(gridPane);

    /*
     * Forces the content of the ScrollPane to have the same dimensions
     * as the viewport. However, because of the min-size configuration above,
     * the GridPane can never be smaller than its preferred size. This means
     * the ScrollPane will grow its content to fit the viewport but won't
     * shrink its content to fit the viewport.
     */
    scrollPane.setFitToWidth(true);
    scrollPane.setFitToHeight(true);

    primaryStage.setScene(new Scene(scrollPane, 600, 400));
    primaryStage.show();
  }
}

请注意，根据您的用例，您可能不需要将内容的最小大小配置为与其首选大小相同。

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