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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package java.awt;


The GridLayout class is a layout manager that lays out a container's components in a rectangular grid. The container is divided into equal-sized rectangles, and one component is placed in each rectangle. For example, the following is an applet that lays out six buttons into three rows and two columns: 


import java.awt.*;
import java.applet.Applet;
public class ButtonGrid extends Applet {
    public void init() {
        setLayout(new GridLayout(3,2));
        add(new Button("1"));
        add(new Button("2"));
        add(new Button("3"));
        add(new Button("4"));
        add(new Button("5"));
        add(new Button("6"));
    }
}



 If the container's ComponentOrientation property is horizontal and left-to-right, the above example produces the output shown in Figure 1. If the container's ComponentOrientation property is horizontal and right-to-left, the example produces the output shown in Figure 2. 

Figures










Figure 1: Horizontal, Left-to-Right
Figure 2: Horizontal, Right-to-Left





 When both the number of rows and the number of columns have been set to non-zero values, either by a constructor or by the setRows and setColumns methods, the number of columns specified is ignored. Instead, the number of columns is determined from the specified number of rows and the total number of components in the layout. So, for example, if three rows and two columns have been specified and nine components are added to the layout, they will be displayed as three rows of three columns. Specifying the number of columns affects the layout only when the number of rows is set to zero. 
Author: Arthur van Hoff
Since:  1.0
/**
 * The {@code GridLayout} class is a layout manager that
 * lays out a container's components in a rectangular grid.
 * The container is divided into equal-sized rectangles,
 * and one component is placed in each rectangle.
 * For example, the following is an applet that lays out six buttons
 * into three rows and two columns:
 *
 * <hr><blockquote>
 * <pre>
 * import java.awt.*;
 * import java.applet.Applet;
 * public class ButtonGrid extends Applet {
 *     public void init() {
 *         setLayout(new GridLayout(3,2));
 *         add(new Button("1"));
 *         add(new Button("2"));
 *         add(new Button("3"));
 *         add(new Button("4"));
 *         add(new Button("5"));
 *         add(new Button("6"));
 *     }
 * }
 * </pre></blockquote><hr>
 * <p>
 * If the container's {@code ComponentOrientation} property is horizontal
 * and left-to-right, the above example produces the output shown in Figure 1.
 * If the container's {@code ComponentOrientation} property is horizontal
 * and right-to-left, the example produces the output shown in Figure 2.
 *
 * <table style="float:center;width:600">
 * <caption style="display:none">Figures</caption>
 * <tr style="text-align:center">
 * <td><img SRC="doc-files/GridLayout-1.gif"
 *      alt="Shows 6 buttons in rows of 2. Row 1 shows buttons 1 then 2.
 * Row 2 shows buttons 3 then 4. Row 3 shows buttons 5 then 6.">
 * </td>
 *
 * <td style="text-align:center"><img SRC="doc-files/GridLayout-2.gif"
 *              alt="Shows 6 buttons in rows of 2. Row 1 shows buttons 2 then 1.
 * Row 2 shows buttons 4 then 3. Row 3 shows buttons 6 then 5.">
 * </td>
 * </tr>
 *
 * <tr style="text-align:center">
 * <td>Figure 1: Horizontal, Left-to-Right</td>
 *
 * <td>Figure 2: Horizontal, Right-to-Left</td>
 * </tr>
 * </table>
 * <p>
 * When both the number of rows and the number of columns have
 * been set to non-zero values, either by a constructor or
 * by the {@code setRows} and {@code setColumns} methods, the number of
 * columns specified is ignored.  Instead, the number of
 * columns is determined from the specified number of rows
 * and the total number of components in the layout. So, for
 * example, if three rows and two columns have been specified
 * and nine components are added to the layout, they will
 * be displayed as three rows of three columns.  Specifying
 * the number of columns affects the layout only when the
 * number of rows is set to zero.
 *
 * @author  Arthur van Hoff
 * @since   1.0
 */
public class GridLayout implements LayoutManager, java.io.Serializable {
    /*
     * serialVersionUID
     */
    private static final long serialVersionUID = -7411804673224730901L;

    
This is the horizontal gap (in pixels) which specifies the space
between columns.  They can be changed at any time.
This should be a non-negative integer.

