Develop Reference

How add a jtextfield to a jpanel that has paint component?

I'm making a game and I want to add a JTextField to a JPanel that has Paint Component. I repaint the JPanel every 16 milliseconds.
I add() the textfield to the panel but it show up only for a single frame when i click on it.
Then I tried to repaint() the textfield but now it is flashing.
public class Screen extends JPanel {
public Screen() {
JTextField txt = new JTextField();
txt.setBounds(10, 10, 300, 50);
this.add(txt);
}
#Override
public void paint(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
g2D.setColor(Color.BLACK);
g2D.fillRect(0, 0, this.getWidth(), this.getHeight());
g2D.setColor(Color.WHITE);
g2D.fillRect(0, 0, this.getWidth(), 20);
txt.repaint();
}
}
I want to show the textfield on the top of the panel

JTextField txt = new JTextField();
When you create a JTextField you should use code like:
JTextField txt = new JTextField(10);
Now the text field can calculate its own preferred size.
//txt.setBounds(10, 10, 300, 50);
Don't use setBounds() to give a component a size. Again each Swing component is responsible for determining its own preferred size. Then the layout manager will set the size/location of the component on the panel.
//public void paint(Graphics g) {
public void paintComponent(Graphics g)
{
super.paintComponent(g);
// add custom painting here
}
Don't override paint(). Custom painting is done by overriding the paintComponent() method. And the first statement in the method should be super.paintComopnent(g)
//g2D.setColor(Color.BLACK);
//g2D.fillRect(0, 0, this.getWidth(), this.getHeight());
Don't paint the background of the panel. That is the job of the panel and that is why you need to super.paintComponent(), to make sure the background is painted.
Then in the constructor of your JPanel class you simply use setBackground( Color.BLACK )
//txt.repaint();
Don't ever invoke repaint() on any component in a painting method.
Read the section from the Swing tutorial on Custom Painting for working examples to get you started. Use the demo code as the starting point for you program. Then you simply add a JTextField to the panel, so it will be a single line of code that is needed to display the text field.

It seems like you want to have a JTextField on a black panel. You don't need to set the colour of the panel every time in paint() method. Instead add this to the constructor:
public Screen() {
setOpaque(true);
setBackground(Color.BLACK);
//...
}
and remove paint() method.
Also, if you want to use absolute positioning with setBounds() method then you should set the layout to null setLayout(null) in constructor. If you use absolute positioning you will also need to specify the size of the panel explicitly. However, I would still suggest you use a layout manager that takes care of panel sizing as well.
See this post for more information about absolute positioning.

Issue on label and panel's transparency

Here there is my frame:
As you can see, there are some components (JLabel, JPanel, JTable, JScrollPane) on which I called the metod setBackgroundColor(new Color(r, g, b, a)).
At each update of the frame, these components show new "shadows" of other components of the frame.
How can I eliminate these "shadows"?

At each update of the frame, these components show new "shadows" of other components of the frame
Swing does not support semi transparent colors correctly since Swing expects components to be either fully opaque or fully transparent.
Therefore you need to make sure the parent component is painted first to reset the background and then manually paint the background of the component:
JPanel panel = new JPanel()
{
protected void paintComponent(Graphics g)
{
g.setColor( getBackground() );
g.fillRect(0, 0, getWidth(), getHeight());
super.paintComponent(g);
}
};
panel.setOpaque(false); // background of parent will be painted first
panel.setBackground( new Color(255, 0, 0, 20) );
frame.add(panel);
See Backgrounds With Transparency for more information and a reusable class that will do this painting for you.

