MultiLine Label
// This example is from the book _Java in a Nutshell_ by David Flanagan. //Written by David Flanagan. Copyright (c) 1996 O'Reilly & Associates. //You may study, use, modify, and distribute this example for any purpose. //This example is provided WITHOUT WARRANTY either expressed or implied. import java.awt.Canvas; import java.awt.Color; import java.awt.Dimension; import java.awt.Font; import java.awt.FontMetrics; import java.awt.Graphics; import java.util.StringTokenizer; public class MultiLineLabel extends Canvas { public static final int LEFT = 0; // Alignment constants public static final int CENTER = 1; public static final int RIGHT = 2; protected String[] lines; // The lines of text to display protected int num_lines; // The number of lines protected int margin_width; // Left and right margins protected int margin_height; // Top and bottom margins protected int line_height; // Total height of the font protected int line_ascent; // Font height above baseline protected int[] line_widths; // How wide each line is protected int max_width; // The width of the widest line protected int alignment = LEFT; // The alignment of the text. // This method breaks a specified label up into an array of lines. // It uses the StringTokenizer utility class. protected void newLabel(String label) { StringTokenizer t = new StringTokenizer(label, "\n"); num_lines = t.countTokens(); lines = new String[num_lines]; line_widths = new int[num_lines]; for (int i = 0; i < num_lines; i++) lines[i] = t.nextToken(); } // This method figures out how the font is, and how wide each // line of the label is, and how wide the widest line is. protected void measure() { FontMetrics fm = getFontMetrics(getFont()); // If we don't have font metrics yet, just return. if (fm == null) return; line_height = fm.getHeight(); line_ascent = fm.getAscent(); max_width = 0; for (int i = 0; i < num_lines; i++) { line_widths[i] = fm.stringWidth(lines[i]); if (line_widths[i] > max_width) max_width = line_widths[i]; } } // Here are four versions of the cosntrutor. // Break the label up into separate lines, and save the other info. public MultiLineLabel(String label, int margin_width, int margin_height, int alignment) { newLabel(label); this.margin_width = margin_width; this.margin_height = margin_height; this.alignment = alignment; } public MultiLineLabel(String label, int margin_width, int margin_height) { this(label, margin_width, margin_height, LEFT); } public MultiLineLabel(String label, int alignment) { this(label, 10, 10, alignment); } public MultiLineLabel(String label) { this(label, 10, 10, LEFT); } // Methods to set the various attributes of the component public void setLabel(String label) { newLabel(label); measure(); repaint(); } public void setFont(Font f) { super.setFont(f); measure(); repaint(); } public void setForeground(Color c) { super.setForeground(c); repaint(); } public void setAlignment(int a) { alignment = a; repaint(); } public void setMarginWidth(int mw) { margin_width = mw; repaint(); } public void setMarginHeight(int mh) { margin_height = mh; repaint(); } public int getAlignment() { return alignment; } public int getMarginWidth() { return margin_width; } public int getMarginHeight() { return margin_height; } // This method is invoked after our Canvas is first created // but before it can actually be displayed. After we've // invoked our superclass's addNotify() method, we have font // metrics and can successfully call measure() to figure out // how big the label is. public void addNotify() { super.addNotify(); measure(); } // This method is called by a layout manager when it wants to // know how big we'd like to be. public Dimension getPreferredSize() { return new Dimension(max_width + 2 * margin_width, num_lines * line_height + 2 * margin_height); } // This method is called when the layout manager wants to know // the bare minimum amount of space we need to get by. public Dimension getMinimumSize() { return new Dimension(max_width, num_lines * line_height); } // This method draws the label (applets use the same method). // Note that it handles the margins and the alignment, but that // it doesn't have to worry about the color or font--the superclass // takes care of setting those in the Graphics object we're passed. public void paint(Graphics g) { int x, y; Dimension d = getSize(); y = line_ascent + (d.height - num_lines * line_height) / 2; for (int i = 0; i < num_lines; i++, y += line_height) { switch (alignment) { case LEFT: x = margin_width; break; case CENTER: default: x = (d.width - line_widths[i]) / 2; break; case RIGHT: x = d.width - margin_width - line_widths[i]; break; } g.drawString(lines[i], x, y); } } }