graphpaperlayout.java

初级学习资料必读本

import java.awt.*;
import java.util.Hashtable;

/** 
 * The <code>GraphPaperLayout</code> class is a layout manager that 
 * lays out a container's components in a rectangular grid, similar
 * to GridLayout.  Unlike GridLayout, however, components can take
 * up multiple rows and/or columns.  The layout manager acts as a
 * sheet of graph paper.  When a component is added to the layout
 * manager, the location and relative size of the component are
 * simply supplied by the constraints as a Rectangle.
 * <p><code><pre>
 * import java.awt.*;
 * import java.applet.Applet;
 * public class ButtonGrid extends Applet {
 *     public void init() {
 *         setLayout(new GraphPaperLayout(new Dimension(5,5)));
 *         // Add a 1x1 Rect at (0,0)
 *         add(new Button("1"), new Rectangle(0,0,1,1));
 *         // Add a 2x1 Rect at (2,0)
 *         add(new Button("2"), new Rectangle(2,0,2,1));
 *         // Add a 1x2 Rect at (1,1)
 *         add(new Button("3"), new Rectangle(1,1,1,2));
 *         // Add a 2x2 Rect at (3,2)
 *         add(new Button("4"), new Rectangle(3,2,2,2));
 *         // Add a 1x1 Rect at (0,4)
 *         add(new Button("5"), new Rectangle(0,4,1,1));
 *         // Add a 1x2 Rect at (2,3)
 *         add(new Button("6"), new Rectangle(2,3,1,2));
 *     }
 * }
 * </pre></code>
 *
 * @author      Michael Martak
 */

public class GraphPaperLayout implements LayoutManager2 {
    int hgap;            //horizontal gap
    int vgap;            //vertical gap
    Dimension gridSize;  //grid size in logical units (n x m)
    Hashtable compTable; //constraints (Rectangles)
    
    /**
     * Creates a graph paper layout with a default of a 1 x 1 graph, with no
     * vertical or horizontal padding.
     */
    public GraphPaperLayout() {
        this(new Dimension(1,1));
    }
    
    /**
     * Creates a graph paper layout with the given grid size, with no vertical
     * or horizontal padding.
     */
    public GraphPaperLayout(Dimension gridSize) {
        this(gridSize, 0, 0);
    }
    
    /**
     * Creates a graph paper layout with the given grid size and padding.
     * @param gridSize size of the graph paper in logical units (n x m)
     * @param hgap horizontal padding
     * @param vgap vertical padding
     */
    public GraphPaperLayout(Dimension gridSize, int hgap, int vgap) {
        if ((gridSize.width <= 0) || (gridSize.height <= 0)) {
            throw new IllegalArgumentException(
                "dimensions must be greater than zero");
        }
        this.gridSize = new Dimension(gridSize);
        this.hgap = hgap;
        this.vgap = vgap;
        compTable = new Hashtable();
    }
    
    /**
     * @return the size of the graph paper in logical units (n x m)
     */
    public Dimension getGridSize() {
        return new Dimension( gridSize );
    }
    
    /**
     * Set the size of the graph paper in logical units (n x m)
     */
    public void setGridSize( Dimension d ) {
        setGridSize( d.width, d.height );
    }
    
    /**
     * Set the size of the graph paper in logical units (n x m)
     */
    public void setGridSize( int width, int height ) {
        gridSize = new Dimension( width, height );
    }
    
    public void setConstraints(Component comp, Rectangle constraints) {
        compTable.put(comp, new Rectangle(constraints));
    }
    
    /**
     * Adds the specified component with the specified name to
     * the layout.  This does nothing in GraphPaperLayout, since constraints
     * are required.
     */
    public void addLayoutComponent(String name, Component comp) {
    }

    /**
     * Removes the specified component from the layout.
     * @param comp the component to be removed
     */
    public void removeLayoutComponent(Component comp) {
        compTable.remove(comp);
    }

    /**
     * Calculates the preferred size dimensions for the specified 
     * panel given the components in the specified parent container.
     * @param parent the component to be laid out
     *  
     * @see #minimumLayoutSize
     */
    public Dimension preferredLayoutSize(Container parent) {
        return getLayoutSize(parent, true);
    }

    /** 
     * Calculates the minimum size dimensions for the specified 
     * panel given the components in the specified parent container.
     * @param parent the component to be laid out
     * @see #preferredLayoutSize
     */
    public Dimension minimumLayoutSize(Container parent) {
        return getLayoutSize(parent, false);
    }
    
    /** 
     * Algorithm for calculating layout size (minimum or preferred). 
     * <p>
     * The width of a graph paper layout is the largest cell width
     * (calculated in <code>getLargestCellSize()</code> times the number of 
     * columns, plus the horizontal padding times the number of columns 
     * plus one, plus the left and right insets of the target container. 
     * <p>
     * The height of a graph paper layout is the largest cell height
     * (calculated in <code>getLargestCellSize()</code> times the number of 
     * rows, plus the vertical padding times the number of rows 
     * plus one, plus the top and bottom insets of the target container. 
     * 
     * @param parent the container in which to do the layout.
     * @param isPreferred true for calculating preferred size, false for
     *                    calculating minimum size.
     * @return the dimensions to lay out the subcomponents of the specified
     *         container.
     * @see java.awt.GraphPaperLayout#getLargestCellSize
     */
    protected Dimension getLayoutSize(Container parent, boolean isPreferred) {
        Dimension largestSize = getLargestCellSize(parent, isPreferred);
        Insets insets = parent.getInsets();
        largestSize.width = ( largestSize.width * gridSize.width ) +
            ( hgap * ( gridSize.width + 1 ) ) + insets.left + insets.right;
        largestSize.height = ( largestSize.height * gridSize.height ) +
            ( vgap * ( gridSize.height + 1 ) ) + insets.top + insets.bottom;
        return largestSize;
    }
    
