1 GUI. Java. GUI TextField GUI. 1 TextFieldExample.java import java.awt.*; import java.awt.event.*; import javax.swing.*; (display) GUI GUI

Transcription

1 Java ( ) (display) GUI GUI GUI GUI Java TextField TextArea 2 TextField ( ) GUI TextArea GUI 1 1 TextFieldExample.java import javax.swing.*; public class TextFieldExample extends Applet implements ActionListener { display = new TextField("Please input"); display.addactionlistener(this); if (evt.getsource() == display) { repaint(); g.drawstring(display.gettext(), 100, 100); java.awt.event import 1

2 implements ActionListener Java TextField ActionListener (implement) ActionListener actionperformed display (display) ( ) ( ) TextFieldExample init TextField (new) display display (add ) Button TextField GUI addactionlistener ( ) addactionlistener GUI ( ) actionperformed ( this actionperformed this ) GUI display repaint paint paint WWW (submit) ( ) (radix base number) Java Integer.parseInt(str) str 2

3 2 TextFieldExample.java import java.applet.applet; public class TextFieldExample extends Applet implements ActionListener { Button submit; display = new TextField("Please input"); display.addactionlistener(this); submit = new Button("submit"); add(submit); submit.addactionlistener(this); if (evt.getsource() == display evt.getsource() == submit) { repaint(); g.drawstring(display.gettext(), 100, 100); Integer.parseInt(str, radix) str radix Integer.parseInt(str) Integer.parseInt(str, radix) Java ( ) ( ) (overload) Integer.parseInt(str) Integer.parseInt(str, radix) 3 Bin2Dec.java public class Bin2Dec { public static void main(string[] args) { System.out.println(Integer.parseInt(args[0], 2)); Integer.parseInt 3 3

4 2 10 Java ( ) H:> java Bin2Dec ( ) Integer.toBinaryString(n) Integer.toOctalString(n) Integer.toHexString(n) Integer.toString(n) ( ) parseint 3 GUI 3 GUI TextField Bin2DecApplet.java import java.applet.applet; public class Bin2DecApplet extends Applet implements ActionListener { display = new TextField("0", 20); display.addactionlistener(this); if (evt.getsource() == display) { repaint(); int n = Integer.parseInt(display.getText(), 2); g.drawstring(integer.tostring(n), 100, 100); 4

5 1 init() ( ) 2 display.selectall(); display.requestfocus(); 2 TextField 0, 1 Java catch-throw ( ) (exception) (throw ) Java ( ) catch throws Exception Exception ( ) try-catch ( Java ) parseint paint paint try { int n = Integer.parseInt(display.getText(), 2); g.drawstring(integer.tostring(n), 100, 100); catch (NumberFormatException e) { g.drawstring(" 2 ", 100, 100); try try catch throw catch NumberFormatException parseint e 5

6 5 RadixConverter.java import java.applet.applet; public class RadixConverter extends Applet implements ActionListener { Button bin, oct, dec, hex; int number = 0; int radix = 10; display = new TextField(Integer.toString(number), 20); display.selectall(); display.requestfocus(); bin = new Button("bin"); setup(bin); oct = new Button("oct"); setup(oct); dec = new Button("dec"); setup(dec); hex = new Button("hex"); setup(hex); void setup(button b) { add(b); b.addactionlistener(this); try { number = Integer.parseInt(display.getText(), radix); catch (NumberFormatException e) { number = 0; display.settext("0"); if (evt.getsource() == bin) { radix = 2; display.settext(integer.tobinarystring(number)); else if (evt.getsource() == oct) { radix = 8; display.settext(integer.tooctalstring(number)); else if (evt.getsource() == dec) { radix = 10; display.settext(integer.tostring(number)); else if (evt.getsource() == hex) { radix = 16; display.settext(integer.tohexstring(number)); 6