JTextField 初始提示文字不能显示，需获焦再失焦后才能显示 求解

Question

java JTextField 

Answer 1

 
public class ListPanelUI {
    private JPanel listJPanel; // 较低层面板-此面板用来承装滚动面板和搜索框
    private JTextField textFieldSearch;// 用来搜索滴
    private JScrollPane listJScrollPane; // 滚动面板-此面板承装列表
    private JList IdNameList;
    private DefaultListModel model = new DefaultListModel();// 列表模型
    private static ListPanelUI singlistpJPanel = null;// 单例调用
    static String initStr = "快速查找“学号”“姓名”";
    public static ListPanelUI getInstance() {
if(null==singlistpJPanel){
singlistpJPanel=new ListPanelUI();
}
        return singlistpJPanel;
    }
 
    private ListPanelUI() {
        InitlistJPanel();
    }
 
    /*
     * 获取整合后的面板
     */
    public JPanel getlistJPanel() {
        return listJPanel;
    }
 
    /*
     * 初始化承装滚动面板和搜索框的底层面板
     */
    public void InitlistJPanel() {
        listJPanel = new JPanel();
        listJPanel.setLayout(null);
        listJPanel.add(InitlistJScrollPane());
        listJPanel.add(InittextFieldSearch());
    }
 
    /*
     * 初始化搜索输入框
     */
    public JTextField InittextFieldSearch() {
        textFieldSearch = new JTextField(initStr);
        textFieldSearch.setForeground(Color.LIGHT_GRAY);
        textFieldSearch.setBounds(10, 590, 161, 27);
        textFieldSearch.addFocusListener(new FocusListener() {
           public void focusGained(FocusEvent e) {
               JTextField src = (JTextField) e.getSource();
               src.setForeground(Color.blue);
               if (src.getText().equals(initStr)){
                   src.setText(null);
               }
           }
           public void focusLost(FocusEvent e) {
               JTextField src = (JTextField) e.getSource();
               if (src.getText().trim().isEmpty()) {
                   src.setText(initStr);
                   src.setForeground(Color.LIGHT_GRAY);
               }
           }
        });
        
        textFieldSearch.addKeyListener(new KeyListener() {
            @Override
            public void keyTyped(KeyEvent e) {
            }
             
            @Override
            public void keyReleased(KeyEvent e) {
            }
             
            @Override
            public void keyPressed(KeyEvent e) {                 
            }
        });
         
        return textFieldSearch;
    }
     
    public void FindTheItem() {
        String key = textFieldSearch.getText();
        if ((key == null) || (key.trim().isEmpty())) {
            // 处理为空格的时候
            textFieldSearch.setText("");// 当为空格的时候直接删除
        }
        if (model.contains(key)) {
            int index = model.indexOf(key);
            IdNameList.setSelectedIndex(index);
        }else {
            IdNameList.clearSelection();
            System.out.println("没有元素");
        }
    }
 
    /*
     * 初始化承装列表的滚动面板
     */
    public JScrollPane InitlistJScrollPane() {
        listJScrollPane = new JScrollPane();
        listJScrollPane.setBounds(10, 10, 161, 570);
        listJScrollPane.setColumnHeaderView(new JLabel("学生列表",
                SwingConstants.CENTER));
        listJScrollPane.setViewportView(InitJList());
        return listJScrollPane;
    }
 
    /*
     * 初始化Jlist
     */
    public JList InitJList() {
        System.out.println("Jlist初始化");
        // 初始化一个List
        IdNameList = new JList();
        //下面作为测试，注释掉先
        //// 设置列表的选择模式为单选
        //IdNameList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        //final StuEbi ebi = StuEbiFactory.getStuEbi();
        //List<StudentModel> list = ebi.getAll();
        //
        //IdNameList.setModel(model);// 将model设置给列表
        //IdNameList.setListData(list.toArray());
        //IdNameList.setSelectedIndex(0);
        //// 监听选择
        //IdNameList.addListSelectionListener(new ListSelectionListener() {
        //    @Override
        //    public void valueChanged(ListSelectionEvent e) {
        //        if (e.getValueIsAdjusting()){//通过此处判断来过滤多余的事件
        //        }else {
        //            StudentModel selectedStuModel = (StudentModel) IdNameList.getSelectedValue();
        //            String nameString = selectedStuModel.getName();
        //            Speaker temp = Speaker.getInstance();
        //            temp.SpeakWords(nameString);
        //
        //            SpeakNameFace.lblShowNumLabel.setText(selectedStuModel.getId());
        //            SpeakNameFace.lblNowShowLabel.setText(nameString);
        //        }
        //    }
        //});
        return IdNameList;
    }
     
    /**
     * 获取列表当前选择的下一个
     * 若当前项的索引小于最大索引值 则选择到下个索引值
     * 否则弹出消息框
     * @return
     */
    public boolean SetNextselected(){
        //获取当前选中的索引值
        int selectedindex = IdNameList.getSelectedIndex();
        System.out.println("当前索引："+selectedindex+"最大索引："+IdNameList.getLastVisibleIndex());
        if(selectedindex<IdNameList.getLastVisibleIndex()){
            //TODO 此处还需完善 列表向上滚 还没有做完善的处理
            IdNameList.setSelectedIndex(selectedindex+1);
            IdNameList.scrollRectToVisible(IdNameList.getCellBounds(selectedindex, selectedindex+2));
            return true;
        }else {
            JOptionPane.showConfirmDialog(null, "已到最后！");
            return false;
        }
    }
    public boolean SetBeforeselected(){
        int selectedindex = IdNameList.getSelectedIndex();
        System.out.println("当前索引："+selectedindex+"最小索引："+IdNameList.getFirstVisibleIndex());
        if(selectedindex>0){
            IdNameList.setSelectedIndex(selectedindex-1);
            IdNameList.scrollRectToVisible(IdNameList.getCellBounds(selectedindex-1, selectedindex));
            return true;
        }else {
            JOptionPane.showConfirmDialog(null, "已到最前！");
            return false;
        }
    }
public static void main(String args[]){
JFrame jframe=new JFrame("ListPanelUI");
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setBounds(10, 10, 300, 700);
jframe.add(ListPanelUI.getInstance().getlistJPanel());
jframe.setVisible(true);
}
}
显示正常。

Answer 2

把
private static ListPanelUI singlistpJPanel = new ListPanelUI();// 单例调用
static String initStr = "快速查找“学号”“姓名”";
对换即可 其实就是静态变量初始化顺序的问题
搞定