    /** 
     * Algorithm for calculating the largest minimum or preferred cell size.
     * <p>
     * Largest cell size is calculated by getting the applicable size of each
     * component and keeping the maximum value, dividing the component's width
     * by the number of columns it is specified to occupy and dividing the
     * component's height by the number of rows it is specified to occupy.
     * 
     * @param parent the container in which to do the layout.
     * @param isPreferred true for calculating preferred size, false for
     *                    calculating minimum size.
     * @return the largest cell size required.
     */
    protected Dimension getLargestCellSize(Container parent,
                                           boolean isPreferred) {
        int ncomponents = parent.getComponentCount();
        Dimension maxCellSize = new Dimension(0,0);
        for ( int i = 0; i < ncomponents; i++ ) {
            Component c = parent.getComponent(i);
            Rectangle rect = (Rectangle)compTable.get(c);
            if ( c != null && rect != null ) {
                Dimension componentSize;
                if ( isPreferred ) {
                    componentSize = c.getPreferredSize();
                } else {
                    componentSize = c.getMinimumSize();
                }
                // Note: rect dimensions are already asserted to be > 0 when the
                // component is added with constraints
                maxCellSize.width = Math.max(maxCellSize.width,
                    componentSize.width / rect.width);
                maxCellSize.height = Math.max(maxCellSize.height,
                    componentSize.height / rect.height);
            }
        }
        return maxCellSize;
    }

    /** 
     * Lays out the container in the specified container.
     * @param parent the component which needs to be laid out 
     */
    public void layoutContainer(Container parent) {
        synchronized (parent.getTreeLock()) {
            Insets insets = parent.getInsets();
            int ncomponents = parent.getComponentCount();

            if (ncomponents == 0) {
                return;
            }
            
            // Total parent dimensions
            Dimension size = parent.getSize();
            int totalW = size.width - (insets.left + insets.right);
            int totalH = size.height - (insets.top + insets.bottom);

            // Cell dimensions, including padding
            int totalCellW = totalW / gridSize.width;
            int totalCellH = totalH / gridSize.height;

            // Cell dimensions, without padding
            int cellW = (totalW - ( (gridSize.width + 1) * hgap) )
                    / gridSize.width;
            int cellH = (totalH - ( (gridSize.height + 1) * vgap) )
                    / gridSize.height;
                
            for ( int i = 0; i < ncomponents; i++ ) {
                Component c = parent.getComponent(i);
                Rectangle rect = (Rectangle)compTable.get(c);
                if ( rect != null ) {
                    int x = insets.left + ( totalCellW * rect.x ) + hgap;
                    int y = insets.top + ( totalCellH * rect.y ) + vgap;
                    int w = ( cellW * rect.width ) - hgap;
                    int h = ( cellH * rect.height ) - vgap;
                    c.setBounds(x, y, w, h);
                }
            }
        }
    }
    
    // LayoutManager2 /////////////////////////////////////////////////////////
    
    /**
     * Adds the specified component to the layout, using the specified
     * constraint object.
     * @param comp the component to be added
     * @param constraints  where/how the component is added to the layout.
     */
    public void addLayoutComponent(Component comp, Object constraints) {
        if (constraints instanceof Rectangle) {
            Rectangle rect = (Rectangle)constraints;
            if ( rect.width <= 0 || rect.height <= 0 ) {
                throw new IllegalArgumentException(
                    "cannot add to layout: rectangle must have positive width and height");
            }
            if ( rect.x < 0 || rect.y < 0 ) {
                throw new IllegalArgumentException(
                    "cannot add to layout: rectangle x and y must be >= 0");
            }
            setConstraints(comp, rect);
        } else if (constraints != null) {
            throw new IllegalArgumentException(
                "cannot add to layout: constraint must be a Rectangle");
        }
    }

    /** 
     * Returns the maximum size of this component.
     * @see java.awt.Component#getMinimumSize()
     * @see java.awt.Component#getPreferredSize()
     * @see LayoutManager
     */
    public Dimension maximumLayoutSize(Container target) {
        return new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE);
    }

    /**
     * Returns the alignment along the x axis.  This specifies how
     * the component would like to be aligned relative to other 
     * components.  The value should be a number between 0 and 1
     * where 0 represents alignment along the origin, 1 is aligned
     * the furthest away from the origin, 0.5 is centered, etc.
     */
    public float getLayoutAlignmentX(Container target) {
        return 0.5f;
    }

    /**
     * Returns the alignment along the y axis.  This specifies how
     * the component would like to be aligned relative to other 
     * components.  The value should be a number between 0 and 1
     * where 0 represents alignment along the origin, 1 is aligned
     * the furthest away from the origin, 0.5 is centered, etc.
     */
    public float getLayoutAlignmentY(Container target) {
        return 0.5f;
    }

    /**
     * Invalidates the layout, indicating that if the layout manager
     * has cached information it should be discarded.
     */
    public void invalidateLayout(Container target) {
        // Do nothing
    }
}