title: Place multiple JPanels on top of each other
body: <p>I have this code, and it makes a JPanel and adds it to a JScrollPanel. It works fine, but when I try to add a second JPanel it removes the first one and adds the second one. I would like to be able to place JPanels on top of JPanels, how can I do that?</p>
  
  <pre><code>// Location of an image:
  String file = wfc.getSelectedFile().getPath();
  
  // Creates images from different types:
  ImageHandler image = new ImageHandler();
  BufferedImage imageData = image.imageData(file);
  
  // Extends JPanel, Layer is a JPanel
  Layer layer = new Layer(image.width(), image.height());
  layer.setImage(imageData);
  layer.setSizeFromLoaded();
  // A list of all the JPanels added
  Layers.set(Layers.layers.size(), layer);
  
  // Adds a JPanel to the JScrollPanel
  imagePane.getViewport().add(layer, BorderLayout.CENTER);
  </code></pre>
  
  <p>Here is the full method, it opens a file browser, then when the image is selected it runs the above code</p>
  
  <pre><code>private void jMenuItem1ActionPerformed(java.awt.event.ActionEvent evt) {
      WebFileChooser wfc = null;
      if(wfc == null){
          wfc = new WebFileChooser(this, "Open an Image");
          wfc.setSelectionMode(SelectionMode.SINGLE_SELECTION);
          wfc.setAvailableFilter(GlobalConstants.IMAGES_AND_FOLDERS_FILTER);
          wfc.setChooseFilter(GlobalConstants.IMAGES_FILTER);
          wfc.setCurrentDirectory("/Users");
      }
      wfc.setVisible(true);
  
      if(wfc.getResult() == StyleConstants.OK_OPTION){
          String file = wfc.getSelectedFile().getPath();
  
          ImageHandler image = new ImageHandler();
          BufferedImage imageData = image.imageData(file);
  
          Layer layer = new Layer(image.width(), image.height());
          layer.setImage(imageData);
          layer.setSizeFromLoaded();
          Layers.set(Layers.layers.size(), layer);
  
          imagePane.getViewport().add(layer, BorderLayout.CENTER);
      }
  }
  </code></pre>