JavaFX 未渲染数组中较早的项目，无法找到问题，相信线程可能是问题所在

Question

我编写了一个画线算法，在计算每个点时可以正确运行，但是当它被渲染时，程序会跳过近 20 个点，无法找到问题。

我试图弄乱算法，特别是 for 循环，它将点添加到计算线的位置列表中，因为我在其他版本的代码中遇到了问题。我只是一辈子都找不到代码的问题，我对 Java 还很陌生，你可能会从下面混乱的代码中看出这一点。它说不要发布整个文件，但我无法确定哪里出了问题。我对下面混乱的代码感到非常抱歉，我只是不知道出了什么问题。

package sample;

import com.sun.jdi.ArrayReference;

import javafx.application.Application;

import javafx.application.Platform;

import javafx.scene.Group;

import javafx.scene.canvas.Canvas;

import javafx.scene.canvas.GraphicsContext;

import javafx.scene.paint.Color;

import javafx.scene.Scene;

import javafx.stage.Stage;

import java.util.ArrayList;

class PositionCounter {

    public int position;

    public void setPosition(int newPos){

        position = newPos;

    }

}

public class Main extends Application {

//    public void drawRectangle(int x1, int y1, int x2, int y2, Stage primStage, GraphicsContext gc){

//        drawLine(x1, y2, x2, y2 , primStage, gc);

//        drawLine(x1, y1, x2, y2, primStage, gc);

//        drawLine(x1, y1, x1 , y2, primStage, gc);

//        drawLine(x2, y1, x2 , y2, primStage, gc);

//        drawLine(x1, y1, x2, y1 , primStage, gc);

//

//    }

//

    public void fillPosition(ArrayList<Integer[]> points, GraphicsContext gc, int positionInArray ){

        gc.fillRect(points.get(positionInArray)[0], points.get(positionInArray)[1], squareWidth / 2, squareWidth / 2);

        //System.out.println("(" + points.get(positionInArray)[0] + ", " + points.get(positionInArray)[1]);

    }

    public void drawLine(int x1, int y1, int x2, int y2, Stage primStage, GraphicsContext gc){

        ArrayList<Integer[]> points = calculateLine(x1, y1, x2, y2, gc);

        PositionCounter position = new PositionCounter();

        Thread thread = new Thread(new Runnable() {

            @Override

            public void run() {

                    Runnable updater = new Runnable() {

                        @Override

                        public void run() {

                            fillPosition(points, gc, position.position);

                        }

                    };

