Why do JFrames make java components indiscernible?

In general, the problems you are facing are because Swing uses Layout Managers to position components within their parent containers. Check the tutorials within this link...

http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html

public controlFrame() {
            
            this.setSize(900, 600);
            this.setBackground(Color.PINK);
            
            this.setVisible(true);
            textarea = new JTextArea();
           textarea.setSize(500, 100);
            textarea.setLocation(100, 100);
            textarea.setText("Text Area");
            
            textarea.setVisible(true);
            add(textarea);
	    this.pack();
 

	
            
      }

Select allOpen in new window

In general, the problems you are facing are because Swing uses Layout Managers to position components within their parent containers.

Yes, but of course AWT is no different in that respect. Layout manages are AWT

Now, it seems that once I have instantiated the frame, it vanishes. I added Sleeps around to help lengthen the time of the program before it ends. The frame still vanishes, at once!
Is the layout manager system simple?
It creates a textArea out of the frame, over in the top left corner in its own window, not added inside the frame! ! ?


import java.awt.Color;

import javax.swing.*;


public class controlFrame extends JFrame {
      
      JTextArea textarea;
      
      
      
      public controlFrame() {
            
            this.setSize(900, 600);
            this.setBackground(Color.PINK);
            
            this.setVisible(true);
            textarea = new JTextArea();
            textarea.setSize(200, 80);
            textarea.setLocation(100, 100);
            textarea.setText("Text Area");
            
            textarea.setVisible(true);
            add(textarea);
            this.pack();
            
            try {
                  Thread.sleep(5000);
            } catch (InterruptedException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
            }
            
      }

      
      
      public static void main(String[] args) {
            
            JFrame f = new controlFrame();

            System.out.println("After new controlframe");
            try {
                  Thread.sleep(15000);
            } catch (InterruptedException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
            }

            
            
      }
}

Your ctor isn't making a lot of sense at the moment. This makes a bit more:

    public controlFrame() {
        setSize(900, 600);
        setBackground(Color.PINK);

        textarea = new JTextArea();
        textarea.setText("Text Area");

        add(textarea);
        setVisible(true);

        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

Select allOpen in new window

Though i'm not sure what the sleeping is about

The sleep is to try and make the JVM stay alive long enough, so that it doesn't let the frame disappear.
Does the frame die because it has no listeners?
Thx

The sleeps() don't do anything, except delay your disappointment.

A JFrame will stay resident until you either stop the JVM or close the window by calling the static JFrame dispose.

Good, thanks

THis works. The window stays alive, but the pink background is all covered by the blue textArea. The textArea cant seem to be resized. It explodes, no matter what. Also, pack() seemed to be responsible for shrinking the window. If I take it out, the window is permanent and the right size, but all blue.
?

      public controlFrame() {
            
            this.setSize(900, 600);
            this.setBackground(Color.PINK);
            
            textarea= new JTextArea();
            textarea.setBackground(Color.BLUE);
            textarea.setSize(200, 140);
            add(textarea);
            textarea.setText("setText");
            
            this.setVisible(true);
            }

Also, pack() seemed to be responsible for shrinking the window.

That's because your complaint was the fact that nothing fitted.

Back to the main point :

import java.awt.Color;
import javax.swing.*;
import java.awt.BorderLayout;

public class controlFrame extends JFrame {
      
      JTextArea textarea;
            
      public controlFrame() {
            
this.setLayout(new BorderLayout());

            this.setSize(700, 400);
           // this.setBackground(Color.PINK);
this.getContentPane().setBackground(Color.PINK);
	this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
            
            this.setVisible(true);
            textarea = new JTextArea();
	this.getContentPane().add(textarea,BorderLayout.NORTH);
           textarea.setSize(500, 100);
           // textarea.setLocation(100, 100);
            textarea.setText("Text Area");
            this.setVisible(true);
            //textarea.setVisible(true);
            
	 

	
            
      }
      public static void main(String[] args) {
            
           controlFrame f =  new controlFrame();

		                        
      }
}

Select allOpen in new window

THis works. The window stays alive, but the pink background is all covered by the blue textArea. The textArea cant seem to be resized. It explodes, no matter what.

Because the frame uses a BorderLayout by default. If there is one component added, it's added BorderLayout.CENTER. That sizes the component to the whole available window area. Calling setSize on the added component is ignored.

Also, pack() seemed to be responsible for shrinking the window.

It sizes a window just large enough to accommodate the preferred size of its children, and no larger.

If I take it out, the window is permanent and the right size, but all blue.

See first paragraph above

So, if I'd like specific sizes, positioning for my textFields and labels for aesthetic needs, I can't place them at x,y, with xSize , ySize ?

I'm sure I could once design a frame precisely. Was that only AWT

?
Thanks

You can use a GridBagLayout to obtain the finest control.

It looks like (null) was the correct answer!

Thanks

:)