Question

我不知道为什么，但我无法从代码中调用方法paint(Graphics g)。我有MouseListeners：

    @Override
    public void mouseReleased(MouseEvent e) {       
        pointstart = null;
    }

    @Override
    public void mousePressed(MouseEvent e) {
        pointstart = e.getPoint();
    }

和MouseMotionListeners：

    @Override
    public void mouseMoved(MouseEvent e) {
        pointend = e.getPoint();
    }

    @Override
    public void mouseDragged(MouseEvent arg0) {
        pointend = arg0.getPoint();
        // ==========================================================================
        //          call repaint:

        repaint();


        // ==========================================================================
    }

和我的paint方法：

public void paint(Graphics g){
    super.paint(g); //here I have my breakpoint in debugger
    g.translate(currentx, currenty);
    if(pointstart!=null){
        g.setClip(chartPanel.getBounds());
        g.setColor(Color.BLACK);
        g.drawLine(pointstart.x, pointstart.y, pointend.x, pointend.y);
    }
}

初始化方法中的

：

currentx = chartPanel.getLocationOnScreen().x;
currenty = Math.abs(chartPanel.getLocationOnScreen().y - frame.getLocationOnScreen().y);

全班同学，这是我的工作框架，它延伸JFrame。

问题是，该程序没有call绘制方法。我在调试器中检查过。我试过paintComponent执行此操作，没有super.paint(g)。最好的是，我从我的其他项目复制的代码，它工作得很好。

更新：这是我想在面板上绘制线条的代码（无论是面板/图表面板/等）。而且它不会画画。我尝试通过paint（Graphics g）{super.paint（g）.....}来做到这一点，但它也没有。单击“线”按钮后，绘画应该显示。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JToolBar;
import javax.swing.SwingConstants;
import javax.swing.JScrollPane;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

public class Window extends JFrame {
private JFrame frame;
public JPanel panelbuttons;
public JPanel panelscrollpane;
public JButton btnLine;
public JToolBar toolBar;
public JScrollPane scrollPane;
public JPanel panel;

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Window window = new Window();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

public Window() {
    initialize();
}

private void initialize() {
    frame = new JFrame();
    frame.setBounds(100, 100, 644, 430);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    panel = new JPanel();

    panelbuttons = new JPanel();
    frame.getContentPane().add(panelbuttons, BorderLayout.WEST);
    panelbuttons.setLayout(new BorderLayout(0, 0));

    toolBar = new JToolBar();
    toolBar.setOrientation(SwingConstants.VERTICAL);
    panelbuttons.add(toolBar, BorderLayout.WEST);

    btnLine = new JButton("line");
    btnLine.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            panel.addMouseListener(mouselistenerLine);
            panel.addMouseMotionListener(mousemotionlistenerLine);
        }
    });
    toolBar.add(btnLine);

    panelscrollpane = new JPanel();
    frame.getContentPane().add(panelscrollpane, BorderLayout.CENTER);
    panelscrollpane.setLayout(new BorderLayout(0, 0));



    scrollPane = new JScrollPane(panel);
    panel.setLayout(new BorderLayout(0, 0));
    scrollPane.setViewportBorder(null);
    panelscrollpane.add(scrollPane);
    panelscrollpane.revalidate();
}

    Point pointstart = null;
    Point pointend = null;

private MouseListener mouselistenerLine = new MouseListener() {


        @Override
        public void mouseReleased(MouseEvent e) {
            System.out.println("I'm in first listener. - mouse Released");
            pointstart = null;
        }

        @Override
        public void mousePressed(MouseEvent e) {
            System.out.println("I'm in first listener. - mousePressed");
            pointstart = e.getPoint();
        }

        @Override
        public void mouseExited(MouseEvent e) {
        }

        @Override
        public void mouseEntered(MouseEvent e) {
        }

        @Override
        public void mouseClicked(MouseEvent e) {
        }

    };

    private MouseMotionListener mousemotionlistenerLine = new MouseMotionListener() {

            @Override
            public void mouseMoved(MouseEvent e) {
                System.out.println("I'm in second listener. - mouseMoved");
                pointend = e.getPoint();
            }

            @Override
            public void mouseDragged(MouseEvent arg0) {
                System.out.println("I'm in second listener. - mouseDragged");
                pointend = arg0.getPoint();
                repaint();
            }

    };

    public void paintComponent(Graphics g){

        System.out.println("I'm in paintComponent method.");

        if(pointstart!=null){
            System.out.println("I'm drawing.");
            g.setClip(scrollPane.getBounds());
            g.setColor(Color.BLACK);
            g.drawLine(pointstart.x, pointstart.y, pointend.x, pointend.y);

        }
    }
}

Answer 1

您正在创建两个单独的JFrame实例，并且只显示一个。
创建一个实例是因为Window类扩展了JFrame，而第二个是在initialize方法中创建的。

要解决此问题而不需要对代码进行大量更改，请执行以下操作：

private void initialize() {
    frame = this;
    frame.setBounds(100, 100, 644, 430);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

顺便说一句。将paintComponent(Graphic g)更改为paint(Graphic g)，因为JFrame不是JComponent。

Answer 2

在ChartPanel上下文中，考虑org.jfree.chart.annotations之一，例如XYLineAnnotation，图示here和here。

Answer 3

调用repaint()将触发您的paint(Graphics g)方法被调用。因此，您无需明确调用paint()。

paint方法没有被调用

3 个答案: