Adding scrollbars to a applet?
I am trying to write a small java applet for my personal interest, but I can't seem to figure out how to add scroll bars to my applet. What I have so far is this
import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.io.IOException;
public class SimpleApplet extends JApplet {
public SimpleApplet() {
JPanel p = new JPanel();
p.setLayout(new GridLayout(20, 3, 3, 3));
p.add(new JLabel("Username"));
p.add(new JTextField());
p.add(new JLabel("Password"));
p.add(new JPasswordField());
p.add(new JLabel("Username"));
p.add(new JTextField());
p.add(new JLabel("Password"));
p.add(new JPasswordField());
p.add(new JLabel("Username"));
p.add(new JTextField());
p.add(new JLabel("Password"));
p.add(new JPasswordField());
p.add(new JLabel("Username"));
p.add(new JTextField());
p.add(new JLabel("Password"));
p.add(new JPasswordField());
Container content = getContentPane();
JScrollPane scroller = new JScrollPane();
scroller.setLayout(new BorderLayout());
content.setLayout(new GridBagLayout()); // Used to center the panel
content.add(scroller);
//content.add(p);
public static void main(String[] args) throws IOException, ClassNotFoundException {
SimpleApplet J = new SimpleApplet();
}when I try to run this the applet fails, but if I delete all the lines with scroller the applet runs fine expect that I can't see some the textfield on the applet unless I enlarge it. I want to add a scrollbar in so that I can scroll down to the unseen parts without enlarging the applet screen. Can any1 help me figure out what i'm doing wrong?
Encephalopathic wrote:
bigauto wrote:
I'm still running the applet in eclipse and I haven't tested it on a webpage yet. It shouldn't matter whether it on eclipse or a webpage should it? The applet itself didn't become small, but all the components like the textfield became micoscope.Does it matter if the application is ran on eclipse or a webpage?1) did you look at my example? Did you get rid of your setting the contentpane's layout to gridbaglayout? the contentpane by default uses borderlayout and this should let the jscrollpane fill your applet. If you don't do this, you may need to set a preferred size for your jscrollpane.
2) I think that you can size the applet in Eclipse's Run Dialog, but I'm not sure. You size it in "real life" in the HTML code (I think).Thanks a lot. That fixed it.
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Help With adding a scrollbar to my applet
This is the source code of my applet.I wat to have an autoscroll on this applet
i think it is usefull if i put here all the code for my project.
======================================================
Class ConsolePanel:
The file defines a class ConsolePanel. Objects of type
ConsolePanel can be used for simple input/output exchanges with
the user. Various routines are provided for reading and writing
values of various types from the output. (This class gives all
the I/O behavior of another class, Console, that represents a
separate window for doing console-style I/O.)
This class is dependent on another class, ConsoleCanvas.
Note that when the console has the input focus, it is outlined with
a bright blue border. If, in addition, the console is waiting for
user input, then there will be a blinking cursor. If the console
is not outlined in light blue, the user has to click on it before
any input will be accepted.
This is an update an earlier version of the same class,
rewritten to use realToString() for output of floating point
numbers..
package myproj;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JScrollPane;
import javax.swing.JScrollBar;
import javax.swing.*;
public class ConsolePanel extends JTextArea{
static public JScrollPane scrollPane;
// ***************************** Constructors *******************************
public ConsolePanel() { // default constructor just provides default window title and size
setBackground(Color.white);
setLayout(new BorderLayout(0, 0));
canvas = new ConsoleCanvas(500,1000);
scrollPane = new JScrollPane(canvas);
scrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize( new Dimension( 1000,10000) );
add("Center", scrollPane);
//scrollPane.getVerticalScrollBar().setUnitIncrement(1);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public void clear() { // clear all characters from the canvas
canvas.clear();
// *************************** I/O Methods *********************************
// Methods for writing the primitive types, plus type String,
// to the console window, with no extra spaces.
// Note that the real-number data types, float
// and double, a rounded version is output that will
// use at most 10 or 11 characters. If you want to
// output a real number with full accuracy, use
// "con.put(String.valueOf(x))", for example.
public void put(int x) {
put(x, 0);
} // Note: also handles byte and short!
public void put(long x) {
put(x, 0);
public void put(double x) {
put(x, 0);
} // Also handles float.
public void put(char x) {
put(x, 0);
public void put(boolean x) {
put(x, 0);
public void put(String x) {
put(x, 0);
// Methods for writing the primitive types, plus type String,
// to the console window,followed by a carriage return, with
// no extra spaces.
public void putln(int x) {
put(x, 0);
newLine();
} // Note: also handles byte and short!
public void putln(long x) {
put(x, 0);
newLine();
public void putln(double x) {
put(x, 0);
newLine();
} // Also handles float.
public void putln(char x) {
put(x, 0);
newLine();
public void putln(boolean x) {
put(x, 0);
newLine();
public void putln(String x) {
put(x, 0);
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with a minimum field width of w,
// and followed by a carriage return.
// If outut value is less than w characters, it is padded
// with extra spaces in front of the value.
public void putln(int x, int w) {
put(x, w);
newLine();
} // Note: also handles byte and short!
public void putln(long x, int w) {
put(x, w);
newLine();
public void putln(double x, int w) {
put(x, w);
newLine();
} // Also handles float.
public void putln(char x, int w) {
put(x, w);
newLine();
public void putln(boolean x, int w) {
put(x, w);
newLine();
public void putln(String x, int w) {
put(x, w);
newLine();
// Method for outputting a carriage return
public void putln() {
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with minimum field width w.
public void put(int x, int w) {
dumpString(String.valueOf(x), w);
} // Note: also handles byte and short!
public void put(long x, int w) {
dumpString(String.valueOf(x), w);
public void put(double x, int w) {
dumpString(realToString(x), w);
} // Also handles float.
public void put(char x, int w) {
dumpString(String.valueOf(x), w);
public void put(boolean x, int w) {
dumpString(String.valueOf(x), w);
public void put(String x, int w) {
dumpString(x, w);
// Methods for reading in the primitive types, plus "words" and "lines".
