如何在 eclipse 插件中获取活动页面？

Question

我需要在 Eclipse 编辑器中获取活动页面。当我搜索它时，我发现了以下代码：

IWorkbench wb = PlatformUI.getWorkbench();
IWorkbenchWindow win = wb.getActiveWorkbenchWindow();
IWorkbenchPage page = win.getActivePage();
ITextEditor editor = (ITextEditor) page.getActiveEditor();

但是，当我使用此代码时，它会生成以下错误消息：

java.lang.NullPointerException
    at kr.ac.jbnu.ssel.instantfeedback.views.InstantFeedbackView$1.elementChanged(InstantFeedbackView.java:136)
    at org.eclipse.jdt.internal.core.DeltaProcessor$3.run(DeltaProcessor.java:1662)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.jdt.internal.core.DeltaProcessor.notifyListeners(DeltaProcessor.java:1652)
    at org.eclipse.jdt.internal.core.DeltaProcessor.fireReconcileDelta(DeltaProcessor.java:1504)
    at org.eclipse.jdt.internal.core.DeltaProcessor.fire(DeltaProcessor.java:1463)
    at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:765)
    at org.eclipse.jdt.internal.core.JavaModelOperation.runOperation(JavaModelOperation.java:790)
    at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1250)
    at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.reconcile(JavaReconcilingStrategy.java:128)
    at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.access$0(JavaReconcilingStrategy.java:110)
    at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy$1.run(JavaReconcilingStrategy.java:90)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.reconcile(JavaReconcilingStrategy.java:87)
    at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.reconcile(JavaReconcilingStrategy.java:154)
    at org.eclipse.jdt.internal.ui.text.CompositeReconcilingStrategy.reconcile(CompositeReconcilingStrategy.java:89)
    at org.eclipse.jdt.internal.ui.text.JavaCompositeReconcilingStrategy.reconcile(JavaCompositeReconcilingStrategy.java:104)
    at org.eclipse.jface.text.reconciler.MonoReconciler.process(MonoReconciler.java:73)
    at org.eclipse.jface.text.reconciler.AbstractReconciler$BackgroundThread.run(AbstractReconciler.java:207)

我该如何解决这个问题？

添加 这是我的 elementChanged() 函数。它在方法中。

private void addListenerToCheckChange_save() {
  JavaCore.addElementChangedListener(new IElementChangedListener() {

    @Override
    public void elementChanged(ElementChangedEvent event) {
      IWorkbench wb = PlatformUI.getWorkbench();
      IWorkbenchWindow win = wb.getActiveWorkbenchWindow();
      IWorkbenchPage page = win.getActivePage();
      ITextEditor editor = (ITextEditor) page.getActiveEditor();
      IJavaElement javaElement = JavaUI.getEditorInputJavaElement(editor.getEditorInput());
      if (javaElement instanceof ICompilationUnit) {
        ITextSelection sel = (ITextSelection) editor.getSelectionProvider().getSelection();
        IJavaElement selected = null;
        try {
          ...
        } catch (JavaModelException JME) {
          JME.printStackTrace();
        }
      }
    }
  });
}

我尝试修改它以在我的视图类中实现 IElementChangedListener。这是修改过的。

@Override
public void elementChanged(ElementChangedEvent arg0) {
  Display.getCurrent().asyncExec(new Runnable() {

    @Override
    public void run() {
      IWorkbench wb = PlatformUI.getWorkbench();
      IWorkbenchWindow win = wb.getActiveWorkbenchWindow();
      IWorkbenchPage page = win.getActivePage();
      ITextEditor editor = (ITextEditor) page.getActiveEditor();
      IJavaElement javaElement = JavaUI.getEditorInputJavaElement(editor.getEditorInput());
      if (javaElement instanceof ICompilationUnit) {
        ITextSelection sel = (ITextSelection) editor.getSelectionProvider().getSelection();
        IJavaElement selected = null;
        try {
          ...
        } catch (JavaModelException JME) {
          JME.printStackTrace();
        }
      }
    }
  });       
}

但是，修改后的一个不起作用...

Answer 1

您正在从以下位置获取活动工作台窗口的空值：

IWorkbenchWindow win = wb.getActiveWorkbenchWindow();

这是因为您的代码在不是主 UI 线程的线程中运行 - 在这种情况下，getActiveWorkbenchWindow 返回 null。

要使用这样的 UI 操作，您需要安排在 UI 线程中运行您的代码，可能使用Display.asyncExec。比如：

public void elementChanged(ElementChangedEvent event) {

   ... code not run in UI thread

   Display.getDefault().asyncExec(() ->
     {
       ... code to run in UI thread
     });
}

（使用 Java 8 lambda，对于较旧的 Java，使用 Runnable）。