无法使用MouseListener的输入

Question

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
public class Viewer implements MouseListener
{
  static int counter = 0;
  static double x1, x2, x3, y1, y2, y3;
  public static void main (String [] args)
  {
    JFrame outerFrame = new JFrame();
    JPanel panel = new JPanel();

    panel.setSize(400,400);
    outerFrame.setSize(400, 400);
    outerFrame.setTitle("Drawing Triangle");
    outerFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    outerFrame.add(panel);
    panel.addMouseListener(new MouseAdapter(){

      @Override
      public void mousePressed(MouseEvent e){
        if(counter == 0) {
          x1 = e.getX();
          y1 = e.getY();

        } else if(counter == 1) {
          x2 = e.getX();
          y2 = e.getY();

        } else if(counter == 2) {
          x3 = e.getX();
          y3 = e.getY();

        }

        counter++;
      }

    });
    System.out.println(x2);
    System.out.println(y2);
    System.out.println(x1);
    System.out.println(y1);    
    System.out.println(x3);
    System.out.println(y3);

    TriangleComponent component = new TriangleComponent(x1, x2, x3, y1, y2, y3);

    outerFrame.add(component);
    outerFrame.setVisible(true);

  }
}

I am trying to use users mouse input to make them draw a triangle. I also have a trianglecomponent class as well as a constructor that uses the xs and ys here.So I used the println's at the end and saw that code runs before xs and ys. How can I change this to get the xs and ys from the mouse before drawing anything

Answer 1

您需要使绘图成为事件处理的一部分，因此将侦听器之后的所有内容移到侦听器中，以便在您单击第三次单击后立即绘制三角形。

Answer 2

In your code you are creating the TriangleComponent before knowing where to draw it (x1, x2, y1, ecc...).

To solve this, simply create the TriangleComponent after you have all the coordinates (after the third click):

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
public class Viewer implements MouseListener
{
  static int counter = 0;
  static double x1, x2, x3, y1, y2, y3;
  public static void main (String [] args)
  {
    final JFrame outerFrame = new JFrame();
    JPanel panel = new JPanel();

    panel.setSize(400,400);
    outerFrame.setSize(400, 400);
    outerFrame.setTitle("Drawing Triangle");
    outerFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


    outerFrame.add(panel);
    panel.addMouseListener(new MouseAdapter(){

      @Override
      public void mousePressed(MouseEvent e){
        if(counter == 0) {
          x1 = e.getX();
          y1 = e.getY();

        } else if(counter == 1) {
          x2 = e.getX();
          y2 = e.getY();

        } else if(counter == 2) {
          x3 = e.getX();
          y3 = e.getY();

          TriangleComponent component = new TriangleComponent(x1, x2, x3, y1, y2, y3);

          outerFrame.add(component);

          System.out.println(x2);
          System.out.println(y2);
          System.out.println(x1);
          System.out.println(y1);    
          System.out.println(x3);
          System.out.println(y3);
        }

        counter++;
      }

    });

    panel.setFocusable(true);

    outerFrame.setVisible(true);
  }
}