// The "getln..." methods discard any extra input, up to and including
// the next carriage return.
// A "word" read by getlnWord() is any sequence of non-blank characters.
// A "line" read by getlnString() or getln() is everything up to next CR;
// the carriage return is not part of the returned value, but it is
// read and discarded.
// Note that all input methods except getAnyChar(), peek(), the ones for lines
// skip past any blanks and carriage returns to find a non-blank value.
// getln() can return an empty string; getChar() and getlnChar() can
// return a space or a linefeed ('\n') character.
// peek() allows you to look at the next character in input, without
// removing it from the input stream. (Note that using this
// routine might force the user to enter a line, in order to
// check what the next character.)
// Acceptable boolean values are the "words": true, false, t, f, yes,
// no, y, n, 0, or 1; uppercase letters are OK.
// None of these can produce an error; if an error is found in input,
// the user is forced to re-enter.
// Available input routines are:
// getByte() getlnByte() getShort() getlnShort()
// getInt() getlnInt() getLong() getlnLong()
// getFloat() getlnFloat() getDouble() getlnDouble()
// getChar() getlnChar() peek() getAnyChar()
// getWord() getlnWord() getln() getString() getlnString()
// (getlnString is the same as getln and is onlyprovided for consistency.)
public byte getlnByte() {
byte x = getByte();
emptyBuffer();
return x;
public short getlnShort() {
short x = getShort();
emptyBuffer();
return x;
public int getlnInt() {
int x = getInt();
emptyBuffer();
return x;
public long getlnLong() {
long x = getLong();
emptyBuffer();
return x;
public float getlnFloat() {
float x = getFloat();
emptyBuffer();
return x;
public double getlnDouble() {
double x = getDouble();
emptyBuffer();
return x;
public char getlnChar() {
char x = getChar();
emptyBuffer();
return x;
public boolean getlnBoolean() {
boolean x = getBoolean();
emptyBuffer();
return x;
public String getlnWord() {
String x = getWord();
emptyBuffer();
return x;
public String getlnString() {
return getln();
} // same as getln()
public String getln() {
StringBuffer s = new StringBuffer(100);
char ch = readChar();
while (ch != '\n') {
s.append(ch);
ch = readChar();
return s.toString();
public byte getByte() {
return (byte) readInteger( -128L, 127L);
public short getShort() {
return (short) readInteger( -32768L, 32767L);
public int getInt() {
return (int) readInteger((long) Integer.MIN_VALUE,
(long) Integer.MAX_VALUE);
public long getLong() {
return readInteger(Long.MIN_VALUE, Long.MAX_VALUE);
public char getAnyChar() {
return readChar();
public char peek() {
return lookChar();
public char getChar() { // skip spaces & cr's, then return next char
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
return readChar();
public float getFloat() { // can return positive or negative infinity
float x = 0.0F;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
} else {
Float f = null;
try {
f = Float.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
x = f.floatValue();
break;
return x;
public double getDouble() {
double x = 0.0;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
} else {
Double f = null;
try {
f = Double.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
x = f.doubleValue();
break;
return x;
public String getWord() {
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
StringBuffer str = new StringBuffer(50);
while (ch != ' ' && ch != '\n') {
str.append(readChar());
ch = lookChar();
return str.toString();
public boolean getBoolean() {
boolean ans = false;
while (true) {
String s = getWord();
if (s.equalsIgnoreCase("true") || s.equalsIgnoreCase("t") ||
s.equalsIgnoreCase("yes") || s.equalsIgnoreCase("y") ||
s.equals("1")) {
ans = true;
break;
} else if (s.equalsIgnoreCase("false") || s.equalsIgnoreCase("f") ||
s.equalsIgnoreCase("no") || s.equalsIgnoreCase("n") ||
s.equals("0")) {
ans = false;
break;
} else {
errorMessage("Illegal boolean input value.",
"one of: true, false, t, f, yes, no, y, n, 0, or 1");
return ans;
// ***************** Everything beyond this point is private *******************
// ********************** Utility routines for input/output ********************
private ConsoleCanvas canvas; // the canvas where I/O is displayed
private String buffer = null; // one line read from input
private int pos = 0; // position next char in input line that has
// not yet been processed
private String readRealString() { // read chars from input following syntax of real numbers
StringBuffer s = new StringBuffer(50);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == '.') {
s.append(readChar());
ch = lookChar();
while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == 'E' || ch == 'e') {
s.append(readChar());
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
return s.toString();
private long readInteger(long min, long max) { // read long integer, limited to specified range
long x = 0;
while (true) {
StringBuffer s = new StringBuffer(34);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (s.equals("")) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
} else {
String str = s.toString();
try {
x = Long.parseLong(str);
} catch (NumberFormatException e) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
continue;
if (x < min || x > max) {
errorMessage("Integer input outside of legal range.",
"Integer in the range " + min + " to " + max);
continue;
break;
return x;
private static String realToString(double x) {
// Goal is to get a reasonable representation of x in at most
// 10 characters, or 11 characters if x is negative.
