如何禁用或启用按钮取决于Jlist中的组件数

Question

everyone. I am implementing drag and drop GUI. What I want to do at the moment is disable or able the buttons on my GUI depends on the number of components of Jlist.

Here is my code

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.swing.*;
import javax.swing.GroupLayout.Alignment;
import javax.swing.LayoutStyle.ComponentPlacement;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

@SuppressWarnings("serial")
public class FileDragDemo extends JPanel {
    private JList list = new JList();

public FileDragDemo() {
  list.setDragEnabled(true);
  list.setTransferHandler(new FileListTransferHandler(list));


  JScrollPane scrollPane = new JScrollPane(list);





  JButton btnCompare = new JButton("Compare");
  btnCompare.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent arg0) {

      }
  });

  JButton btnAnalyze = new JButton("Analyze");
  btnAnalyze.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {


      }
  });

  JButton btnRefresh = new JButton("Refresh");
  btnRefresh.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
          DefaultListModel listModel = (DefaultListModel) list.getModel();
          listModel.removeAllElements();

      }
  });



  if (list.getModel().getSize() > 1){
      btnAnalyze.setEnabled( false );
  }

//      if (listModel.getSize() > 1){
//          btnAnalyze.setEnabled( false );
//      }

  GroupLayout groupLayout = new GroupLayout(this);
  groupLayout.setHorizontalGroup(
      groupLayout.createParallelGroup(Alignment.LEADING)
          .addGroup(groupLayout.createSequentialGroup()
              .addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 316, GroupLayout.PREFERRED_SIZE)
              .addPreferredGap(ComponentPlacement.RELATED)
              .addGroup(groupLayout.createParallelGroup(Alignment.LEADING, false)
                  .addComponent(btnRefresh, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                  .addComponent(btnAnalyze, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                  .addComponent(btnCompare, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
              .addContainerGap())
  );
  groupLayout.setVerticalGroup(
      groupLayout.createParallelGroup(Alignment.LEADING)
          .addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 144, GroupLayout.PREFERRED_SIZE)
          .addGroup(groupLayout.createSequentialGroup()
              .addContainerGap()
              .addComponent(btnCompare)
              .addPreferredGap(ComponentPlacement.RELATED)
              .addComponent(btnAnalyze)
              .addPreferredGap(ComponentPlacement.RELATED)
              .addComponent(btnRefresh))
  );
  setLayout(groupLayout);
 }



 private static void createAndShowGui() {
  FileDragDemo mainPanel = new FileDragDemo();

  JFrame frame = new JFrame("FileDragDemo");
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.getContentPane().add(mainPanel);
  frame.pack();
  frame.setLocationByPlatform(true);
  frame.setVisible(true);
 }

 public static void main(String[] args) {
  SwingUtilities.invokeLater(new Runnable() {
     public void run() {
        createAndShowGui();
     }
  });
 }
}

@SuppressWarnings("serial")
class FileListTransferHandler extends TransferHandler {
private JList list;


public FileListTransferHandler(JList list) {
   this.list = list;
}

public int getSourceActions(JComponent c) {
   return COPY_OR_MOVE;
}

public boolean canImport(TransferSupport ts) {
   return ts.isDataFlavorSupported(DataFlavor.javaFileListFlavor);
}

 public boolean importData(TransferSupport ts) {
   try {
      @SuppressWarnings("rawtypes")
      List data = (List) ts.getTransferable().getTransferData(
            DataFlavor.javaFileListFlavor);
      if (data.size() < 1) {
         return false;
      }

      DefaultListModel listModel = new DefaultListModel();
      for (Object item : data) {
         File file = (File) item;
         listModel.addElement(file);

      }

      list.setModel(listModel);
      return true;

   } catch (UnsupportedFlavorException e) {
      return false;
   } catch (IOException e) {
      return false;
   }
}
}

When drag and dropped elements in Jlist are more than 1, I want to disable btnAnalyze. Also when drag adn dropped element in Jlist is 1, I want to disable btnCompare.

Please help me out. Thanks

Answer 1

myJList.getModel().getSize();

will give you the number of components in yout JList .

