Ok, so I know it has been a long time since a post, but it has been really busy with work and family. I have been busy coding and learning lots of new stuff. I work with a great bunch of developers and my current team lead is a great mentor.
Well for the new year the wife and I decided to get back into shape. I started hitting the gym and so did she but she is also doing weight watchers with a friend. One of the things they do is they have to calculate points on a daily basis. These points are comprised of calories, fat and fiber. There is a formula for these three which in turn results in the number of points a particular item is. A few months ago I convinced the wife to get a windows mobile device (woo hoo!) and she is a good power user. So one night she asks me, “Is there a way I can just enter in the calories, fat and fiber on my phone and it tell me how many points something is?”. I did some searching and there are numerous online versions of the calculator but no native ones for windows mobile. I found the formula here, and started to get to work.
I wanted to approach this application using the MVP design pattern. I know it may be overkill for this simple of an application but I thought it would be good practice.
I started with the interface for the data model, in this case it would be the main caloric properties of food.
namespace WWPC.Common.Interfaces
{
public interface IFoodModel
{
int Fiber { get; set; }
int Calories { get; set; }
float Fat { get; set; }
int Points { get; set; }
int CalculatePoints();
}
}
I then wrote up the interface for the view for the model.
namespace WWPC.Common.Interfaces
{
public interface IFoodCalcView
{
int Calories { get; }
int Fiber { get; }
float Fat { get; }
int Points { set; }
event EventHandler DataChanged;
}
}
Next, came the interface for the presenter.
public interface IFoodCalcPresenter
{
void OnCalculatePoints();
}
Ok, now that I got my main interfaces in place, time to code up the implementation. I started with the model first since this was the class that would provide the implementation for calculating the caloric points. Using the formula mentioned above, the CalculatePoints() method came out like so:
public int CalculatePoints()
{
var calories = Convert.ToDecimal(Calories);
var cal = calories / 50;
var totalFat = Convert.ToDecimal(Fat);
var fat = totalFat / 12;
var fiber = Convert.ToDecimal(Fiber);
return Points = Convert.ToInt32(Math.Round(cal + fat - (fiber/5), 0));
}
With the model complete, I then moved to the presenter. The presenter would be responsible for binding the model to the view responding to the data changes in the view and rebinding those changes to the model. I made the presenter with an overloaded constructor to take a view and a model. The presenter then binds to the data changed event on the view which enables the presenter to update the model from the view. The OnCalculatePoints() method will update the view with the points value after using the model for calculation.
namespace WWPC.Common
{
public class FoodPresenter : IFoodCalcPresenter
{
private readonly IFoodCalcView _View;
private readonly IFoodModel _Model;
public FoodPresenter(IFoodCalcView view, IFoodModel model)
{
_View = view;
_View.DataChanged += new EventHandler(_View_DataChanged);
_Model = model;
}
void _View_DataChanged(object sender, EventArgs e)
{
SetModelFromView();
}
private void SetModelFromView()
{
_Model.Calories = _View.Calories;
_Model.Fat = _View.Fat;
_Model.Fiber = _View.Fiber;
}
#region IFoodCalcPresenter Members
public void OnCalculatePoints()
{
_View.Points = _Model.CalculatePoints();
}
#endregion
}
}
With the presenter done it was time to implement the view. I wanted a simple mobile form where you can enter in data quickly and then calculate the results. I initially tried using a label to display the result, but did not like it. I then tried a mobile gauge control, but that took up too much space on the small screen. Finally I decided to use the notification class for windows mobile. I did not use the managed wrapper version, I used the the version created by Christopher Fairbairn, found here. This version has an awesome implementation which exposes many features of the notification class. I wanted to give the user the ability to dismiss the notification when they were done reading the results. Also using the notification class the UI was able show the needed text boxes for entry and the SIP panel along with the results without needing to scroll the screen. Here is a screen shot of the main form.
Now with the controls in place on the form, I can implement the view. The form creates a new presenter and passed into it a new model during construction. When the calculate menu option is clicked the main form raises the data changed event then calls the OnCalculateMethod on the presenter. When the presenter binds the model to the view, during the set of the points value, the notification is shown to the user via the ShowNotification method.
namespace WWPC.Calc
{
public partial class WWPCalculator : Form, IFoodCalcView
{
private readonly FoodPresenter _Presenter;
private NotificationWithSoftKeys _Notification;
public WWPCalculator()
{
InitializeComponent();
_Presenter = new FoodPresenter(this,new FoodModel());
}
public int Calories
{
get { return (string.IsNullOrEmpty(txtCalories.Text)) ? 0 :
Int32.Parse(txtCalories.Text); }
}
public int Fiber
{
get { return (cmbFiber.Text == "4 or more") ? 4 :
(string.IsNullOrEmpty(cmbFiber.Text)) ? 0 :Int32.Parse(cmbFiber.Text); }
}
public float Fat
{
get { return (string.IsNullOrEmpty(txtFat.Text)) ? 0 : float.Parse(txtFat.Text); }
}
public int Points
{
set
{
ShowPointsNotification(value);
}
}
public event EventHandler DataChanged;
private void mnuExit_Click(object sender, EventArgs e)
{
this.Close();
}
private void mnuCalculate_Click(object sender, EventArgs e)
{
if (DataChanged != null)
this.DataChanged(sender, e);
_Presenter.OnCalculatePoints();
}
private void mnuClear_Click(object sender, EventArgs e)
{
txtCalories.Text = string.Empty;
txtFat.Text = string.Empty;
cmbFiber.Text = "0";
}
private void ShowPointsNotification(int points)
{
_Notification = new NotificationWithSoftKeys
{
Text = String.Format("Total Points:{0}", points),
Caption = "Weight Watchers Point Calculator",
RightSoftKey = new NotificationSoftKey(SoftKeyType.Dismiss, "Dismiss"),
};
_Notification.RightSoftKeyClick+=new EventHandler(_Notification_RightSoftKeyClick);
_Notification.Visible = true;
}
void _Notification_RightSoftKeyClick(object sender, EventArgs e)
{
if (_Notification == null) return;
_Notification.Visible = false;
_Notification = null;
}
}
}
Now, when it is all put together, it looks like so.
Below is a link to the source code. The project was done using Visual Studio 2008 against the windows mobile 5 sdk. It will also work against windows mobile 6 sdk, I just chose version 5 since that is the common sdk. Thanks for reading!!