if (Double.isNaN(x)) {
return "undefined";
if (Double.isInfinite(x)) {
if (x < 0) {
return "-INF";
} else {
return "INF";
if (Math.abs(x) <= 5000000000.0 && Math.rint(x) == x) {
return String.valueOf((long) x);
String s = String.valueOf(x);
if (s.length() <= 10) {
return s;
boolean neg = false;
if (x < 0) {
neg = true;
x = -x;
s = String.valueOf(x);
if (x >= 0.00005 && x <= 50000000 &&
(s.indexOf('E') == -1 && s.indexOf('e') == -1)) { // trim x to 10 chars max
s = round(s, 10);
s = trimZeros(s);
} else if (x > 1) { // construct exponential form with positive exponent
long power = (long) Math.floor(Math.log(x) / Math.log(10));
String exp = "E" + power;
int numlength = 10 - exp.length();
x = x / Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
} else { // constuct exponential form
long power = (long) Math.ceil( -Math.log(x) / Math.log(10));
String exp = "E-" + power;
int numlength = 10 - exp.length();
x = x * Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
if (neg) {
return "-" + s;
} else {
return s;
private static String trimZeros(String num) { // used by realToString
if (num.indexOf('.') >= 0 && num.charAt(num.length() - 1) == '0') {
int i = num.length() - 1;
while (num.charAt(i) == '0') {
i--;
if (num.charAt(i) == '.') {
num = num.substring(0, i);
} else {
num = num.substring(0, i + 1);
return num;
private static String round(String num, int length) { // used by realToString
if (num.indexOf('.') < 0) {
return num;
if (num.length() <= length) {
return num;
if (num.charAt(length) >= '5' && num.charAt(length) != '.') {
char[] temp = new char[length + 1];
int ct = length;
boolean rounding = true;
for (int i = length - 1; i >= 0; i--) {
temp[ct] = num.charAt(i);
if (rounding && temp[ct] != '.') {
if (temp[ct] < '9') {
temp[ct]++;
rounding = false;
} else {
temp[ct] = '0';
ct--;
if (rounding) {
temp[ct] = '1';
ct--;
// ct is -1 or 0
return new String(temp, ct + 1, length - ct);
} else {
return num.substring(0, length);
private void dumpString(String str, int w) { // output string to console
for (int i = str.length(); i < w; i++) {
canvas.addChar(' ');
for (int i = 0; i < str.length(); i++) {
if ((int) str.charAt(i) >= 0x20 && (int) str.charAt(i) != 0x7F) { // no control chars or delete
canvas.addChar(str.charAt(i));
} else if (str.charAt(i) == '\n' || str.charAt(i) == '\r') {
newLine();
private void errorMessage(String message, String expecting) {
// inform user of error and force user to re-enter.
newLine();
dumpString(" *** Error in input: " + message + "\n", 0);
dumpString(" *** Expecting: " + expecting + "\n", 0);
dumpString(" *** Discarding Input: ", 0);
if (lookChar() == '\n') {
dumpString("(end-of-line)\n\n", 0);
} else {
while (lookChar() != '\n') {
canvas.addChar(readChar());
dumpString("\n\n", 0);
dumpString("Please re-enter: ", 0);
readChar(); // discard the end-of-line character
private char lookChar() { // return next character from input
if (buffer == null || pos > buffer.length()) {
fillBuffer();
if (pos == buffer.length()) {
return '\n';
return buffer.charAt(pos);
private char readChar() { // return and discard next character from input
char ch = lookChar();
pos++;
return ch;
private void newLine() { // output a CR to console
canvas.addCR();
private void fillBuffer() { // Wait for user to type a line and press return,
// and put the typed line into the buffer.
buffer = canvas.readLine();
pos = 0;
private void emptyBuffer() { // discard the rest of the current line of input
buffer = null;
public void clearBuffers() { // I expect this will only be called by
// CanvasApplet when a program ends. It should
// not be called in the middle of a running program.
buffer = null;
canvas.clearTypeAhead();
private void jbInit() throws Exception {
this.setNextFocusableComponent(scrollPane);
this.setToolTipText("");
} // end of class Console
============================================================
Class ConsoleCanvas:
/* A class that implements basic console-oriented input/output, for use with
Console.java and ConsolePanel.java. This class provides the basic character IO.
Higher-leve fucntions (reading and writing numbers, booleans, etc) are provided
in Console.java and ConolePanel.java.
(This vesion of ConsoleCanvas is an udate of an earilier version, rewritten to
be compliand with Java 1.1. David Eck; July 17, 1998.)
(Modified August 16, 1998 to add the
a mousePressed method to ConsoleCanvas. The mousePressed method requests
the focus. This is necessary for Sun's Java implementation -- though not,
apparently for anyone else's. Also added: an isFocusTraversable() method)
MouseListener interface and
Minor modifications, February 9, 2000, some glitches in the graphics.
package myproj;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ConsoleCanvas extends JTextArea implements FocusListener, KeyListener,
MouseListener {
// public interface, constructor and methods
public ConsoleCanvas(int u,int y) {
addFocusListener(this);
addKeyListener(this);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public final String readLine() { // wait for user to enter a line of input;
// Line can only contain characters in the range
// ' ' to '~'.
return doReadLine();
public final void addChar(char ch) { // output PRINTABLE character to console
putChar(ch);
public final void addCR() { // add a CR to the console
putCR();
public synchronized void clear() { // clear console and return cursor to row 0, column 0.
