Java : how to get the active editor in a thread?

Question

My problem is the following one : I am working with 2 plugins : let's call them A and B.
When I start the application, A starts B and gives him a parameter : the current ActiveEditor. B can now perform some actions on the current editor. Everything is fine for this point.
However, the parameter is given only when A is instantiated, so if the current editor changes, B is not aware of the change.
I tried to use a Thread, started by A, getting the active editor every two seconds and setting it into B. Problem : NullPointerException every time =>

java.lang.NullPointerException: while trying to invoke the method org.eclipse.ui.IWorkbenchWindow.getActivePage() of a null object returned from org.eclipse.ui.IWorkbench.getActiveWorkbenchWindow()
at com.highdeal.tests.cortex.eclipse.RefreshThread.run(RefreshThread.java:14)

Here is the code of the thread started by the plugin A :

public class RefreshThread extends Thread {

public void run(){
    while (true){
        try{
            Thread.sleep(1000);
            IEditorPart iep = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().getActiveEditor();
            new SampleAction(iep);
        } catch (Exception e){
            e.printStackTrace();
        }

    }
}

}

When I migrate the following piece of code into the constructor of the Plugin A, it works correctly :

IEditorPart iep = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().getActiveEditor();
new SampleAction(iep);

Thanks for reading. Ask me if you need further explanations.

Answer 1

PlatformUI.getWorkbench().getActiveWorkbenchWindow() always returns null when it is called from a background thread (that is a thread which is not the UI thread).

A better way to do this is to use IPartListener to listen for the active part being changed.

IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();

window.getPartService().addPartListener(part listener);

(must be run in the UI thread).

The part listener will be told about each part being activated and you can check if this is a new editor.

Answer 2

要在其他线程而不是UIThread中运行UI代码，请使用UIThreadSynchronizer或Display.syncExec（）\\ asyncExec（）调用。