[FLASH] Percentage Preloader with Load Bar


Author:
by Shane Waldeck aka Lostinbeta
Source: http://www.kirupa.com/developer/mx/percentagepreloader.htm

Introduction
This tutorial will explain step by step how to create your own preloader that displays the percentage of your file that is loaded, and has a load bar that shows graphically how much is loaded. You may or may not be surprised at how easy something like this really is, I guess you won’t know until the end of the tutorial. The movie below demonstrates what the preloader will look like. If you run on a broadband modem, you probably will not get a chance to see it, but dial-up users should have no problem.

If you are lazy and don’t feel like building it yourself you can download the partial .fla file from this link – download partial fla file – The partial .fla file contains only the contents needed, you will add the ActionScript and such as needed.

Ok, now let’s start…
These next steps should help you on your way to building your own percentage preloader:

 

  1. First you want to create a new document of course, it doesn’t matter what size. My example is 300×200 if you would like to go by that.
  2. Ok, to actually get started on making this preloader we will start with the load bar. Name the current layer “loadBar” (no quotes). Use the rectangle tool to create your rectangle. I made a 100×10 grey rectangle. Be sure your rectangle has no outline, if you forget to disable the outline before making your shape, you can always double click on the outline after you make your shape and use the Delete key to remove it.
  3. Now select your rectangle shape and hit the F8 key on your keyboard to open the “New Symbol” panel. In here you will call your movie clip “loadBar” (no quotes) and set it’s registration point to the left center. Don’t forget to select the type of symbol as “Movie Clip” as well. You will also select your loadBar movie clip on the stage and hit CTRL+F3 on your keyboard to open the “Properties” panel and give your movie clip the instance name “loadBar” (no quotes). Check screenshot below for visual aid.
    150loadBar
    Images from Knowledges Photo Storage
  4. Ok, so we don’t just want a bar that appears out of nowhere right? Well in this case we will create a new layer. Rename this layer to be called “border” (no quotes). Now inside this layer you will use the line tool and draw a border around your loadBar movie clip. Be sure this layer is above the loadBar layer so you can see the outline clearly. Check below screenshot to see what I mean.
    150loadBarOutline
    Images from Knowledges Photo Storage
  5. Alright, so we now are finished setting up our “fancy” load bar, it is time to get started on our percentage text area. Create a new layer and rename this layer to “loadText” (no quotes). Use the Text Tool to create a text area the size you want. It really only has to be one line long, and not even that long across. Just long enough to fit a maximum of 4 characters in this case. With this text box selected, hit CTRL+F3 on your keyboard to open up the “Properties” panel and be sure the drop down box is set to “Dynamic” text and you give the text box the var name “loadText” (no quotes). See below example to see what I mean.

     

    150loadText
  6. Well, believe it or not, we are finished building the preloader. Now all we have to do is add the actions to make it work! Create a new layer and rename it to “actions” (no quotes). Right click on frame two and choose “Insert Blank Keyframe” so that you have two keyframes set up to put actions in. Be sure that all your frames below that span the two frames so your preloader doesn’t strobe. To do this, right click on the second frame in each layer and choose “Insert Frame”. Your timeline should look something like mine below. Just ignore the 3rd frame in my screenshot, as that is the actual start of my movie and the lowercase “a” letters on the frames are frames that contain actions, which we are going to get to in a little bit.
     

     

    150timeline 

     

     

  7. Ok, now we will start on the actual preloader code. Right click on the empty keyframe in frame one of the actions layer. Go to “Actions” in the context menu to open up the “Actions” panel. Use the below code (which will be explain later in this tutorial).

    <!–Start Coding
    bytes_loaded = Math.round(this.getBytesLoaded());
    bytes_total = Math.round(this.getBytesTotal());
    getPercent = bytes_loaded/bytes_total;
    this.loadBar._width = getPercent*100;
    this.loadText = Math.round(getPercent*100)+”%”;
    if (bytes_loaded == bytes_total) {
    this.gotoAndPlay(3);
    }
    End Coding–>

  8. Now right click on the empty keyframe in frame two of the actions layer and open the “Actions” panel. Apply these actions to the frame.

