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);
}
}
}
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