drawString method doesn't work

Question

I have a JPanel object of which I'm using it as a canvas to draw rectangular shapes and call updateString(String c, int x, int) method to draw a String c whenever I call that method in my main.

I also have local variable called private Graphics page; on the top of my code. Here's updateString() method:

public void updateString(String c, int ind1, int ind2)
{
    for( int i = 0; i < Math.pow(DIMENSION, 2); i++ )
        if( grid[i].contains(new Point(ind1, ind2)))
        {
            page.drawString( c, (int) grid[i].getCenterX(), (int) grid[i].getCenterY());
            repaint();
            return;
        }
}

grid[] is my Rectangle objects' array to store the data of the Rectangle objects and I actually draw them inside my paintComponent() method.

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    page = g;
    for( int i = 0; i < Math.pow(DIMENSION, 2); i++ )
    {
        g.drawRect(grid[i].x, grid[i].y, grid[i].width, grid[i].height);
    }
}

the point that I couldn't understand is why whenever I call the updateString() method, it just doesn't update and put the String in the middle of the rectangle that I initially drew?

Thank you.

Hovercraft Full Of Eels · Accepted Answer · 2015-04-03T12:05:02.090

4

This is very very wrong:

page = g;

You don't want to save the Graphics object to a field since this object is not long-lasting and this will lead to graphics failures, or NPE's or worse.

Instead either

Do your drawing directly in your paintComponent method. This can be done by say creating an List<String> and storing your Strings to this List, then iterating through the List inside of paintComponent, drawing each line.
Or draw in a BufferedImage, which is then drawn in the paintComponent method.
Or put your text in some text component such as a JLabel or JTextArea.

edited Apr 03 '15 at 12:05

answered Apr 03 '15 at 12:00

Hovercraft Full Of Eels

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Aha so It just terminates itself when the method is over. But is there any way to do that drawing inside another method? – Burak. Apr 03 '15 at 12:03
@VerumInfiniti: Why not just put a JLabel in the middle and set its text? – Hovercraft Full Of Eels Apr 03 '15 at 12:05
Because my assignment was telling me so, anyway, I will do it in your way. I have considered before it, however, couldn't be sure because I thought that there must be a way to do this easy drawString thing. – Burak. Apr 03 '15 at 12:08
@VerumInfiniti: Please edit your question and show *all* requirements, especially those that pertain to your problem. A few images of what you're trying to create might help as well as more detail on the problem itself. – Hovercraft Full Of Eels Apr 03 '15 at 12:09

drawString method doesn't work

1 Answers1