Lecture 35





Log into Windows/ACENET. Open the Game
of Life project.
Go to the course webpage and download the
game configuration files, glider.gol, lwss.gol
and pulsar.gol, to the project folder.
Project 4 is posted, due next Friday.
Note: No class next Friday (April 15) due to
EECS senior project presentations.
Questions?
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
1
Outline

DisplayGeneration( ) method

Next button Click handler

Interesting initial configurations

Configuration files

Load and Save button Click handlers

FileDialogs and FileStreams
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
2
DisplayGeneration( )


DisplayGeneration( ) is a method that
transfers the new generation states back to the
displayed Label grid using nested for-loops for
each row and column index. It also updates the
generation count label (lblGenerationCount).
Write this method. It does not receive or return
anything. Here is its algorithm:
1. Declare and initialize rowMax to grid.GetUpperBound(0)
2. Declare and initialize colMax to grid.GetUpperBound(1)
3. Loop index row from 0 to rowMax by 1
3.1 Loop index col from 0 to colMax by 1
3.1.1 Set grid[i,j].Text to newGrid[i,j]
4. Set lblGenerationCount.Text to generationCount.ToString( )
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
3
btnNext_Click( )



The last step to a complete application is to
finish the Next button Click handler
(btnNext_Click).
This handler parses the user input in the
textboxes to get the number of generations to
simulate (n) and the time between updates (t).
A generation is simulated by calling the
ComputeGeneration( ) method followed by
calling the DisplayGeneration( ) method.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
4
btnNext_Click( )


The loop for each generation is provided, along
with the code that updates the form to display
the new generation state and the code that
pauses the application between generation
updates.
Write the calls to ComputeGeneration( ) and
DisplayGeneration( ) as indicated in the
comments.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
5
Running the Application



To simulate a generation, click the Next button.
If you want to see multiple generations for a
click, enter a number in the first textbox.
If you want the simulation of multiple
generations to go faster, enter a lower number
in the second textbox. If want it to go slower,
enter a larger number. (250 ms is 1/4 of a
second.)
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
6
Check These Out!

Here are some interesting initial configurations.
The left one is called a glider. The right one is
called a light-weight spaceship (LWSS).
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
7
Check This Out!

This one is
called a
pulsar.
Change the
first argument
to MakeGrid
to 20 to get a
big enough
grid. Be sure
to change it
back.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
8
Configuration Files



Clicking in an initial configuration each time the
program is started is tedious. We would like to
be able to read configurations in from a textfile.
In order to do so, we first define the file format
for the Game of Life application.
Each line of the text file will contain "*" (for live
cells) or " " (for dead cells). The first line will be
row 0, the second line will be row 1, etc.
Since the game grid can be of different sizes,
the dimensions of the grid also must be stored.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
9
Configuration Files

For this project, configuration files will have the
following format:



The first line will contain the row dimension, e.g., 10
The second line will contain the column dimension,
e.g., 20
The rest of the lines will be the rows of the
configuration. Each line will have at most column
dimension characters. There will be at most row
dimension lines of the configuration.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
10
Configuration Files


For example, glider.gol is the configuration file
for the glider automata example. (This file can
be opened in MSVS.) The first two lines
indicated the grid should be 10x20.
Note that although each line may have up to 20
characters and there may be up to 10 lines, the
first line is blank and there are only 4 lines in
the file. We will assume that the configuration
is not larger than the specified dimensions.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
11
Loading a Configuration

Double-click on the Load button to get its Click
handler stub. We want this handler to do the
following:




Ask the user for a filename to open via an
OpenFileDialog.
If the user clicks "Cancel", go back to waiting
Otherwise, open the configuration files, read the
dimensions, remove the old grid, and create an
appropriate sized grid
Then read the rest of lines of the file and set the
game grid accordingly.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
12
Reading from a File

In computer programs, files are accessed for
reading using the following steps:




Ask the user for a filename. In the C# GUI, this is
done using an OpenFileDialog
Using the provided filename, create a
StreamReader object and attach the file to it.
Once a file is open, reading from a file is like
reading from the console, we use the ReadLine( )
method on the StreamReader object.
When the program is done using a file, it should
close the StreamReader object.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
13
OpenFileDialog

