I have a weird Problem with my Java GUI.
I can access the Methods in the Main Class from another Class but i cannot access the Swing Components.
Let me show you how i built the whole thing
Main Class:
public class GUI extends JFrame {
static Code c = new Code();
static Draw panel = new Draw();
JTextArea codelog;
JLabel lblFile;
...
...
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
GUI frame = new GUI();
frame.create();
}
});
}
public void create() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(1280,720);
...
...
contentPane = new JPanel();
setContentPane(contentPane);
contentPane.setBackground(Color.DARK_GRAY);
GridBagLayout gbl_contentPane = new GridBagLayout();
setResizable(false);
...
...
panel.setBackground(Color.BLACK);
gbc_panel.fill = GridBagConstraints.BOTH;
gbc_panel.gridx = 1;
gbc_panel.gridy = 1;
contentPane.add(panel, gbc_panel);
codelog = new JTextArea();
codelog.setEditable(true);
JScrollPane scrollPane_1 = new JScrollPane(codelog);
codelog.setLineWrap(true);
scrollPane_1.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
codelog.setVisible(true);
scrollPane_1.setVisible(true);
GridBagConstraints gbc_scrollPane_1 = new GridBagConstraints();
gbc_scrollPane_1.gridheight = 2;
gbc_scrollPane_1.gridwidth = 4;
gbc_scrollPane_1.fill = GridBagConstraints.BOTH;
gbc_scrollPane_1.gridx = 8;
gbc_scrollPane_1.gridy = 1;
contentPane.add(scrollPane_1, gbc_scrollPane_1);
...
...
}
public void refresh(){
panel.repaint();
}
}
I am using static Code c and static Draw panel to avoid multiple instances as i also have to create Objects of the Main class in other classes.
The other Class named Code
public class Code {
...
...
static GUI g = new GUI();
String test;
...
...
public void hpgl(){
g.codelog.append(test); // gives me nullPointerException !!
g.refresh // works
...
...
}
}
The Problem is that i can access the Methods of the Main Class (GUI) from other classes (such as Code) but i cannot access the Components (such as JTextArea).
The refresh() Method in the Main Class proves it. I can access the Method and in the Main Class the repaint() works. But if i try to repaint from another class using GUI.panel.repaint() it won't work because i would in that case access the panel directly from Code Class.
The Same goes for the JTextArea. I am trying to append codelog from Code but it won't let me do it. If i create a Method in Main Class which appends the Textarea and then call the Method from Code Class it works. But using g.codelog.append(test) gives me a Java null pointer exception
So i can access the Methods but i cannot access the Swing Components.
Can you guys please help me. I don't want to have to write an extra Method in the Main Class for every single Swing Component i want to modify.
Thank You
The UI which is visible on the screen is not the same UI you have created in your Code class. If you want Code to be able to access the UI properties, you will need to pass a reference of the GUI to it.
Having said that, I would be apposed to exposing the UI components directly to any class an instead provide getters and setters (where applicable) to provide access to the information been managed. This prevents rouge classes from making changes to the UI which it should be allowed to do (like remove components)
Depending on what you are doing, an Observer Pattern might be a better choice, where by Code is notified by GUI when something it might be interested in changes. If done through the use of interfaces, this will reduce the coupling between your classes and make it more flexible
Beware static is not a mechanism for providing cross object communication and should be avoid if at all possible, especially in something as dynamic as a GUI.
I was able to solve the Problem following MadProgrammer's Suggestion.
This is what i changed.
I have 3 Classes:
Main Class
Draw
Code
Main Class
public class GUI extends JFrame {
Draw panel = new Draw(this);
Code c = new Code(this);
...
...
}
Code Class
public class Code {
private GUI g;
private Draw b;
public Code(GUI g){
this.g = g;
}
...
...
}
Draw Class
public class Draw extends JPanel{
private GUI x;
private Code c;
public Draw(GUI x){
this.x = x;
}
...
...
}
I removed all the Static declarations. It is now working. I can access the Swing Components in the Main Class now.
Is this the Professional way to do it? or is there still room for improvement. This is the first time i used the passing reference way to do it. Until now i always used static Objects.
Thank You
Related
How can I embed a PApplet into a JApplet ?
I wanted to add it to a JPanel inside the applet, but I couldn't.
If any of you know how I can do this. ??
As of Processing 3, you can no longer do this. PApplet no longer extends Applet, so it can't be treated as a component.
For 95% of users, this is okay. Applets are dead anyway, so you really shouldn't be using them. If at all possible, you should try deploying with Processing.js.
If you need to execute a Processing sketch from Java code, then you should use the PApplet.main("YourSketchNameHere"); function to launch it. Processing will take care of the window for you.
