如何防止JList在单元格边界外进行选择？ [英] How to prevent JList from making selection outside cell bounds?

问题描述

有什么方法可以阻止JList在用户点击列表下方的元素时选择最后一个元素吗？

这是有人问这里的问题，我有同样的问题。那个人发现了一个马马虎虎的解决方案（通过覆盖processMouseEvent（）），但我想知道是否有更好/更优雅的方法来做到这一点。

That is the question someone asked here and I have the same problem. That guy found a so-so solution (by overriding processMouseEvent() ) but I want to know if there is a better/more elegant way to do it.

好的，更详细。
如果你有一个JList，并且有一些空间没有被任何单元/元素占用，你点击那个空格，那么JList中的最后一个元素就被选中了。

Ok, more detail. If you have a JList and there is some space unoccupied by any cell/element and you click that space then the last element in the JList got selected.

有关实际示例，请尝试 JList Swing Tutorial示例， 点击空格，看看Rollo已被选中。

For a real example try this JList Swing Tutorial example, click the white space and see that Rollo got selected.

推荐答案

参见 https://forums.oracle.com/forums/thread.jspa?threadID=2206996

import java.awt.EventQueue;
import java.awt.Point;
import java.awt.Toolkit;
import java.awt.event.InputEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;

public class TestJList {
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JList list = new JList(new Object[] { "One", "Two", "Three" }) {
                    @Override
                    public int locationToIndex(Point location) {
                        int index = super.locationToIndex(location);
                        if (index != -1 && !getCellBounds(index, index).contains(location)) {
                            return -1;
                        }
                        else {
                            return index;
                        }
                    }
                };

                list.addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseClicked(MouseEvent e) {
                        JList list = (JList) e.getSource();
                        if (list.locationToIndex(e.getPoint()) == -1 && !e.isShiftDown()
                                && !isMenuShortcutKeyDown(e)) {
                            list.clearSelection();
                        }
                    }

                    private boolean isMenuShortcutKeyDown(InputEvent event) {
                        return (event.getModifiers() & Toolkit.getDefaultToolkit()
                                .getMenuShortcutKeyMask()) != 0;
                    }
                });

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.getContentPane().add(new JScrollPane(list));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}

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