I'm just learning Java and I'm having problems drawing the GUI. If I try to put code to draw the GUI in the paint method the applet flickers and is unusable. Can someone please tell me what's wrong with the code? It's an applet that converts currency and allows you to edit the exchange rates. The code is below, I hope it keeps the formatting.
/* All packages are imported here. */
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
/* Applet class*/
publicclass Currency extends Applet implements ActionListener, ItemListener {
/* All variables, buttons, and fields are declared here. */
privateint Iface;
privatedouble usExchRate, euroExchRate, pesoExchRate, poundExchRate, rubleExchRate, canExchRate;
private Choice ICurrency, FCurrency;
private Button exchRatesIface, convIface; /* convert, */
private TextField currInput, currOutput, usExch, euroExch, pesoExch, poundExch, rubleExch, canExch;
private Label LInitScreen, LUsExch, LEuroExch, LPesoExch, LPoundExch, LRubleExch, LCanExch, LBlank;
private Panel init = new Panel();
private Panel con1 = new Panel();
private Panel con2 = new Panel();
private Panel ex1 = new Panel();
private Panel ex2 = new Panel();
private String ChoiceIn, ChoiceOut;
/* Init method that every applet needs */
publicvoid init(){
/* Create and add contents of ListBox for input currency */
ICurrency = new Choice();
ICurrency.add("From");
ICurrency.add("Canadian Dollar"); ICurrency.add("U.S. Dollar");
ICurrency.add("Mexican Peso"); ICurrency.add("British Pound");
ICurrency.add("Russian Ruble"); ICurrency.add("Euro");
ICurrency.addItemListener(this);
/* Create and add contents of ListBox for output currency */
FCurrency = new Choice();
FCurrency.add("To");
FCurrency.add("Canadian Dollar"); FCurrency.add("U.S. Dollar");
FCurrency.add("Mexican Peso"); FCurrency.add("British Pound");
FCurrency.add("Russian Ruble"); FCurrency.add("Euro");
FCurrency.addItemListener(this);
/* Create buttons */
//convert = new Button("Convert");
exchRatesIface = new Button("Set Exchange Rates");
convIface = new Button("Calculate Funds Conversion");
/* Initialize exchange rates. These are not final variables because they will change.
* This rate is to convert to Canadian dollars.*/
usExchRate = 0.68; euroExchRate = 0.75; pesoExchRate = 100; poundExchRate = 0.25;
rubleExchRate = 1000; canExchRate = 1;
/* Create TextFields for applet */
currInput = new TextField(10); currOutput = new TextField(10); usExch = new TextField(5);
euroExch = new TextField(5); pesoExch = new TextField(5); canExch = new TextField(5);
poundExch = new TextField(5); rubleExch = new TextField(5);
currInput.setText("0");
currOutput.setText("0");
/* Create labels for applet */
LCanExch = new Label("Canadian Exchange Rate", Label.CENTER);
LUsExch = new Label("U.S. Exchange Rate", Label.CENTER);
LEuroExch = new Label("Euro Exchange Rate", Label.CENTER);
LPesoExch = new Label("Peso Exchange Rate", Label.CENTER);
LPoundExch = new Label("Pound Exchange Rate", Label.CENTER);
LRubleExch = new Label("Ruble Exchange Rate", Label.CENTER);
LBlank = new Label("", Label.CENTER);
LInitScreen = new Label("What do you want to do?", Label.CENTER);
/* Add the itemListener to all the buttons and TextFields */
//convert.addActionListener(this);
exchRatesIface.addActionListener(this);
convIface.addActionListener(this); currInput.addActionListener(this);
usExch.addActionListener(this); euroExch.addActionListener(this);
pesoExch.addActionListener(this); poundExch.addActionListener(this);
rubleExch.addActionListener(this);
/* create the initial screen */
initialScreen();
//converter();
//exchange();
}
/* Method called to draw the first screen */
publicvoid initialScreen(){ // Iface = 1
Iface = 1;
add(init);
init.setLayout(new GridLayout(3,1));
init.add(LInitScreen);
init.add(convIface);
init.add(exchRatesIface);
}
/* Method called to add appropriate pieces to Exchange Rates interface */
publicvoid exchange(){ // Iface = 2
Iface = 2;
add(ex1); add(ex2);
ex1.setLayout(new GridLayout(6,2));
