Java MouseEvent，检查是否按下 [英] Java MouseEvent, check if pressed down

问题描述

我有一个实现MouseListener(JPanel)的类.当我在面板上单击时，会发生某些事情.我想要的是某种while循环，只要按下鼠标左键即可循环.

I have a class that implements MouseListener (JPanel). When I click on the panel something happens. What I want is some kind of while-loop that loops as long as left mousebutton is pressed down.

@Override
public void mousePressed(MouseEvent e) {
    while(e.isPressedDownD) {      // <--
        //DO SOMETHING
    }
}

这显然行不通，但我希望您了解我正在努力实现的目标. 全班学习:

This obviously doesn't work, but I hope you understand what I'm trying to achieve. The whole class for those that are interested:

package control;

import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import model.GridModel;
import view.GUIView;

public class MapListener implements MouseListener{
    private GridModel model;
    private GUIView view;
    private int posX;
    private int posY;

    public MapListener(GridModel model, GUIView view) {
        this.model = model;
        this.view = view;
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        posX = e.getX();
        posY = e.getY();
        model.setMouseAtX(posX);
        model.setMouseAtY(posY);
        view.paintTile();
        System.out.println("X: " + posX + " Y: " + posY);
    }

    @Override
    public void mouseEntered(MouseEvent e) {
    }

    @Override
    public void mouseExited(MouseEvent arg0) {
    }

    @Override
    public void mousePressed(MouseEvent e) {
        while(e.getModifiers() == MouseEvent.MOUSE_PRESSED) { //Obviously doesn't work
            //DO SOMETHING
        }
    }

    @Override
    public void mouseReleased(MouseEvent arg0) {
    }
}

推荐答案

其他答案指出，在鼠标事件侦听器方法中，不是是完成工作的地方.

As pointed out by other answers, the place to do your work is not in the mouse event listener methods.

在MouseEvent中也没有明确的按鼠标"概念，因此您必须自己进行跟踪.我提供了如何执行此操作的示例.还要注意MouseEvent.BUTTON1引用，因为这只是为了跟踪鼠标左键的状态.

Also there is no explicit "mouse pressed" notion in MouseEvent, so you must track that yourself. I have provided an example of how to do this. Also note the MouseEvent.BUTTON1 references, as this is just to track the state of the left mouse button.

这是您必须开始学习并发性的地方.因此，我添加了一个同步方法，因为您需要注意，当多个线程同时访问属性时会发生有趣的事情，而synchronized是保持这种理智的机制.在本示例的范围之外，请考虑进一步阅读.

This is where you must start to learn about concurrency. For that reason, I've added in a synchronized method as you need to be aware that funny things happen when multiple threads access properties at the same time, and synchronized is a mechanism for keeping this sane. Consider it further reading beyond the scope of this example.

未经测试，但这应该可以工作:

Untested, but this should work:

volatile private boolean mouseDown = false;

public void mousePressed(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1) {
        mouseDown = true;
        initThread();
    }
}

public void mouseReleased(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1) {
        mouseDown = false;
    }
}

volatile private boolean isRunning = false;
private synchronized boolean checkAndMark() {
    if (isRunning) return false;
    isRunning = true;
    return true;
}
private void initThread() {
    if (checkAndMark()) {
        new Thread() {
            public void run() {
                do {
                    //do something
                } while (mouseDown);
                isRunning = false;
            }
        }.start();
    }
}

这篇关于Java MouseEvent，检查是否按下的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！