multilinelabel.java

一个非常好的ssh客户端实现

// 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.

package com.mindbright.gui;

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

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 = this.getFontMetrics(this.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 preferredSize() {
        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 minimumSize() {
        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 = this.size();
        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);
        }
    }
}