Question

好的，我正在创建一个函数grapher，我想当你将鼠标移动到一条线上时它会显示坐标。因此，我在面板上设置了一个基本的束带，以显示鼠标坐标，但我无法正常重绘。它似乎画得很好但是在绘画之前没有清除内容这里是我到目前为止的代码。

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();        
}

这里有一些关于代码正在做什么的图像顶部的数字是鼠标位置。重新开始计划：http://snag.gy/BFrUj.jpg。我将鼠标移动一点后：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，这意味着如果你处理图形上下文，其他任何东西都不能绘制它。除非您创建上下文，否则不应该将其丢弃

你的另一个问题是，你实际上并没有调用super.paintComponent，它负责为绘画准备图形上下文（通过清除要绘制的图像），而是调用super.paintComponents(g) ......最后不是 s ......

Answer 2

出于某种原因，当我直接在面板上绘制时，它会产生叠加效果，但如果我添加一个白色矩形作为背景来解决问题。

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

g2d.setColor(Color.white);
g2d.fillRect(0, 0, getWidth(), getHeight());
g2d.setColor(new Color(0x7e7e7e));

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

这似乎解决了这个问题。如果有人能解释为什么直接绘制到面板覆盖层或有更好的解决方案，请回答。

Jpanel重绘鼠标移动事件

2 个答案: