jcomboBox显示长项目的内容

如果JComboBox列表中的内容过长的话，下拉框中不全部显示 
解决方法一：当鼠标放在这个过长的项目中时显示tooltip，提示用户选择这项的全部信息 
setComboBoxUI(combobox); 

private void setComboBoxUI(final JComboBox combobox) {
    combobox.setUI(new WindowsComboBoxUI() {
        protected ComboPopup createPopup() {
            return new BasicComboPopup(combobox) {
                protected JList createList() {
                    return new JList(comboBox.getModel()) {
                        public void processMouseEvent(MouseEvent e) {
                            if (e.isControlDown()) {
                                e = new MouseEvent((Component) e.getSource(), e.getID(), e.getWhen(),
                                        e.getModifiers() ^ InputEvent.CTRL_MASK, e.getX(), e.getY(),
                                        e.getClickCount(), e.isPopupTrigger());
                            }
                            super.processMouseEvent(e);
                        }

                        public String getToolTipText(MouseEvent event) {
                            int index = locationToIndex(event.getPoint());
                            if (index != -1) {
                                Object value = getModel().getElementAt(index);
                                ListCellRenderer renderer = getCellRenderer();
                                Component rendererComp =
                                        renderer.getListCellRendererComponent(this, value, index, true, false);
                                if (rendererComp.getPreferredSize().width > getVisibleRect().width) {
                                    return value == null ? null : value.toString();
                                } else {
                                    return null;
                                }
                            }
                            return null;
                        }

                        public Point getToolTipLocation(MouseEvent event) {
                            int index = locationToIndex(event.getPoint());
                            if (index != -1) {
                                Rectangle cellBounds = getCellBounds(index, index);
                                return new Point(cellBounds.x, cellBounds.y);
                            }
                            return null;
                        }
                    };
                }
            };
        }
    });
}



解决方法二：获取最大长项目宽度，并设置为弹出下拉框时的宽度 
combobox.setUI(new LargerComboBoxUI()); 

class LargerComboBoxUI extends BasicComboBoxUI {
    protected ComboPopup createPopup() {
        return new LargerComboPopup(comboBox);
    }

    public class LargerComboPopup extends BasicComboPopup {
        public LargerComboPopup(JComboBox comboBox) {
            super(comboBox);
        }

        public void show() {
            int selectedIndex = comboBox.getSelectedIndex();
            if (selectedIndex == -1) {
                list.clearSelection();
            } else {
                list.setSelectedIndex(selectedIndex);
                list.ensureIndexIsVisible(selectedIndex);
            }

            Insets insets = getInsets();
            Dimension listDim = list.getPreferredSize();
            boolean hasScrollBar = scroller.getViewport().getViewSize().height != listDim.height;
            if (hasScrollBar) {
                JScrollBar scrollBar = scroller.getVerticalScrollBar();
                listDim.width += scrollBar.getPreferredSize().getWidth();
            }

            int width = Math.max(listDim.width, comboBox.getWidth() - (insets.right + insets.left));
            int height = getPopupHeightForRowCount(comboBox.getMaximumRowCount());
            Rectangle popupBounds = computePopupBounds(0, comboBox.getHeight(), width, height);

            Dimension scrollSize = popupBounds.getSize();
            scroller.setMaximumSize(scrollSize);
            scroller.setPreferredSize(scrollSize);
            scroller.setMinimumSize(scrollSize);

            list.revalidate();
            show(comboBox, popupBounds.x, popupBounds.y);
        }
    }
}

来源：https://www.cnblogs.com/tiankafei/p/10340541.html