Getting new sizes immediately after calilng setVisible

Question

How can I get the new sizes after hiding/showing a panel? I have a left and right panels, and a thin vertical bar in between that will alternatively collapse/expand the left panel whenever a user click on it. There's a PDF document in the right panel and I want it to do a "fit to page" calculation immediately after the left panel hides/shows. If I do it without the invokeLater() method, the sizes after setVisible() doesn't change and then the sizes will always be one click "behind". Like for example, when I first click on the vertical bar, the left panel collapses and the PDF page size stays the same. After the second click on the bar, the left panel expands (right panel gets smaller) and the PDF page gets bigger and fits the previous size of the right panel when the left panel was collapsed. It's like the program is recording the previous sizes, not new ones. I understand that there's an event dispatching thread and the sizes wont be updated until after the layout calculation has been done in the thread. How can I make it to do the layout immediately after calling setVisible()? I can bear with this, but there's a noticeable "fit to page" lag after the left panel changes its visibility. Is there a better way to do this?
Here's the snippet of the code:
This is where the visibility changes and where it calls the "fit to page" (fitPdfToViewport) method.
public void toggleMenuButtonVisibility(){
     final PdfViewerPanel viewPanel = efbFrame.getPdfViewerPanel();
     this.menuContentPanel.setVisible(this.hidden);
     this.hidden = !hidden;
     if(viewPanel.isFitToPage){
//          viewPanel.validate();
//          this.menuContentPanel.validate();
          Runnable blah = new Runnable(){
               public void run(){
                    viewPanel.fitPdfToViewport();
          SwingUtilities.invokeLater(blah);
}This is the "fit to page" method:
public void fitPdfToViewport(){
     this.pdfController.setZoom(1.0f);     //reset the PDF dimension
     Dimension viewDim = this.documentPanel.getSize();
     Dimension pdfDim = this.pdfController.getDocumentViewSize();
     if(pdfDim != null && viewDim != null){
          float vRatio = (float)viewDim.height / pdfDim.height;
          float hRatio = (float)viewDim.width / pdfDim.width;
          float ratio = (vRatio > hRatio) ? hRatio : vRatio;
          this.pdfController.setMinumumZoom(ratio);
          this.pdfController.setZoom(ratio);
}Thanks in advance, guys!

Answer 1

Add a ComponentListener to your panel containing the PDF. On componentResize() you add your code.