I'm a newbie Java guy so I'm probably doing this entire thing completely wrong. I have to do this giant project for software engineering class. The code is about 2,000 lines long so this is skeleton code
public class BookRental extends JFrame{
public Client currentClient = new Client(); // creating client object
//rest of declared variables.
public class Client{ //Client class containing all get/set methods for each variable
private username;
private void setUsername(String u){
username = u;
}
public String getUsername(){
return username;
}
public class LoginPanel extends JPanel{} //Panel to show and receive login info.
public class RegisterPanel extends JPanel{} //Panel to register.
public class MenuPanel extends JPanel{ //Panel showing main menu.
//At this point currentClient will contain values
public ClientInfoPanel(){
initComponents();
}
private void initComponents(){
infoPanelUserName = new JLabel();
infoPanelFullName.setText("Currently logged in as: " + currentClient.getUsername());
}
private JLabel infoPanelUserName;
}
public class ClientInfoPanel extends JPanel{} //Panel to print currentClient info to screen using JLabel objects
private void ViewClientInfoButtonActionPerformed(event){ // Using button in Menu Panel to setVisibility of clientInfoPanel to (true)
//At this point there will be a value for currentClient
clientInfoPanel = new ClientInfoPanel();
this.add(clientInfoPanel);
menuPanel.setVisible(false);
clientInfoPanel.setVisible(true);
}
public BookRental(){initComponents();} //Constructor
private void initComponents(){} // Creates all panels and sets visibility off, besides login
public static void main(String args[]){
new BookRental().setVisible(true);
}
}
I already am pretty sure I am doing this COMPLETELY wrong, however my question is why can't I access currentClient inside of ClientInfoPanel? Say for this JLabel:
infoPanelUserName.setText("Currently logged in as: " + currentClient.getUsername());
The ClientInfoPanel recognizes currentClient exists and that the getUsername() method exists, however it prints:
"Currently logged in as: "
The code you showed looks fine, so the problem is somewhere else, or this code is not representative of what you have. Also, you ARE accessing currentClient successfully, unless you're getting a NullPointerException or catching it somewhere, then the .getUsername() call IS resolving. So the problem is actually with .getUsername(), somehow username is uninitialized when you call .getUsername();
As a test, can you call .setUsername() on currentClient right before you call .getUsername()? That should help us narrow down the problem, isolate it to either the class access or the variable being initialized.
Also, do you know how to debug with breakpoints? You mentioned you're new, so you might not know this is possible. If you're using Eclipse (or another good IDE) you can set breakpoints and run the program in DEBUG build, then the program will freeze when it hits the line you set a breakpoint on, and you can watch as the program moves line by line, and see the variables as they are updated by the program. Google java debug tutorial. :)
I agree (not sure whether I should add since someone else already answered, what is the etiquette?). I ran this fine and it showed me a panel with the user logged in as Me as set in the BookRental constructor:
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class BookRental extends JFrame{
public Client currentClient = new Client(); // creating client object
//rest of declared variables.
public class Client{ //Client class containing all get/set methods for each variable
private String username;
private void setUsername(String u){
username = u;
}
public String getUsername(){
return username;
}
}
public class ClientInfoPanel extends JPanel{ //Panel showing main menu.
//At this point currentClient will contain values
public ClientInfoPanel(){
initComponents();
}
private void initComponents(){
infoPanelUserName = new JLabel();
infoPanelUserName.setText("Currently logged in as: " + currentClient.getUsername());
this.add(infoPanelUserName);
}
private JLabel infoPanelUserName;
}
public ClientInfoPanel clientInfoPanel;
//Constructor
public BookRental(){
currentClient.setUsername("Me");
initComponents();
}
private void initComponents(){
clientInfoPanel = new ClientInfoPanel();
this.add(clientInfoPanel);
clientInfoPanel.setVisible(true);
}
public static void main(String args[]){
new BookRental().setVisible(true);
}
}
Related
i open a new internalframe in this main frame, i have 2 class,
DisplayInternalFrame aDisplay = new DisplayInternalFrame(name, surname);
desktop.add(aDisplay);
aDisplay.setMaximum(true);
aDisplay.show()
i have a desktop pane and its name desktop, this is my main frame, the internal frame is loading when the application runs,
now my 2nd class is internalframe, it has a table, i want to open new internal frame when people push a table item, my table name is errorTable
private void errorTableMouseClicked(java.awt.event.MouseEvent evt) {
errorInternalFrame acceptFrame = new errorInternalFrame();
desktop.add(acceptFrame);
the desktop is on the class 1 so i cant reach desktop cuz now i am on the internalframe event,
basically when people push an item on the table on the internalframe, open a new internal frame, or something like this.
