GridBagLayout读取的组件

Question

I created an ArrayList of JLabel s of size n and placed the JLabel s inside an JInternalFrame with the help of a GridBagLayout manager so that the grid fits my purpose.

Now I want to replace some of those JLabel s or even remove them. Removing the k-th JLabel does work well with

innerframe.remove( ListOfLabels.get(k) );
ListOfLabels.remove(k);

(By the way if I'm using only one of those the JLabel is not removed from the internal frame -- why ? If I remove other objects like Checkboxe s, it sufficies to use only innerframe.remove(ListOfCBoxes.get(k)); )

Even the other JLabel s stay at their position, what did not work, when I placed the JLabel s inside the surrounding JFrame . But I'm not able to readd a JLabel after editing it's content. I'm trying

//Initialization 

ArrayList<JLabel> ListOfLabels = new ArrayList<JLabel>(n);
GridBagLayout GridBLayout_innerframe = new GridBagLayout();
GridBagConstraints GridBConstraints_innerframe = new GridBagConstraints();
JInternalFrame innerframe = new JInternalFrame();
innerframe.setLayout(GridBLayout_innerframe);

// Creating components of innerframe, arranging them in a grid and adding them. 
// This seems to work.

innerframe.remove( ListOfLabels.get(k) );
ListOfLabels.remove(k);

labelk = new JLabel("New content");
ListOfLabels.add(labelk);
GridBConstraints_innerframe.gridy = k ;
GridBLayout_innerframe.setConstraints(ListOfLabels.get(n-1), GridBConstraints_innerframe) ;
innerframe.add(ListOfLabels.get(n-1)) ;

Of course the same constraints were used for the k-th JLabel before and I did not erase this information. I hoped I can overwrite it.

However the result is that the JLabel s that I removed stay removed and the ones I want to add do not appear. Even after ''refreshing'' the window. There is also no error message from Eclipse.

Can someone please find my mistake and explain how to readd components into a hopefully already existing grid :/

Answer 1

You are removing the JLabel without saying the Component that you did this. You need to call the revalidate() method just after adding/removing a Component when it's already visible.

So, in case innerframe is visible and you called innerframe.remove(...) , you need to call:

innerframe.revalaidate();

Then innerframe notices that Component s where added or removed and re-assigns the Component s that are now in the Component (calling the LayoutManager , repainting, ...).

Answer 2

It's a bad idea to remove/add components in a complex layout. In such cases I would provide a full relayout: clear the container (use the method removeAll() ) and add all the required components again. Of course you must call revalidate() and repaint() for the top changed container.