如何通过单击按钮重新绘制jpanel并在2个面板之间切换

Question

I am trying to repaint a panel with a button click, but its not happening. i tried using many methods like setEnabled(true), setVisible(true), repaint(), but none of these are working. And also i want to switch between two panels, like, if i click the "Total Vote" button, one panel should display, when i click on "Departmentwise Vote", another panel should display in the same place.

please help. Thanks in advance.

here im providing the code :

public class RSummary extends JFrame implements ActionListener
{
    JFrame rframe = new JFrame();
    JPanel panel1, panel2, panel3, panel4, panel5;
    JTable table;
    JScrollPane scroll;
    JSplitPane splitPane;
    JButton butx;

   public RSummary()
   {

    rframe.setSize(550,300);
    rframe.setLocationRelativeTo(null);

    setSize(550,300);
        rframe.setTitle("Summary Report");

        /* Total Vote  & Department wise vote buttons */
           panel1= new JPanel();
          JButton but1 = new JButton("TOTAL VOTE");
          JButton but2 = new JButton("DEPTARTMENT WISE VOTE");
          but1.addActionListener(this);
          panel1.add(but1);
          panel1.add(but2);

          /* Report contents according to button */
          panel2 = new JPanel();
         String[] columnNames = {"Name", "Department","Phno","LUID","Select"};
        DefaultTableModel model1 = new DefaultTableModel();
        model1.setColumnIdentifiers(columnNames);
        table = new JTable();
        table.setModel(model1); 
        table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
        table.setFillsViewportHeight(true);
        scroll = new JScrollPane(table);
        panel2.add(scroll);
        panel2.setVisible(false);


        /* close button */
        panel3 = new JPanel();
        JButton but4= new JButton("CLOSE");
        but4.addActionListener(this);
        panel3.add(but4);


        /* Page heading */
        panel4 = new JPanel();
        JLabel lab =new JLabel("VOTE SUMMARY REPORT");
        panel4.add(lab);


        /* dummy panel */
        panel5 = new JPanel();
        JButton butx = new JButton("Hello butx");
        panel5.add(butx);


    splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, panel1, panel2);
    rframe.add(splitPane);
    rframe.add(panel3,BorderLayout.SOUTH);
    rframe.add(panel4,BorderLayout.NORTH);

    rframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    rframe.setVisible(true);

}  

    public void actionPerformed(ActionEvent ae)
    { 
String action=ae.getActionCommand();

if(action == "CLOSE")
{
    rframe.setVisible(false);
}
if(action == "TOTAL VOTE")
{
    panel2.setVisible(true);  //this code is not working, i want the solution here. 
}

    }
   public static void main(String args[]) throws ClassNotFoundException, SQLException
   {
        new RSummary();

   } 
    }

Answer 1

The first problem is you're comparing the object references of your String values and not there contents...

if(action == "TOTAL VOTE")

Because of the way String s are managed by Java, it is very unlikely that these will ever be equal.

String comparison in Java is done using String#equals

if ("TOTAL VOTE".equals(action)) 

Your second problem may be related to the fact the setVisible may not be invalidating the container hierarchy, which would tell the layout framework that the containers need to be updated.

You have two solutions, the first would be to call revalidate on the parent container, the second, and better, would be to use a CardLayout , which is designed to just what you are trying to do...

Take a look at How to use Card Layout for more details

Update after running the Code

You have a series of compounding issues...

• You never set the action command of any of the buttons, so when the actionPerformed event is raised, the action is actually null
• RSummary extends from JFrame , yet you create a second JFrame called rframe . This is very confusing and could potentially lead to more problems if you're not dealing with the correct frame.

Start by setting the actionCommand property of your buttons...

JButton but1 = new JButton("TOTAL VOTE");
but1.setActionCommand("TOTAL VOTE");

Then remove extends JFrame from RSummary , as it is doing nothing but adding to the confusion and adds no benefit

Setting a frame invisible will not "close" it. Instead use JFrame#dispose

Finally, making a component visible while it's part of split pane won't resize the split divider. Once you've made the corrections, you will need to manually move the divider.

You may consider placing a empty panel into the split pane and using a CardLayout , add the other components to it, switching them in and out using the CardLayout

Updated with modified code

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.SQLException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;

public class RSummary extends JFrame implements ActionListener {

    JFrame rframe = new JFrame();
    JPanel panel1, panel2, panel3, panel4, panel5;
    JTable table;
    JScrollPane scroll;
    JSplitPane splitPane;
    JButton butx;

    public RSummary() {

        rframe.setSize(550, 300);
        rframe.setLocationRelativeTo(null);

        setSize(550, 300);
        rframe.setTitle("Summary Report");

        /* Total Vote  & Department wise vote buttons */
        panel1 = new JPanel();
        JButton but1 = new JButton("TOTAL VOTE");
        but1.setActionCommand("TOTAL VOTE");
        JButton but2 = new JButton("DEPTARTMENT WISE VOTE");
        but1.addActionListener(this);
        panel1.add(but1);
        panel1.add(but2);

        /* Report contents according to button */
        panel2 = new JPanel();
        String[] columnNames = {"Name", "Department", "Phno", "LUID", "Select"};
        DefaultTableModel model1 = new DefaultTableModel();
        model1.setColumnIdentifiers(columnNames);
        table = new JTable();
        table.setModel(model1);
        table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
        table.setFillsViewportHeight(true);
        scroll = new JScrollPane(table);
        panel2.add(scroll);
        panel2.setVisible(false);


        /* close button */
        panel3 = new JPanel();
        JButton but4 = new JButton("CLOSE");
        but4.addActionListener(this);
        panel3.add(but4);


        /* Page heading */
        panel4 = new JPanel();
        JLabel lab = new JLabel("VOTE SUMMARY REPORT");
        panel4.add(lab);


        /* dummy panel */
        panel5 = new JPanel();
        JButton butx = new JButton("Hello butx");
        panel5.add(butx);

        splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, panel1, panel2);
        rframe.add(splitPane);
        rframe.add(panel3, BorderLayout.SOUTH);
        rframe.add(panel4, BorderLayout.NORTH);

        rframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        rframe.setVisible(true);

    }

    public void actionPerformed(ActionEvent ae) {
        String action = ae.getActionCommand();

        if ("CLOSE".equals(action)) {
            rframe.dispose();
        }
        if ("TOTAL VOTE".equals(action)) {
            panel2.setVisible(true);  //this code is not working, i want the solution here. 
            panel2.getParent().revalidate();
        }

    }

    public static void main(String args[]) throws ClassNotFoundException, SQLException {
        new RSummary();

    }

}

Answer 2

To switch panels you can do:

rframe.remove (panelToRemove);
rframe.add(panelToShow);

Is this the answer to your question or why do you want to repaint?

Geosearchef

UPDATE: To summarize: MadProgrammer is right, you have to replace if(action == "TOTAL VOTE") by if(action.equals("TOTAL VOTE")) (same for CLOSE)

and you have to add an actionCommand:

JButton but1 = new JButton("TOTAL VOTE");
but1.addActionListener(this);
but1.setActionCommand("TOTAL VOTE");

To change panels:

if (action.equals("TOTAL VOTE")) {
    try{rframe.remove(panel1;)}catch(Exception e){}//clear window, maybe there is a method
    try{rframe.remove(panel2;)}catch(Exception e){}
    try{rframe.remove(panel3;)}catch(Exception e){}
    rframe.add(panel2);//the panel you want to show
}

Of course, you have to get references to the panels to actionPerformed(ActionEvent ae) .