A Different Way to use JPopupMenu

To Swing developers, JPopupMenu must be a familiar component. However, most people only take it as 'right-click popup menu’. Actually, there are much more usages of JPopupMenu, so with the help of it, all the requirement involving popup effects can be met. For example, if we input "import java.util." with development tools and the drop up menu with the probable options listed will pop up automatically when inputting ".".

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Point;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPopupMenu;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;

import twaver.TWaverUtil;

public class PopupTipDemo extends JFrame {

    String[] messages = new String[] {
            "getTWaverJava()",
            "getTWaverWeb()",
            "getTWaverFlex()",
            "getTWaverDotNET()",
            "getTWaverGIS()",
            "getTWaverHTML5()",
            "getTWaverJavaFX()",
            "getTWaver...", };

    JLabel label = new JLabel("TWaver makes everything easy!");
    JList list = new JList(messages);
    JComponent tip = new JScrollPane(list);
    JTextArea text = new JTextArea();
    JPopupMenu popup = new JPopupMenu();

    public PopupTipDemo() {
        super("www.servasoftware.com");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.getContentPane().setLayout(new BorderLayout());
        this.getContentPane().add(new JScrollPane(text), BorderLayout.CENTER);
        this.tip.setPreferredSize(new Dimension(230, 80));
        this.label.setForeground(Color.BLUE);
        this.label.setHorizontalAlignment(SwingConstants.CENTER);
        this.popup.setLayout(new BorderLayout());
        this.popup.add(label, BorderLayout.NORTH);
        this.popup.add(tip, BorderLayout.CENTER);

        this.text.setText("// Try to press '.'\nimport twaver.Node;\nimport twaver.Link;\nimport twaver.network");
        this.text.setBackground(Color.WHITE);
        this.text.setForeground(Color.BLUE);
        this.text.setCaretColor(Color.RED);

        this.text.addKeyListener(new KeyAdapter() {
            public void keyReleased(KeyEvent e) {
                if (popup.isShowing()) {
                    popup.setVisible(false);
                } else if (e.getKeyCode() == KeyEvent.VK_PERIOD) {
                    Point point = text.getCaret().getMagicCaretPosition();
                    if (point != null) {
                        popup.show(text, point.x, point.y);
                    }
                    text.requestFocus();
                }
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                PopupTipDemo demo = new PopupTipDemo();
                demo.setSize(400, 200);
                TWaverUtil.centerWindow(demo);
                demo.setVisible(true);
            }
        });
    }
}

In fact, in Demo of TWaver Java, QuickSearch (the well-encapsulated component--twaver.swing.TDropDownSelector) is equipped with the feature described above. Through the following several lines of codes in demo.DemoUtil can realize the drop-down effect. What you need to do is only to focus on the contents you want to show on the menu.

// create drop down selector
final TDropDownSelector selector = new TDropDownSelector(txtSearch, new JScrollPane(list)){
    public Dimension getSelectorSize(){
        int width = this.getSize().width;
        if(width < 200){
            width = 200;
        }
        return new Dimension(width, 320);
    }
};