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Flash CS3 Professional Beyond the Basics
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Calculating a scroll percent


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Flash CS3 Professional Beyond the Basics

with Todd Perkins

Video: Calculating a scroll percent

In order to connect our scrollbar to a text field, we need to get something called a scroll percent. And by scroll percent I mean the percentage that the scrollbar is scrolled down. With that value we can then move our text field. The file that I'm working in is called 03_Scroll_Percent.fla in the Chapter 04 folder in the Exercise Files folder. Let's select the first keyframe of the actions layer and open the Actions panel by pressing Option+F9 on the Mac, or F9 on the PC. At the very top of your code, below the other two variables that were already created, create a new variable called scrollPercent, capital P. The data type of this variable will be a Number and we'll set the initial value to 0. At the bottom of the dragScroller function, below all the rest of the code inside of that function, type stage.addEventListener.
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  1. 3m 30s
    1. Welcome
      1m 20s
    2. Getting the most from this training
      1m 20s
    3. Using the exercise files
      50s
  2. 15m 28s
    1. Managing digital assets
      4m 9s
    2. Creating custom keyboard shortcuts
      5m 1s
    3. Creating custom color swatches
      3m 41s
    4. Creating a custom template
      2m 37s
  3. 14m 38s
    1. Working with variables
      3m 41s
    2. Using functions
      3m 30s
    3. Working with events
      2m 11s
    4. Using event listeners
      2m 42s
    5. Working with arrays
      2m 34s
  4. 29m 41s
    1. Understanding dynamic text fields
      2m 37s
    2. Loading text from an external file
      6m 42s
    3. Reading HTML from a text field
      5m 29s
    4. Applying CSS with ActionScript
      7m 0s
    5. Applying external CSS to a text field
      7m 53s
  5. 45m 27s
    1. Masking dynamic text
      4m 59s
    2. Dragging the Scroll Bar
      7m 3s
    3. Calculating a scroll percent
      5m 20s
    4. Setting scroll boundaries
      4m 9s
    5. Connecting the ScrollBar to the text field
      2m 55s
    6. Easing the text with the ScrollBar
      4m 12s
    7. Scrolling the text with buttons
      2m 38s
    8. Animating the scrolling text with the buttons
      4m 26s
    9. Setting boundaries for the scrolling text
      4m 26s
    10. Easing the text using the buttons
      1m 37s
    11. Connecting the ScrollBar to the Scroll buttons
      3m 42s
  6. 20m 46s
    1. Organizing a complex object into layers
      1m 51s
    2. Duplicating MovieClips
      1m 29s
    3. Undocking the timeline
      1m 20s
    4. Animating a complex MovieClip
      4m 36s
    5. Creating an animated Hinge effect
      5m 13s
    6. Creating complex animations
      6m 17s
  7. 28m 1s
    1. Controlling objects with buttons
      4m 6s
    2. Understanding frame labels
      3m 25s
    3. Using buttons to navigate labeled frames
      2m 30s
    4. Nesting code within MovieClips
      5m 8s
    5. Adding sound to the application
      2m 34s
    6. Adding drag interactivity to the robot
      6m 1s
    7. Animating the dragged robot
      4m 17s
  8. 20m 3s
    1. Understanding components
      2m 30s
    2. Using components to setup a form
      3m 45s
    3. Setting up the form to send an email
      3m 38s
    4. Working with form variables
      6m 11s
    5. Skinning components
      3m 59s
  9. 27m 40s
    1. Using transparency in a video
      4m 16s
    2. Working with embedded video
      3m 38s
    3. Animating a VideoClip
      2m 53s
    4. Creating an advanced animation with video
      2m 40s
    5. Working with the bitmap data class
      3m 37s
    6. Working with the bitmap class
      1m 40s
    7. Copying the video to create a reflection
      1m 35s
    8. Reflecting the video
      2m 42s
    9. Enhancing a video reflection with a mask
      4m 39s
  10. 1h 38m
    1. Viewing the finished MP3 player
      1m 45s
    2. Understanding the project flow
      2m 52s
    3. Preparing to build the MP3 player
      5m 11s
    4. Understanding classes and packages
      5m 32s
    5. Creating the MP3 player class
      9m 59s
    6. Loading sounds from external files
      9m 20s
    7. Accessing ID3 tag information
      6m 11s
    8. Controlling sound playback with Play and Pause buttons
      11m 3s
    9. Changing tracks
      12m 1s
    10. Displaying the current volume
      9m 33s
    11. Changing the volume
      6m 40s
    12. Wiring the progress bar
      8m 4s
    13. Building the progress bar slider
      10m 4s
  11. 5m 36s
    1. Making Flash movies accessible
      1m 49s
    2. Adding a name and description to your Flash movie
      52s
    3. Accessibility and text fields
      2m 55s
  12. 12m 2s
    1. Understanding Flash Mobile
      35s
    2. Exploring Device Central
      1m 45s
    3. Updating Device Profiles
      1m 7s
    4. Creating a Flash file from Device Central
      2m 7s
    5. Creating and testing Flash Lite applications
      2m 48s
    6. Downloading the Flash Lite player for Windows Mobile
      1m 44s
    7. Getting a Flash Lite application onto your phone
      1m 56s
  13. 27s
    1. Goodbye
      27s