Strange repositioning using repaint();

I have a JSlider in a JPanel that return me a value of R-G-B .
I create it, in the Costructor of JPanel. I draw in same Panel (using paintComponent) a little circle, and I change his color using the Slider. I want that the color change in contemporany of slider shift.
So, i use the method repaint.. Next to Panel there is another Panel, with two button.. If I use method repaint in first panel , the buttons of second panel duplicated in the topLeft of First Panel. Why? Thank's you.
First Panel:
public class OptionsPanel extends JPanel {
static JSlider RBG = new JSlider(0,255);
OptionsPanel(){
this.setVisible(false);
this.setSize(350,1000);
this.setLayout(null);
this.setBackground(new Color(200,200,0));
Main.f1.add(this);
RBG.setVisible(true);
RBG.setSize(255,50);
RBG.setLocation(30,240);
this.add(RBG);
LotL lotl = new LotL();
Button save = new Button("Save");
save.setVisible(true);
save.setSize(100,40);
save.setLayout(null);
save.setLocation(60,300);
save.addActionListener(lotl);
save.setBackground(Color.yellow);
save.identificatore=3;
this.add(save);
}
boolean draw=false;
#Override
public void paintComponent(Graphics g){
g.drawOval(50,100,70,70);
g.setColor(new Color(RBG.getValue(),180,200));
g.fillOval(50,100,70,70);
repaint();
}
}
Second Panel:
public class FirstPanel extends JPanel{
FirstPanel(){
this.setVisible(true);
this.setSize(1000,1000);
this.setLayout(null);
this.setBackground(new Color(255,200,180));
Main.f1.add(this);
Button start = new Button("Start Game!");
Button options = new Button("Options");
LotL LotL = new LotL();
start.setVisible(true);
start.setSize(200,80);
start.setLayout(null);
start.setLocation(400,450);
start.addActionListener(LotL);
start.setBackground(Color.green);
start.identificatore=1;
this.add(start);
options.setVisible(true);
options.setSize(200,70);
options.setLayout(null);
options.setLocation(400,550);
options.addActionListener(LotL);
options.setBackground(Color.green);
options.identificatore=2;
this.add(options);
}
}

You've broken the paint chain...
#Override
public void paintComponent(Graphics g){
g.drawOval(50,100,70,70);
g.setColor(new Color(RBG.getValue(),180,200));
g.fillOval(50,100,70,70);
repaint();
}
Graphics is a shared resource, which gets passed to ALL the components that are painted during a given paint cycle.
One of the jobs of paintComponent is to prepare the Graphics context for painting, but filling with the components background color.
You MUST call super.paintComponent before performing any custom painting.
#Override
protected void paintComponent(Graphics g){
super.paintComponent(g);
g.drawOval(50,100,70,70);
g.setColor(new Color(RBG.getValue(),180,200));
g.fillOval(50,100,70,70);
}
Also, there is never any need for paintComponent to be public, no one should ever be calling directly and NEVER modify the state of a component from within any paint method which may trigger a repaint, you will get yourself into a infinite loop which will eventually consume your CPU and make you computer unusable.
Take a look at Painting in AWT and Swing and Performing Custom Painting for more details
You should also avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify

Scrolls not appears

I want add JScrolpane to JPanel, but that not appears. In JLabel works fine and its very easy. I am using JPanel beacuse I'll add some image proccessing stuff to my program. There is my code:
public void draw(){
panel=new JPanel(){
protected void paintComponent(Graphics g){
Graphics g2 = g.create();
g2.drawImage(image, 0, 0, this);
g2.dispose();
}
};
panel.setBorder(BorderFactory.createEtchedBorder());
panel.setPreferredSize(new Dimension(400, 330));
s=new JScrollPane(panel);
s.setPreferredSize(new Dimension(400,285));
this.getContentPane().add(s,BorderLayout.CENTER);
add(panel);
revalidate();
repaint();
}

s=new JScrollPane(panel);
s.setPreferredSize(new Dimension(400,285));
this.getContentPane().add(s,BorderLayout.CENTER);
add(panel); // ****** ????????????
revalidate();
repaint();
}
You're adding the JPanel to the GUI not the JScrollPane, so you really shouldn't expect to see any scrollpanes if they've not been added anywhere.
Solution: Add your JScrollPane, s, that holds the JPanel to the GUI, not JPanel itself.