See Also:
@serial
/**
     * This is the horizontal gap (in pixels) which specifies the space
     * between columns.  They can be changed at any time.
     * This should be a non-negative integer.
     *
     * @serial
     * @see #getHgap()
     * @see #setHgap(int)
     */
    int hgap;
    
This is the vertical gap (in pixels) which specifies the space
between rows.  They can be changed at any time.
This should be a non negative integer.

See Also:
@serial
/**
     * This is the vertical gap (in pixels) which specifies the space
     * between rows.  They can be changed at any time.
     * This should be a non negative integer.
     *
     * @serial
     * @see #getVgap()
     * @see #setVgap(int)
     */
    int vgap;
    
This is the number of rows specified for the grid.  The number
of rows can be changed at any time.
This should be a non negative integer, where '0' means
'any number' meaning that the number of Rows in that
dimension depends on the other dimension.

See Also:
@serial
/**
     * This is the number of rows specified for the grid.  The number
     * of rows can be changed at any time.
     * This should be a non negative integer, where '0' means
     * 'any number' meaning that the number of Rows in that
     * dimension depends on the other dimension.
     *
     * @serial
     * @see #getRows()
     * @see #setRows(int)
     */
    int rows;
    
This is the number of columns specified for the grid.  The number
of columns can be changed at any time.
This should be a non negative integer, where '0' means
'any number' meaning that the number of Columns in that
dimension depends on the other dimension.

See Also:
@serial
/**
     * This is the number of columns specified for the grid.  The number
     * of columns can be changed at any time.
     * This should be a non negative integer, where '0' means
     * 'any number' meaning that the number of Columns in that
     * dimension depends on the other dimension.
     *
     * @serial
     * @see #getColumns()
     * @see #setColumns(int)
     */
    int cols;

    
Creates a grid layout with a default of one column per component,
in a single row.

Since:1.1
/**
     * Creates a grid layout with a default of one column per component,
     * in a single row.
     * @since 1.1
     */
    public GridLayout() {
        this(1, 0, 0, 0);
    }

    
Creates a grid layout with the specified number of rows and
columns. All components in the layout are given equal size.

 One, but not both, of rows and cols can be zero, which means that any number of objects can be placed in a row or in a column. 
Params:
  • rows –   the rows, with the value zero meaning
                  any number of rows.
  • cols –   the columns, with the value zero meaning
                  any number of columns.
/**
     * Creates a grid layout with the specified number of rows and
     * columns. All components in the layout are given equal size.
     * <p>
     * One, but not both, of {@code rows} and {@code cols} can
     * be zero, which means that any number of objects can be placed in a
     * row or in a column.
     * @param     rows   the rows, with the value zero meaning
     *                   any number of rows.
     * @param     cols   the columns, with the value zero meaning
     *                   any number of columns.
     */
    public GridLayout(int rows, int cols) {
        this(rows, cols, 0, 0);
    }

    
Creates a grid layout with the specified number of rows and
columns. All components in the layout are given equal size.


In addition, the horizontal and vertical gaps are set to the
specified values. Horizontal gaps are placed between each
of the columns. Vertical gaps are placed between each of
the rows.

 One, but not both, of rows and cols can be zero, which means that any number of objects can be placed in a row or in a column. 
 All GridLayout constructors defer to this one. 
Params:
  • rows –   the rows, with the value zero meaning
                  any number of rows
  • cols –   the columns, with the value zero meaning
                  any number of columns
  • hgap –   the horizontal gap
  • vgap –   the vertical gap
Throws:
/**
     * Creates a grid layout with the specified number of rows and
     * columns. All components in the layout are given equal size.
     * <p>
     * In addition, the horizontal and vertical gaps are set to the
     * specified values. Horizontal gaps are placed between each
     * of the columns. Vertical gaps are placed between each of
     * the rows.
     * <p>
     * One, but not both, of {@code rows} and {@code cols} can
     * be zero, which means that any number of objects can be placed in a
     * row or in a column.
     * <p>
     * All {@code GridLayout} constructors defer to this one.
     * @param     rows   the rows, with the value zero meaning
     *                   any number of rows
     * @param     cols   the columns, with the value zero meaning
     *                   any number of columns
     * @param     hgap   the horizontal gap
     * @param     vgap   the vertical gap
     * @exception   IllegalArgumentException  if the value of both
     *                  {@code rows} and {@code cols} is
     *                  set to zero
     */
    public GridLayout(int rows, int cols, int hgap, int vgap) {
        if ((rows == 0) && (cols == 0)) {
            throw new IllegalArgumentException("rows and cols cannot both be zero");
        }
        this.rows = rows;
        this.cols = cols;
        this.hgap = hgap;
        this.vgap = vgap;
    }

    
Gets the number of rows in this layout.

