The following example illustrates using ContainerListener on AWT Frame.
ContainerEvent is generated whenever a component is added or removed on/from a container.
getChild(): This method returns the component that is affected (added/removed whatever that applies). This returns Component which is typecasted here to Label
FrameContainerEvent(): Code illustrating the use of ContainerListener on AWT Frame is written here.
Next: Using ComponentListener for AWT Button
import java.awt.*;
import java.awt.event.*;
class FrameContainerEvent extends Frame implements ContainerListener
{
Button add,remove;
int i;
public FrameContainerEvent()
{
createAndShowGUI();
}
private void createAndShowGUI()
{
setTitle("ContainerEvent on AWT Frame");
setLayout(new FlowLayout());
// Create and add a button
add=new Button("Add Label");
add(add);
remove=new Button("Remove Label");
add(remove);
// Add ActionListener to buttons
add.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae)
{
addLabel();
}
});
remove.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae)
{
removeLabel();
}
});
// Add ContainerListener
addContainerListener(this);
setSize(400,400);
setVisible(true);
}
public void addLabel()
{
// Add the label
add(new Label("Label "+i++));
// For updating the UI when the label is added
javax.swing.SwingUtilities.updateComponentTreeUI(this);
}
public void removeLabel()
{
// If there are no labels, do nothing
if(i<1) return;
// Remove the last label
remove(getComponents()[getComponents().length-1]);
// Decrement i value
i--;
// Update gui
javax.swing.SwingUtilities.updateComponentTreeUI(this);
}
public void componentAdded(ContainerEvent ce)
{
Label l=(Label)ce.getChild();
setTitle("Added "+l.getText());
}
public void componentRemoved(ContainerEvent ce)
{
Label l=(Label)ce.getChild();
setTitle("Removed "+l.getText());
}
public static void main(String args[])
{
new FrameContainerEvent();
}
}
ContainerEvent is generated whenever a component is added or removed on/from a container.
getChild(): This method returns the component that is affected (added/removed whatever that applies). This returns Component which is typecasted here to Label
FrameContainerEvent(): Code illustrating the use of ContainerListener on AWT Frame is written here.
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