java为什么我试图在eclipse中打开编辑器时IWorkbenchPage页面为空？

Question

我发现了以下示例代码：

File fileToOpen = new File("externalfile.xml");

if (fileToOpen.exists() && fileToOpen.isFile()) {
IFileStore fileStore = EFS.getLocalFileSystem().getStore(fileToOpen.toURI());
IWorkbenchPage page = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();

try {
    IDE.openEditorOnFileStore( page, fileStore );
} catch ( PartInitException e ) {
    //Put your exception handler here if you wish to
}
} else {
//Do something if the file does not exist
}

当我运行插件时，eclipse报告IWorkbenchPage页面为空

我以这种方式实现我的代码：

public void openFile(Path filepath) throws Exception
{
    File fileToOpen = new File(filepath.toString());

    if (fileToOpen.exists() && fileToOpen.isFile()) {
        IFileStore fileStore = EFS.getLocalFileSystem().getStore(fileToOpen.toURI());
        IWorkbenchPage page = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();

        try {
            IDE.openEditorOnFileStore( page, fileStore );
        } catch ( PartInitException e ) {
            //Put your exception handler here if you wish to
        }
    } else {
        //Do something if the file does not exist
    }               
}

方法openFile是从同一类中的另一个方法调用的

这是我的样本处理程序（不是我自己写的）：

public class SampleHandler<IWorkspace> extends AbstractHandler {

public SampleHandler() {
}

public Object execute(ExecutionEvent event) throws ExecutionException { 
    String pagetitle = "";
    String worspacelocation = "";

    try{
    //salvo in workspacelocation il path del workspace
    worspacelocation =ResourcesPlugin.getWorkspace().getRoot().getLocation().toString();
    }
    catch (Exception e)
    {
        JFrame frame = new JFrame("Workspace Location Error");
           JOptionPane.showMessageDialog(frame,"Impossibile determinare il workspace");     
        e.printStackTrace();
    }   
    try{
    IEditorPart editor = HandlerUtil.getActiveEditor(event);
    if (editor.getTitle() != null)
    {
        pagetitle = editor.getTitleToolTip();       
    }   
    else
    {
        pagetitle = null;
    }}
    catch (Exception e){
        System.out.print("errore:" + e.getMessage());
        e.printStackTrace();}   
    NewFrame.main(null, pagetitle,worspacelocation);        
    return null;
}