Clear Screen

[James Hambrick]

I have an Applet that has three buttons on it, one being a clear screen button. I have it setup right now so it draws a rectangle the size of the applet and fills it with the background color. But when it does that my other two buttons disappear until I mouse over them again. Is there a better way to clear screen or anyway for the buttons to show back up after the "clear screen"?

[Ernest Friedman-Hill]

Don't draw the rectangle over the buttons! Instead of drawing directly on the applet, pack a subclass of JPanel into the applet , and do the drawing in that JPanel's paintComponent() method.

[James Hambrick]

Sounds like a good idea, I'll just have to figure out how to do that. My book I have isn't very good. Ill research it on various websites. Thanks for the advice.

[James Hambrick]

I have created a JPanel with
JPanel jp = new JPanel();

and set the layout
jp.setLayout(new FlowLayout());

This is the only code I have added so far. Is there something I'm missing???

I'm not sure how to draw on it. I have this code which draws.

 
public void paint(Graphics g){
if("Red".equals(SetFontColor)){
g.setColor(Color.red);
g.drawLine(PmouseX,PmouseY,RmouseX,RmouseY);
PmouseX = 0;
PmouseY = 0;
RmouseX = 0;
RmouseY = 0;
}

if("Black".equals(SetFontColor)){
g.setColor(Color.black);
g.drawLine(PmouseX,PmouseY,RmouseX,RmouseY);
PmouseX = 0;
PmouseY = 0;
RmouseX = 0;
RmouseY = 0;
}

 
if(clearScreen){
g.setColor(Color.white);
g.fillRect(0,0,300,300);
clearScreen = false;
}


 
}
 

public void update (Graphics g) {
paint(g);
        
    }

[James Hambrick]

I changed the name of the method from Paint(raphics g) to paintComponent(Graphics g) along with the editions I mentioned earlier and when I click Clear Screen the Red and Black buttons do not go away, but now I cant draw on the Panel. Any ideas why?

    
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
 
/*
<Applet code = "Lines" width = 800 heigth = 800>
</Applet>
*/
 
//Lines inherits JApplet class
public class Lines extends JApplet
implements MouseListener, MouseMotionListener,ActionListener{

int pMouseX,pMouseY,rMouseX,rMouseY;
Boolean clearScreen = false;
String setFontColor;
//Color setFontColor = new java.awt.Color();

 
public void init(){

//Get content Pane
Container contentPane = getContentPane();
//set layout
contentPane.setLayout(new FlowLayout());
 
JPanel jp = new JPanel();
jp.setLayout(new FlowLayout());

//Create Buttons
JButton btnClearScreen = new JButton("Clear Screen");
JButton btnFontRed = new JButton("Red");
JButton btnFontBlack = new JButton("Black");
 

//Add listeners to buttons
btnClearScreen.addActionListener(this);
btnFontRed.addActionListener(this);
btnFontBlack.addActionListener(this);
 
//Add actioncommand to buttons
btnClearScreen.setActionCommand("Clear");
btnFontRed.setActionCommand("Red");
btnFontBlack.setActionCommand("Black");

//add mouse listeners
addMouseListener(this);
addMouseMotionListener(this);
 
//add buttons to content Pane
contentPane.add(btnClearScreen);
contentPane.add(btnFontRed);
contentPane.add(btnFontBlack);



//set background to white
contentPane.setBackground(Color.white);
//set defualt foreground color
setFontColor = "Black";



}
 

public void actionPerformed(ActionEvent evt) {
String action;
action = evt.getActionCommand();
if("Clear".equals(action)){
clearScreen = true;

}
if("Red".equals(action)){
setFontColor = "Red";
 

}
if("Black".equals(action)){
setFontColor = "Black";
}
repaint();
 


}

 
public void mouseClicked(MouseEvent me){
}
 
public void mouseEntered(MouseEvent me){
}
 
public void mouseExited(MouseEvent me){
}
 
public void mousePressed(MouseEvent me){
pMouseX = me.getX();
pMouseY = me.getY();

}
 
public void mouseReleased(MouseEvent me){
rMouseX = me.getX();
rMouseY = me.getY();
repaint();

}
 
public void mouseDragged(MouseEvent me){
}
 
public void mouseMoved(MouseEvent me){
}
 

public void paintCompenent(Graphics g){
if("Red".equals(setFontColor)){
g.setColor(Color.red);
g.drawLine(pMouseX,pMouseY,rMouseX,rMouseY);
//pMouseX = 0;
//pMouseY = 0;
//rMouseX = 0;
//rMouseY = 0;
}

if("Black".equals(setFontColor)){
g.setColor(Color.black);
g.drawLine(pMouseX,pMouseY,rMouseX,rMouseY);
//pMouseX = 0;
//pMouseY = 0;
//rMouseX = 0;
//rMouseY = 0;
}

 
if(clearScreen){
g.setColor(Color.white);
g.fillRect(0,0,300,300);
clearScreen = false;

}


 
}
 

public void update (Graphics g) {
paint(g);
        
    }
}
 

 

 

 

[Ernest Friedman-Hill]

If you override paintComponent(), you MUST start off by calling super.paintComponent(). !

[James Hambrick]

I was told to
"do the drawing in that JPanel's paintComponent() method" so I thought that is what I did. I dont have any examples of this so im kinda taking a shot in the dark when trying to implement the suggestions I get. If I call super.paintComponent() then I get an erros that says cannot find symbol.

[James Hambrick]

I think when I get home I will design this in NetBeans and see what it looks like. Even Sun's tutorial is not enough for me. Im using a content Pane and in Suns tutorials they are using Frames.

[kunu patel]

James Hambrick wrote:I have created a JPanel with
JPanel jp = new JPanel();

and set the layout
jp.setLayout(new FlowLayout());

This is the only code I have added so far. Is there something I'm missing???

I'm not sure how to draw on it. I have this code which draws.

 
public void paint(Graphics g){
if("Red".equals(SetFontColor)){
g.setColor(Color.red);
g.drawLine(PmouseX,PmouseY,RmouseX,RmouseY);
PmouseX = 0;
PmouseY = 0;
RmouseX = 0;
RmouseY = 0;
}

if("Black".equals(SetFontColor)){
g.setColor(Color.black);
g.drawLine(PmouseX,PmouseY,RmouseX,RmouseY);
PmouseX = 0;
PmouseY = 0;
RmouseX = 0;
RmouseY = 0;
}

 
if(clearScreen){
g.setColor(Color.white);
g.fillRect(0,0,300,300);
clearScreen = false;
}


 
}
 

public void update (Graphics g) {
paint(g);
        
    }

can you give full code for this clear screen applet ,...so i easily understand..