Shifting of Focus in Applet

Member

Updated: Oct 27, 2024

Views: 1.7K

Hello!!

Below is the code of an applet where i have mapped the directional keys to increase and decrease the radius of an oval.

The applet is running well but whenever i am adding any component like textbox,button or label the key events under which the radius is changed are not working and hence oval radius is not changing.Any Solution ?

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import java.applet.*;
/*
<applet code=a.class align=right width=800 height=800>
</applet>
*/
public class a extends Applet
implements KeyListener
{
   
    int X=20,Y=30,xr=100,xy=100,r=70,r1=r,ix=200,iy=200,i;
    Image image;
    AudioClip audio;
    String msg="key pressed";
    TextField t;
    Button b;
    public void init()
    {
       
        //requestFocusInWindow();
        //setLayout(null);
        addKeyListener(this);
       
        //requestFocus();
        setBackground(Color.green);
        setForeground(Color.blue);
        image = getImage(getDocumentBase(), "image22.jpg");
        audio = getAudioClip(getDocumentBase(), "chicken.au");
        /*t=new TextField();
        add(t);
        t.setBounds(500, 500, 100, 100);
        b= new Button();
        add(b);*/
     
     
    }
   
   
   
   
    public void keyPressed(KeyEvent k)
    {
         
        showStatus("KeyDown");
        int key=k.getKeyCode();
        switch(key)
        {
            case KeyEvent.VK_UP:
                //showStatus("Move to Up");
               
               
                audio.play();
                msg = msg + "<up arrow>";
                r=r+6;
                iy++;
                break;
            case KeyEvent.VK_DOWN:
                //showStatus("Move to Down");
               
                audio.play();
                msg += "<DOWN arrow>";
                r=r-6;
                iy--;
                break;
            case KeyEvent.VK_RIGHT:
                //showStatus("Move to Down");
                //msg += "<DOWN arrow>";
               
                ix++;
                break;
            case KeyEvent.VK_LEFT:
               
                //showStatus("Move to Down");
                //msg += "<DOWN arrow>";
                ix--;
                break;
           
        }
        repaint();
    }
   
   
    public void keyReleased(KeyEvent k)
    {
        requestFocusInWindow();     
        //audio.stop();
        showStatus("Key Up");
    }
    public void keyTyped(KeyEvent k)
    {
        requestFocusInWindow();     
        //t.setFocusable(false);
    }
    public void paint(Graphics g)
    {
        //g.drawString(msg,X,Y);
        // g.drawOval(xr-(r/2), xr-(r/2), r, r);
       
        g.drawImage(image, ix, iy, this);
        g.fillOval(xr-(r/2), xr-(r/2), r, r);
        g.drawOval(xr-(r1/2+5), xr-(r1/2+5), r1+10, r1+10);
       
       
                 
    }
 
}

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Replies

Rohanz21

Member • Sep 20, 2012

Here's the code after adding components and here the keyPressed method is not working.

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import java.applet.*;
/*
<applet code=a.class align=right width=800 height=800>
</applet>
*/
public class a extends Applet
implements KeyListener
{
   
    int X=20,Y=30,xr=100,xy=100,r=70,r1=r,ix=200,iy=200,i;
    Image image;
    AudioClip audio;
    String msg="key pressed";
    TextField t;
    Button b;
    public void init()
    {
       
        //requestFocusInWindow();
        //setLayout(null);
        addKeyListener(this);
       
        //requestFocus();
        setBackground(Color.green);
        setForeground(Color.blue);
        image = getImage(getDocumentBase(), "image22.jpg");
        audio = getAudioClip(getDocumentBase(), "chicken.au");
        t=new TextField();
        add(t);
        t.setBounds(500, 500, 100, 100);
        b= new Button();
        add(b);
     
     
    }
   
   
   
   
    public void keyPressed(KeyEvent k)
    {
         
        showStatus("KeyDown");
        int key=k.getKeyCode();
        switch(key)
        {
            case KeyEvent.VK_UP:
                //showStatus("Move to Up");
               
               
                audio.play();
                msg = msg + "<up arrow>";
                r=r+6;
                iy++;
                break;
            case KeyEvent.VK_DOWN:
                //showStatus("Move to Down");
               
                audio.play();
                msg += "<DOWN arrow>";
                r=r-6;
                iy--;
                break;
            case KeyEvent.VK_RIGHT:
                //showStatus("Move to Down");
                //msg += "<DOWN arrow>";
               
                ix++;
                break;
            case KeyEvent.VK_LEFT:
               
                //showStatus("Move to Down");
                //msg += "<DOWN arrow>";
                ix--;
                break;
           
        }
        repaint();
    }
   
   
    public void keyReleased(KeyEvent k)
    {
        requestFocusInWindow();     
        //audio.stop();
        showStatus("Key Up");
    }
    public void keyTyped(KeyEvent k)
    {
        requestFocusInWindow();     
        //t.setFocusable(false);
    }
    public void paint(Graphics g)
    {
        //g.drawString(msg,X,Y);
        // g.drawOval(xr-(r/2), xr-(r/2), r, r);
       
        g.drawImage(image, ix, iy, this);
        g.fillOval(xr-(r/2), xr-(r/2), r, r);
        g.drawOval(xr-(r1/2+5), xr-(r1/2+5), r1+10, r1+10);
       
       
                 
    }
 
}

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xero

Member • Sep 20, 2012

its just a matter of focus; when you don't have any components added in the applet the focus is applet itself, thus, the applet responds to the keylisteners as you have implemented. Now, once you add widgets like textbox. button etc. the focus shifts to either of these components, the focus either goes to textbox or button, but not the applet, thus the failing of keylisteners.

If you want the keylisteners to work at all times then you have register the components to keylistener.
t.addKeyListener(this);
b.addKeyListener(this);

If you want the keylisteners to work only while focusing on applet
this.setFocusable(true),
This will also enable the applet to include itself during tabbed focusing.

Let me know in case you have any questions.

Regards.

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Rohanz21

Member • Sep 22, 2012

Thanks a lot xero for the help.

Yes the trouble was that i couldn't find a way to shift the focus on the applet like in case of components whom i could focus by using the component name with dot operator using the requestFocus() or requestFocusInWindow() methods.

Your second method solved the problem.

Thanks again!!

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xero

Member • Sep 23, 2012

welcome 😀

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