🚀 go-pugleaf

On Sun, 31 Dec 2000 08:07:40 -0600, James A. Schulz wrote:

> My table is fairly big, 55x25).  I want to initialize all the
> cells to hold the same (blank) character, but I certainly don't
> want to write out those vectors.  

> I tried using a for loop in the context to a custom tablemodel
> declaration, like this:
> 
>   TableModel tm = new AbstractTableModel() {
>     PcCharacter[][] data =
>       {{blankPcCharacter,blankPcCharacter,blankPcCharacter},
>        {blankPcCharacter,blankPcCharacter,blankPcCharacter}};
    :
>     for (i = 0;i < 2;i++){
>       for(ii=0;ii<3;ii++){
>         data[i][ii] = blankPcCharacter
>       }
>     }
>   };
> 
> but the compiler doesn't like thiis.  How do I use for loops
> to initialize my table:

I can see two things that would cause the compiler to object.  First, 
you reference "blankPcCharacter", but I do not see a declaration for 
it.  Second, the statement "data[i][ii] = ..." does not end in a 
semicolon.

What your code does is declare the table with an initializer, which 
would assign values to your table, and then replace the values in the 
loop below.  There should be no need to provide an initializer if you 
are going to redo this in the loop.

The code below is close to what you want, but you have to realize how 
multiple dimension arrays work in Java.  Actually there is no such 
thing as a multiple dimension array;  instead, you have use an array of 
arrays.

If you declare an array of objects, it will be initialized to all null 
references, so you have to allocate objects and store the references in 
the array.  Given the following code:

    PcCharacter[][] data;

This declares a reference to an array of (array of PcCharacter) which 
is initialized to null.  You can initialize it with:

    PcCharacter[][] data = new PcCharacter[25][];

Now you have an array of 25 references to (array of PcCharacter), but 
each of those 25 references will be null, so you must initialize each 
of those arrays as well.

    PcCharacter[][] data = new PcCharacter[25][];
    for ( int i = 0;  i < 25;  ++ i ) {
        data[i] = new PcCharacter[80];
    }

Now you have an array of 25 references to arrays of 80 references to 
PcCharacter.  But the references to PcCharacter are null.  So you can 
initialize those with:

    PcCharacter[][] data = new PcCharacter[25][];
    for ( int i = 0;  i < 25;  ++ i ) {
        data[i] = new PcCharacter[55];
        for ( int j = 0;  j < 55;  ++ j ) {
            data[i][j] = blankPcCharacter;
        }
    }

Now you have a 55 x 25 array of references to PcCharacter, but note 
that they all reference the *same* PcCharacter object.  If you change 
the PcCharacter in one cell, it will change the PcCharacters in all 
cells, since they are all the same PcCharacter.  So you may want to 
change this code to read:

            data[i][j] = new PcCharacter();

But instead of doing that, you could leave the values null, and just 
make sure the rest of your code treats the null value as meaning empty.  
So your renderer would change as follows:

      if ( c != null ) {
         setForeground(c.getForeground());
         setBackground(c.getBackground());
      } else {
         setForeground(DEFAULT_FOREGROUND);
         setBackground(DEFAULT_BACKGROUND);
      }

Depending on how sparse your table is, that could save allocating a lot 
of objects.


> Also, you will note a call to repaint() in my tablemodel
> declaration (above).  With out this setValueAt does not
> paint the cell, my question is about whether this call to
> repaint() is the best, most efficient way to handle this.

No.  You are repainting the entire table when any cell changes.  The 
cell is not repainted because you have not informed the JTable that it 
has changed.  There are a number for fireXXX() methods provided by 
AbstractTableModel for informing listeners of changes.  For a single 
cell change, the way to do this is:

    fireTableCellUpdated( row, column );

-- 
Regards,

John McGrath [TeamB]

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