可编辑的组合框JComboBox实现可删除,可添加下拉选项效果

亦凉 2022-09-10 02:27 140阅读 0赞

参考文章：[可编辑的组合框JComboBox实现可删除下拉选项效果][JComboBox]

[JComboBox监听回车键][JComboBox 1]

# LabelCellRender类 #

package org.fiend.swing.test.demo.jcombobox;
    
    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    
    /**
     * 带键盘事件的渲染器
     *  事件加到JCombox的编辑框中，通过编辑框的KeyListener事件进行监听
     * @author pelang 2021-09-03 14:43:23
     */
    public class LabelCellRender extends JLabel implements ListCellRenderer, KeyListener {
        private static final long serialVersionUID = 1L;
        private final JComboBox comboBox;
    
        private int selectedIndex = -1;
    
        /**
         * 构造函数
         * @param comboBox 当前渲染器所属的JComboBox
         */
        public LabelCellRenderer(final JComboBox comboBox) {
            setOpaque(true);
            this.comboBox = comboBox;
            this.comboBox.getEditor().getEditorComponent().addKeyListener(this);
        }
    
        public Component getListCellRendererComponent(JList list,
                                                      Object value,
                                                      int index,
                                                      boolean isSelected,
                                                      boolean cellHasFocus) {
    
            this.setText(value.toString());
            this.setFont(this.comboBox.getFont());
    
            Color background;
            Color foreground;
            if (isSelected) {
                background = Color.decode("#3399FE");
                foreground = Color.WHITE;
                this.selectedIndex = index;
            } else {
                background = Color.WHITE;
                foreground = Color.BLACK;
            }
    
            setBackground(background);
            setForeground(foreground);
    
            return this;
        }
    
        @Override
        public void keyPressed(KeyEvent e) {
            int keyCode = e.getKeyCode();
    
            if (keyCode == 38) {// 按向上的方向键则索引减一
                int index = this.comboBox.getSelectedIndex();
                if (index == 0) {
                    return;
                }
                index--;
                this.comboBox.setSelectedIndex(index);
            } else if (keyCode == 40) {// 按向下的方向键则索引加一
                int index = this.comboBox.getSelectedIndex();
                if (index == this.comboBox.getItemCount() - 1) {
                    return;
                }
                index++;
                this.comboBox.setSelectedIndex(index);
            } else if (keyCode == 127) {
                // 为防止误删除，只有在下来选项可视的情况下才可以执行删除操作
                if (this.comboBox.isPopupVisible()) {
                    // 下来选框可见的情况下，设置Delete对文本框内文字操作无效
                    JTextField textField = ((JTextField) this.comboBox.getEditor().getEditorComponent());
                    String text = textField.getText();
                    int position = ((JTextField) this.comboBox.getEditor().getEditorComponent()).getCaretPosition();
    
                    // 如果是按Delete键则移除当前选中的Item
                    if (this.selectedIndex >= 0 && this.selectedIndex < this.comboBox.getItemCount()) {
                        this.comboBox.removeItemAt(this.selectedIndex);
                        textField.setText(text);
                        textField.setCaretPosition(position);
                    }
                    //此处代码在JDK1.6起作用，在JDK1.7失效，请注意
                    e.setKeyCode(-1);
                }
            }
        }
    
        @Override
        public void keyReleased(KeyEvent e) {
        }
    
        @Override
        public void keyTyped(KeyEvent e) {
    
        }
    }

# LabelCellRenderTest类 #

package org.fiend.swing.test.demo.jcombobox;
    
    import javax.swing.*;
    import java.awt.event.KeyAdapter;
    import java.awt.event.KeyEvent;
    
    /**
     * JCombobox添加和删除item功能
     * @author pelang 2021-09-03 14:45:14
     */
    public class LabelCellRenderTest {
        public static void main(String[] args) {
            JFrame jFrame = new JFrame("可删除下拉列表测试");
            jFrame.setSize(280, 60);
            jFrame.setLocationRelativeTo(null);
            jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    
            JComboBox<String> comboBox = new JComboBox<>();
            //只有为true的时候才能进行删除
            comboBox.setEditable(true);
            comboBox.setRenderer(new LabelCellRender(comboBox));
    
            comboBox.addItem("张三");
            comboBox.addItem("李四");
            comboBox.addItem("王五");
            comboBox.addItem("赵六");
    
            // 添加监听事件
            comboBox.getEditor().getEditorComponent().addKeyListener(new KeyAdapter(){
                @Override
                public void keyPressed(KeyEvent e) {
                    int keyCode = e.getKeyCode();
                    
                    // 回车键添加新的item到下拉列表
                    if(keyCode == KeyEvent.VK_ENTER){
                        String s = (String)comboBox.getEditor().getItem();
                        System.out.println(s);
    
                        // 添加新的item到jCombobox列表
                        comboBox.addItem(s);
                        comboBox.setSelectedIndex(comboBox.getItemCount() -1);
                    }
    
                    // 添加删除功能, 该删除功能与LabelCellRender类无关
                    if (keyCode == 127) {
                        // 为防止误删除，只有在下来选项可视的情况下才可以执行删除操作
                        if (comboBox.isPopupVisible()) {
                            // 如果是按Delete键则移除当前选中的Item, index==0时不能删除
                            int selectedIndex = comboBox.getSelectedIndex();
                            if (selectedIndex > 0 && selectedIndex < comboBox.getItemCount()) {
                                comboBox.removeItemAt(selectedIndex);
                                comboBox.hidePopup();
                                // comboBox.setSelectedIndex(comboBox.getItemCount() - 1);
                                comboBox.showPopup();
                            }
    
                            //此处代码在JDK1.6起作用，在JDK1.7失效，请注意
                            e.setKeyCode(-1);
                        }
                    }
                }
            });
    
            jFrame.add(comboBox);
            jFrame.setVisible(true);
        }
    }

[JComboBox]: https://blog.csdn.net/niqingyang/article/details/84696738
[JComboBox 1]: https://fiend.blog.csdn.net/article/details/120083880