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Creating a Smart Clip Calendar Control in Flash

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Smart Clips are a fantastic time-saving feature of Flash 5 that allow you to create reusable components that you can tailor to different situations. In this article, David Emberton walks you through the creation of a Smart Clip Calendar Control and its implementation as part of a fictional diary.
This article is derived from the book Flash 5 Magic (New Riders, 2001), by David J. Emberton and J. Scott Hamlin.
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Smart Clips are a fantastic time-saving feature of Flash 5. They allow you to create what's known as parameterized content—in other words, reusable components that you can quickly tailor to any number of different situations. Smart Clips differ from regular movie clips because each instance of a Smart Clip can be configured differently by setting its parameters—hence the term parameterized.

This article deals with the creation of a Smart Clip calendar control and its implementation as part of a fictional diary (see Figure 1). The Smart Clip has a fairly generic function: to allow the user to select a particular date so that it can be inserted into the movie and then customized using a special custom UI (or user interface) that is actually built in Flash!

Once you've mastered this technique, you'll be able to create any number of Smart Clips of your own, complete with attractive Flash-based interfaces. You can then use these at your workplace, distribute them free, or even sell them to other Flash developers. Because Smart Clips are so flexible, you'll find that it's easier than ever to build modular, reusable Flash components.

Figure 1 A look at the finished product.

Scripting the Calendar

The calendar control begins its life as an ordinary movie clip symbol. It's actually constructed fairly simply, as a grid of text fields that are filled with numbers depending on the month and year currently being displayed. The fields and buttons have all been laid out for you, so the following steps concentrate on the ActionScript code that makes the calendar work:

  1. Download the source file archive, open the unzipped MegansDiary_start.fla file, and save it to your hard drive. The final file is MegansDiary_final.fla.

  2. Open the Library window and locate the Calendar Control symbol (see Figure 2). Double-click to edit it.

    Figure 2 Locate the Calendar Control symbol in the library.

    The symbol is made up of background graphics, a text field for displaying the current month and year, a grid of date fields, and two arrow buttons on either side for scrolling between months. Each of the date fields in the grid is an instance of the same movie clip, containing a text field for holding its date number as well as a simple button that allows the user to click the selected date.

  3. Select the empty keyframe on the ActionScript layer, and then open the Actions panel.

  4. Insert the code to create an array of month names (see Figure 3).

    // Declare array of month names
    Months = new Array("January","February","March","April","May",
    "June","July","August","September","October","November","December");

    You do this first to make sure that the Months array is available to the other functions. ActionScript deals with dates as numbers and expresses months specifically as a number between 0 (for January) and 11 (for December). This zero-based counting system works perfectly with the Array object because its first element is always numbered 0 also. So, by creating an array of text strings that correspond to each of the 12 months, you have an easy way of plugging any month number into the Months array to get a text version. For example, if ActionScript gives you a date number 3, it's a simple matter to evaluate Months[3] to get the text string April.

    Figure 3 Notice that Flash keeps all the data for the Months array on one line.

    NOTE

    Although ActionScript uses zero-based counting for months, it uses regular one-based counting for years and days. So, even though month 3 equals April, day number 15 is just 15—there is no day 0.

  5. Insert the ActionScript to initialize the calendar by creating a new Date object and then setting its basic properties (see Figure 4).

    // Initialize Calendar
    CalendarDate = new Date();
    if (ShowYear != "Now") {
      CalendarDate.setYear(ShowYear);
    }
    if (ShowMonth != "Now") {
      CalendarDate.setMonth(ShowMonth);
    }
    DrawCalendar();.

    Date is one of the predefined ActionScript objects, so you don't have to design your own date-handling objects. When the new Date object, CalendarDate, is created here, it is set by default to the current time according to the system clock.

    Figure 4 Make sure that you have entered the Date object and initialized its properties correctly.

    Part of the Smart Clip customization that will be added later, however, is the ability to override the default behavior and actually specify what month and year the calendar will display. So, two if statements check to determine the value of the Smart Clip parameters ShowYear and ShowMonth. If they equal Now, nothing is changed; otherwise the values are used as arguments for the setYear and setMonth methods of CalendarDate (inherited from the Date object).

    The final line in this block invokes the function DrawCalendar(), which analyzes the current month and displays the correct information in each of the date fields in the grid. The DrawCalendar() function is added in step 7.

  6. Add this code to enable the calendar:

    // Send Date function
    function SendDate(Day) {
      DateSelected = new Date(CurrentYear, CalendarDate.getMonth(), Day);
        
      if (SendDateTo != "") {
      
        DateTarget = eval(SendDateTo);
        DateTarget(DateSelected);
      }
    }

    The calendar, invoked whenever the user clicks an individual date button, determines what date has been selected. That information is stored in a new Date object and is passed to a function specified in another of the Smart Clip parameters, SendDateTo. Even though SendDateTo is a variable, it can be used in conjunction with eval to point to a function.

  7. To insert the DrawCalendar() function, which is required to update the calendar and its grid of date fields, insert this code next:

    // Draw Calendar function
    function DrawCalendar() {
      CurrentMonth = Months[CalendarDate.getMonth()];
      CurrentYear = CalendarDate.getFullYear();
      CalendarText = CurrentMonth + " " + CurrentYear;

    This first block of statements (see Figure 5) acts to convert numerical date information into a more readable text string displayed at the top of the calendar in "Month Year" format. The CurrentMonth variable is obtained by accessing the element of the Months array corresponding to the currently displayed month. Calendar.getMonth() returns a number equal to the current month of the CalendarDate object. This function call is used to access the corresponding element of the Months array, which is Months[CalendarDate.getMonth()]. The result is the text name of the current month.

    CurrentYear is slightly easier to determine; you use the fairly straightforward getFullYear method of CalendarDate. Then CalendarText, the variable attached to the text field at the top of the calendar box, is set to the CurrentMonth text concatenated (or combined) with a space and CurrentYear.

    Figure 5 Make sure that the code for enabling the calendar and the DrawCalendar() function are entered correctly.

  8. Insert this code to determine the first day of the current month:

      CalendarDate.setDate(1);
      FirstDayNumber = CalendarDate.getDay();
      if (FirstDayNumber == 0) {
        FirstDayNumber = 7;
      }
      TotalDays = GetDaysInMonth(CalendarDate.getMonth(), CurrentYear);

    This block of code (see Figure 6) is designed to figure out what day of the week the first day of the current month falls on. This is important for properly displaying the current month of dates because they all need to line up correctly with the matching Mondays, Tuesdays, and Wednesdays. Because the setDate() method of CalendarDate sets the current date to 1 (the first of the month), the getDay() method can then be used to get the corresponding number of the first day in the current month. This number determines whether the first day falls on a Monday, Tuesday, or whatever. (The total number of days in the current month, determined by a function that you add in a later step, makes sure that only the correct number of days is shown in each month.)

    Figure 6 Make sure that the code you inserted for determining the first day of the month is in the correct position.

  9. Insert this code to create a for loop (see Figure 7) that paves the way for the fresh date information by looping through all the date field movie clips and setting their _visible properties to false:

      for (Counter = 0; Counter <= 42; Counter ++) {
        eval("Field" + Counter)._visible = false;
      }

    This hides all the dates in the grid, and only the relevant ones will be reactivated in the next block of the code. The number 42 appears because that is the total number of fields in the grid. That's much more than 31, granted, but, depending on the day of the week that the first of the month falls on, all the dates following can be displaced farther down the grid and past the 31st field.

    Figure 7 Make sure that the for loop is inserted correctly.

  10. Insert the code for a second for loop that counts through the TotalDays in the currently selected month, sets their _visible properties to true, and then sets the value of the DateField text field in each date in the grid. The DateField values are set to Counter + 1, because Counter starts at 0 even though the first actual date number is 1.

      for (Counter = 0; Counter < TotalDays; Counter ++) {
        eval("Field" + (FirstDayNumber + Counter))._visible = true;
        eval("Field" + (FirstDayNumber + Counter) + ".DateField") 
        = Counter + 1;
      }
    }
  11. Insert the code for the first of two supplementary functions that calculate the correct number of days in any given month, based on what you already know about month lengths and leap years.

    // Determine number of days in the month
    function GetDaysInMonth(Month, Year) {
      if (Month==0 || Month==2 || Month==4 || Month==6 
      || Month==7 || Month==9 || Month==11) {
        
        Days = 31;
      } else if (Month==3 || Month==5 || Month==8 || Month==10) {
        Days = 30;
      } else if (Month==1) {
        if (IsLeapYear(Year)) {
          Days = 29;
        } else {
          Days = 28;
        }
      }
      return (Days);
    }

    This function simply takes the Month and Year arguments passed to it and cycles through a series of if statements to determine the number of days in the month. The Year value is passed on to the next and final function, IsLeapYear().

    The double pipe, ||, is another way of writing or, which allows for multiple arguments to be written into the same if statement. The if statement in this code block is the code equivalent of the old rhyme "30 days has September, April, June, and November. All the rest have 31, excepting February in a line, which in a leap year has 29."

    The return() action is used to send values back to whatever object called the function. In this case, it returns the number of days in the specified month.

  12. Insert the last block of code to complete Calendar Control (see Figure 8):

    // Check for leap years
    function IsLeapYear (Year) {
      if (((Year % 4)==0) && ((Year % 100)!=0) || ((Year % 400)==0)) {
        return (true);
      } else {
     
        return (false);
      }
    }

    This function uses a lesser-known operator called modulo. You can learn more about modulo in the ActionScript reference that came with your software. In a nutshell, it divides one value by another and returns the remainder. This is the same process taught to schoolchildren as a precursor to short division. If Year can be divided by 4 and 400 to have no remainder, but when divided by 100 it does have a remainder, it's considered to be a leap year. The return action is then used to pass a true or false value back to the GetDaysInMonth() function from whence it was called.

    The Calendar Control symbol is effectively complete, but before you drag an instance of it onto the Stage, it needs to be set up as a Smart Clip, and part of that process involves preparing the custom user interface.

    Figure 8 Make sure that the code that checks for leap years is inserted correctly.

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