无法更新JList

Question

我在MediaLibrary.java中有一个方法如下

private void playListActionPerformed(java.awt.event.ActionEvent evt) {                                         

    mediaLibraryDTO dto=new mediaLibraryDTO();
    dto.setSongList(currentSongField.getText());
    new Dashboard().libraryList(dto);
}

同样，我有MediaLibraryDTO.java如下

public class mediaLibraryDTO {
    private String songList;

    public String getSongList() {
        return songList;
    }

    public void setSongList(String songList) {
        this.songList = songList;
    }

}

同样，我在Dashboard.java中有一个方法如下

public void libraryList(mediaLibraryDTO dto) {
    File file = new File(dto.getSongList());
    JOptionPane.showMessageDialog(null, file);
    JList list = new JList(model);
    model.addElement(file.toString());
    playList.setModel(model);
}