问题是计算线函数返回正确的点，只是没有正确渲染它们。

Answer 1

我建议您使用Timeline而不是Thread. 它可以使用 a 来完成Thread，但Timeline专为此类情况而设计。画线方法：public void drawLine(int x1, int y1, int x2, int y2, Stage primStage, GraphicsContext gc){    ArrayList<Integer[]> points = calculateLine(x1, y1, x2, y2, gc);    PositionCounter position = new PositionCounter();    int dy = Math.abs(y2 - y1);    int dx = Math.abs(x2 - x1);    int m = (dy >= dx) ? dy : dx;    AtomicInteger counter = new AtomicInteger();    Timeline animationTimeline = new Timeline(new KeyFrame(Duration.millis(20), (ActionEvent t) -> {        position.setPosition(counter.getAndIncrement());        fillPosition(points, gc, position.position);    }));    animationTimeline.setCycleCount(points.size());    animationTimeline.play();}完整代码：import com.sun.jdi.ArrayReference;import javafx.application.Application;import javafx.application.Platform;import javafx.scene.Group;import javafx.scene.canvas.Canvas;import javafx.scene.canvas.GraphicsContext;import javafx.scene.paint.Color;import javafx.scene.Scene;import javafx.stage.Stage;import java.util.ArrayList;import java.util.concurrent.atomic.AtomicInteger;import javafx.animation.KeyFrame;import javafx.animation.Timeline;import javafx.event.ActionEvent;import javafx.event.EventHandler;import javafx.util.Duration;class PositionCounter{    public int position;    public void setPosition(int newPos)    {        position = newPos;    }}public class JavaFXTestingGround extends Application{//    public void drawRectangle(int x1, int y1, int x2, int y2, Stage primStage, GraphicsContext gc){//        drawLine(x1, y2, x2, y2 , primStage, gc);//        drawLine(x1, y1, x2, y2, primStage, gc);//        drawLine(x1, y1, x1 , y2, primStage, gc);//        drawLine(x2, y1, x2 , y2, primStage, gc);//        drawLine(x1, y1, x2, y1 , primStage, gc);////    }//    public void fillPosition(ArrayList<Integer[]> points, GraphicsContext gc, int positionInArray)    {        gc.fillRect(points.get(positionInArray)[0], points.get(positionInArray)[1], squareWidth / 2, squareWidth / 2);        //System.out.println("(" + points.get(positionInArray)[0] + ", " + points.get(positionInArray)[1]);    }    public void drawLine(int x1, int y1, int x2, int y2, Stage primStage, GraphicsContext gc)    {        ArrayList<Integer[]> points = calculateLine(x1, y1, x2, y2, gc);        PositionCounter position = new PositionCounter();        int dy = Math.abs(y2 - y1);        int dx = Math.abs(x2 - x1);        int m = (dy >= dx) ? dy : dx;        AtomicInteger counter = new AtomicInteger();        Timeline animationTimeline = new Timeline(new KeyFrame(Duration.millis(20), (ActionEvent t) -> {            position.setPosition(counter.getAndIncrement());            fillPosition(points, gc, position.position);        }));        animationTimeline.setCycleCount(points.size());        animationTimeline.play();    }    @Override    public void start(Stage primaryStage) throws Exception    {        //STUFF        Group root = new Group();        Scene scene = new Scene(root, 400, 400);        scene.setFill(Color.GOLD);        Canvas canvas = new Canvas(400, 400);        GraphicsContext gc = canvas.getGraphicsContext2D();        root.getChildren().add(canvas);        //////////        gc.fillRect(0, 200, 400, 1);        gc.fillRect(0, 100, 400, 1);        gc.fillRect(0, 300, 400, 1);        gc.fillRect(200, 0, 1, 400);        gc.fillRect(100, 0, 1, 400);        gc.fillRect(300, 0, 1, 400);        // drawRectangle(50, 50, 350, 250, primaryStage, gc);        //drawLine(50, 250, 350, 250 , primaryStage, gc);        //drawLine(50, 50, 350, 250, primaryStage, gc);        //drawLine(50, 50, 50 , 250, primaryStage, gc);        //drawLine(350, 50, 350 , 250, primaryStage, gc);        drawLine(50, 50, 350, 50, primaryStage, gc);        //////////        primaryStage.setScene(scene);        primaryStage.show();        /////////    }    int squareWidth = 2;    public ArrayList<Integer[]> calculateLine(int x1, int y1, int x2, int y2, GraphicsContext gc)    {        ArrayList<Integer[]> points = new ArrayList<Integer[]>();        int dy = Math.abs(y2 - y1);        int dx = Math.abs(x2 - x1);        int sx = (x1 < x2) ? 1 : -1;        int sy = (y1 < y2) ? 1 : -1;        int err = dx - dy;        int x = x1;        int y = y1;        int e2 = 0;        Integer[] pos = new Integer[2];        pos[0] = x;        pos[1] = y;        points.add(pos);        int m = (dy >= dx) ? dy : dx;        for (int i = 0; i <= m; i++) {            e2 = 2 * err;            if (e2 > -dy) {                err = err - dy;                x = x + sx;                Integer[] position = new Integer[2];                position[0] = x;                position[1] = y;                points.add(position);            }            if (e2 < dx) {                err = err + dx;                y = y + sy;                Integer[] position = new Integer[2];                position[0] = x;                position[1] = y;                points.add(position);            }        }        return points;    }    public static void main(String[] args)    {        launch(args);    }}