border layout

[poornima viswa]

consider the code below
import java.awt.*;
public class TestFrame extends Frame
{
Button bNorth = new Button("North");
Button bSouth = new Button("South");
Button bEast = new Button("East");
Button bWest = new Button("West");
Button bCenter = new Button("Center");
public TestFrame()
{
setLayout(new FlowLayout());
add(bNorth);
add(bSouth);
add(bWest);
add(bEast);
add(bCenter);
setLayout(new BorderLayout());
validate();
setSize(300,300);
setVisible(true);
}
public static void main(String args[])
{
TestFrame tf = new TestFrame();
}
}
Will compile and run cleanly, but no component is visible.
I thought last button added will appear in the centre of the frame but why nothing is visible in the frame.

[Aru Ven]

Poornima,
After u changed the layout from FlowLayout to Borderlayout, U will have to "explicitly add the components again" to the new layout for it to appear.
But the opposite is not true. Means Frame has BorderLayout as its default layout. If u add items to the frame & then change it to a differnt layout. The components still appear. Without the need to explicitly add them to the new layout.
Hope I made sense.
Aruna

[Sivaram Ghorakavi]

Poornima,
First time the Frame has set with FlowLayout manager,new instance, and all the buttons are added to this instance of LayoutManager. And when the layout manager is reset with new instance of BorderLayout and since no components are added to it nowthing will be displayed. It's over writing the previous layout manger.

[poornima viswa]

thankx Aru and Sivaram