如何使用paint（）和run（）或其他保留以前的更改

Question

如何使用repaint()和run()保留以前的更改，或者是否有其他解决方案。

我的代码运行良好。此代码描绘了3个椭圆形。当我在文本框中输入x坐标的输入时，它会绘制/绘制新的椭圆。但是，每当我在文本框中输入和更改x坐标时，椭圆就会重新定位。我想要做的是保留我之前做出的改变。例如，当您点击see coordinates按钮时，我会在开始时获得3个椭圆，然后在输入后获得4个等等，然后单击add coordinate按钮。

这是我的代码： /deleted/

非常感谢任何帮助。

[编辑]

我正在实施K-最近邻居。到目前为止，我所做的是： 1.created a gray panel of size 500x500 from (0,0)

2.gets file using browse button.

3.gets string and tokenize

4.token[0]= k-nearest, token[1]= total neighbors

5.token[2]= x-coordinate, token[3]= y-coordinate, token[4]= type of cluster and so on.

6.input x-coord and y-coord

7.compute distance between coordinates from txt file and input

8.draw shape according to minimum distance

这是我的代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.util.*;
import java.lang.Math;

public class Knn extends JFrame implements ActionListener{

JPanel grid,panel;
JLabel xlab,ylab;
JTextArea xtex,ytex,temp;
JButton cbut,fbut;
String text;
int k, ktotal, x, y,xcori,ycori;
String[] token;
int[] itoken;
boolean paint=false, paintclass=false;
double ans,xcord,ycord;
double[] dtoken,ansarray,xarray,yarray;
Map<Double, Double> anshash;

public Knn(){
    super("K-Nearest Neighbor");
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setSize(600,500);
    //this.pack();
    this.setVisible(true);
    this.setResizable(true);
    this.setLayout(null);

    grid= new JPanel();
    grid.setBackground(Color.GRAY);
    grid.setBounds(0,0,500,500);

    panel= new JPanel();
    //panel.setLayout(null);
    panel.setBounds(500,0,100,100);

    temp= new JTextArea();

    xlab= new JLabel("X");
    xtex= new JTextArea("",1,7);
    ylab= new JLabel("Y");
    ytex= new JTextArea("",1,7);
    cbut= new JButton("classify");
    fbut= new JButton("Browse");
    panel.add(xlab);
    panel.add(xtex);
    panel.add(ylab);
    panel.add(ytex);
    panel.add(cbut);
    panel.add(fbut);

    this.add(grid);
    this.add(panel);

    fbut.addActionListener(this);
    cbut.addActionListener(this);
}

public double formula(double x1, double y1, double x2, double y2){
    double tmpans= Math.pow((x2-x1),2.0) + Math.pow((y2-y1),2.0);
    ans= Math.sqrt(tmpans);
    return ans;
}

public void actionPerformed(ActionEvent e){ 
    if(e.getSource()==fbut){        //choose file input coordinates
        JFileChooser fileChooser= new JFileChooser();
        int returnVal = fileChooser.showOpenDialog(this);
        if(returnVal == JFileChooser.APPROVE_OPTION){
            File file = fileChooser.getSelectedFile();
            try {
                //output file content to text box, copy to a string
                temp.read( new FileReader(file.getAbsolutePath()),null);
                text= temp.getText();
            }catch(IOException ex){
                ex.printStackTrace();
            }
        }

        token = text.split("\\W+");
        itoken=new int[token.length];
        int i=0;
        for (String str : token){
            itoken[i++] = Integer.parseInt(str);    //convert from string to integer
        }

        for (i = 4; i < itoken.length; i += 3) {    //x50
            itoken[i-2]= itoken[i-2] * 50;
            itoken[i-1]= itoken[i-1] * 50;
        }

        paint=true;
        repaint();
    }
    if(e.getSource()==cbut){
        solveClass();
    }
}

public void paint(Graphics g){
    super.paint(g);
    if (paint) {
        for (int i = 4; i < itoken.length; i += 3) {
            x = itoken[i-2];
            y = itoken[i-1];
            if(itoken[i]==1)
                g.fillRect(x - 5, y - 5, 10, 10);
            if(itoken[i]==2)
                g.fillOval(x - 5, y - 5, 10, 10);
            if(itoken[i]==3)
                g.drawOval(x - 5, y - 5, 10, 10);
        }
    }
    if(paintclass){
        if(anshash.get(ansarray[0])==1)
            g.fillRect(xcori - 5, ycori - 5, 10, 10);
        if(anshash.get(ansarray[0])==2)
            g.fillOval(xcori - 5, ycori - 5, 10, 10);
        if(anshash.get(ansarray[0])==3)
            g.drawOval(xcori - 5, ycori - 5, 10, 10);
    }
}

public void solveClass(){
    String xcors= xtex.getText();
    String ycors= ytex.getText();

    dtoken=new double[itoken.length];
    xarray=new double[itoken[1]];
    yarray=new double[itoken[1]];
    ansarray=new double[itoken[1]];

    int j=0;
    for (String str : token)
            dtoken[j++] = Double.parseDouble(str);  //convert from string to double

    //convert to int
    xcori= Integer.parseInt(xcors);
    ycori= Integer.parseInt(ycors);

    //convert to double
    xcord= Double.parseDouble(xcors);
    ycord= Double.parseDouble(ycors);

    int q=0;
    for (int i = 3; i < itoken.length; i += 3) {
        xarray[q]= dtoken[i-1];
        yarray[q]= dtoken[i];
        q++;
    }

    for (int i = 0; i < xarray.length; i ++)
        ansarray[i]= formula(xcord,ycord,xarray[i]*50,yarray[i]*50);    //x50

    anshash= new HashMap<Double,Double>();
    int r=0;
    for(int i = 4; i < itoken.length; i += 3){
        anshash.put(ansarray[r], dtoken[i]);
        r++;
    }

    Arrays.sort(ansarray);  //sort

    paintclass=true;
    repaint();

}


public static void main(String[] args){
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            Knn knn= new Knn();
        }
    });

}
}

这是文本文件：

3 5 
1 2 1
4 3 2
7 5 2
6 9 3
5 5 1

Answer 1

  

“但是，每当我在文本框中输入和更改x坐标时，椭圆就会重新定位。我想要做的是保留我之前做过的更改”

使用List球对象。这是Ball类

public class Ball {
    int x;
    int y;
    public Ball(int x, int y) {
        this.x = x;
        this.y = y;
    }
    public void drawball(Graphics g) {
        g.fillOval(x, y, 20, 20);
    }
}

这是JPanel类

public class BallPanel extends JPanel {
    private List<Ball> balls;

    @Override
    protected void paintComponent(Graphics g) {
        super.paintCompoent(g);
        for (Ball ball: balls) {
            ball.drawBall(g);
        }
    }
}

基本点是保持球位置的数据结构。您可能还希望为x和y设置getter和setter，以便操作它们的位置。

要添加更多球，您需要做的就是添加到List和new Ball(...)并致电repaint();

---

这是一个正在运行的例子。只需输入x和y小于500，然后点击按钮即可。你会看到更多的球被添加。您可以在actionPerformed中看到我添加new Ball的位置以及paintCompoent我在那里循环播放List

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class TestBall extends Frame implements ActionListener {

    private JTextField enterX;
    private JTextField enterY;
    private JLabel labelX;
    private JLabel labelY;
    private JButton addBall;
    private List<Ball> balls;
    private BallPanel ballPanel;

    public TestBall() {
        balls = new ArrayList<>();
        ballPanel = new BallPanel();

        JPanel p1 = new JPanel();
        labelX = new JLabel("Enter X");
        enterX = new JTextField(6);
        labelY = new JLabel("Enter Y");
        enterY = new JTextField(6);
        addBall = new JButton("Add Ball");
        addBall.addActionListener(TestBall.this);

        p1.add(labelX);
        p1.add(enterX);
        p1.add(labelY);
        p1.add(enterY);
        p1.add(addBall);

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(ballPanel, BorderLayout.CENTER);
        frame.add(p1, BorderLayout.PAGE_START);
        frame.pack();
        frame.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        int x = Integer.parseInt(enterX.getText());
        int y = Integer.parseInt(enterY.getText());
        balls.add(new Ball(x, y));
        ballPanel.repaint();

    }

    public class BallPanel extends JPanel {

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(500, 500);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            for (Ball ball : balls) {
                ball.drawBall(g);
            }
        }
    }

    public class Ball {

        int x;
        int y;

        public Ball(int x, int y) {
            this.x = x;
            this.y = y;
        }

        public void drawBall(Graphics g) {
            g.fillOval(x, y, 20, 20);
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new TestBall();
            }
        });
    }
}