java - Jpanel 用鼠标移动事件重绘

Question

好的，这就是我正在制作的函数绘图器，我希望当您将鼠标移动到线上时，它会显示坐标。所以我在面板上设置了一个基本的拉绳来显示鼠标坐标，但我无法正常重新绘制。它似乎画得很好，但在绘画之前并没有清除内容，这是我迄今为止的代码。

public class Grapher extends JPanel implements MouseMotionListener{
private final int BORDER_GAP = 15;
private final int MAX_SCORE = 20;
private final int PREF_WIDTH = 800;
private final int PREF_HEIGHT = 650;
private final int GRAPH_POINT_WIDTH = 12;
private static final int GRAPH_INTERVAL = 15;

private static Point mse;

private List<Point> values;

public Grapher(List<Point> values) {
    setMse(new Point(0,0));
    this.values = values;
    addMouseMotionListener(this);
}

public void paintComponent(Graphics g){
    super.paintComponents(g);

    Graphics2D g2d = (Graphics2D) g;
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

    float xScale = ((float) getWidth() - 2 * BORDER_GAP) / (values.size()-1);
    float yScale = ((float) getHeight() - 2 * BORDER_GAP) / (MAX_SCORE-1);

    g2d.drawString(xScale+"", 50, 50);
    g2d.drawString(yScale+"", 50, 70);
    g2d.drawString(getWidth()/2+"", 50, 90);
    g2d.drawString(mse.x +"  " + mse.y, 50, 30);

    //create axis
    g2d.setColor(new Color(0x7e7e7e));
    //x line
    g2d.drawLine(BORDER_GAP, (getHeight() - BORDER_GAP)/2, getWidth() - BORDER_GAP, (getHeight() - BORDER_GAP)/2);
    //y line
    g2d.drawLine(getWidth()/2, getHeight() - BORDER_GAP, getWidth()/2, BORDER_GAP);

}

public Dimension getPreferredSize(){
    return new Dimension(PREF_WIDTH, PREF_HEIGHT);
}

private static void createAndShowGui(){
    List<Point> values = new ArrayList<Point>();
    int maxDataPoints = 20;

    for (int i = -GRAPH_INTERVAL; i <= GRAPH_INTERVAL; i++) {
        String val = "";
        try {
            val = EquationSolver.solveEquation(variableReplace('x', i));
        } catch (Exception e) {
            val ="0";
            e.printStackTrace();
        }
        System.out.println(i + "= " + val);
        values.add(new Point(i, Integer.parseInt(val)));
    }

    Grapher panel = new Grapher(values);

    JFrame frame = new JFrame("Grapher");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(panel);
    frame.pack();
    //frame.setLocationByPlatform(true);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);

}


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

@Override
public void mouseMoved(MouseEvent e) {
    setMse(new Point(e.getX(), e.getY()));
    removeAll();
    repaint();      
}

@Override
public void mouseDragged(MouseEvent e) {
    setMse(new Point(e.getX(), e.getY()));
    //repaint();        
}

好的，这里有一些关于代码正在做什么的图像最上面的数字是鼠标位置。编程的新开始:http://snag.gy/BFrUj.jpg 。当我稍微移动鼠标后:http://snag.gy/lNqie.jpg

感谢您的帮助。

Answer 1

我建议您遇到的主要问题与g.dispose()

有关

图形上下文是共享的，这意味着如果您处理图形上下文，则没有其他东西可以对其进行绘制。除非您创建上下文，否则永远不应该处置它

您的另一个问题是，您实际上并没有调用 super.paintComponent，它负责准备绘画的图形上下文(通过清除要绘制的区域)，而是您正在调用 super.paintComponents(g) ...而不是最后的 s ...