ex1.add(LCanExch); ex1.add(canExch);
ex1.add(LUsExch); ex1.add(usExch);
ex1.add(LEuroExch); ex1.add(euroExch);
ex1.add(LPesoExch); ex1.add(pesoExch);
ex1.add(LPoundExch); ex1.add(poundExch);
ex1.add(LRubleExch); ex1.add(rubleExch);
ex2.add(convIface);
// display all the current exchange rates
canExch.setText(canExchRate + "");
usExch.setText(usExchRate + "");
euroExch.setText(euroExchRate + "");
pesoExch.setText(pesoExchRate + "");
poundExch.setText(poundExchRate + "");
rubleExch.setText(rubleExchRate + "");
}
/* Method called to add appropriate pieces to Converter interface */
publicvoid converter(){ // Iface = 3
Iface = 3;
add(con1); add(con2);
con1.setLayout(new GridLayout(2,2));
con1.add(ICurrency);
con1.add(currInput);
con1.add(FCurrency);
con1.add(currOutput);
con2.add(exchRatesIface);
}
/* Implementation of ActionListener */
publicvoid actionPerformed(ActionEvent ae) { // used for buttons and TextFields
Object source = ae.getSource(); double val = 0.0;
/* the next four "if"s are for changing interfaces */
if (source == exchRatesIface){
if (Iface == 1){
remove(init);
exchange();
}
else{
remove(con1);
remove(con2);
exchange();
}
}
if (source == convIface){
if(Iface == 1){
remove(init);
converter();
}
else{
remove(ex1);
remove(ex2);
converter();
}
}
/* end of "if"s for changing interfaces */
/* this section is for setting the exchange rates */
/*c.add(LCanExch); c.add(canExch);
c.add(LUsExch); c.add(usExch);
c.add(LEuroExch); c.add(euroExch);
c.add(LPesoExch); c.add(pesoExch);
c.add(LPoundExch); c.add(poundExch);
c.add(LRubleExch); c.add(rubleExch);*/
if (source == canExch){
return;
//repaint();
}
if (source == usExch){
usExchRate = Double.parseDouble(usExch.getText());
//repaint();
}
if (source == euroExch){
euroExchRate = Double.parseDouble(euroExch.getText());
//repaint();
}
if (source == pesoExch){
pesoExchRate = Double.parseDouble(pesoExch.getText());
//repaint();
}
if (source == poundExch){
poundExchRate = Double.parseDouble(poundExch.getText());
//repaint();
}
if (source == rubleExch){
rubleExchRate = Double.parseDouble(rubleExch.getText());
//repaint();
}
// End of setting the exchange rates
/* These "if"s are for conversion and indicate when a value has been entered
* in the "to" TextField */
if (source == currInput){ // a value has been entered for conversion
try {
val = Double.parseDouble(currInput.getText());
} catch(Exception e){
val = 0.0;
}
//if (ChoiceIn.equals("Canadian Dollar")){
// currOutput.setText((val*canExchRate) + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("Canadian Dollar")) {
currOutput.setText(val + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("U.S. Dollar")) {
currOutput.setText(val * usExchRate + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("Mexican Peso")) {
currOutput.setText(val * pesoExchRate + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("British Pound")) {
currOutput.setText(val * poundExchRate + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("Russian Ruble")) {
currOutput.setText(val * rubleExchRate + "");
}
if (ChoiceIn.equals("Canadian Dollar") && ChoiceOut.equals("Euro")) {
currOutput.setText(val * euroExchRate + "");
}
// Here's the U.S. Dollar
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("Canadian Dollar")){
currOutput.setText(val*1/usExchRate + "");
}
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("U.S. Dollar")){
currOutput.setText(val + "");
}
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("Mexican Peso")){
currOutput.setText(val*1/usExchRate*pesoExchRate + "");
}
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("British Pound")){
currOutput.setText(val*1/usExchRate*poundExchRate + "");
}
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("Russian Ruble")){
currOutput.setText(val*1/usExchRate*rubleExchRate + "");
}
if (ChoiceIn.equals("U.S. Dollar") && ChoiceOut.equals("Euro")){
currOutput.setText(val*1/usExchRate*euroExchRate + "");
}
// Here's the Mexican Peso
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("Canadian Dollar")){