    <!– Start Coding
    this.gotoAndPlay(1);
    End Coding –>

  9. Well that is it. Your movie should start on frame three of your timeline. Stay tuned below for the explanation of the code I used.
  10.  

     

Alright, now that you have completed the tutorial and hopefully got everything working correctly, I will not go through what this code junk actually means.

What we have to do is go through the code line by line and interpret it. A lot like poetry, ActionScript is just as beautiful and translated in the same manner.

Frame 1 Actions

bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}
This declares the variable “bytes_loaded” which uses a feature in Flash called getBytesLoaded and determines how many bytes of your movie have been loaded thus far by the viewer. The Math.round() in the code tells Flash to round the number off so it becomes a whole number instead of an eight decimal places number…. because let’s be honest, who wants to read a percentage that is eight decimal digits.
bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}
This declares the variable “bytes_total” which uses a feature in Flash called getBytesTotal and determines how many bytes your entire movie contains for the viewer to download. I already explained the Math.round() part for the getBytesLoaded. Using getBytesTotal and getBytesLoaded we can determine what percentage we have loaded and have yet to load.
bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}
Here we are declaring a variable which I named getPercent. We will take the variables bytes_loaded and bytes_total and divide them so we can determine how much has been loaded thus far in our movie. I declared it in a variable because we will be using it twice in the script, so instead of typing it out twice, I decided to declare it in a variable and use that variable later in the script.
bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}
This is where we work with our preloader bar. It takes the value produced by the getPercent variable and multiplies it by 100. You may ask why the 100 is blue above, and I will tell you why. The 100 is blue because you can multiply it by whatever you would like, the number you place there determines the ending width of your loadBar movie clip. Since you drew the border for your clip on the stage already, I recommend using the width of your movie clip on the stage. You can select your clip and open the properties panel to see what the width is. Of course…. this.loadBar is your loadBar movie clip and the _width at the end is what allows you to change the width of the clip so it can grow and fill in your border ouline of your original loadBar clip.
bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}
Alright, just like in the last one, the this.loadText here targets the dynamic textbox you placed on your stage and had given the var name “loadText”. You will see we use the Math.round() feature again so we don’t have odd decimal numbers that no one wants to see. We use the same method as changing the width of the loadBar to get the percent of the movie loaded. Of course though, the 100 at the end of this one has to remain at 100 so you can go through your movie from 0% to 100%. The +”%” at the end just tacks on a percent symbol in your text box so that the viewer knows it is referring to the percent loaded.
bytes_loaded = Math.round(this.getBytesLoaded());
bytes_total = Math.round(this.getBytesTotal());
getPercent = bytes_loaded/bytes_total;
this.loadBar._width = getPercent*100;
this.loadText = Math.round(getPercent*100)+”%”;
if (bytes_loaded == bytes_total) {
this.gotoAndPlay(3);
}

This would be your final if statement. What it says is that if the number produced in the variable bytes_loaded is finally equal to the number produced from the variable bytes_total then the movie should gotoAndPlay the 3rd frame on the timeline.

 


Frame 2 Actions

this.gotoAndPlay(1);
Well this is pretty self explanitory, but I will explain anyway. Ok, if all the bytes are not loaded in your movie in frame one, it will automatically move on to frame two, since we can’t let it pass frame two yet because the movie isn’t loaded we will have to send it back to frame one. This will keep looping around over and over until both the bytes_loaded and the bytes_total variables are equal in numbers. Then the if statement declared at the end of the actions in frame one will send the movie directly to frame three and your movie will start from there.

 

 

If for any reason you still don’t understand something, or for some reason your preloader does not work, you may download the full working .fla file here – download full fla file – Please note this .fla file was done in Flash MX and can not be viewed through Flash 5.

 

-Shane Waldeck aka Lostinbeta
http://www.lostinbeta.com/

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