if (OSC == null) {
return;
currentRow = 0;
currentCol = 0;
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(4, 4, getSize().width - 8, getSize().height - 8);
OSCGraphics.setColor(Color.black);
repaint();
try {
Thread.sleep(25);
} catch (InterruptedException e) {}
// focus and key event handlers; not meant to be called excpet by system
public void keyPressed(KeyEvent evt) {
doKey(evt.getKeyChar());
public void keyReleased(KeyEvent evt) {}
public void keyTyped(KeyEvent evt) {}
public void focusGained(FocusEvent evt) {
doFocus(true);
public void focusLost(FocusEvent evt) {
doFocus(false);
public boolean isFocusTraversable() {
// Allows the user to move the focus to the canvas
// by pressing the tab key.
return true;
// Mouse listener methods -- here just to make sure that the canvas
// gets the focuse when the user clicks on it. These are meant to
// be called only by the system.
public void mousePressed(MouseEvent evt) {
requestFocus();
public void mouseReleased(MouseEvent evt) {}
public void mouseClicked(MouseEvent evt) {}
public void mouseEntered(MouseEvent evt) {}
public void mouseExited(MouseEvent evt) {}
// implementation section: protected variables and methods.
protected StringBuffer typeAhead = new StringBuffer();
// Characters typed by user but not yet processed;
// User can "type ahead" the charcters typed until
// they are needed to satisfy a readLine.
protected final int maxLineLength = 256;
// No lines longer than this are returned by readLine();
// The system effectively inserts a CR after 256 chars
// of input without a carriage return.
protected int rows, columns; // rows and columns of chars in the console
protected int currentRow, currentCol; // current curson position
protected Font font; // Font used in console (Courier); All font
// data is set up in the doSetup() method.
protected int lineHeight; // height of one line of text in the console
protected int baseOffset; // distance from top of a line to its baseline
protected int charWidth; // width of a character (constant, since a monospaced font is used)
protected int leading; // space between lines
protected int topOffset; // distance from top of console to top of text
protected int leftOffset; // distance from left of console to first char on line
protected Image OSC; // off-screen backup for console display (except cursor)
protected Graphics OSCGraphics; // graphics context for OSC
protected boolean hasFocus = false; // true if this canvas has the input focus
protected boolean cursorIsVisible = false; // true if cursor is currently visible
private int pos = 0; // exists only for sharing by next two methods
public synchronized void clearTypeAhead() {
// clears any unprocessed user typing. This is meant only to
// be called by ConsolePanel, when a program being run by
// console Applet ends. But just to play it safe, pos is
// set to -1 as a signal to doReadLine that it should return.
typeAhead.setLength(0);
pos = -1;
notify();
protected synchronized String doReadLine() { // reads a line of input, up to next CR
if (OSC == null) { // If this routine is called before the console has
// completely opened, we shouldn't procede; give the
// window a chance to open, so that paint() can call doSetup().
try {
wait(5000);
} catch (InterruptedException e) {} // notify() should be set by doSetup()
if (OSC == null) { // If nothing has happened for 5 seconds, we are probably in
// trouble, but when the heck, try calling doSetup and proceding anyway.
doSetup();
if (!hasFocus) { // Make sure canvas has input focus
requestFocus();
StringBuffer lineBuffer = new StringBuffer(); // buffer for constructing line from user
pos = 0;
while (true) { // Read and process chars from the typeAhead buffer until a CR is found.
while (pos >= typeAhead.length()) { // If the typeAhead buffer is empty, wait for user to type something
cursorBlink();
try {
wait(500);
} catch (InterruptedException e) {}
if (pos == -1) { // means clearTypeAhead was called;
return ""; // this is an abnormal return that should not happen
if (cursorIsVisible) {
cursorBlink();
if (typeAhead.charAt(pos) == '\r' || typeAhead.charAt(pos) == '\n') {
putCR();
pos++;
break;
if (typeAhead.charAt(pos) == 8 || typeAhead.charAt(pos) == 127) {
if (lineBuffer.length() > 0) {
lineBuffer.setLength(lineBuffer.length() - 1);
eraseChar();
pos++;
} else if (typeAhead.charAt(pos) >= ' ' &&
typeAhead.charAt(pos) < 127) {
putChar(typeAhead.charAt(pos));
lineBuffer.append(typeAhead.charAt(pos));
pos++;
} else {
pos++;
if (lineBuffer.length() == maxLineLength) {
putCR();
pos = typeAhead.length();
break;
if (pos >= typeAhead.lengHi
I don't understand the exact need you want
you want to add Scrolling facility to your Entire Applet or only for the Textarea Class?
In first case
Create the ScrollPane and add it to the applet contentPane. and put entire components to a Panel and just add it to scroll pane.
Regards
Vinoth -
hi everybody,
a have a simple ??
i'm working on a chat application. my message displaying area is a canvas.i have added scroll-bars to it using scroll-pane
"sp = new ScrollPane(ScrollPane.SCROLLBARS_ALWAYS);"
now what i want is the scrollbars should adjust automatically to
display the last message and also i should be able to adjust them
manually so that i can view the previous messages.
i have tried setScrollposition() it works well also but then i'm not
able to adjust scrollbars manually.
this interface is in AWT.
please tell me a solution.its a bit urgent.
thankx and regards
asheetBecause your canvas is growing.(I think)
The new size of the canvas causes it to be layd out again. And laying out a component usually causes flickering (depending on the plattform). I guess the workaround would be to use a canvas just as big as the shown part of it. Add a scrollbar by its side (not a scrollpane) and use the scrollposition to choose what part of the text that should be painted. That way you can use doublebuffering, and avoid the problem completly. (No resizing of components means nothing is layd out again)
Ragnvald Barth
Software engineer -
Adding ScrollBars to JTextPane
I migrated from TextArea to JTextPane in a simple chat program in order to display colors and styled font sizes. The problem is that the border and scroll bars previously given by TextArea are gone when I switched to JTextPane. I managed to place a border. But I cannot figure out how to add at least vertical scroll bars to the TextArea. I tried to use JScrollPane and then added the JTextPane to it, but then I cannot see what I type.
