Making a Component Draggable in Java
In this section, you will learn how to make a component draggable in java.
This program provides the drag and drop feature from one component to another.
This program shows a text box and a label on the frame. When you drag the label
and drop to the text box then the text of the label is copied to the text box.
For the pictorial representation of the application result is given as follows:
Code Description:
There are several APIs has been used to make the component draggable in the
program. These are explained as follows:
TransferHandler:
This is the class of the javax.swing.*; package. This is used to
transfer the transferable swing component from on the another. Both components
should be the swing component. This class is helpful to copy from one component
to another via clipboard.
setTransferHandler():
This is the method of the TransferHandler class which makes the component
able to transfer the specified part of the component in the TransferHandler() as
parameter which specifies the the property of the component which has to be
dragged and dropped. This program specifies the text of the label to be dragged
and drop to the text box using the string "text".
MouseListener:
This is the interface which receives the different mouse events. Mouse events can be like:
pressing or releasing the mouse, click, enter or exit the mouse etc. are handled
through the MouseEvent generated by the MouseListener interface. This program
uses the instance of the MouseListener.
exportAsDrag():
This is the method of the TransferHandler class which initiates the
component to drag and drop from one to another swing component. This method
takes three arguments like: JComponent, Active event, and another is the Action
which has to be done. Here, the constant property COPY of the TransferHandler
class has been used to copy the text from the label to the text box.
Here is the code of the program:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SwingDragDrop{
JTextField txtField;
JLabel lbl;
public static void main(String[] args){
SwingDragDrop sdd = new SwingDragDrop();
}
public SwingDragDrop(){
JFrame frame = new JFrame("Drag Drop Demo");
txtField = new JTextField(20);
lbl = new JLabel("This is the text for drag and drop.");
lbl.setTransferHandler(new TransferHandler("text"));
MouseListener ml = new MouseAdapter(){
public void mousePressed(MouseEvent e){
JComponent jc = (JComponent)e.getSource();
TransferHandler th = jc.getTransferHandler();
th.exportAsDrag(jc, e, TransferHandler.COPY);
}
};
lbl.addMouseListener(ml);
JPanel panel = new JPanel();
panel.add(txtField);
frame.add(lbl, BorderLayout.CENTER);
frame.add(panel, BorderLayout.NORTH);
frame.setSize(400, 400);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
}
}
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