Absolute Layout Manager

Absolute Layout Manager

Do you know of any LayoutManager that would allow me to lay out components exactly where I want them, or any other way of doing so?

There is no standard AWT or Swing LayoutManager implementation that will perform absolute positioning of components. Instead, java.awt.Component, and therefore every subclass of Component, contains a setLocation method that allows a component to be positioned using coordinates that are interpreted relative to the component’s parent container. To position components absolutely without any interference from a layout manager, you have to set the layout manager of the container to null. You also have to set the sizes of your components explicitly, not relying on a layout manager to size your components for you automatically. The following code listing demonstrates how to do this. It places a button inside a frame at a randomlocation. Every time you press the button, it moves itself to a new random location within the frame.

import java.awt.*;import java.awt.event.*;public final class AbsoluteLayout {  public static int random(int min, int range) {    double dRange = range;    double result;    result = Math.rint(Math.random()*dRange);    return (int)(min + (int)result);  }  public static void main(String[] args) {    Button button;    Frame frame;    WindowListener exitListener;    exitListener = new WindowAdapter() {      public void windowClosing(WindowEvent e) {	Window window = e.getWindow();	window.setVisible(false);	window.dispose();	System.exit(0);      }    };    button = new Button("Press me");    // Explicitly size the button, otherwise it will be a mere point.    button.setSize(100, 25);    // Add an ActionListener that will randomly move the button    button.addActionListener(new ActionListener() {      public void actionPerformed(ActionEvent e) {	Component source, parent;	Dimension sourceSize, parentSize;	source = (Component)e.getSource();	sourceSize = source.getSize();	parent = source.getParent();	parentSize = parent.getSize();	source.setLocation(random(0, parentSize.width - sourceSize.width),			   random(0, parentSize.height - sourceSize.height));      }    });    frame = new Frame();    // Don't forget to set the layout manager to null!  Otherwise it will    // interfere with your positioning and sizing.    frame.setLayout(null);    frame.add(button);    frame.addWindowListener(exitListener);    frame.setSize(400, 400);    // Dispatch an initial event to randomly place the button.    button.dispatchEvent(			 new ActionEvent(button,					 ActionEvent.ACTION_PERFORMED, null));    frame.setVisible(true);  }}
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