如何在标题栏上加一个问号按钮

如何在标题栏上加一个问号按钮

Windows系统中用以激活上下文帮助的有两种方式，
    1. F1，
    2. 标题栏上的问号按钮.

SWT支持第一种方式。只要对一个控件加上SWT.Help事件的Listener就可以了。

我却没有找到怎样在标题栏上加上一个问号的方法。只好借助JNI了，先查需要哪个Win32 API的函数。那是
SetWindowLong(hWnd,  GWL_EXSTYLE,  WS_EX_CONTEXTHELP)函数，其中hWnd是对话框的句柄，WS_EX_CONTEXTHELP激活了上下文问号按钮.  然后了我们可以定义一个Java  Native的方法以及相应的C函数, 并把C函数做成一个DLL的库, 从Java中调用SetWindowLong以激活问号按钮。

幸运的是SWT已经为我们作了大部分工作了，org.eclipse.swt.internal.win32.OS类中已经定义了SetWindowLong函数, 也就是说我们不需要自己写JNI的接口.  当然OS类位于一个internal的包了, internal包里的类要谨慎使用. 另外即使在SWT的CVS库里也没有定义WS_EX_CONTEXTHELP这个常数, 这说明SWT目前还不支持标题栏上的问号按钮, 可能是因为其他的窗口系统下不支持的缘故.在这篇里,我只考虑Windows的情况.

在我们写代码之前,需要知道WS_EX_CONTEXTHELP具体的值, 查MSDN或者用VC++里的打开定义功能, 查到WS_EX_CONTEXTHELP = 0x400.

public   class  HelpButton {

     public   static   final  String HELP_TEXT  =   " HELP_TEXT " ;
     public   static   final  String HELP_IMAGE  =   " HELP_IMAGE " ;

     private  Shell parent;
     private  Shell helpShell;
     private  Label helpImageLabel;
     private  Label helpTextLabel;

     private   static   final   int  WS_EX_CONTEXTHELP  =   0x400 ;

     public  HelpButton(Shell shell) {
         int  style  =  OS.GetWindowLong(shell.handle, OS.GWL_EXSTYLE);
        OS.SetWindowLong(shell.handle, OS.GWL_EXSTYLE, style
                 |  WS_EX_CONTEXTHELP);

         this .parent  =  shell;
        helpShell  =   new  Shell(parent, SWT.ON_TOP  |  SWT.TOOL);
        GridLayout gridLayout  =   new  GridLayout();
        gridLayout.numColumns  =   2 ;
        gridLayout.marginWidth  =   2 ;
        gridLayout.marginHeight  =   2 ;
        helpShell.setLayout(gridLayout);
        Display display  =  shell.getDisplay();
        helpShell.setBackground(display
                .getSystemColor(SWT.COLOR_INFO_BACKGROUND));

        helpImageLabel  =   new  Label(helpShell, SWT.NONE);
        helpImageLabel.setForeground(display
                .getSystemColor(SWT.COLOR_INFO_FOREGROUND));
        helpImageLabel.setBackground(display
                .getSystemColor(SWT.COLOR_INFO_BACKGROUND));
        helpImageLabel.setLayoutData( new  GridData(GridData.FILL_HORIZONTAL
                 |  GridData.VERTICAL_ALIGN_CENTER));

        helpTextLabel  =   new  Label(helpShell, SWT.NONE);
        helpTextLabel.setForeground(display
                .getSystemColor(SWT.COLOR_INFO_FOREGROUND));
        helpTextLabel.setBackground(display
                .getSystemColor(SWT.COLOR_INFO_BACKGROUND));
        helpTextLabel.setLayoutData( new  GridData(GridData.FILL_HORIZONTAL
                 |  GridData.VERTICAL_ALIGN_CENTER));

        Listener listener  =   new  Listener() {
             public   void  handleEvent(Event event) {
                 if  (helpShell.isVisible())
                    helpShell.setVisible( false );
            }
        };
        helpTextLabel.addListener(SWT.MouseDown, listener);
        helpImageLabel.addListener(SWT.MouseDown, listener);
        parent.addListener(SWT.MouseDown, listener);
    }

     public   void  activeHelpListener( final  Control control) {
        control.addListener(SWT.Help,  new  Listener() {
             public   void  handleEvent(Event event) {
                Control control  =  (Control) event.widget;
                String text  =  control.getData(HELP_TEXT).toString();
                Object img  =  control.getData(HELP_IMAGE);
                 if  (img  instanceof  Image) {
                    helpImageLabel.setImage((Image) img);
                }
                helpTextLabel.setText(text);
                Rectangle controlRect  =  control.getBounds();
                Display display  =  parent.getDisplay();
                Point pt  =  display.map(parent,  null , control.getLocation());
                helpShell.pack();
                helpShell.setLocation(pt.x  +  controlRect.width  /   2 , pt.y
                         +  controlRect.height  /   2 );
                helpShell.setVisible( true );
            }
        });
    }
}

测试程序

public   class  HelpButtonTest {

     public   static   void  main(String[] args) {
         final  Display display  =   new  Display();
         final  Shell shell  =   new  Shell(display, SWT.DIALOG_TRIM);
        shell.setLayout( new  RowLayout());
        HelpButton helpButton  =   new  HelpButton(shell);
        
        Button button  =   new  Button(shell, SWT.PUSH);
        button.setText( " Button " );
        helpButton.activeHelpListener(button);
        button.setData(HelpButton.HELP_TEXT,  " Click me to get 1 million EURO. " );
        Image image  =   new  Image(display, HelpButtonTest. class
                .getResourceAsStream( " information.gif " ));
        button.setData(HelpButton.HELP_IMAGE, image);
        
        button  =   new  Button(shell, SWT.PUSH);
        button.setText( " Eclipse SWT " );
        helpButton.activeHelpListener(button);
        button.setData(HelpButton.HELP_TEXT,  " Click me to get 100 million EURO. " );
        image  =   new  Image(display, HelpButtonTest. class
                .getResourceAsStream( " warning.gif " ));
        button.setData(HelpButton.HELP_IMAGE, image);
        
        shell.setSize( 200 ,  100 );
        shell.open();
         while  ( ! shell.isDisposed()) {
             if  ( ! display.readAndDispatch())
                display.sleep();
        }
         if  (image  !=   null )
            image.dispose();
        display.dispose();
    }
}

转载请保留 http://www.blogjava.net/xilaile/archive/2007/02/23/100397.html