currOutput.setText(val*1/pesoExchRate + "");
}
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("U.S. Dollar")){
currOutput.setText(val*1/pesoExchRate*usExchRate + "");
}
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("Mexican Peso")){
currOutput.setText(val + "");
}
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("British Pound")){
currOutput.setText(val*1/pesoExchRate*poundExchRate + "");
}
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("Russian Ruble")){
currOutput.setText(val*1/pesoExchRate*rubleExchRate + "");
}
if (ChoiceIn.equals("Mexican Peso") && ChoiceOut.equals("Euro")){
currOutput.setText(val*1/pesoExchRate*euroExchRate + "");
}
// here's the British Pound
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("Canadian Dollar")){
currOutput.setText(val*1/poundExchRate + "");
}
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("U.S. Dollar")){
currOutput.setText(val*1/poundExchRate*usExchRate + "");
}
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("Mexican Peso")){
currOutput.setText(val*1/poundExchRate*pesoExchRate + "");
}
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("British Pound")){
currOutput.setText(val + "");
}
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("Russian Ruble")){
currOutput.setText(val*1/poundExchRate*rubleExchRate + "");
}
if (ChoiceIn.equals("British Pound") && ChoiceOut.equals("Euro")){
currOutput.setText(val*1/poundExchRate*euroExchRate + "");
}
// Here's the Russian Ruble
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("Canadian Dollar")){
currOutput.setText(val*1/rubleExchRate + "");
}
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("U.S. Dollar")){
currOutput.setText(val*1/rubleExchRate*usExchRate + "");
}
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("Mexican Peso")){
currOutput.setText(val*1/rubleExchRate*pesoExchRate + "");
}
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("British Pound")){
currOutput.setText(val*1/rubleExchRate*poundExchRate + "");
}
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("Russian Ruble")){
currOutput.setText(val + "");
}
if (ChoiceIn.equals("Russian Ruble") && ChoiceOut.equals("Euro")){
currOutput.setText(val*1/rubleExchRate*euroExchRate + "");
}
// Here's the European Economic Union's Euro
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("Canadian Dollar")){
currOutput.setText(val*1/euroExchRate + "");
}
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("U.S. Dollar")){
currOutput.setText(val*1/euroExchRate*usExchRate + "");
}
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("Mexican Peso")){
currOutput.setText(val*1/euroExchRate*pesoExchRate + "");
}
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("British Pound")){
currOutput.setText(val*1/euroExchRate*poundExchRate + "");
}
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("Russian Ruble")){
currOutput.setText(val*1/euroExchRate*rubleExchRate + "");
}
if (ChoiceIn.equals("Euro") && ChoiceOut.equals("Euro")){
currOutput.setText(val + "");
}
// End of conversion "if"s
}
// implementation of the itemListener Interface
publicvoid itemStateChanged(ItemEvent ie){ // used for lists, and combo boxes
Object source = ie.getSource();
if (source == ICurrency){
ChoiceIn = ICurrency.getSelectedItem();
}
else{ ChoiceOut = FCurrency.getSelectedItem();
}
}
/* Paint method that every applet needs */
//public void paint(Graphics g){
//}
}
no joe validate wont reduce the number flickerence. its same as the repaint.. pls reply if u know any more opening for this ans. I also actually looking for this issue
Validate() worked great for me. Rather than calling repaint() which I didn't have to do anyway because I didn't even implement it, the validate() call fixed the problems. I got a good mark on the assignment so it must have worked alright. I only lost marks for some code redundancy. The instructor said I could have put the exchange rates in an array and saved myself some time.
Previous Topic
