将DropShadow应用为JavaFX画布上的单独图层

Question

我正在制作一个油漆程序，但是用户在图纸周围有一个DropShadow。当它们擦除时，它也会擦掉DropShadow。如果我试图重新应用DropShadow（让它围绕绘图的新边界），它可以工作，但它使已经应用的DropShadow的其余部分变暗，我不想要。

我能想到的解决方案有两个方面：

1. 删除DropShadow效果并在每次擦除时重新应用它。据我所知，这在使用GraphicsContext.applyEffect()时是不可能的
2. 将DropShadow应用于单独的画布上并清除它并在每次擦除时重绘。下面的代码实现了我对此解决方案的尴尬尝试。

这是目前发生的事情的图片：

这是我的代码

FXMLDocument.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.canvas.Canvas?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.Pane?>

<AnchorPane id="AnchorPane" prefHeight="399.0" prefWidth="465.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="cartographerfx.FXMLDocumentController">
    <children>
      <Pane fx:id="canvasPane" layoutX="26.0" layoutY="20.0" prefHeight="362.0" prefWidth="417.0" style="-fx-border-style: solid;">
         <children>
            <Canvas fx:id="canvas" height="362.0" onMouseDragged="#CanvasMouseDragged" onMousePressed="#CanvasMouseDown" onMouseReleased="#CanvasMouseUp" width="417.0" />
         </children>
      </Pane>
    </children>
</AnchorPane>

F XML document controller.Java

package cartographerfx;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.effect.DropShadow;
import javafx.scene.input.MouseButton;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;

/**
 *
 * @author Dan
 */
public class FXMLDocumentController implements Initializable {

    @FXML
    Canvas canvas;
    Canvas shadowLayer;

    @FXML
    Pane canvasPane;

    private GraphicsContext gc;
    private GraphicsContext sgc;
    private boolean isDragging;
    private double lastX;
    private double lastY;

    @FXML
    public void CanvasMouseDragged(MouseEvent event) {

        if (isDragging) {
            if (event.getButton() == MouseButton.PRIMARY) {

                gc.setStroke(Color.BLUE);

                gc.setLineWidth(10);
                gc.strokeLine(lastX, lastY, event.getX(), event.getY());
            } else if (event.getButton() == MouseButton.SECONDARY) {
                gc.clearRect(event.getX(), event.getY(), 10, 10);
            }

            lastX = event.getX();
            lastY = event.getY();
        }


    }

    @FXML
    public void CanvasMouseDown(MouseEvent event) {
        isDragging = true;

        lastX = event.getX();
        lastY = event.getY();

        if (event.getButton() == MouseButton.MIDDLE)
        {
            sgc = gc;
            sgc.applyEffect(new DropShadow());

        }
    }

    @FXML
    public void CanvasMouseUp(MouseEvent event) {
        isDragging = false;
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {

        gc = canvas.getGraphicsContext2D();
        isDragging = false;

        shadowLayer = new Canvas(canvas.getWidth(), canvas.getHeight());

        sgc = shadowLayer.getGraphicsContext2D();
        canvasPane.getChildren().add(shadowLayer);
        shadowLayer.toBack();
    }

}

cartographer FX.Java

package cartographerfx;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

/**
 *
 * @author Dan
 */
public class CartographerFX extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        Scene scene = new Scene(root);

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

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}

Answer 1

我不明白为什么当场景图更适合任务时，每个人似乎都在使用Canvas。你为什么不用普通的Pane和Path。然后，您可以将阴影效果直接应用于路径。场景图的优点是你可以根据需要单独编辑每个元素，而画布基本上只是一个图像，一旦绘制它就无法编辑。