"the desktop is on the class 1 so i cant reach desktop cuz now i am on the internalframe event, "
What you can do is create an interface with a method to addToDesktop
public interface AddableDesktop {
public void addToDesktop();
}
Then in your class with the desktop, implement it
public class Main extends JFrame implements AddableDesktop {
private JDesktopPane desktop;
#Override
public void addToDesktop() {
errorInternalFrame acceptFrame = new errorInternalFrame();
desktop.add(acceptFrame);
acceptFrame.setVisible(true);
}
}
You'll also need to pass the Main instance (which is an instance of AddableDesktop) to the DisplayInternalFrame. Then you can call the addToDesktop method.
public class DisplayInternalFrame extends JInternalFrame {
private AddableDesktop addableDesktop;
public DisplayInternalFrame(String name, String surname, AddableDesktop ad) {
this.addableDesktop = ad;
}
...
private void errorTableMouseClicked(java.awt.event.MouseEvent evt) {
addableDesktop.addToDesktop();
}
}
When you create the DisplayInternalFrame in your Main class, you'll pass the Main instance to the contructor
DisplayInternalFrame aDisplay =
new DisplayInternalFrame(name, surname, Main.this);
This may not be the exact set up you're looking for, but it shows how you provide functionality from one class to the another.
I'm new to Java and I've hit a brick wall. I want to access GUI components (that have been created in one class) from another class. I am creating a new GUI class from one class, like so;
GUI gui = new GUI();
and I can access the components in that class, but when I go to a different class I cant. I really just need to access the JTextAreas to update their content. Could someone point me in the right direction please, any help is greatly appreciated.
GUI Class:
public class GUI {
JFrame frame = new JFrame("Server");
...
JTextArea textAreaClients = new JTextArea(20, 1);
JTextArea textAreaEvents = new JTextArea(8, 1);
public GUI()
{
frame.setLayout(new FlowLayout(FlowLayout.LEADING, 5, 3));
...
frame.setVisible(true);
}
}
First respect encapsulation rules. Make your fields private. Next you want to have getters for the fields you need to access.
public class GUI {
private JTextField field = new JTextField();
public GUI() {
// pass this instance of GUI to other class
SomeListener listener = new SomeListener(GUI.this);
}
public JTextField getTextField() {
return field;
}
}
Then you'll want to pass your GUI to whatever class needs to access the text field. Say an ActionListener class. Use constructor injection (or "pass reference") for the passing of the GUI class. When you do this, the GUI being referenced in the SomeListener is the same one, and you don't ever create a new one (which will not reference the same instance you need).
public class SomeListener implements ActionListener {
private GUI gui;
private JTextField field;
public SomeListener(GUI gui) {
this.gui = gui;
this.field = gui.getTextField();
}
}
Though the above may work, it may be unnecesary. First think about what exactly it is you want to do with the text field. If some some action that can be performed in the GUI class, but you just need to access something in the class to perform it, you could just implement an interface with a method that needs to perform something. Something like this
public interface Performable {
public void someMethod();
}
public class GUI implements Performable {
private JTextField field = ..
public GUI() {
SomeListener listener = new SomeListener(GUI.this);
}
#Override
public void someMethod() {
field.setText("Hello");
}
}
public class SomeListener implements ActionListener {
private Performable perf;
public SomeListener(Performable perf) {
this.perf = perf;
}
#Override
public void actionPerformed(ActionEvent e) {
perf.someMethod();
}
}
Several approaches are possible:
The identifier gui is a reference to your GUI instance. You can pass gui to whatever class needs it, as long as you respect the event dispatch thread. Add public accessor methods to GUI as required.
Declarations such as JTextArea textAreaClients have package-private accessibility. They can be referenced form other classes in the same package.
Arrange for your text areas to receive events from another class using a PropertyChangeListener, as shown here.
The best option to access that text areas is creating a get method for them. Something like this:
public JTextArea getTextAreaClients(){
return this.textAreaClients;
}
And the same for the other one.So to access it from another class:
GUI gui = new GUI();
gui.getTextAreaClients();
Anyway you will need a reference for the gui object at any class in which you want to use it, or a reference of an object from the class in which you create it.
EDIT ---------------------------------------
To get the text area from GUI to Server you could do something like this inside of Create-Server.
GUI gui = new GUI();
Server server = new Server();
server.setTextAreaClients(gui.getTextAreaClients());
For this you should include a JTextArea field inside of Server and the setTextAreaClients method that will look like this:
JTextArea clients;
public void setTextAreaClients(JTextArea clients){
this.clients = clients;
}
So in this way you will have a reference to the JTextArea from gui.
here i add a simple solution hope it works good,
Form A
controls
Textfield : txtusername
FormB fb = new FormB();
fb.loginreset(txtusername); //only textfield name no other attributes
Form B
to access FormA's control
public void ResetTextbox(JTextField jf)
{
jf.setText(null); // or you can set or get any text
}
There is actually no need to use a class that implements ActionListener.
It works without, what might be easier to implement:
public class SomeActionListener {
private Gui gui;
private JButton button1;
public SomeActionListener(Gui gui){
this.gui = gui;
this.button1 = gui.getButton();
this.button1.addActionListener(l -> System.out.println("one"));
}
}
and then, like others have elaborated before me in this topic:
public class GUI {
private JButton button = new JButton();
public GUI() {
// pass this instance of GUI to other class
SomeActionListener listener = new SomeActionListener(GUI.this);
}
public JButton getButton() {
return button;
}
}
I am building my own GUI that will display a list of Friend's objects in list form. The first problem I ran into is that when I run the code without a constructor, everything works fine. But when I create a constructor for my GUI class, the error message displayed:
load: GUIapp.class is not public or has no public constructor.
java.lang.IllegalAccessException: Class sun.applet.AppletPanel can not access a member of class GUIapp with modifiers ""
at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
at java.lang.Class.newInstance0(Class.java:349)
at java.lang.Class.newInstance(Class.java:308)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:807)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:714)
at sun.applet.AppletPanel.run(AppletPanel.java:368)
at java.lang.Thread.run(Thread.java:680)
My Code:
public class GUIapp extends JApplet{
/*
* Attributes
*/
//** Friends Objects**//
private FriendsGroup a;
private ArrayList<friends> friendList;
//** PANEL **//
private JPanel outerPanel;
//** Button **//
private JButton button1;
/*
* Constructor for Getting all the friends set up
*/
private GUIapp(){
a = null; //initialize variable
try {
a = new FriendsGroup("friends.txt"); //import friend list
} catch (IOException e) {
System.out.println("Fail Import.");
}
friendList = a.getFriendsGroup(); //return an arrayList of Friends Object
}
/*
* Create Stuff
*/
public void createStuff() {
outerPanel = new JPanel(); //create outer panel
button1 = new JButton("Click Me");
outerPanel.add(button1,BorderLayout.SOUTH);
}
/*
* Initialize Stuff
*
*/
public void init(){
createStuff(); //initialize create stuff
this.add (outerPanel);
}
}
In the Above Code, if you take out the constructor, it seems to work perfectly. My Question is, what is wrong with the code? Why can't I seem to create a constructor to load in data first?
My Second Question is how would I go about create a panel whereby it displays a list of friends names? Theses names are imported and stored in the arraylist of friends Object called friendList stored in the constructor.
Thanks,
when you are defining a constructor by yourself
compiler will not create the default constructor
since your defined constructor is private
you will not have a public constructor
so simply create a public constructor
public GUIapp(){
// your code
}
because you define constructor private change it to;
public GUIapp(){
a = null; //initialize variable
try {
a = new FriendsGroup("friends.txt"); //import friend list
} catch (IOException e) {
System.out.println("Fail Import.");
}
friendList = a.getFriendsGroup(); //return an arrayList of Friends Object
}
The problem is this: private GUIapp(){. That means that your constructor is available only to that class. Usually constructors are public, although there do exist exceptions, example of which could be the Singleton Pattern.
Removing the constructor works because each class, by default has a parameterless constructor. Take a look at this tutorial for more information on access modifiers.
Alternatively, you could have a method like so in your GUIapp class:
public static GUIapp getInstance() { return new GUIapp(); }
and you call that from your main class, but I think that in this case, changing your constructor from private to public should be enough.
Regarding your second question, this tutorial should be of help.