Returns:   the number of rows in this layout
Since:    1.1
/**
     * Gets the number of rows in this layout.
     * @return    the number of rows in this layout
     * @since     1.1
     */
    public int getRows() {
        return rows;
    }

    
Sets the number of rows in this layout to the specified value.

Params:
  • rows –   the number of rows in this layout
Throws:
Since:       1.1
/**
     * Sets the number of rows in this layout to the specified value.
     * @param        rows   the number of rows in this layout
     * @exception    IllegalArgumentException  if the value of both
     *               {@code rows} and {@code cols} is set to zero
     * @since        1.1
     */
    public void setRows(int rows) {
        if ((rows == 0) && (this.cols == 0)) {
            throw new IllegalArgumentException("rows and cols cannot both be zero");
        }
        this.rows = rows;
    }

    
Gets the number of columns in this layout.

Returns:    the number of columns in this layout
Since:     1.1
/**
     * Gets the number of columns in this layout.
     * @return     the number of columns in this layout
     * @since      1.1
     */
    public int getColumns() {
        return cols;
    }

    
Sets the number of columns in this layout to the specified value. Setting the number of columns has no affect on the layout if the number of rows specified by a constructor or by the setRows method is non-zero. In that case, the number of columns displayed in the layout is determined by the total number of components and the number of rows specified. 
Params:
  • cols –   the number of columns in this layout
Throws:
Since:       1.1
/**
     * Sets the number of columns in this layout to the specified value.
     * Setting the number of columns has no affect on the layout
     * if the number of rows specified by a constructor or by
     * the {@code setRows} method is non-zero. In that case, the number
     * of columns displayed in the layout is determined by the total
     * number of components and the number of rows specified.
     * @param        cols   the number of columns in this layout
     * @exception    IllegalArgumentException  if the value of both
     *               {@code rows} and {@code cols} is set to zero
     * @since        1.1
     */
    public void setColumns(int cols) {
        if ((cols == 0) && (this.rows == 0)) {
            throw new IllegalArgumentException("rows and cols cannot both be zero");
        }
        this.cols = cols;
    }

    
Gets the horizontal gap between components.

Returns:      the horizontal gap between components
Since:       1.1
/**
     * Gets the horizontal gap between components.
     * @return       the horizontal gap between components
     * @since        1.1
     */
    public int getHgap() {
        return hgap;
    }

    
Sets the horizontal gap between components to the specified value.

Params:
  • hgap –   the horizontal gap between components
Since:       1.1
/**
     * Sets the horizontal gap between components to the specified value.
     * @param        hgap   the horizontal gap between components
     * @since        1.1
     */
    public void setHgap(int hgap) {
        this.hgap = hgap;
    }

    
Gets the vertical gap between components.

Returns:      the vertical gap between components
Since:       1.1
/**
     * Gets the vertical gap between components.
     * @return       the vertical gap between components
     * @since        1.1
     */
    public int getVgap() {
        return vgap;
    }

    
Sets the vertical gap between components to the specified value.

Params:
  • vgap –  the vertical gap between components
Since:       1.1
/**
     * Sets the vertical gap between components to the specified value.
     * @param         vgap  the vertical gap between components
     * @since        1.1
     */
    public void setVgap(int vgap) {
        this.vgap = vgap;
    }

    
Adds the specified component with the specified name to the layout.

Params:
  • name – the name of the component
  • comp – the component to be added
/**
     * Adds the specified component with the specified name to the layout.
     * @param name the name of the component
     * @param comp the component to be added
     */
    public void addLayoutComponent(String name, Component comp) {
    }

    
Removes the specified component from the layout.

