java - 画箭头不起作用

Question

我正在尝试在 JavaFX 中绘制箭头。我做了所有的数学计算，甚至还考虑了弧度的问题。由于某种原因，我的箭头没有正确绘制。我几乎认为这与三角函数的域/范围有关，但我不能确定。

这是我的代码:

package com.neonorb.test;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.shape.Line;
import javafx.stage.Stage;

public class ArrowTest extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        double startx = 200;
        double starty = 100;
        double endx = 100;
        double endy = 300;

        double arrowAngle = Math.toRadians(45.0);
        double arrowLength = 10.0;

        double lineAngle = Math.atan((startx - endx) / (starty - endy));

        double x1 = Math.asin((arrowAngle + lineAngle) / arrowLength) + endx;
        double y1 = Math.acos((arrowAngle + lineAngle) / arrowLength) + endy;

        double x2 = Math.asin((arrowAngle - lineAngle) / arrowLength) + endx;
        double y2 = Math.acos((arrowAngle - lineAngle) / arrowLength) + endy;

        Group root = new Group();

        Line line = new Line(startx, starty, endx, endy);
        Line arrowHead1 = new Line(endx, endy, x1, y1);
        Line arrowHead2 = new Line(endx, endy, x2, y2);

        root.getChildren().addAll(line, arrowHead1, arrowHead2);

        primaryStage.setScene(new Scene(root, 800, 600));
        primaryStage.show();
    }
}

Answer 1

^{很难用比......更多的东西来“回答”这个(非问题)}

...你的数学在几个方面都搞砸了:

• 应该是 sin 和 cos，而不是 asin 和 acos
• 应该是sin(x)*length，而不是sin(x/length)
• sin 和 cos 已交换
• 直线的角度最好使用 atan2 计算(您使用的 atan 函数有一些问题，显然，特别是使用 starty==endy )
• “偏移”应添加到线角度 - 特别是，它应该是 lineAngle - arrowAngle 而不是 arrowAngle - lineAngle

更新后的整个代码:

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.shape.Line;
import javafx.stage.Stage;


public class ArrowTest extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
        double startx = 200;
        double starty = 100;
        double endx = 100;
        double endy = 300;

        double arrowAngle = Math.toRadians(45.0);
        double arrowLength = 10.0;

        double lineAngle = Math.atan2(starty - endy, startx - endx);

        double x1 = Math.cos(lineAngle + arrowAngle) * arrowLength + endx;
        double y1 = Math.sin(lineAngle + arrowAngle) * arrowLength + endy;

        double x2 = Math.cos(lineAngle - arrowAngle) * arrowLength + endx;
        double y2 = Math.sin(lineAngle - arrowAngle) * arrowLength + endy;

        Group root = new Group();

        Line line = new Line(startx, starty, endx, endy);
        Line arrowHead1 = new Line(endx, endy, x1, y1);
        Line arrowHead2 = new Line(endx, endy, x2, y2);

        root.getChildren().addAll(line, arrowHead1, arrowHead2);

        primaryStage.setScene(new Scene(root, 800, 600));
        primaryStage.show();
    }
}