在沒有滾動條的JList上滾動

Question

我有這個自定義代碼的JList使用ActionMapAction。現在我可以使用自定義向上和向下箭頭buttom但我不能使用鼠標的滾動在jLIST上上下滾動。

我該如何實現滾動鼠標滾動上下滾動JList？

jlist.setFont(new Font("Calibri",Font.BOLD,16)); 
jlist.setCellRenderer(new Renderer()); 
jlist.setFixedCellWidth(100); 
jlist.setBorder(new EmptyBorder(10,10, 10, 10)); 
jlist.addMouseListener(new MouseListener(){ 

    public void mouseClicked(MouseEvent arg0) { 

    } 

    public void mouseEntered(MouseEvent arg0) { 

    } 

    public void mouseExited(MouseEvent arg0) { 

    } 

    public void mousePressed(MouseEvent e) { 
     JList<String> jl = (JList<String>)e.getSource(); 
     if(e.getClickCount() == 2){ 
      jlist.setCellRenderer(new Renderer(true)); 
      int index = jl.locationToIndex(e.getPoint()); 
      new OneToOneChat(jlist.getModel().getElementAt(index).toString()); 
      System.out.print(index); 
     } 
    } 
    public void mouseReleased(MouseEvent e) { 
     jlist.setCellRenderer(new Renderer(false)); 
    } 

}); 


jsp = new JScrollPane(jlist); 
jsp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER); 

JScrollBar customScroll = jsp.getVerticalScrollBar(); 
add(jsp); 
BasicArrowButton top = new BasicArrowButton(BasicArrowButton.TOP); 
top.setAction(new ActionMapAction("", customScroll, "negativeUnitIncrement")); 
add(top,BorderLayout.NORTH); 

BasicArrowButton bottom = new BasicArrowButton(BasicArrowButton.SOUTH); 
bottom.setAction(new ActionMapAction("", customScroll, "positiveUnitIncrement")); 
add(bottom,BorderLayout.SOUTH); 
} 

Answer 1

您應該實現MouseWheelListener並添加到JList。

見http://docs.oracle.com/javase/tutorial/uiswing/events/mousewheellistener.html

Answer 2

我真的不明白，是由產生的MouseWheelEvent所以聽者並不像我雖然這將是簡單的所有事件。但無論如何，基本思路是使用默認的行動從垂直滾動條做滾動：

import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 

public class MouseWheelScroller implements MouseWheelListener 
{ 
    public void mouseWheelMoved(MouseWheelEvent e) 
    { 
     // Ignore events generated with a rotation of 0 
     // (not sure why these events are generated) 

     int rotation = e.getWheelRotation(); 

     if (rotation == 0) 
      return; 

     // Get the appropriate Action key for the given rotation 
     // (unit/block scroll is system dependent) 

     String key = null; 

     if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL) 
     { 
      key = (rotation < 0) ? "negativeUnitIncrement" : "positiveUnitIncrement"; 
     } 
     else 
     { 
      key = (rotation < 0) ? "negativeBlockIncrement" : "positiveBlockIncrement"; 
     } 

     // Get the Action from the scrollbar ActionMap for the given key 

     JScrollPane scrollPane = (JScrollPane)e.getComponent(); 
     JScrollBar vertical = scrollPane.getVerticalScrollBar(); 

     ActionMap map = vertical.getActionMap(); 
     Action action = (Action)map.get(key); 
     ActionEvent event = new ActionEvent(vertical, ActionEvent.ACTION_PERFORMED, ""); 

     // Invoke the Action the appropriate number of times to simulate 
     // default mouse wheel scrolling 

     int unitsToScroll = Math.abs(e.getUnitsToScroll()); 

     for (int i = 0; i < unitsToScroll; i++) 
      action.actionPerformed(event); 
    } 

    private static void createAndShowUI() 
    { 
     DefaultListModel<String> model = new DefaultListModel<String>(); 

     for (int i = 0; i < 200; i++) 
     { 
      model.addElement("" + i); 
     } 

     JList<String> list = new JList<String>(model); 
     list.setVisibleRowCount(20); 

     JScrollPane scrollPane = new JScrollPane(list, JScrollPane.VERTICAL_SCROLLBAR_NEVER, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER); 
     scrollPane.addMouseWheelListener(new MouseWheelScroller()); 

     JFrame frame = new JFrame("Mouse Wheel Scroller"); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.add(scrollPane); 
     frame.pack(); 
     frame.setLocationByPlatform(true); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) 
    { 
     EventQueue.invokeLater(new Runnable() 
     { 
      public void run() 
      { 
       createAndShowUI(); 
      } 
     }); 
    } 
}