The OpenFileDialog
GUI element is
created by the
program. A variable
is declare and the
dialog is created
using the new
operator:
OpenFileDialog fileChooser = new OpenFileDialog();
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
14
OpenFileDialog

To make the dialog pop up and get the file
name from the user, call the ShowDialog( )
method and save the result in a DialogResult
variable:
DialogResult result = fileChooser.ShowDialog();

Check if the user clicked "Cancel" and if so, go
back to waiting
// Check if user clicked Cancel
if (result == DialogResult.Cancel) return;
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
15
File Streams

A file stream is a program object that is opened
(i.e., attached to a physical file) when it is
created. StreamReader objects are used to
read data from a file:
// Open the file chosen in the dialog
StreamReader fileInput = new StreamReader (fileChooser.FileName);

First we need to read and parse the dimensions
of the configuration from the first two lines:
int newRowSize = int.Parse(fileInput.ReadLine());
int newColSize = int.Parse(fileInput.ReadLine());
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
16
Making a New Grid

To make a new grid, we have to remove the old
first, then call the MakeGrid( ) method:
int rowMax = grid.GetUpperBound(0);
int colMax = grid.GetUpperBound(1);
for (int row = 0; row <= rowMax; row++)
{
for (int col = 0; col <= colMax; col++)
{
this.Controls.Remove(grid[i,j]);
}
}
MakeGrid (newRowSize, newColSize);
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
17
Reading and Configuring Rows


The basic idea is to read the rest of the lines
from the file stream one at a time. We keep
track of which row is being configured and use
a line to set the cells in the current row.
We take advantage of two things to determine
when to stop reading in lines.


The ReadLine( ) method returns null, when it is
called after all the lines in a file have been read.
The assignment operator (=) returns the value of
the assignment.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
18
Reading and Configuring Rows
string line;
int currentRow = 0;
// Read lines one at a time until end of file
while ((line = fileInput.ReadLine()) != null)
{
// For each character in the line
for (int col = 0; col < line.Length; col++)
{
grid[currentRow, col].Text = line[col];
}
currentRow++; // go to next row
}
fileInput.Close(); // done with the file
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
19
Updating the GUI

In addition to the grid, we also need to reset the
generation count label (should really be done in
MakeGrid( )):
lblGenerationCount.Text = "0";

And finally, we need to update the form to make
it redraw itself:
this.Update();
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
20
Saving a Configuration

Double-click on the Save button to get its Click
handler stub. This handler is straightforward.
We want it to do:




Ask the user for a filename to save to via an
SaveFileDialog.
If the user clicks "Cancel", go back to waiting
Otherwise, open the file and write the row
dimension of the current grid on a line, then the
column dimension on a line
Then write a line for each row of the grid.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
21
Writing to a File

In computer programs, files are accessed for
writing using the following steps:




Ask the user for a filename. In the C# GUI, this is
done using an SaveFileDialog
Using the provided filename, create a StreamWriter
object and attach the file to it.
Once a file is open, reading from a file is like writing
to the console, we use the WriteLine( ) method on
the StreamWriter object.
It is very important to close a file that is written to so
that the (new) contents are saved to the disk.
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
22
Saving a Configuration
SaveFileDialog fileChooser = new SaveFileDialog();
DialogResult result = fileChooser.ShowDialog();
// Check if user clicked Cancel
if (result == DialogResult.Cancel) return;
// Open the file chosen in the dialog
StreamWriter fileOutput = new StreamWriter (fileChooser.FileName);
// Write dimensions
int rowMax = ...
int colMax = ...
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
23
Saving a Configuration
fileOutput.WriteLine(rowMax+1);
fileOutput.WriteLine(colMax+1);
// Create a line for each grid row and write it
for (int row = 0; row <= rowMax; row++)
{
string line = ""; // empty string
for (int col = 0; col <= colMax; col++)
{ // append cell state to line
line = line + grid[row,col].Text;
}
fileOutput.WriteLine(line); // write to file
}
fileOutput.Close(); // done with file
Friday, April 8
CS 205 Programming for the Sciences - Lecture 35
24