JComboBox更改下拉弹出窗口

基本上是在其派生的JTextField下面显示的JComboBox的弹出窗口，如何改变JComboBox弹出窗口的方向，并在顶部/上方显示JComboBox的弹出窗口

编辑：基本JComboBox的代码示例

import java.awt.Dimension; import javax.swing.*; import javax.swing.plaf.basic.BasicComboBoxRenderer; public class HighRowCombo { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { new HighRowCombo().makeUI(); } }); } public void makeUI() { Object[] data = {"One", "Two with text", "Three with long text, with long text,with long text "}; JComboBox comboBox = new JComboBox(data); JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLocationRelativeTo(null); frame.add(comboBox); frame.pack(); BasicComboBoxRenderer renderer = (BasicComboBoxRenderer) comboBox.getRenderer(); Dimension size = renderer.getPreferredSize(); size.height += 50; renderer.setPreferredSize(size); frame.setVisible(true); } } 

编辑第二。 MacOX代码

 import java.awt.*; import javax.swing.*; public class TestHighRow { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel"); } catch (Exception e) { e.printStackTrace(); } new TestHighRow().makeUI(); } }); } public void makeUI() { Object[] data = {"One", "Two", "Three"}; JComboBox comboBox = new JComboBox(data); comboBox.setPreferredSize(comboBox.getPreferredSize()); comboBox.setRenderer(new HighRowRenderer(comboBox.getRenderer())); JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); frame.getContentPane().add(comboBox); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static class HighRowRenderer implements ListCellRenderer { private final ListCellRenderer delegate; private int height = -1; public HighRowRenderer(ListCellRenderer delegate) { this.delegate = delegate; } @Override public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) { Component component = delegate.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus); Dimension size = component.getPreferredSize(); if (height == -1) { height = size.height + 50; } size.height = height; component.setPreferredSize(size); if (component instanceof JLabel) { ((JLabel) component).setHorizontalTextPosition(JLabel.CENTER); } return component; } } } 

Answer 1

尝试在combobox弹出窗口中找到的setPopupAbove（）方法。

Answer 2

在我的系统上，如果JComboBox靠近屏幕底部并且没有足够的空间向下打开它，它将向上打开。 （这是你的意思吗？）

鉴于这一事实，我怀疑改变定义的行为会很容易。

Answer 3

在Mac OS X上，我收到以下exception。 显然， com.apple.laf.AquaComboBoxRenderer不是BasicComboBoxRenderer的子类。

附录： ClassCastException消失了，下面显示了“EDIT 2nd.Code for MacOX”的屏幕截图：

线程“AWT-EventQueue-0”中的exceptionjava.lang.ClassCastException：
     com.apple.laf.AquaComboBoxRenderer无法强制转换为
     javax.swing.plaf.basic.BasicComboBoxRenderer
  在HighRowCombo.makeUI（HighRowCombo.java:26）
  在HighRowCombo $ 1.run（HighRowCombo.java:13）
  在java.awt.event.InvocationEvent.dispatch（InvocationEvent.java:209）
   at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:678）
   at java.awt.EventQueue.access $ 000（EventQueue.java:86）
   at java.awt.EventQueue $ 1.run（EventQueue.java:639）
   at java.awt.EventQueue $ 1.run（EventQueue.java:637）
   at java.security.AccessController.doPrivileged（Native Method）
   at java.security.AccessControlContext $ 1.doIntersectionPrivilege（AccessControlContext.java:87）
   at java.awt.EventQueue.dispatchEvent（EventQueue.java:648）
   at java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:296）
   at java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:211）
   at java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:201）
   at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:196）
   at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:188）
   at java.awt.EventDispatchThread.run（EventDispatchThread.java:122）

Answer 4

 package com.example.swing; import javax.swing.JList; import javax.swing.ListCellRenderer; import java.awt.Component; import java.awt.Dimension; public class PaddingListCellRenderer implements ListCellRenderer { private final ListCellRenderer original; private final int hpadding; private final int vpadding; public PaddingListCellRenderer(ListCellRenderer original, int hpadding, int vpadding) { this.original = original; this.hpadding = hpadding; this.vpadding = vpadding; } @Override @SuppressWarnings("unchecked") public Component getListCellRendererComponent(JList list, Type value, int index, boolean isSelected, boolean cellHasFocus) { final Component component = original.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus); component.setPreferredSize(null); final Dimension pref = component.getPreferredSize(); component.setPreferredSize(new Dimension(pref.width + 2 * hpadding, pref.height + 2 * vpadding)); return component; } }