You ened to change syour constructor to public and debug into:
a.getFriendsGroup();
Its not clear what this methode does, and i assume for some reason (maby the list from the file is empt) the methode tries to access a non assigned object which causes null reference exception, try to debug into the methode to see where this happends or post the code of the methode.
I can't .setText(...) for a JTextField outside of the class that creates the gui. I'm very confused and I feel like there is something basic I am missing. I need some help here.
Here is what I am doing:
In a class (called MainClass) I create an instance of a class that creates my gui
TestText gui = new TestText();
with a constructor that sets the default settings (a JTextField and a button with a listener). Then I call the a setter that I wrote, where I pass it a string that is to set the text of the JTextField:
gui.setText("new");
But "new" doesn't show up on the gui.
I know my setter works from within the class because if I make a call to the setter from the button that I created in gui then the changes show up on the gui.
The part that really confuses me is this: If I call my getter just before my setter, then it returns the old value. Then if I call the getter again after I call the setter then it returns the new value, while the gui continues to show the old value. I thought that maybe it just isn't repainting the gui so I tried all kinds of permutations of .invalidate(), .validate(), .update() and .repaint(), all from the MainClass and from inside the setter. But none did anything.
Is it possible that I somehow have 2 different instances of the gui and I'm only editing one of them?
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class TestText {
private JTextField textField;
private JButton button;
private JPanel frame;
JFrame jFrame;
public void setText(String text) {
textField.setText(text);
}
public String getText() {
return textField.getText();
}
public TestText() {
this.textField.setText("98.6");
this.jFrame = new JFrame("TestText");
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setText("new (button)");
}
});
}
public void setData(TestText data) {
data.setText("new (setData)");
}
public void getData(TestText data) {
}
public boolean isModified(TestText data) {
return false;
}
public void createGui(String[] args) {
jFrame.setContentPane(new TestText().frame);
jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jFrame.pack();
jFrame.setVisible(true);
}
}
and then here's the main class that I'm trying to create the gui from:
public class MainClass {
public static void main(String[] args) {
TestText gui = new TestText();
gui.createGui(null);
System.out.println(gui.getText());
gui.setData(gui);
System.out.println(gui.getText());
gui.setText("new (MainClass)");
System.out.println(gui.getText());
}
}
It looks like you're missing the reference to the text field I think...
gui.referenceToTextField.setText("new word");
EDIT: Very nice SSCCE! However, there are several problems (not in the order provided, necessarily).
You are overriding the setText() method. Don't do this unless you want the method to do something different—why you would want to do this I have no idea.
You aren't even using the args array in the createGui() method. You can create methods without specifying any parameters/arguments.
The getData() method is, right now, useless (If I were you, given what you're trying to accomplish, I would remove the method entirely). I'm assuming, from the apt method name (another good thing to do), that you want to retrieve the data from the text field. Put this line inside the method (and change the word void to String) and you should be set!
return textField.getText();
Truthfully, this shouldn't even run due to a NullPointerException. You aren't initializing any of the components other than the JFrame. You need to do things like textField = new JTextField(20).
Even if you could run this, the button wouldn't work at all because the button hasn't been told that it does anything. To do this call button.addActionListener() with the name of the listening class as the argument. If the GUI and listening classes happen to be in one class together (like I will show you in a minute), the argument is simply this.
You aren't adding any components to the frame. For every component you wish to put into your frame, you must call add(Component cmpt).
Having said this, I think I'm just going to try to recreate what you're trying to do here into one class. You don't really need two separate classes unless the listening portion is excessively long.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class TestText extends JFrame implements ActionListener {
JTextField textField = new JTextField(20);
JButton set = new JButton("Set Text");
JButton get = new JButton("Get Text");
public TestText() {
super();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(textField);
set.addActionListener(this); //this tells the program that the button actually triggers an event
add(set);
get.addActionListener(this);
add(get);
pack();
setVisible(true);
}
public void actionPerformed(ActionEvent event) {
if (event.getSource() == set) {
textField.setText(JOptionPane.showInputDialog(null, "Enter a new word for the text field:"));
} else {
System.out.println(textField.getText());
}
}
public static void main(String[] args) {
TestText tt = new TestText();
}
}
After doing some reading I think it is due to my code not accessing the Event Dispatch Thread like #camickr suggested. Here is some documentation that helped me solve my problem.
I'm using netbeans to program something with a user interface...
I hava a main class that named "NewJFrame.java"(A) and one more class
that named "NewClass.java"(B). Class A is extended to class B like this:
public class NewClass extends NewJFrame{
...
