Question

我的java gui有问题:(我希望你会帮助我:)。

我有一个黑色的gui，当我在gui中用鼠标点击时，程序会将点击的坐标保存在Point之前。然后，当我点击第二个位置时，程序会在Point current中保存第二个点击坐标，并在“previous”和“current”之间画一条线。

但是现在我希望当我第三次在gui中点击时，程序将在第二次点击和第三次点击之间绘制一条线，依此类推。第五个之间的第四个。

我该怎么做？

这是我的代码：

 public class OdometerPanel extends JPanel {
    private double totalDistance;
    private Point previous = null, current = null;
    private ArrayList<Point> travelledPoints;
    private int p1x, p2x, p1y, p2y;
    private double distance;
    JLabel pointco = new JLabel("");
    JLabel trav = new JLabel("Travelled Distance: " + distance);

public OdometerPanel() {
  LineListener listener = new LineListener();
  addMouseListener(listener);
  addMouseMotionListener(listener);

  trav.setForeground(Color.green);
  pointco.setForeground(Color.yellow);
  add(pointco);
  add(trav);
  setBackground(Color.black);
  setPreferredSize(new Dimension(400, 200));
  }

  public void paintComponent(Graphics page)
  {
      super.paintComponent(page);

    page.setColor (Color.yellow);
    if (previous != null && current != null)
     page.drawLine(previous.x, previous.y, current.x, current.y);
  }


  private class LineListener implements MouseListener,
                                     MouseMotionListener
   {
   public void mouseClicked(MouseEvent event)
  {        

      if(previous == null && current == null) {
     previous = event.getPoint();
      p1x = (int) previous.getX();
      p1y = (int) previous.getY();
      pointco.setText("P(" + p1x + "," + p1y + ")");
      }
      else {
          current = event.getPoint();
          p2x = (int) current.getX();
          p2y = (int) current.getY();
          distance = (int) Math.sqrt((p2x - p1x)*(p2x - p1x) + (p2y - p1y) * (p2y - p1y));
          trav.setText("Travelled Distance: " + distance);
          pointco.setText("P(" + p2x + "," + p2y + ")");
          repaint(); 
      }

   }

   public void mousePressed(MouseEvent event) {}
   public void mouseReleased(MouseEvent event) {}
   public void mouseEntered(MouseEvent event) {}
   public void mouseExited(MouseEvent event) {}
   public void mouseMoved(MouseEvent event) {}
   public void mouseDragged(MouseEvent event) {}       
    }
  }

提前谢谢你：D``

Answer 1

您的mouseClicked代码应该更多。

if(current == null) {
    current = event.getPoint();
    p1x = (int) current.getX(); p1y = (int) current.getY();
    pointco.setText("P(" + p1x + "," + p1y + ")");
} else {
    previous = current;
    current = event.getPoint();
    p1x = (int) previous.getX();
    p1y = (int) previous.getY();
    p2x = (int) current.getX();
    p2y = (int) current.getY();
    distance = (int) Math.sqrt((p2x - p1x)*(p2x - p1x) + (p2y - p1y) * (p2y - p1y));
    trav.setText("Travelled Distance: " + distance);
    pointco.setText("P(" + p2x + "," + p2y + ")");
    repaint();
}

不确定previous = current是否真的有效。你可能需要更像

的东西

previous = new Point(current.getX(), current.getY());

这取决于Point类可用的构造函数。

Answer 2

我假设您想要同时绘制多条线，这意味着您需要保留所有点的列表。

在主要班级：

List<Point> points = new ArrayList<>();

@Override
public void paintComponent(Graphics page) {
    super.paintComponent(page);

    page.setColor(Color.yellow);

    for(int i= 1; i < points.size(); i++) {
        Point p1 = points.get(i-1);
        Point p2 = points.get(i);
        page.drawLine(p1.x, p1.y, p2.x, p2.y);
    }
}

在MouseListener中

public void mouseClicked(MouseEvent event) {
    points.add(event.getPoint());
}

在java中的每次鼠标点击中生成一系列行

2 个答案: