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6.3 Insets

The Insets class provides a way to encapsulate the layout margins of the four different sides of a container. The class helps in laying out containers. The Container can retrieve their values through the getInsets() method, then analyze the settings to position components. The different inset values are measured in pixels. The space reserved by insets can still be used for drawing directly within paint(). Also, if the LayoutManager associated with the container does not look at the insets, the request will be completely ignored.

Insets Methods

Variables

There are four variables for insets, one for each border.

public int top

This variable contains the border width in pixels for the top of a container.

public int bottom

This variable contains the border width in pixels for the bottom of a container.

public int left

This variable contains the border width in pixels for the left edge of a container.

public int right

This variable contains the border width in pixels for the right edge of a container.

Constructors

public Insets (int top, int left, int bottom, int right)

The constructor creates an Insets object with top, left, bottom, and right being the size of the insets in pixels. If this object was the return object from the getInsets() method of a container, these values represent the size of a border inside that container.

Miscellaneous methods

public Object clone ()

The clone() method creates a clone of the Insets so the same Insets object can be associated with multiple containers.

public boolean equals(Object object) (New)

The equals() method defines equality for insets. Two Insets objects are equal if the four settings for the different values are equal.

public String toString ()

The toString() method of Insets returns the current settings. Using the new Insets (10, 20, 30, 40) constructor, the results would be:

java.awt.Insets[top=10,left=20,bottom=30,right=40]

Insets Example

The following source code demonstrates the use of insets within an applet's Panel. The applet displays a button that takes up the entire area of the Panel, less the insets, then draws a rectangle around that area. This is shown visually in Figure 6.1. The example demonstrates that if you add components to a container, the LayoutManager deals with the insets for you in positioning them. But if you are drawing directly to the Panel, you must look at the insets if you want to avoid the requested area within the container.

import java.awt.*;
import java.applet.*;
public class myInsets extends Applet {
    public Insets insets () {
        return new Insets (50, 50, 50, 50);
    }
    public void init () {
        setLayout (new BorderLayout ());
        add ("Center", new Button ("Insets"));
    }
    public void paint (Graphics g) {
        Insets i = insets();
        int width  = size().width - i.left - i.right;
        int height = size().height - i.top - i.bottom;
        g.drawRect (i.left-2, i.top-2, width+4, height+4);
        g.drawString ("Insets Example", 25, size().height - 25);
    }
}

To change the applet's insets from the default, we override the insets() method to return a new Insets object, with the new values.


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