You dont honor the paint chain, call super.paintComponent(g) as first call in overridden paintComponent method. i.e
#Override
protected void paintComponent(Graphics g){
super.paintComponent(g);
//draw here
}
or visual artifacts may occur.
Also note the #Override annotation which should be used with overridden methods in order to gain the advantage of compiler checking that we overrode the method correctly.
There is no need for getContentPane().add(..) simply call add on JFrame instance as add(..) along with remove(..) and setLayout(..) have been forward to the JFrames contentPane
Also not a good idea to go extending JFrame for nor reason, simply create an instance and use that i.e:
JFrame frame=new JFrame("Title here");
...
frame.add(..);
...
frame.pack();
frame.visible(true);
Also draw onto the Graphics object passed into paintComponent g dont go creating your own in paintComponent. Unless of course you're doing if for the reason #HFOE mentioned in below comment :).
No need for this parameter in drawImage(..) unless your JPanel implements on ImageObserver or the image may not be fully loaded when painting occurs. Simply use null.
And just for the cherry on top use some Graphics2D and RenderHints as seen here. This will allow for a better quality image to be drawn and text.

I got it! The main reason for me was no-layout manager and no-declarated size of this. There is my code:
public void draw(){
panel=new JPanel(new BorderLayout()){
#Override
protected void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(img, 0, 0, null);
}
};
panel.setBounds(0, 0, img.getWidth(), img.getHeight());
panel.setPreferredSize(new Dimension(img.getWidth(),obraz.getHeight()));
JScrollPane scrolls=new JScrollPane(panel,ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
add(scrolls);
validate();
repaint();
}
But if someone will want copy this code in the future, there is one thing to be known- a size of Jpanel isn't refreshing (it's always one size of first opened image), but I have scrolsl and I am satisfied for now ;). Thanks a lot for everyone.

Turning a JFrame black when opening another window

I wan't to make my main JFrame become darken when the focus is on another window.
This is an example from the game Football Manager 2012. First the main window is selected and it looks like it should, then when it is loading, it turns darker and unselectable. I wan't to have this effects on my own application, but im not really sure how, not even sure what to google?
Im guessing its a JWindow that appears and the JFram becomes unselectable in the background. I'm planing to use it on a help-window in my application, that is a JWindow right now.

Andrew Thompson has the right idea, only it's easier to use the glass pane feature of your frame's JRootPane. Here's some working code: In your frame class, invoke
getRootPane().setGlassPane(new JComponent() {
public void paintComponent(Graphics g) {
g.setColor(new Color(0, 0, 0, 100));
g.fillRect(0, 0, getWidth(), getHeight());
super.paintComponent(g);
}
});
Then, to show the "curtain", invoke
getRootPane().getGlassPane().setVisible(true);
In the code above, change the alpha transparency value of 100 in order to find the suitable darkness.
..wan't the JFrame to go back to normal after the new window is closed. I tried setVisible(false) but it didn't work.
It works in this example.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class ShadowedFrame extends JFrame {
ShadowedFrame() {
super("Shadowed Frame");
getRootPane().setGlassPane(new JComponent() {
public void paintComponent(Graphics g) {
g.setColor(new Color(0, 0, 0, 100));
g.fillRect(0, 0, getWidth(), getHeight());
super.paintComponent(g);
}
});
JButton popDialog = new JButton("Block Frame");
popDialog.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
getRootPane().getGlassPane().setVisible(true);
JOptionPane.showMessageDialog(ShadowedFrame.this, "Shady!");
getRootPane().getGlassPane().setVisible(false);
}
});
setContentPane(popDialog);
pack();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationByPlatform(true);
setSize(350,180);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new ShadowedFrame().setVisible(true);
}
});
}
}

(Untested, but..) Seems like a good task for a JLayeredPane. Create a JComponent that is set transparent and add that to the top level of the layered pane. In the paintComponent(Graphics) method of the component, set a semi-transparent color and fill the full area with it. In normal use (non-dimmed), call customComponent.setVisible(false).
Update
Or, as Ingo pointed out, use the glass pane.
I'm guessing its a JWindow that appears and the JFrame becomes unselectable in the background
It is more likely a modal JDialog. When a modal dialog is visible, the frame/window that is the owner becomes inaccessible (cannot be clicked on).