Can you please help?
CSYou are doing the correct thing. To add scrolling to any Swing component you add the component to a JScrollPane and then add the JScrollPane to your container.
If you cannot see what you are typing that may be because you didn't give your component enough space and the scrollbars of the JScrollPane are taking up all the space. Give your component more space and see if that fixes the problem.
HTH
Bryan -
Illegal start of type error when adding for loop to applet
I have typed the following applet to print a horizontal row of stars with the length entered by the user (i.e. user enters 4 and applet prints out 4 stars in a row). Here is my code:
import java.awt.Graphics;
import javax.swing.*;
public class Histograms extends JApplet
String input = "";
int number;
public void init()
input = JOptionPane.showInputDialog ( null,
"Enter a number\nbetween 1 and 30:" );
number = Integer.parseInt( input );
public void paint ( Graphics g )
for ( int counter = 1; counter <= number; counter++ )
System.out.print( "*" );
System.out.println();
};Now I am trying to make it do this 5 times, so it seems like just surrounding the init and paint methods in a for loop (i.e. for ( int i=1; i <= 5; i++ ) ) would do the trick but when I do that I get an illegal start of type error when trying to compile. Does anyone know why this error would show up. The most common reply to questions of this sort seems to be to check the closing braces but I have checked very carefully after adding the for loop and don't see any problems with mismatched braces. Could you please help me get on the right track as to how I can make this applet print a horizontal row of stars five times? All help is appreciated.Hello JTMOBOP:
You were correct in figuring that I was trying to get the applet to print five rows of stars of different length according to five different inputs from the user. I tried your suggestions, and the code now does compile and run, but it still does not run properly (i.e. only asks user once for input and displays row of stars but does not show an input dialog again). Here is the code I have retyped:
import java.awt.Graphics;
import javax.swing.*;
public class Histograms extends JApplet
String input = "";
int[] number = new int[5];
public void init()
for ( int i = 0; i < 5; i++ )
input = JOptionPane.showInputDialog ( null,
"Enter a number\nbetween 1 and 30:" );
number[i] = Integer.parseInt( input );
public void paint ( Graphics g )
for ( int i = 0; i < 5; i++ )
for ( int myNumber = 0; myNumber <= number; myNumber++ )
System.out.print( "*" );
System.out.println();
Any ideas what's going on here?
Also, your comments about not being able to loop a method make sense. Thank you for the input so far. -
Adding Scrollbar and buttons to Dynamic Text
Hello,
I am trying to connect dynamic text to scrollbar and buttons. I did tutorial and Lynda.com and practically pasted the code in with my file names and for some reason it does not work. It says I have a "Access of Undefined Property mask_mc" Did I need to create a variable for this? I didn't in the tutorial.
Right now I have the dynamic text loading successfuly in 2 different places and I wantd to add the scrollbar. I put the variables on frame 1 code and then I put the actually load code on the frame where it is needed.
Any suggestions?
Thanks! Sandra
HERE IS CODE FOR FRAME 1:
var textLoader:URLLoader = new URLLoader();
var textReq:URLRequest;
var scrollPercent:Number = 0;
var minScroll:Number;
var maxScroll:Number;
var targetScroll:Number = philText_mc.y;
var easing:Number = 5;
var scrollAmt:Number = 15;
var scrollDirection:Number = 0;
HERE IS CODE FOR FRAME WHERE TEXT LOADS:
textReq = new URLRequest("text_philosophy.txt");
function philosophyTextLoaded(event:Event):void {
philText_mc.philosophy_txt.text = textLoader.data;
minScroll = philText_mc.y;
maxScroll = minScroll - philText_mc.height + mask_mc.height;
function dragScroller(event:MouseEvent):void
var dragX:Number = line_mc.x - scroller_mc.width/2 + 1;
var dragY:Number = line_mc.y;
var dragW:Number = 0;
var dragH:Number = line_mc.height - scroller_mc.height;
scroller_mc.startDrag(false, new Rectangle(dragX,dragY,dragW,dragH));
stage.addEventListener(MouseEvent.MOUSE_UP, stopDragging);
stage.addEventListener(Event.ENTER_FRAME, setScrollPercent);
stage.removeEventListener(Event.ENTER_FRAME, scrollText);
function stopDragging(event:MouseEvent):void
scroller_mc.stopDrag();
function setScrollPercent(event:Event):void
scrollPercent = (scroller_mc.y - line_mc.y) / (line_mc.height - scroller_mc.height);
if(scrollPercent < 0)
scrollPercent = 0;
else if(scrollPercent > 1)
scrollPercent = 1;
targetScroll = (scrollPercent * (maxScroll - minScroll)) + minScroll;
philText_mc.y -= (philText_mc.y - targetScroll) / easing;
function scrollUp(event:MouseEvent):void
setDirection(scrollAmt);
function scrollDown(event:MouseEvent):void
setDirection(-scrollAmt);
function setDirection(dir:Number):void
scrollDirection = dir;
stage.addEventListener(Event.ENTER_FRAME, scrollText);
stage.addEventListener(MouseEvent.MOUSE_UP, stopScrolling);
stage.removeEventListener(Event.ENTER_FRAME, setScrollPercent);
function scrollText(event:Event):void
targetScroll += scrollDirection;
philText_mc.y -= (philText_mc.y - targetScroll) / easing;
if(philText_mc.y > minScroll)
philText_mc.y = minScroll;
targetScroll = minScroll;
else if(philText_mc.y < maxScroll)
philText_mc.y = maxScroll;
targetScroll = maxScroll;
scrollPercent = (philText_mc.y - minScroll) / (maxScroll - minScroll);
scroller_mc.y = (scrollPercent * (line_mc.height - scroller_mc.height)) + line_mc.y;
function stopScrolling(event:MouseEvent):void
scrollDirection = 0;
textLoader.load(textReq);
scroller_mc.buttonMode = true;
philText_mc.external_txt.autoSize = TextFieldAutoSize.LEFT;
scroller_mc.addEventListener(MouseEvent.MOUSE_DOWN, dragScroller);
textLoader.addEventListener(Event.COMPLETE, philosophyTextLoaded);
up_btn.addEventListener(MouseEvent.MOUSE_DOWN, scrollUp);
down_btn.addEventListener(MouseEvent.MOUSE_DOWN, scrollDown);Hello again,
Maybe I am asking this question wrong. Instead of making you try and figure out what's going on in my file what I really need to know is how you would take this code I am attaching and make it happen on another frame besides frame 1 and it doesn't appear on frame 1. I think this may help me understand a little better.
