Question

我正在通过覆盖paint（g）在JPanel上绘制网格，并用它标记点击网格上的某些点，但主要问题是，如果有人最小化网格或将其拖动到屏幕周围，那么屏幕变成空白。我无法弄清楚如何更改我的代码，以便在每次屏幕最小化或拖动时刷新它，请帮我处理代码。

这是我的代码： -

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;

public class draw extends JPanel {

private int x,y,X,Y,xmin,xmax,ymin,ymax;
private int clickParam = 0;
private double d, theta;
private ArrayList<Integer> ab = new ArrayList<Integer>();
private ArrayList<Integer> or = new ArrayList<Integer>();
private ArrayList<Double> distance = new ArrayList<Double>();
private ArrayList<Double> angle = new ArrayList<Double>();
Graphics2D g2d = null;

 public void drawing(){

     repaint();

 }
 @Override
 public void paintComponent(Graphics g){

     super.paintComponent(g);
     Graphics2D g2 = (Graphics2D) g;

     g2d = g2;
     int stroke[]={1,2,3,4,5};

     g2.setStroke(new BasicStroke(stroke[1]));
     xmin = 150;
     ymin = 150;
     xmax = 650;
     ymax = 650;
     int xsize = xmax - xmin;
     int ysize = ymax - ymin;
     g2.drawRect(xmin, ymin, xsize, ysize);
     for(int i=50;i<=xsize;i+=50){

        g2.drawLine(xmin+i, ymin, xmin+i, ymax);
        g2.drawLine(xmin, ymin+i, xmax, ymin+i);

        }
     g2.setStroke(new BasicStroke(stroke[0]));
     for(int i=10;i<=xsize;i+=10){

        g2.drawLine(xmin+i, ymin, xmin+i, ymax);
        g2.drawLine(xmin, ymin+i, xmax, ymin+i);

        }

 }
 public void drawPoints(Graphics2D g2){

     if(x >= xmin && x <= xmax && y >= ymin && y <= ymax)
            g2.fillOval(x-3, y-3, 7, 7);

 }
 public void onClick(){

     addMouseListener(new MouseAdapter(){

         @Override
         public void mousePressed(MouseEvent e){

                setxy(e);
                setXY();               
                clickParam = 2;
                drawPoints(g2d);

                if(x >= xmin && x <= xmax && y >= ymin && y <= ymax){

                    setDistance();
                    setAngle();
                    display();
                }   
             }

     });

 }
 public void setxy(MouseEvent e){

    x = e.getX();
    y = e.getY();
    if(x >= xmin && x <= xmax && y >= ymin && y <= ymax){
    ab.add(x);
    or.add(y);
    }  
 }
 public void setXY(){

     X = x - xmin;
     Y = ymax - y;

 }
 public void setDistance(){

     d = Math.sqrt(Math.pow(X/10, 2) + Math.pow(Y/10, 2));
     distance.add(d);

 }
 public void setAngle(){

     theta = Math.atan2(Y,X)*180/Math.PI;
     angle.add(theta);

 }
 public void display(){

     System.out.println("(X,Y) = ("+(X/10)+","+(Y/10)+")"+" & (d,theta) = ("+d+","+theta+")");

 }
 }

和主要课程： -

import java.awt.Dimension;
import javax.swing.*;

public class mainClass {

public static void main(String args[]){
    JFrame jframe = new JFrame("TEST");
    draw d = new draw();
    jframe.setPreferredSize(new Dimension(1000,1000));
    jframe.pack();
    jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jframe.add(d);
    jframe.setVisible(true);
    jframe.setResizable(false);
    d.drawing();
    d.onClick();


}

}

Answer 1

onClick，因此永远不会添加MouseListener。
创建Point的列表，并在paintComponent方法中循环显示。
drawPoints只应在paintComponent方法中调用，因为它需要当前的Graphics2D对象。

重组代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;

public class Draw extends JPanel { // Class names should start with an uppercase letter

    private int xmin, xmax, ymin, ymax;
    private ArrayList<Point> points = new ArrayList<Point>(); // Create a list where all clicked points will be stored

    public Draw() {
        xmin = 150;
        ymin = 150;
        xmax = 650;
        ymax = 650;
        addMouseListener(new MouseAdapter() { // Add MouseListener in the constructor
            @Override
            public void mousePressed(MouseEvent e) {
                Point point = new Point(e.getX(), e.getY());
                if (point.x >= xmin && point.x <= xmax && point.y >= ymin
                        && point.y <= ymax) {
                    points.add(point); // Add the point to the list
                    repaint();
                }
            }
        });
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        int stroke[] = { 1, 2, 3, 4, 5 };

        g2.setStroke(new BasicStroke(stroke[1]));
        int xsize = xmax - xmin;
        int ysize = ymax - ymin;
        g2.drawRect(xmin, ymin, xsize, ysize);
        for (int i = 50; i <= xsize; i += 50) {
            g2.drawLine(xmin + i, ymin, xmin + i, ymax);
            g2.drawLine(xmin, ymin + i, xmax, ymin + i);

        }
        g2.setStroke(new BasicStroke(stroke[0]));
        for (int i = 10; i <= xsize; i += 10) {
            g2.drawLine(xmin + i, ymin, xmin + i, ymax);
            g2.drawLine(xmin, ymin + i, xmax, ymin + i);

        }
        drawPoints(g2);
    }

    private void drawPoints(Graphics2D g2) {
        for (Point point : points) { // Loop through the list of points
            g2.fillOval(point.x - 3, point.y - 3, 7, 7);
        }
    }

    public static void main(String args[]) {
        JFrame jframe = new JFrame("TEST");
        Draw d = new Draw();
        jframe.setSize(800,800);
        jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jframe.setContentPane(d);
        jframe.setVisible(true);
    }

}

每次窗口最小化或拖出屏幕时，绘制的JPanel都会刷新

1 个答案: