Question

这是我的代码......

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.lang.*;

public class LineDrawing {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createWindow();
            }
        });
    }

    private static void createWindow() {
        JFrame mainFrame = new JFrame();

        mainFrame.add(new myPanel());
        mainFrame.setExtendedState(JFrame.MAXIMIZED_BOTH);
        mainFrame.setBackground(Color.white);
        mainFrame.setLocationRelativeTo(null);
        mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainFrame.setVisible(true);
    }
}

class myPanel extends JPanel {
    int startX;
    int startY;
    int endX;
    int endY;

    public myPanel() {

        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                startX = e.getX();
                startY = e.getY();
                repaint(startX, startY, endX, endY);
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                endX = e.getX();
                endY = e.getY();
                repaint(startX, startY, endX, endY);
            }

            @Override
            public void mouseClicked(MouseEvent e) {
                startX = e.getX();
                endX = startX;
                startY = e.getY();
                endY = startY;
                repaint(startX, startY, endX, endY);
            }
        });

        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                endX = e.getX();
                endY = e.getY();
                repaint(startX, startY, endX, endY);
            }
        });
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.black);
        g.drawLine(startX, startY, endX, endY);
        repaint();
    }
}

我正在尝试绘制多条线，同时保持前一条线仍然存在于屏幕（框架）上... 但是，当我再次点击时，前一行会被擦掉或擦除......

我正在设计一个图形分析应用程序（它将告诉输入的图形是否是同构的......

我的问题是我无法绘制多条线但只能绘制一条线......

Answer 1

我的问题是我无法绘制多条线但只能绘制一条线......

它仅绘制1行，因为您只在paintComponent中绘制了1行。请注意，图纸不是累积的。

CostofA.keys()

要绘制多条线条（如图形），您需要一个数据结构来保存每个图形的数据。然后你可以迭代它并从那里绘制多条线。

因此只保留一组情节protected void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.black); g.drawLine(startX,startY,endX,endY); //this will draw only one line.. repaint(); //do not do this! }。您可以为Plot：

创建一个类

(startX, startY, endX, endY)

然后在显示面板中，保留一个绘图列表：

public class Plot
{
    private int startX;
    private int startY;
    private int endX;
    private int endY;

    public Plot(int startX, int startY, int endX, int endY){
        this.startX = startX;
        this.startY = startY;
        this.endX = endX ;
        this.endY = endY ;
    }

    public void draw(Grpahics g){
        g.setColor(Color.black);
        g.drawLine(startX,startY,endX,endY);        
    }
}

最后，在您的class MyPanel extends JPanel { private ArrayList<Plot> plots; public MyPanel(){ plots = new ArrayList<Plot>(); } public void addPlot(int x1, int y1, int x2, int y2){ plots.add(new Plot(x1, y1, x2, y2)) } //Invoke addPlot() in your mouseListener after you get startXY & endXY //Invoke repaint() after addPlot() //Don't have to do this: "repaint(startX,startY,endX,endY);" }：

中

paintComponent()

此外，您不应在@Override protected void paintComponent(Graphics g){ super.paintComponent(g); for(Plot p : plots) p.draw(g); //Each plot will draw itself }内致电repaint()。当您需要刷新屏幕时，可以在paintComponent()之外拨打电话。

无法一次绘制多条线

1 个答案: