javase开发问题贴（持续更新）

1.模态框

//设置模态，阻塞其它窗体setModal(true);//一点要在setVisible(true);之前，//而且一帮setvisibale要放在最后，否则会有监听事件没有监听到

• 正确的顺序
  1.监听事件
  2.模态
  3.可见

JSplitPane设置比例问题

根据 setDividerLocation(int) 来实现此方法。此方法以分隔窗格的当前大小为基础迅速改变窗格的大小。如果分隔窗格没有正确地实现并且不显示在屏幕上，此方法将不产生任何影响（新的分隔条位置将成为 0（当前的 size * proportionalLocation ））。

看完后没什么概念。。。只觉得写的不是那么直白，也许确有什么猫腻在里边。特别是”如果分隔窗格没有正确地实现并且不显示在屏幕上，此方法将不产生任何影响”这句，没大理解。。。

因而去看看JSplitPane的源码。关于setDividerLocation大致如下:

    public void setDividerLocation(double proportionalLocation) {         if (proportionalLocation < 0.0 ||            proportionalLocation > 1.0) {             throw new IllegalArgumentException("proportional location must " +                                                "be between 0.0 and 1.0.");         }         if (getOrientation() == VERTICAL_SPLIT) {             setDividerLocation((int)((double)(getHeight() - getDividerSize()) *                                      proportionalLocation));         } else {             setDividerLocation((int)((double)(getWidth() - getDividerSize()) *                                      proportionalLocation));         }     } 

这下有些明白了，setDividerLocation(double)这个函数会用到getWidth()或者getHeight()这样的函数，而java桌面程序在没有主窗体setVisible之前，如果使用布局，尚未validate()和paint()每个组件的宽和高默认都是0。也就是说一定要在主窗体setVisible(true)之后再使用setDividerLocation(double)才会有效。

3.分隔条的使用

 //创建水平分隔线 JSeparator separator = new JSeparator();    separator.setOrientation(JSeparator.HORIZONTAL); verticalBox.add(separator);//在容器中add

4.设置边框

label[i].setBorder(BorderFactory.createEtchedBorder());

5.JScorllPane添加容器

//我们一帮都是直接new JScorllOane(容器)//因为它只能放一个容器,add的方法jsPane.getViewport().add(verticalBox);

6. JScorllPane添加多个容器

//我们可以先new一个JPanel或者Box，把其它的容器先放到JPanel或Box上面再把它放到JScorllPane中，下面的代码实现在JScollPanel中放置做个Label显示图片的功能。 private JScrollPane jsPane;    public void initScan()    {        jsPane = new JScrollPane();        //JPanel panel = new JPanel();        Box verticalBox   = Box.createVerticalBox();         File file = new File("tmp/");        String[] files = file.list();        label = new JLabel[files.length];        int i = 0;        for(String e: files)        {            if (!e.endsWith("png")) continue;             System.out.println(e);            label[i] = new JLabel();            label[i].setIcon(new ImageIcon(MyOfficeImage.tmpDir + e));            label[i].setBorder(BorderFactory.createEtchedBorder());            //panel.add(label[i]);            verticalBox.add(label[i]);//          JSeparator separator = new JSeparator();   //创建水平分隔线  //          separator.setOrientation(JSeparator.HORIZONTAL); //          verticalBox.add(separator);            //jsPane.getViewport().add(label[i]);            i++;        }        jsPane.getViewport().add(verticalBox);        contentPanel.add(jsPane, BorderLayout.CENTER);//jsPane    }

7. 文字的居中显示和swing布局

• 如果直接放在FlowLayout里，控件会从左往右，从上到下排列，不会占满整块布局。
• 如果放在BorderLayout中，则会占满整个布局，这样控件就是按比例放大的，就会自动居中了。
• 如果不想居中，或者绝得BorderLayout的North和sourth占的地方还是太大，可以用toolBar来放置控件

public class MyScanDialog extends JDialog {    private final JPanel contentPanel = new JPanel();    private JTextArea textArea = new JTextArea();    private JLabel[] label;    private JScrollPane jsPane;    public void initScan()    {        jsPane = new JScrollPane();        //JPanel panel = new JPanel();        Box verticalBox   = Box.createVerticalBox();         File file = new File("tmp/");        String[] files = file.list();        label = new JLabel[files.length];        int i = 0;        for(String e: files)        {            if (!e.endsWith("png")) continue;             System.out.println(e);            label[i] = new JLabel();            label[i].setIcon(new ImageIcon(MyOfficeImage.tmpDir + e));            label[i].setBorder(BorderFactory.createEtchedBorder());            //panel.add(label[i]);            verticalBox.add(label[i]);//          JSeparator separator = new JSeparator();   //创建水平分隔线  //          separator.setOrientation(JSeparator.HORIZONTAL); //          verticalBox.add(separator);            //jsPane.getViewport().add(label[i]);            i++;        }        jsPane.getViewport().add(verticalBox);        contentPanel.add(jsPane, BorderLayout.CENTER);//jsPane    }    /**     * Launch the application.     */    public static void main(String[] args) {        //String content = MyPdf.readPdf("E:\\杂项\\CMake Practice.pdf");        //String content = MyWord.readDoc("E:\\杂项\\毕业论文开题报告范文.doc");        //textArea.setText(content);//差点闹了个笑话        //JFrame.setDefaultLookAndFeelDecorated(true);        //必须要有这一句，因为英文解释里大概是可以设置了这个，修饰的那些东西就会由lookfeel提供        JDialog.setDefaultLookAndFeelDecorated(true);        EventQueue.invokeLater(new Runnable() {            public void run()             {                try                 {                    SubstanceLookAndFeel.setCurrentButtonShaper(new org.jvnet.substance.button.ClassicButtonShaper());                }                 catch (Exception e)                 {                    e.printStackTrace();                }                MyScanDialog dialog = null;                try {                    dialog= new MyScanDialog();                    dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);                    dialog.initScan();                      dialog.setVisible(true);                } catch (Exception e) {                    e.printStackTrace();                }            }        });        //SwingUtilities.updateComponentTreeUI(dialog);    }    /**     * Create the dialog.     */    public MyScanDialog()    {        setBounds(100, 100, 657, 484);        getContentPane().setLayout(new BorderLayout());        contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));        getContentPane().add(contentPanel, BorderLayout.CENTER);        contentPanel.setLayout(new BorderLayout());        JPanel panel = new JPanel();        contentPanel.add(panel, BorderLayout.NORTH);        panel.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));        JLabel label = new JLabel("hah");        label.setFont(new Font("宋体", Font.PLAIN, 22));        panel.add(label);       }}

8.系统目录树

如果要实现调用系统本地小图标,只需要重写DefaultTreeCellRenderer
clientTree.setCellRenderer(new MyTreeCellRender());

public class MyTreeCellRender extends DefaultTreeCellRenderer{    /**     *      */    private static final long serialVersionUID = 1L;    public static Icon getSmallIcon(File file)    {        if (file != null && file.exists())        {            FileSystemView fsv = FileSystemView.getFileSystemView();            return fsv.getSystemIcon(file);        }        return null;    }    private static String getTreePath(TreeNode[] treenode)    {        String tmp = "";         for (int i = 1; i < treenode.length-1; i++)         {             tmp += (treenode[i].toString() + "\\");         }         tmp += treenode[ treenode.length-1 ].toString();         return tmp;    }    /**      * 重写父类DefaultTreeCellRenderer的方法      */      @Override      public Component getTreeCellRendererComponent(JTree tree, Object value,              boolean sel, boolean expanded, boolean leaf, int row,              boolean hasFocus)      {          //执行父类原型操作          super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf,                  row, hasFocus);          setText(value.toString());          //得到每个节点的TreeNode          DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;          String path = getTreePath(node.getPath());        //判断是哪个文本的节点设置对应的值（这里如果节点传入的是一个实体,则可以根据实体里面的一个类型属性来显示对应的图标）          this.setIcon(getSmallIcon(new File(path)));          return this;      }  }private void listClientDirectory()    {         DefaultMutableTreeNode clientRoots = new DefaultMutableTreeNode("电脑");         File[] root = File.listRoots();          clientTree = new JTree(clientRoots);         clientTree.setCellRenderer(new MyTreeCellRender());         JScrollPane clientScrollTree = new JScrollPane(clientTree);          for (int i = 0; i < root.length; i++)          {               if(root[i].canRead())             {                 clientRoots.add(new DefaultMutableTreeNode(root[i].toString()));                             }         }         clientTree.addMouseListener(new MouseListener() {            @Override            public void mouseReleased(MouseEvent e) {                // TODO Auto-generated method stub            }            @Override            public void mousePressed(MouseEvent e) {                // TODO Auto-generated method stub            }            @Override            public void mouseExited(MouseEvent e) {                // TODO Auto-generated method stub            }            @Override            public void mouseEntered(MouseEvent e) {                // TODO Auto-generated method stub            }            @Override            public void mouseClicked(MouseEvent e)             {                // TODO Auto-generated method stub                log.debug(e.getClickCount()+" "+e.getSource().toString());                if (e.getClickCount() >= 1)                {                    DefaultMutableTreeNode node = (DefaultMutableTreeNode) clientTree.getLastSelectedPathComponent(); //返回最后选中的结点                      if (node == null)                    {                        return;                    }                    String nodeName = node.toString();//获得这个结点的名称                    if (nodeName.equals("电脑"))                    {                        return;                    }                    HashMap<String, Integer>map =new HashMap<String, Integer>();                    int i = 0;                    for (i = 0; i < node.getChildCount(); i++)                    {                        map.put(node.getChildAt(i).toString(), 1);                    }                    String filePath = getTreePath(node.getPath());                    File parentFile = new File(filePath);                    if (parentFile.isDirectory())                    {                        log.info(nodeName + " is " + "directory");                        String[] sonFiles = parentFile.list();                        //list获取的将不会是文件路径而只是当前文件名                        for (String file : sonFiles)                        {                            if ( map.containsKey(file) ) continue;                            map.put(file, 2);                            EventQueue.invokeLater(new Runnable()                             {                                public void run()                                 {                                    try                                     {                                                                       node.add(new DefaultMutableTreeNode(file));                                                                                                             }                                     catch (Exception e)                                     {                                        e.printStackTrace();                                    }                                }                             });                                                      }                     }                    else                    {                    }                }               }        });    }

9.在Jtable中更新下载进度

对TabelModel的操作会显示到Table上，所以只要改变TableModel的值就可以，所以只要传TableModel和第几行，第几列就可以。这时候开启一条线程们就可以实时更新

DefaultTableModel tbModel;private int nowSize;private int maxSize;tbModel.setValueAt(object, row, column);//注意对object的操作是没有的，别以为java是传引用，看到里面的源码你会发现，你获取object的时候他是new了一个新的返回给你。

10. java的百分比

private static NumberFormat nt = NumberFormat.getPercentInstance();object = nt.format(nowSize*1.0/maxSize);