Flash Actionscript 3

Referencing a Bitmap on the Stage in ActionScript 3

When working with Flash and ActionScript 3, you may encounter a common challenge: referencing bitmaps that are placed on the stage during the design phase. This can be particularly tricky when you’re looking to swap images dynamically throughout your movie. In this blog post, we will break down how to reference those bitmaps effectively, ensuring a seamless looping experience for your final movie.

The Problem

Imagine you have a movie with several layers, each containing different images (bitmaps). Your final goal is to switch these images at the end of the movie so that it loops continuously without any noticeable breaks. Here’s a quick overview of your setup:

  • You have three bitmap images in your library, each exported with a class name.
  • Your Flash layers are organized as follows:
    • Layer 5: mask2: MovieClip
    • Layer 4: img2: Bitmap
    • Layer 3: mask1: MovieClip
    • Layer 2: img1: Bitmap
    • Layer 1: background: Bitmap

You want to reference these images in your ActionScript code, allowing you to replace img1 with img2, and subsequently img2 with img3, to keep the flow of visuals in your animation.

The Solution

Step 1: Naming the Bitmap Instance

To reference a bitmap, you need to assign an instance name to the bitmap on the stage. This is crucial because simply giving it a class name in the library is not enough. Here’s how you can do this:

  1. Select the Bitmap on Stage: Click on the bitmap image you wish to rename (e.g., img1).
  2. Open the Properties Panel: Look for the properties panel, typically located on the right side of the Flash interface.
  3. Enter an Instance Name: Above the dimensions entry boxes, you will find a text box. Type a name for your bitmap here (e.g., image1).

Step 2: Accessing the Bitmap in ActionScript

With the instance name set, you can now refer to this bitmap in your ActionScript code. This is done by simply using the instance name you assigned. Below is a basic example:

// Example to swap bitmaps
function swapImages():void {
    image1 = new img2(); // Swaps image1 with img2
    image2 = new img3(); // Next swap
}

Step 3: Ensure Dynamic Loading

For more complex sequences, especially if you aim to load images dynamically from a server, make sure your code handles the transitions between images smoothly.

  • Consider using a timer or event listener that listens for the end of the movie.
  • Use functions to replace images.

Troubleshooting Common Issues

You might encounter some issues while trying to reference bitmaps. Here are some common pitfalls and solutions:

  • Instance Name Grayed Out: If the instance name field is grayed out, ensure that the object is a MovieClip or Button. Bitmaps typically need to be converted to MovieClips for easy referencing.
  • Images Reappearing on Mask Trigger: If previously cleared images reappear when masks are activated, double-check your masking logic. Make sure to clear images before masking logic initiates.

Conclusion

Referencing bitmaps on the stage in ActionScript 3 is essential for creating fluid animations where images swap seamlessly. By following the steps outlined above, you can effectively manage your images and deliver a polished end product. Remember to incorporate a dynamic loading strategy as you grow your project to keep your movie fresh and engaging.

By mastering these techniques, you’ll enhance your skills in Flash and ActionScript, leading to greater creative possibilities in your projects.