Also another way I was thinking to get around this would be to pull in an external swf into the spot where I want this text to go because I can make the scrollbars and external text work when it is the only thing going on in the movie. Would this be a bad way to set this up? and also SInce it is an external movie would I have maintimeline issues with mouse/scroller control?
thanks! sandra
Here is working code:
var textLoader:URLLoader = new URLLoader();
var textFile:URLRequest = new URLRequest("text/external.txt");
var scrollPercent:Number = 0;
var minScroll:Number;
var maxScroll:Number;
var targetScroll:Number = text_mc.y;
var easing:Number = 5;
var scrollAmt:Number = 15;
var scrollDirection:Number = 0;
function textLoaded(event:Event):void
text_mc.external_txt.text = textLoader.data;
minScroll = text_mc.y;
maxScroll = minScroll - text_mc.height + mask_mc.height;
function dragScroller(event:MouseEvent):void
var dragX:Number = line_mc.x - scroller_mc.width/2 + 1;
var dragY:Number = line_mc.y;
var dragW:Number = 0;
var dragH:Number = line_mc.height - scroller_mc.height;
scroller_mc.startDrag(false, new Rectangle(dragX,dragY,dragW,dragH));
stage.addEventListener(MouseEvent.MOUSE_UP, stopDragging);
stage.addEventListener(Event.ENTER_FRAME, setScrollPercent);
stage.removeEventListener(Event.ENTER_FRAME, scrollText);
function stopDragging(event:MouseEvent):void
scroller_mc.stopDrag();
function setScrollPercent(event:Event):void
scrollPercent = (scroller_mc.y - line_mc.y) / (line_mc.height - scroller_mc.height);
if(scrollPercent < 0)
scrollPercent = 0;
else if(scrollPercent > 1)
scrollPercent = 1;
targetScroll = (scrollPercent * (maxScroll - minScroll)) + minScroll;
text_mc.y -= (text_mc.y - targetScroll) / easing;
function scrollUp(event:MouseEvent):void
setDirection(scrollAmt);
function scrollDown(event:MouseEvent):void
setDirection(-scrollAmt);
function setDirection(dir:Number):void
scrollDirection = dir;
stage.addEventListener(Event.ENTER_FRAME, scrollText);
stage.addEventListener(MouseEvent.MOUSE_UP, stopScrolling);
stage.removeEventListener(Event.ENTER_FRAME, setScrollPercent);
function scrollText(event:Event):void
targetScroll += scrollDirection;
text_mc.y -= (text_mc.y - targetScroll) / easing;
if(text_mc.y > minScroll)
text_mc.y = minScroll;
targetScroll = minScroll;
else if(text_mc.y < maxScroll)
text_mc.y = maxScroll;
targetScroll = maxScroll;
scrollPercent = (text_mc.y - minScroll) / (maxScroll - minScroll);
scroller_mc.y = (scrollPercent * (line_mc.height - scroller_mc.height)) + line_mc.y;
function stopScrolling(event:MouseEvent):void
scrollDirection = 0;
textLoader.load(textFile);
scroller_mc.buttonMode = true;
text_mc.external_txt.autoSize = TextFieldAutoSize.LEFT;
scroller_mc.addEventListener(MouseEvent.MOUSE_DOWN, dragScroller);
textLoader.addEventListener(Event.COMPLETE, textLoaded);
up_btn.addEventListener(MouseEvent.MOUSE_DOWN, scrollUp);
down_btn.addEventListener(MouseEvent.MOUSE_DOWN, scrollDown); -
WebDynpro ABAP - issue adding scrollbar to table UI element.
Hi WebDynPro experts,
i have an requirement where in table UI element in one of my VIEW requires SCROLLBAR to appear. i did try setting in 'Webdynpro Application' under the parameters tab, new parameter 'WDTABLENAVIGATION' from the F4. However the problem is that i cannot find WDTABLENAVIGATION' via F4 nor can i enter this param manually ????
System info: SAP ECC 6.0 Level 9
whats the best way to achieve this effect.have a look at note 998273.