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Flash CS3 Professional Beyond the Basics
5h 21m Intermediate Dec 06, 2007

Viewers: in countries Watching now:

Through several hands-on tutorials, instructor Todd Perkins shows how to best build dynamic, streamlined sites using Flash CS3 Professional. Learn how to create custom keyboard shortcuts, apply advanced text techniques such as animating scrolling text with custom easing controls, and using advanced animation techniques. Flash CS3 Professional Beyond the Basics covers many challenging features, including adding complex interactivity to a Flash CS3 project and getting Flash content on a phone. Exercise files accompany the tutorials.

Topics include:
  • Customizing Flash CS3 and managing assets Working with ActionScript variables Understanding dynamic text fields Adding interactivity to dynamic text Animating a complex MovieClip Using buttons to navigate labeled frames Working with components Exploring advanced audio and video techniques Creating accessible Flash content Understanding Flash Mobile
Subject:
Web
Software:
Flash Professional
Author:
Todd Perkins

Calculating a scroll percent

In order to connect our scrollbar to a text field, we need to get something called a scroll percent. And by scroll percent I mean the percentage that the scrollbar is scrolled down. With that value we can then move our text field. The file that I'm working in is called 03_Scroll_Percent.fla in the Chapter 04 folder in the Exercise Files folder. Let's select the first keyframe of the actions layer and open the Actions panel by pressing Option+F9 on the Mac, or F9 on the PC. At the very top of your code, below the other two variables that were already created, create a new variable called scrollPercent, capital P. The data type of this variable will be a Number and we'll set the initial value to 0. At the bottom of the dragScroller function, below all the rest of the code inside of that function, type stage.addEventListener.

The event will be an Event.ENTER_FRAME, all caps. And we'll run a function called a setScrollPercent. So once you start dragging the scrollbar it will run this function called setScrollPercent. The functional run as the timeline enters frames or along with the frame rate of the movie. The frame rate of this movie is set to be 24 frames per second. So 24 times per second the setScrollPercent function will run. Let's define the set scroll percent function right below the stop dragging function.

So create the function setScrollPercent. It receives an event with the data type of Event. In the curly braces for this function type scrollPercent equals and then after the = we'll set value of scroll percent. Before we set the value of scroll percent let's talk about what that value is going to be. The value is going to be the amount or the percentage that the scrollbar is dragged down. The value of scroll percent will be between 0 and 1. 0 when the scrollbar is all the way up, and 1 when the scrollbar is all the way down.

So what we're going to need to do to find out what percentage the scrollbar is down, we'll have to divide the scrollbar's current position by the amount that the scrollbar can move down. So type open and close parentheses and in the parentheses type scroller_mc.y - line_mc.y. This value represents how many pixels down the scroller is from the top of the line movie clip. And we'll divide this value in parentheses by the total amount that the scroller can move down. So type / to divide, and then open and close parentheses and a semicolon.

Inside the parentheses type line_mc.height - scroller_mc.height. This is the maximum value that the scrollbar can move down as we set in the last movie. On the next line create a trace statement that traces the value of scroll percent. Let's test the movie and see what the value of scroll percent is when we move the scrollbar. Command+Return on the Mac. Ctrl+Enter on the PC. Move the scrollbar. In the Output window we should see values between 0 and 1.

And I'm getting a negative value, so what I'm going to do is close the Preview window, close the Output window, and return to Flash. Above the trace statement that I just wrote, I'm going to write some conditional statements that make sure that the scroll percent is in the correct boundaries. Type if, and in parentheses type scrollPercent < zero. In the curly braces of that conditional statement, type scrollPercent = 0; This will make sure the scroll percent value never goes below zero.

Below that if statement type else if(scrollPercent > 1) and in curly braces below the else if statement, type scrollPercent = one; Test the movie using Command+Return on the Mac or Ctrl+Enter on the PC. Drag the scrollbar, you should see values between 0 and 1. And close the Preview window and close the Output window. You may have noticed that when you release your mouse button on the scrollbar the enter frame event continues to run.

Or in other words Flash is continuing to calculate the scroll percent every frame. A best practice is to stop those enter frame events. Having a lot of enter frame events running can slow down your Flash movie. So what we want to do is stop this set scroll percent function from running once we release our mouse button. In that stop dragging function at the very bottom, type stage.removeEventListener and in parentheses pass in Event.ENTER_FRAME in all caps, a comma and a space and setScrollPercent); and this will stop the set scroll percent function from running after we've dragged the scrollbar. So press Command+Return on the Mac or Ctrl+Enter on the PC to test the movie. I'm going to drag the scrollbar and release my mouse button.

And notice in the Output window that the values stopped counting. It's always the best practice to remove event listeners especially for enter frame events. Now that we have the scroll percent set up, we can connect our scrollbar to the text field on the stage.

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