I need some help, please. I need to run showErrorMessage(errorMessage) with some delay (2 sec) in separate thread. But if user continues typing and result==true before showErrorMessage method runs, I need to stop executing it.

private class DirectoryVarFieldEditor extends DirectoryFieldEditor
{
    /**
     * Initial path for the Browse dialog.
     */
    private File filterPath = null;
    
    public DirectoryVarFieldEditor(String name, String labelText, Composite parent) {
      //super( name, labelText, parent );
      init(name, labelText);
      setErrorMessage(JFaceResources.getString("DirectoryFieldEditor.errorMessage"));
      setChangeButtonText(JFaceResources.getString("openBrowse"));
      setValidateStrategy(VALIDATE_ON_KEY_STROKE);
      createControl(parent);
      setEmptyStringAllowed(false);
    }
    
    // another code...
    
    @Override
    protected boolean doCheckState() {
      System.out.println("DirectoryVarFieldEditor.doCheckState()");
      String fileName = getTextControl().getText();
      fileName = fileName.trim();
      fileName = TCA3DNKernel.expandEnvironmentVariables(fileName);
      if (fileName.length() == 0 && isEmptyStringAllowed()) 
        return true;
      File file = new File(fileName);
      return file.isDirectory();
    }
    
    //
    @Override
    protected boolean checkState()
    {
      boolean result = false;
      boolean emptyStringAllowed = super.isEmptyStringAllowed();
      Text textField = super.getTextControl();
      String errorMessage = getErrorMessage();
      if (emptyStringAllowed)
      {
        result = true;
      }
    
      if (textField == null)
      {
        result = false;
      } else
      {
        String txt = textField.getText();
        result = (txt.trim().length() > 0) || emptyStringAllowed;
      }
    
      // call hook for subclasses
      result = result && doCheckState();
    
      if (result)
      {
        clearErrorMessage();
      } else
      {
        System.out.println("DirectoryVarFieldEditor.checkState()");
        // showErrorMessage method shoud run with delay:
        showErrorMessage(errorMessage);
      }
      return result;
    }
    
    // another code...

}

Thanks for any hint!!!

CodePudding user response：

In SWT/JFace you can't call GUI operations on background threads (this is the same in most GUI systems).

For this I would use Display.timerExec to run a method after the two seconds. Set a flag if the user types something that the method can check. timerExec runs the code in the UI thread so there are no problems with background threads.

private boolean dataEntered;

...

dataEntered = false;

Display.getCurrent().timerExec(2_000, () -> {
  if (!dataEntered && !getTextControl().isDisposed()) {
     showErrorMessage("xxx");
  }
});

... other code sets dataEntered = true if data is entered

The !getTextControl().isDisposed() check deals with the dialog being closed before the 2 seconds expires.