Seems to available as of SAP_BASIS 700 Support Package 11. -
Adding scrollbars to a panel containing a buffered image
Frame Class:
package HeatMap;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;
import javax.swing.SwingUtilities;
class HeatMapFrame extends JFrame
BufferedImage img;
HeatMapFrame(BufferedImage img)
super("Gene Expression Profile Heatmap");
this.img = img;
HeatMapPane mapPanel = new HeatMapPane(img);
JScrollPane scrollPane = new JScrollPane(mapPanel, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS );
scrollPane.setPreferredSize(new Dimension(640,480));
add(scrollPane,BorderLayout.CENTER);
setSize(640,480);
setLocation(getWidth()/4,getHeight()/4);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
Panel Class:
package HeatMap;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;
public class HeatMapPane extends JPanel
BufferedImage img;
HeatMapPane(BufferedImage img)
this.img = img;
//setSize(640,480);
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Draw image centered.
//int x = (getWidth() - img.getWidth())/2;
//int y = (getHeight() - img.getHeight())/2;
g.drawImage(img, 0, 0, this);
}I`m drawing the BufferedImage to a JPanel and addig the JPanel to a JScrollPane. The problem is that the scrollbars are visible but not active. Scrolling is not working. Can somebody tell me why? Thanks for any advice.Since your HeatMapPane does not declare a preferred size, I'm guessing(1) it is assigned a size of 0x0.
1) I would do more than guess, if you had posted an SSCCE. For an SSCCE to do with images, you might hot-link to some of the images available at my [media page|http://pscode.org/media/#image], or generate an image within the source. -
I am creating an image editor in java and my main class extends jframe. Now the problem arrises when i load an image gretaer than the frame size.
how should i add jscrollpane....
plzz help...how should i add jscrollpane....Add your component to a JScrollPane and add the scroll pane to the frame. The scrollbar appear automatically when the preffered size of the component is greater than the size of the scroll pane.
-
Scrollbar for Selection in applet ?????
Hello Experts,
I have a bizzare requirement from my client.
The problem is :
they want a seperate image to be displayed based on the thumb location of the scrollbar in an Applet
i.e they want me to select & display different image based on scrollbar location.
I feel that's not the purpose of a scrollbar.I was not able to convince the
client.
Any suggestions?suggestions for what?
how to convince your client that this is not a good idea? my suggestion: don't. at the very least, try to make a prototype, and perhaps when they see the prototype will will understand your point of view. If not, don't forget, their your client. If thats what they want, give it to them.
as for how to go about doing it, I suppose you would implement a change listener or an adjustment listener.
btw, what do you mean by a separate image to be displayed. Like, displayed in a separate panel somewhere, or displayed AS the thumb of the scroll bar. or are you not really using a scroll panel, but rather just using a scroll bar to change which image is shown in a main panel?
- Adam -
Mouse released event for scrollbar
Hello,
I have a java.awt.Scrollbar component on applet.
I need to perform actions when user releases the mouse from the
scrollbar. For example the user presses the mouse on the scrollbars
tracking rectangle and starts to track. Then the values of the
scrollbar changes and finally user releases the mouse left button-
this final event (mouse release) is in my interest. How can i get
mouse release event from scrollbar? The AdjustmentListener does not
suit for me because it fires AdjustmentEvents even then when the user
hasn't released the mouse. I need to perform more actions for every
scrollbar's change; so my applet i slow at the moment, because every
"tracking in scrollbar" creates a lot of events before the mouse is
finally released.
I added a MouseListener for my scrollbar, but mouseReleased event does
not work. Can yo help me?
Thank you, any help would be nice.
Here is some demo code i tried:
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Kerimisriba1 extends Applet implements
AdjustmentListener, MouseListener{
Scrollbar kerimisriba=new Scrollbar(Scrollbar.VERTICAL, 20, 5, 1,
100); //algv��rtus, nupu suurus, v�him ja suurim v��rtus
TextField tf=new TextField(10);
public Kerimisriba1(){
setLayout(new BorderLayout());
add(kerimisriba, BorderLayout.WEST);
add(tf, BorderLayout.SOUTH);
//kerimisriba.addAdjustmentListener(this);
kerimisriba.addMouseListener(this);
System.out.println("AdjustmentEvent.TRACK="+AdjustmentEvent.TRACK);
public void adjustmentValueChanged(AdjustmentEvent e){
//System.out.println(e.getAdjustmentType());
// tf.setText(kerimisriba.getValue()+"");
public void mouseReleased(MouseEvent me){
tf.setText("mouseReleased");
public void mouseClicked(MouseEvent me){}
public void mouseEntered(MouseEvent me){}
public void mouseExited(MouseEvent me){}
public void mousePressed(MouseEvent me){}
}I made a screenshot of how the applet works in my computer:
http://charles.pri.ee/scroll.gif
As you see in the java console,
the statement System.out.println("mouseReleased");
does not executes,
in my computer.
I tried this on co-workers comuter with Internet Explorer- there was no mouse release event either.
I hope i'm not very annoying, but i still need help:)
I replaced the constructor with init() method:
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Kerimisriba1 extends Applet implements AdjustmentListener, MouseListener{
Scrollbar kerimisriba=new Scrollbar(Scrollbar.VERTICAL, 20, 5, 1, 100); //algv��rtus, nupu suurus, v�him ja suurim v��rtus
TextField tf=new TextField(10);
public void init(){
kerimisriba.addAdjustmentListener(this);
setLayout(new BorderLayout());
kerimisriba.addMouseListener(this);
add(kerimisriba, BorderLayout.WEST);
add(tf, BorderLayout.SOUTH);
System.out.println("AdjustmentEvent.TRACK="+AdjustmentEvent.TRACK);
public void adjustmentValueChanged(AdjustmentEvent e){
System.out.println(e.getAdjustmentType());
tf.setText(kerimisriba.getValue()+"");
public void mouseReleased(MouseEvent me){
tf.setText("mouseReleased");
System.out.println("mouseReleased");
public void mouseClicked(MouseEvent me){
System.out.println("mouseClicked");
public void mouseEntered(MouseEvent me){}
public void mouseExited(MouseEvent me){}
public void mousePressed(MouseEvent me){
System.out.println("mousePressed"); -
Applet unable to load JARs from URL?
