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how to add a two dimension array JTextField to a JPanel?

Posted on 2003-11-13
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Last Modified: 2012-08-13
Hi, I'm writing an assignment which is almost the same as the little game "Master Mind".
I'm supposed to design a text field which contains 10 rows and 6 columns for users to input their guess (in my case, different kinds of colors), and there's a "OK" botton at the end of each row.
In order to make the checking job easier, I used "static JTextField[][] input_color = new JTextField[10][6]". and I wrote sth as follows:
public testFrame () {
        trial.setLayout(new GridLayout(10, 6));
        for(int i = 0; i < 10; i ++)
          for(int j = 0; j < 6; j ++){
            trial.add(input_color[i][j]);        
        }
}
It compiled well, but the problem came when running it. The error message said "Exception in thread "main" java.lang.NullPointerException".
How should I deal with it? What's the right way to add this stuff to the panel?
Thanks!!!
 
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Question by:Valley617
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3 Comments
 
LVL 7

Accepted Solution

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Igor Bazarny earned 20 total points
ID: 9741036
You have to initialize each row with new array and each entry with new JTextField():
for(int i = 0; i < 10; i ++){
    input_color[i] = new JTextField[6];
    for(int j = 0; j < 6; j ++){
        input_color[i][j] = new JTextField();        
    }
}
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Author Comment

by:Valley617
ID: 9741430
Yup!! Thanks!!
btw, can I simply use "input_color[i].setEditable(false)" to make every element in that row is non-editable?
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LVL 7

Expert Comment

by:Igor Bazarny
ID: 9747030
Same 2-dimentional loop with input_color[i][j].setEditable(false), after you have input_color elements initialized.
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