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Flash Lite 1.1 scrolling background

gioorgionatili | 23 December, 2007 16:37

When you start to develop a Flash Lite 1.1 arcade game is often required to have a background that “loops” under your sprite according to the direction sprite.
This is not a very complicated stuff and now we’ll look very quickly how to implement this with the old Flash Lite 1.1 ActionScript.

Import in the library of your .fla a PNG file with the same height of the screen of your target device and with the width equal to the double of the screen width.
Create a movie clip that contain this file and then create a new symbol in which you have to place an instance of the background and to define the script that handle the scroll.
Organize your timeline in order to have a “move” and an “init” label, a layer for the code and another one for the graphic

fig. 1 


In the “init” frame you define the direction of the scroll, duplicate the bg_mc movie clip and complete the stuffs needed in order to handle your scrolling background.

direction = 1;
duplicateMovieClip("bg_mc", "bg_mc_new", 1000);
bg_mc_new._x = bg_mc._x + bg_mc._width;
bgStartX = _x;
speed = 4;
columnWidth = 320;

Now you are ready to implement the script contained in the move label (remember that the script associated with a frame label in Flash Lite 1.1 are used like functions and can be invoked with the call instruction) that handle the _x of this movie clip

_x -= (speed*direction);

if (_x <= (bgStartX - _width + columnWidth)){  
 _x = bgStartX - columnWidth - speed;
}

if(_x >= 0){  
 _x = - _width/2 + speed;  
}

This script always increment the _x property and then check if the background is going outside the boundaries of the stage.
In order to make the background moving you handle the left and the right arrow pressure moving the background timeline to the frame 2 in order to create a loop

tellTarget("../mainBg_mc"){
  set("direction", -1);
  gotoAndPlay(2); 
 }
 

For reference and in order to be clear this is the file described in this post.

Comments

Welcome

Steve | 01/01/2008, 12:03

Good to see another Flash Lite blog on Forum. This is a useful article - and hope to see many more. Keep up the good work - and weclome Giorgio!

Thanks

gioorgionatili | 02/02/2008, 18:04

gioorgionatili

Hi Steve,
Thank for your welcome message, I hope that this posts help the developer community to complete simple task in the Flash Lite development.

Re: Flash Lite 1.1 scrolling background

fishermann | 22/03/2008, 20:15

Very interesting info, thanks.

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