If you really need to treat a PApplet as a component, then you're going to have to go through its PSurface. The PSurface class contains a getNative() function that returns an object that can be treated as a component. But that's overkill for most Processing users.
Prior to Processing 3, this code should have worked for you as #Kevin has explained. So, if your question is directed towards understanding a legacy code here is what you will need to know:
import javax.swing.JFrame;
import javax.swing.JPanel;
class MyPApplet extends PApplet implements ActionListener{
#Override
public void setup() {
super.setup();
// setup
}
#Override
public void draw() {
// my draw code
}
}
public class PAppletDemo {
public static void main(String[] args) {
final JFrame frame = new JFrame("PApplet in Java Application");
JPanel panel = new JPanel();
//create an instance of your processing applet
final MyPApplet applet = new MyPApplet();
applet.init();
panel.add(applet); // From processing 3, this will give you error that applet is not a Component
frame.add(panel);
frame.setSize(applet.getSize().width, applet.getSize().height +200);
frame.setVisible(true);
}
}
To circumvent this, you will need to use PSurface getNative() function. Please refer to the example and discussion given on this link.
I have these two classes:
ConnectionPanel.class
public class ConnectionPanel extends JPanel implements ActionListener,ItemListener, PropertyChangeListener {
private MasterModel m_masterModel;
private JTextField m_keyField;
public ConnectionPanel(MasterModel masterModel) {
m_masterModel = masterModel;
setLayout(new GridLayout(0, 2));
JPanel panel = null;
panel = new JPanel();
panel.add(new JLabel("Type Key:"));
m_keyField = new JTextField(9);
m_keyField.setText("dertfgdertabcdef");
panel.add(m_keyField);
add(panel);
getChatModel().addPropertyChangeListener(this);
getChatModel().setListen(true);
}
public String getEncryptionKey(){
return m_keyField.getText();
}
}
AudioPlayback.class
public class AudioPlayback extends AudioBase {
// and here I want to be able to get
// somehow String key = ConnectionPanel.getEncryptionKey()
// I tried ConnectionPanel panel = new ConnectionPanel(); but does not work
// it messes my graphical interface
// also there is lots of code here too
}
Do you have any ideas how can I get that field input into my audioplayback.class ?
I totally agree with moffeltje & Luke. This question is simple so that I think you can learn something more basic on Java.
But I review your constructor of ConnectionPanel.Excuse me, do you know constructor?
You can find the details here:
https://docs.oracle.com/javase/tutorial/java/javaOO/constructors.html
Now, let's talk about your code. You only give a constructor with one input parameter to ConnectionPanel so that you can't use the constructor without parameters in AudioPlayback.
But the attribute masterModel seems hasn't been called in your ConnectionPanel so that you can roughly use the following code:
// Notice! Don't do this in your production enviroment. It's only for test otherwise you can make sure that you can give the null value to it.
ConnectionPanel panle = new ConnectionPanel(null);
System.out.println(panel.getEncryptionKey());
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 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 am currently working on a Swing Applet, and am having issues referencing my custom AWT Canvas component (very simple extended class) in other class functions, such as with any other component (i.e. button) normally created with Netbean (7.0)'s designer.
My custom canvas element I add here, I was sure this would be the appropriate place (especially after all other generated components were just created in the same area)
public void init() {
try {
java.awt.EventQueue.invokeAndWait(new Runnable() {
public void run() {
initComponents();
CustomCanvas myCan = new CustomCanvas();
myCan.setBounds(100, 100, 200, 200);
getContentPane().add(myCan);
...
However, unlike the generated components, I cannot access them by name and cannot seem to access them through other means (this.myCan) either. I have set up a sample function that will handle a (generated) button on the Swing form to manipulate the previously instantiated myCan component:
private void btnManipCanvasActionPerformed(java.awt.event.ActionEvent evt) {
//Essentially Was wanting to call something here such as myCan.getGraphics().setRect...
}
Do you know of a way to access myCan there? Am I supposed to place custom initializations of components in a different area so they can be publicly accessed?
Just make the canvas an instance variable, as (I guess) all the other components created by the Netbeans designer:
private CustomCanvas myCan;
public void init() {
try {
java.awt.EventQueue.invokeAndWait(new Runnable() {
public void run() {
initComponents();
myCan = new CustomCanvas();
myCan.setBounds(100, 100, 200, 200);
getContentPane().add(myCan);
// ...
there are possible issues or painting lacks because you probably mixing ATW Components with Swing JComponets,
if there nothing special that came from OpenGL, then look for JPanel instead of AWT Canvas and for all panting in Swing redirect everythigns to JLabel
please read how LayoutManagers works to avoids setBounds(int, int, int, int);