}
Contents of ClassA are public static like this:
public static javax.swing.JTextField TextBox1;
I also has a button in classA .So when I click the button, it will call a function
from the classB and that function needs to edit TextBox1's text...
Here is whats going on when I click the button:
private void jToggleButton1ActionPerformed(java.awt.event.ActionEvent evt) {
String Str1;
NewClass nc = new NewClass();
Str1=nc.call();
}
Here is the funcion in ClassB:
public String call()
{
String Str;
Str = TextBox1.getText();
TextBox1.setText(Str + "1"); //This part isn't work.
JOptionPane.showConfirmDialog(null,Str,"22222222",JOptionPane.PLAIN_MESSAGE);
return Str;
}
So I can read the text of TextBox1 and show it in a messagebox but cannot edit his text.
If I put this code in main class it works perfectly but in another class it doesn't work.
Can someone help me to reslove this problem?
(I'm using netbeans 6.9.1)
I Just Trying to use some another class to add my code because I dont want all the codes stay in same file this is not usefull... Come on someone needs to know how to do that you can't be writing all the codes in a *.java file right?
The problem you are facing has nothing to do with NetBeans IDE,
you will face the same problem with any IDE for this code.
One way of achieving this is by aggregating the NewJFrame class in the NewClass
instead of extending it:
Let me exlplain with some code:
public class NewClass {
private NewJFrame frame = null;
public NewClass(NewJFrame frame) {
this.frame = frame;
}
public String call()
{
String text;
text = frame.TextBox1.getText();
frame.TextBox1.setText(text + "1"); //This will work now.
JOptionPane.showConfirmDialog(null,text,"22222222",JOptionPane.PLAIN_MESSAGE);
return text;
}
}
Here we will receive a reference to the calling JFrame class and will use fields
defined in that class.
private void jToggleButton1ActionPerformed(java.awt.event.ActionEvent evt) {
String Str1;
NewClass nc = new NewClass(this); // see the parameter we are passing here
Str1=nc.call();
}
When we create an object of class NewClass we will pass the reference of the
currently calling NewJFrame object
This will work check it.
Now coming to why your code is not working. When NewClass is extending NewJFrame
and when you create a new object of NewClass class it contains a separate
copy of the NewJFrame which is different from the calling NewJFrame reference hence
the field is getting set in another JFrame and not what you wanted.
with regards
Tushar Joshi, Nagpur
AFAIK Netbeans prevents you from editing by hand GUI's and behaves diferrently depending on strange issues like the one you have... but it was months ago, I dont know if current version sucks that much yet.
I really don't understand why you are forcing yourself to use a new class for this? Even if you NEED to, I don't understand why NewClass extends NewJFrame since you are only creating an instance to call a method that has nothing to do with GUI.
I think creating NewClass isn't necessary. Writing all the code in one class isn't bad by itself. This really depends on MANY factors: how much is "all the code"? Does it make sense to separate responsibilities? Etc, etc...
So make the JTextField and JButton NOT static and NOT public, and simply do everything in there:
private void jToggleButton1ActionPerformed(java.awt.event.ActionEvent evt) {
String str = TextBox1.getText();
TextBox1.setText(str + "1"); //This part isn't work.
JOptionPane.showConfirmDialog(null,Str,"22222222",JOptionPane.PLAIN_MESSAGE);
}
P.S.: variable names are start in lowercase: String str, not String Str.
I Found a solution. I'm throwing the contents whereever I'll use. Here is an Example:
Main class:
private void formWindowOpened(WindowEvent evt) {
Tab1Codes tc1 = new Tab1Codes();
if(!tc1.LockAll(TabMenu1))
System.exit(1);
tc1.dispose();
}
Another class where I added some of my codes:
public boolean LockAll(javax.swing.JTabbedPane TabMenu){
try
{
TabMenu.setEnabledAt(1, false);
TabMenu.setEnabledAt(2, false);
TabMenu.setEnabledAt(3, false);
TabMenu.setEnabledAt(4, false);
}catch(Exception e)
{
JOptionPane.showConfirmDialog(null, "I can't Lock the tabs!",
"Locking tabs...",
JOptionPane.PLAIN_MESSAGE,
JOptionPane.ERROR_MESSAGE);
return false;
}
return true;
}
So, I can edit the contents in another class but it's little useless to send every content I want to read and edit.
If someone knows any short way please write here.