Please let me preface my query with "I have not done applets ever for live business apps, only for uni and that was over a decade ago..." :)
I've been doing a lot of reading the last couple days and have been trying to modify a currently existing applet which unfortunately currently depends on libraries being installed in the ext dir on the user's PC (!). I am modifying it such that 1. it will now make a web service call and 2. it will need to include all of the good libraries that come with making web service calls. My other goal is to change the way the applet is loaded (applet tag) so that the libraries need not be pre-installed in the user's ext dir.
My trouble is, I cannot seem to persuade the applet to load the libraries that co-exist with it. I am loading the applet via a simple test harness page presently, where the HTML file resides in one directory (http://localhost/cis/dictation/test1.html) and the JARs in another (http://localhost/cis/common), but all at the same subdir level under the main web root. I know the applet is loading, as I have a test debug statement which prints out on each invocation.
Note If I load all of the JARs in the dependency hierarchy into the extensions directory, everything works swimmingly.
I have tried multiple variations on the applet tag, not completely sure of what it should look like. Please note when I load the URLs into the browser for each individual library, e.g. http://localhost/cis/common/axis.jar, the browser prompts me to download the JARs, so I know the browser can "see" them.
<applet code="webmedx.client.applet.audio.TransferApplet.class"
codebase="http://localhost/cis/common/"
name=TransferApplet
width=10 height=10
archive="audio.jar,axis.jar,jaxrpc.jar,jndi.jar,commons-logging.jar,commons-discovery.jar"
MAYSCRIPT>
<PARAM NAME="image" VALUE="images/webmedx_icon-32x32.gif">
<PARAM NAME="boxmessage" VALUE="Loading the Webmedx Audio Player">
<PARAM NAME="cache_archive" VALUE="../common/audio.jar">
<PARAM NAME="DebugLevel" value="1">
<PARAM NAME="userenterprise" VALUE="BHS">
<PARAM NAME="userfacility" VALUE="BHS">
<param name="scriptable" value="true">
</applet>Using path relative to the browser URL (http://localhost/cis/dictation/test1.html):
<applet
codebase="../common"
archive="audio.jar,axis.jar,jaxrpc.jar,jndi.jar,commons-logging.jar,commons-discovery.jar"
code="webmedx.client.applet.audio.TransferApplet.class"
name="TransferApplet"
width="0" height="0"
MAYSCRIPT>
<PARAM NAME="image" VALUE="images/webmedx_icon-32x32.gif">
<PARAM NAME="boxmessage" VALUE="Loading the Webmedx Audio Player">
<PARAM NAME="cache_archive" VALUE="../common/audio.jar">
<PARAM NAME="DebugLevel" value="1">
<PARAM NAME="userenterprise" VALUE="BHS">
<PARAM NAME="userfacility" VALUE="BHS">
<param name="scriptable" value="true">
</applet>Each of these results in the java console reporting a NCDFE for javax/xml/rpc/Service, which it should be able to locate in http://localhost/cis/common/jaxrpc.jar.
Then on subsequent page reloads, the java console reports NCDFE's for the newly added class WITHIN the applet jar, webmedx/client/applet/util/cdsproxy/WSAudioArchiveLocator (assuming because it requires javax.xml.rpc.Service, and cannot load it).
Any ideas/help will be very much appreciated :)
Edited by: alexx_wmx on Jul 13, 2010 4:17 PMejp wrote:
Those JARs must be installed in the lib/ext directory of the JRE to work correctly. ..Do they? I am surprised to hear that, but have not dealt with them directly. Why?
Note that I had asked the OP not to split what I feel is one question, into two threads. The other thread is at.. [http://forums.sun.com/thread.jspa?threadID=5444667], which had itself already been spawned from another thread.
(sigh..) Following this topic is beginning to make my head hurt. -
Removing scrollbars on the JSP page of frames created by included JSP files
Hi All,
In the iternet sales B2B application which we are developing, has a blank JSP file. Wherein we are adding other JSP files on it, loading trough JS.
When we are adding it is making the various jsp files in the form of the frames, and each frame has different JSP page. So it is adding scrollbars on each frame if the size of the page exceeds the size of frame.
we don't want the scrollbars. Kindly suggest to remove these scrollbars, and all the pages should look as a single JSP page.
Thanks & Regards
EKtaHi
set scrolling="no" while creating frames
Murali.K.N -
Hi
I want to know that there is an option or solution for my question.
I want when the applet is being started and everything is shown.
Then there are 2 buttons on the bottom with NL|EN so when i push on EN the applet should be in englisch and when i push back on NL the applet must be in Dutch. Is there an way to do this?
SatanduvelThe difficult part is to make all your UIs components notice the change and re-set their text and refresh their appearance.
You could probably extend JPanel and JMenu and pass the necessary Locale to their c'tors. Then those would set up themselves, providing the right texts for the components contained - easiest done by I18N and can be added to the frame/applet which needs to be revalidated.
In other words, you'll have to destroy and rebuild the entire UI.
Which is why this is usually not done in programs.
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