java - Netbeans project, JFrames ran from the main JFrame close all JFrames in project

I have a new netbeans "Java application" project, I am trying to add in a second JFrame from the main JFrame in which users can load files from.

So I have the main JFrame main method

public static void main(String args[]) 
 {


    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(MainView.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);

    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(MainView.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(MainView.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(MainView.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }

    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {

            new MainView().setVisible(true);
        }
    });
}

Which when I hit run this is the JFrame that runs, in the same project I have defined another JFrame object, the input Frame. There is a button in the main frame that when hit, does a .setVisible on the statically defined input JFrame. But if I click "X" on the input frame the main frame also closes?

Any ideas?