[Chapter 18] 18.29 java.awt.GridBagLayout (JDK 1.0)

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| Chapter 18 The java.awt Package |

## 18.29 java.awt.GridBagLayout (JDK 1.0)

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This class implements the `LayoutManager` interface to lay out `Component` objects in a `Container`. It is the most complicated and most powerful `LayoutManager` in the `java.awt` package. It divides the container into a grid of rows and columns (which need not have the same width and height) and places the components into this grid, adjusting the size of the grid cells as necessary to ensure that components do not overlap. Each component controls how it is positioned within this grid by specifying a number of variables (or "constraints") in a `GridBagConstraints` object. Do not confuse this class with the much simpler `GridLayout` which arranges components in a grid of equally sized cells.

Use `setConstraints()` to specify a `GridBagConstraints` object for each of the components in the container. Or, in Java 1.1, specify the `GridBagConstraints` object when adding the component to the container with `add()`. The variables in this object specify the position of the component in the grid, the number of horizontal and vertical grid cells that the component occupies, and also control other important aspects of component layout. See `GridBagConstraints` for more information on these "constraint" variables. `setConstraints()` makes a copy of the constraints object, so you may reuse a single object in your code.

Note that applications should never call the `LayoutManager` methods of this class directly; the `Container` for which the `GridBagLayout` is registered does this.

    public class GridBagLayout extends Object implements LayoutManager2, Serializable {
        // Public Constructor
                public GridBagLayout();
        // Constants
                protected static final int MAXGRIDSIZE;
                protected static final int MINSIZE;
                protected static final int PREFERREDSIZE;
        // Public Instance Variables
                public double[] columnWeights;
                public int[] columnWidths;
                public int[] rowHeights;
                public double[] rowWeights;
        // Protected Instance Variables
                protected Hashtable comptable;
                protected GridBagConstraints defaultConstraints;
                protected GridBagLayoutInfo layoutInfo;
        // Public Instance Methods
                public void addLayoutComponent(String name, Component comp);  // From LayoutManager
            1.1  public void addLayoutComponent(Component comp, Object constraints);  // From LayoutManager2
                public GridBagConstraints getConstraints(Component comp);
            1.1  public float getLayoutAlignmentX(Container parent);  // From LayoutManager2
            1.1  public float getLayoutAlignmentY(Container parent);  // From LayoutManager2
                public int[][] getLayoutDimensions();
                public Point getLayoutOrigin();
                public double[][] getLayoutWeights();
            1.1  public void invalidateLayout(Container target);  // From LayoutManager2
                public void layoutContainer(Container parent);  // From LayoutManager
                public Point location(int x, int y);
            1.1  public Dimension maximumLayoutSize(Container target);  // From LayoutManager2
                public Dimension minimumLayoutSize(Container parent);  // From LayoutManager
                public Dimension preferredLayoutSize(Container parent);  // From LayoutManager
                public void removeLayoutComponent(Component comp);  // From LayoutManager
                public void setConstraints(Component comp, GridBagConstraints constraints);
                public String toString();  // Overrides Object
        // Protected Instance Methods
                protected void AdjustForGravity(GridBagConstraints constraints, Rectangle r);
                protected void ArrangeGrid(Container parent);
                protected GridBagLayoutInfo GetLayoutInfo(Container parent, int sizeflag);
                protected Dimension GetMinSize(Container parent, GridBagLayoutInfo info);
                protected GridBagConstraints lookupConstraints(Component comp);
    }

### Hierarchy:

`Object->GridBagLayout(LayoutManager2(LayoutManager), Serializable)`

java.awt.GridBagConstraints (JDK 1.0) |  | java.awt.GridLayout (JDK 1.0)