Question

我想在自定义弹出菜单中上下自动更新滚动窗格上的滚动条。但它不起作用。看看下面我完全可运行的示例，其中我添加了我自定义的基于JPopupMenu的组件和一个JComboBox来进行比较。如您所见，在JComboBox中，滚动窗格更新其位置，以便始终显示当前选定的项目。但这不适用于我的组件，我不知道如何设置它。

我的SSCCE：

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.ScrollPane;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Vector;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPopupMenu;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;


public class ScrollFocus extends JFrame {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new ScrollFocus();

            }
        });
    }

    public ScrollFocus() {
        this.setLayout(new BorderLayout());
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Vector<String> values = new Vector<>();
        values.add("a");
        values.add("b");
        values.add("c");
        values.add("d");
        values.add("e");
        values.add("f");
        values.add("g");
        values.add("h");
        values.add("i");
        values.add("j");
        JComboBox<String> comboBox = new JComboBox<>(values);
        JScrollPane scrollPane = new JScrollPane(comboBox);
        this.add(scrollPane, BorderLayout.NORTH);

        CustomTextField customTextField = new CustomTextField();
        this.add(customTextField, BorderLayout.CENTER);
        pack();
        setVisible(true);
    }

    class CustomTextField extends JTextField implements FocusListener {

        private CustomPopup customPopup = new CustomPopup();

        public CustomTextField() {
            this.addFocusListener(this);
            this.addKeyListener(new KeyAdapter() {
                @Override
                public void keyPressed(KeyEvent e) {
                    System.out.println("printing...");
                    setPopupSize();
                    setPosition();
                    customPopup.setVisible(true);

                    if(e.getKeyCode() == KeyEvent.VK_UP) {
                        if(customPopup.index < customPopup.getListSize())
                            customPopup.setSelectedIndex(customPopup.index--);
                    }
                    else if(e.getKeyCode() == KeyEvent.VK_DOWN){
                        if(customPopup.index >= 0)
                            customPopup.setSelectedIndex(customPopup.index++);
                    }
                }
            });
        }

        public void setPopupSize() {
            customPopup.setPopupSize(new Dimension(this.getWidth(), 110));
        }

        public void setPosition() {
            customPopup.setLocation(this.getLocation().x, this.getLocation().y);
        }

        @Override
        public void focusGained(FocusEvent e) {

        }

        @Override
        public void focusLost(FocusEvent e) {
            customPopup.setVisible(false);
        }


        class CustomPopup extends JPopupMenu {
            String[] values = new String[]{"Value1", "Value2", "Value3", "Value4", "Value5", "Value6", "Value7",
                    "Value8","Value9", "Value10", "Value11", "Value12", "Value13", "Value14", "Value15", "Value16",};
            JList<String> list = new JList<>(values);
            JScrollPane scrollPane = new JScrollPane(list);
            public int index = 0;

            public CustomPopup() {
                this.setLayout(new GridLayout(0,1));
                this.add(scrollPane);
                pack();
            }

            public void setSelectedIndex(int index) {
                list.setSelectedIndex(index);
            }

            public int getListSize() {
                return values.length;
            }
        }
    }
}

Answer 1

在JComboBox中，滚动窗格更新其位置，以便始终显示当前选定的项目。但这不适用于我的组件，我不知道如何设置它。

list.setSelectedIndex(index);
list.ensureIndexIsVisible(index); // added

另外，不要使用KeyListener。 Swing旨在与Key Bindings一起使用。请阅读How to Use Key Bindings上的Swing教程中的thw部分以获取更多信息。

我自定义组件的JScrollpane没有更新

1 个答案: