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);

    }

}