Params:
  • comp – the component to be removed
/**
     * Removes the specified component from the layout.
     * @param comp the component to be removed
     */
    public void removeLayoutComponent(Component comp) {
    }

    
Determines the preferred size of the container argument using
this grid layout.


The preferred width of a grid layout is the largest preferred
width of all of the components in the container times the number of
columns, plus the horizontal padding times the number of columns
minus one, plus the left and right insets of the target container.


The preferred height of a grid layout is the largest preferred
height of all of the components in the container times the number of
rows, plus the vertical padding times the number of rows minus one,
plus the top and bottom insets of the target container.

Params:
  • parent –   the container in which to do the layout
See Also:
Returns:   the preferred dimensions to lay out the
                     subcomponents of the specified container
/**
     * Determines the preferred size of the container argument using
     * this grid layout.
     * <p>
     * The preferred width of a grid layout is the largest preferred
     * width of all of the components in the container times the number of
     * columns, plus the horizontal padding times the number of columns
     * minus one, plus the left and right insets of the target container.
     * <p>
     * The preferred height of a grid layout is the largest preferred
     * height of all of the components in the container times the number of
     * rows, plus the vertical padding times the number of rows minus one,
     * plus the top and bottom insets of the target container.
     *
     * @param     parent   the container in which to do the layout
     * @return    the preferred dimensions to lay out the
     *                      subcomponents of the specified container
     * @see       java.awt.GridLayout#minimumLayoutSize
     * @see       java.awt.Container#getPreferredSize()
     */
    public Dimension preferredLayoutSize(Container parent) {
      synchronized (parent.getTreeLock()) {
        Insets insets = parent.getInsets();
        int ncomponents = parent.getComponentCount();
        int nrows = rows;
        int ncols = cols;

        if (nrows > 0) {
            ncols = (ncomponents + nrows - 1) / nrows;
        } else {
            nrows = (ncomponents + ncols - 1) / ncols;
        }
        int w = 0;
        int h = 0;
        for (int i = 0 ; i < ncomponents ; i++) {
            Component comp = parent.getComponent(i);
            Dimension d = comp.getPreferredSize();
            if (w < d.width) {
                w = d.width;
            }
            if (h < d.height) {
                h = d.height;
            }
        }
        return new Dimension(insets.left + insets.right + ncols*w + (ncols-1)*hgap,
                             insets.top + insets.bottom + nrows*h + (nrows-1)*vgap);
      }
    }

    
Determines the minimum size of the container argument using this
grid layout.


The minimum width of a grid layout is the largest minimum width
of all of the components in the container times the number of columns,
plus the horizontal padding times the number of columns minus one,
plus the left and right insets of the target container.


The minimum height of a grid layout is the largest minimum height
of all of the components in the container times the number of rows,
plus the vertical padding times the number of rows minus one, plus
the top and bottom insets of the target container.

Params:
  • parent –   the container in which to do the layout
See Also:
Returns:     the minimum dimensions needed to lay out the
                     subcomponents of the specified container
/**
     * Determines the minimum size of the container argument using this
     * grid layout.
     * <p>
     * The minimum width of a grid layout is the largest minimum width
     * of all of the components in the container times the number of columns,
     * plus the horizontal padding times the number of columns minus one,
     * plus the left and right insets of the target container.
     * <p>
     * The minimum height of a grid layout is the largest minimum height
     * of all of the components in the container times the number of rows,
     * plus the vertical padding times the number of rows minus one, plus
     * the top and bottom insets of the target container.
     *
     * @param       parent   the container in which to do the layout
     * @return      the minimum dimensions needed to lay out the
     *                      subcomponents of the specified container
     * @see         java.awt.GridLayout#preferredLayoutSize
     * @see         java.awt.Container#doLayout
     */
    public Dimension minimumLayoutSize(Container parent) {
      synchronized (parent.getTreeLock()) {
        Insets insets = parent.getInsets();
        int ncomponents = parent.getComponentCount();
        int nrows = rows;
        int ncols = cols;

        if (nrows > 0) {
            ncols = (ncomponents + nrows - 1) / nrows;
        } else {
            nrows = (ncomponents + ncols - 1) / ncols;
        }
        int w = 0;
        int h = 0;
        for (int i = 0 ; i < ncomponents ; i++) {
            Component comp = parent.getComponent(i);
            Dimension d = comp.getMinimumSize();
            if (w < d.width) {
                w = d.width;
            }
            if (h < d.height) {
                h = d.height;
            }
        }
        return new Dimension(insets.left + insets.right + ncols*w + (ncols-1)*hgap,
                             insets.top + insets.bottom + nrows*h + (nrows-1)*vgap);
      }
    }

    
Lays out the specified container using this layout.

