java – JMapViewer,MouseListener调用了2次

使用JMapViewer,可以识别组件的奇怪行为.我使用DefaultMapController来获取地图位置(lat,lon).

import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import org.openstreetmap.gui.jmapviewer.DefaultMapController;
import org.openstreetmap.gui.jmapviewer.JMapViewer;

public class Test extends JMapViewer{

public Test() 
{
    addMouseListener(new DefaultMapController(this) {
            public void mouseClicked(MouseEvent e){
            Point  start = e.getPoint();
            System.out.println(e.getPoint());
            }            
       });
  }

protected void paintComponent(Graphics g){super.paintComponent(g);}  

public static void main (String [] args){
            JFrame jf = new JFrame();
            jf.setSize(800, 600);
            Test t= new Test();
            jf.add(t);
            jf.setVisible(true);
    }
}

运行代码,在按下鼠标左键后,方法mouseClicked()被多次调用(2x).更换后

    addMouseListener(new DefaultMapController(this) {

同

    addMouseListener(new MouseAdapter() {

代码正常工作,该方法只被调用1次.问题出在哪儿？它是库中的错误还是语法错误或不安全？如何避免这个问题？谢谢你的帮助.

解决方法:

您的测试扩展了JMapViewer,在instance initializer块中添加了MouseListener.作为consequence,“默认构造函数将调用超类的无参数构造函数.”超类JMapController添加了你的MouseListener – 你第二次猜到了它.

public JMapController(JMapViewer map) {
    this.map = map;
    if (this instanceof MouseListener)
        map.addMouseListener((MouseListener) this);
    …
}

相反,创建一个新的JMapController或DefaultMapController,如here所示,并使用它来构造您的JMapViewer.

import java.awt.EventQueue;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import org.openstreetmap.gui.jmapviewer.DefaultMapController;
import org.openstreetmap.gui.jmapviewer.JMapViewer;

/**
 * @see https://stackoverflow.com/a/39461854/230513
 */
public class TestMapController {

    private void display() {
        JFrame f = new JFrame("TestMapController");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JMapViewer map = new JMapViewer();
        new DefaultMapController(map) {
            @Override
            public void mouseClicked(MouseEvent e) {
                System.out.println(e.getPoint());
            }
        };
        f.add(map);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new TestMapController()::display);
    }
}

标签：java,listener,openstreetmap,click,jmapviewer
来源： https://codeday.me/bug/20191009/1876091.html