And button.setEnabled(false); will disable your Button .

Answer 2

Alright so the only change I really made was to move your FileListTransfer handler into the actual class so that it is really just a sub class and then declared the buttons globally. Give this a go. Basically we are using what Rakesh said and checking what the size is and enabling vs disabling as it goes.

Move Transfer class into same class as rest

Declare Buttons globally

package assistance;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.swing.*;
import javax.swing.GroupLayout.Alignment;
import javax.swing.LayoutStyle.ComponentPlacement;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

@SuppressWarnings("serial")
public class FileDragDemo extends JPanel {

private JList list = new JList();
private JButton btnCompare, btnAnalyze, btnRefresh;

public FileDragDemo() {
    list.setDragEnabled(true);
    list.setTransferHandler(new FileListTransferHandler(list));

    JScrollPane scrollPane = new JScrollPane(list);

    btnCompare = new JButton("Compare");
    btnCompare.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {

        }
    });

    btnAnalyze = new JButton("Analyze");
    btnAnalyze.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

        }
    });

    btnRefresh = new JButton("Refresh");
    btnRefresh.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            DefaultListModel listModel = (DefaultListModel) list.getModel();
            listModel.removeAllElements();

        }
    });

//      if (listModel.getSize() > 1){
//          btnAnalyze.setEnabled( false );
//      }
    GroupLayout groupLayout = new GroupLayout(this);
    groupLayout.setHorizontalGroup(
            groupLayout.createParallelGroup(Alignment.LEADING)
            .addGroup(groupLayout.createSequentialGroup()
                    .addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 316, GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(ComponentPlacement.RELATED)
                    .addGroup(groupLayout.createParallelGroup(Alignment.LEADING, false)
                            .addComponent(btnRefresh, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(btnAnalyze, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(btnCompare, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                    .addContainerGap())
    );
    groupLayout.setVerticalGroup(
            groupLayout.createParallelGroup(Alignment.LEADING)
            .addComponent(scrollPane, GroupLayout.PREFERRED_SIZE, 144, GroupLayout.PREFERRED_SIZE)
            .addGroup(groupLayout.createSequentialGroup()
                    .addContainerGap()
                    .addComponent(btnCompare)
                    .addPreferredGap(ComponentPlacement.RELATED)
                    .addComponent(btnAnalyze)
                    .addPreferredGap(ComponentPlacement.RELATED)
                    .addComponent(btnRefresh))
    );
    setLayout(groupLayout);
}

private static void createAndShowGui() {
    FileDragDemo mainPanel = new FileDragDemo();

    JFrame frame = new JFrame("FileDragDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(mainPanel);
    frame.pack();
    frame.setLocationByPlatform(true);
    frame.setVisible(true);
}

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGui();
        }
    });
}

@SuppressWarnings("serial")
class FileListTransferHandler extends TransferHandler {

    private JList list;

    public FileListTransferHandler(JList list) {
        this.list = list;
    }

    public int getSourceActions(JComponent c) {
        return COPY_OR_MOVE;
    }

    public boolean canImport(TransferSupport ts) {
        return ts.isDataFlavorSupported(DataFlavor.javaFileListFlavor);
    }

    public boolean importData(TransferSupport ts) {
        try {
            @SuppressWarnings("rawtypes")
            List data = (List) ts.getTransferable().getTransferData(
                    DataFlavor.javaFileListFlavor);
            if (data.size() < 1) {
                return false;
            }

            DefaultListModel listModel = new DefaultListModel();
            for (Object item : data) {
                File file = (File) item;
                listModel.addElement(file);

            }

            list.setModel(listModel);
            if (list.getModel().getSize() > 1) {
                btnCompare.setEnabled(true);
                btnAnalyze.setEnabled(false);
            } else if (list.getModel().getSize() == 1) {
                btnCompare.setEnabled(false);
                btnAnalyze.setEnabled(true);
            }
            return true;

        } catch (UnsupportedFlavorException e) {
            return false;
        } catch (IOException e) {
            return false;
        }
    }
  }
}