 This method reshapes the components in the specified target container in order to satisfy the constraints of the GridLayout object. 

The grid layout manager determines the size of individual
components by dividing the free space in the container into
equal-sized portions according to the number of rows and columns
in the layout. The container's free space equals the container's
size minus any insets and any specified horizontal or vertical
gap. All components in a grid layout are given the same size.

Params:
  • parent –   the container in which to do the layout
See Also:
/**
     * Lays out the specified container using this layout.
     * <p>
     * This method reshapes the components in the specified target
     * container in order to satisfy the constraints of the
     * {@code GridLayout} object.
     * <p>
     * The grid layout manager determines the size of individual
     * components by dividing the free space in the container into
     * equal-sized portions according to the number of rows and columns
     * in the layout. The container's free space equals the container's
     * size minus any insets and any specified horizontal or vertical
     * gap. All components in a grid layout are given the same size.
     *
     * @param      parent   the container in which to do the layout
     * @see        java.awt.Container
     * @see        java.awt.Container#doLayout
     */
    public void layoutContainer(Container parent) {
      synchronized (parent.getTreeLock()) {
        Insets insets = parent.getInsets();
        int ncomponents = parent.getComponentCount();
        int nrows = rows;
        int ncols = cols;
        boolean ltr = parent.getComponentOrientation().isLeftToRight();

        if (ncomponents == 0) {
            return;
        }
        if (nrows > 0) {
            ncols = (ncomponents + nrows - 1) / nrows;
        } else {
            nrows = (ncomponents + ncols - 1) / ncols;
        }
        // 4370316. To position components in the center we should:
        // 1. get an amount of extra space within Container
        // 2. incorporate half of that value to the left/top position
        // Note that we use trancating division for widthOnComponent
        // The reminder goes to extraWidthAvailable
        int totalGapsWidth = (ncols - 1) * hgap;
        int widthWOInsets = parent.width - (insets.left + insets.right);
        int widthOnComponent = (widthWOInsets - totalGapsWidth) / ncols;
        int extraWidthAvailable = (widthWOInsets - (widthOnComponent * ncols + totalGapsWidth)) / 2;

        int totalGapsHeight = (nrows - 1) * vgap;
        int heightWOInsets = parent.height - (insets.top + insets.bottom);
        int heightOnComponent = (heightWOInsets - totalGapsHeight) / nrows;
        int extraHeightAvailable = (heightWOInsets - (heightOnComponent * nrows + totalGapsHeight)) / 2;
        if (ltr) {
            for (int c = 0, x = insets.left + extraWidthAvailable; c < ncols ; c++, x += widthOnComponent + hgap) {
                for (int r = 0, y = insets.top + extraHeightAvailable; r < nrows ; r++, y += heightOnComponent + vgap) {
                    int i = r * ncols + c;
                    if (i < ncomponents) {
                        parent.getComponent(i).setBounds(x, y, widthOnComponent, heightOnComponent);
                    }
                }
            }
        } else {
            for (int c = 0, x = (parent.width - insets.right - widthOnComponent) - extraWidthAvailable; c < ncols ; c++, x -= widthOnComponent + hgap) {
                for (int r = 0, y = insets.top + extraHeightAvailable; r < nrows ; r++, y += heightOnComponent + vgap) {
                    int i = r * ncols + c;
                    if (i < ncomponents) {
                        parent.getComponent(i).setBounds(x, y, widthOnComponent, heightOnComponent);
                    }
                }
            }
        }
      }
    }

    
Returns the string representation of this grid layout's values.

Returns:    a string representation of this grid layout
/**
     * Returns the string representation of this grid layout's values.
     * @return     a string representation of this grid layout
     */
    public String toString() {
        return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap +
                                       ",rows=" + rows + ",cols=" + cols + "]";
    }
}