A Simple Back Button

 

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My projector plays a movie that is like an index. In it users can click to go to a section, move forward, etc. How can I make a back button (similar to a web browser) so they can retrace their steps?

This process involves 2 basic components.  The first is a simple list.  We want to track where the person goes, but not every frame.  We could set a script that triggers every frame and checks the last marker, but that hogs unnecessary processor power.  For this example we will use a simple frame script.   The nice part of this approach is that you only add a "back state" on the frames you drop the script on.  To generate our list of digital footprints we can retrace, we can start with a simple call to a global variable and add the current frame to the list.   Something like add gBackList, the frame.  This will add to the global list gBackList with the current frame number.  Simple enough.  Well how do we go back a frame?  If we went to the last entry in the list we would end up at the current frame or section, so we need to look one back, at the next-to-last frame in the list.  Further more we need to also remove the last entry from the list when jumping back, as it is no longer in our linear path. To track this we use another global variable.  In this example it is called gBack.  If gBack is true then the last navigation method was the back button.   If it is false, we are progressing in a forward direction.  The back button would look something like this... global gBack, gBackList on mouseUp me howMany = gBackList.count if howMany > 1 then --There is a back state gBack = true go gBackList[howMany - 1] end if end The if statement keeps us from getting errors if the user is at the starting point of the back list.  (No where else to back track to.)  Now that we have established that the back button has been clicked and we have jumped back to the correct frame we need a frame script.  Using the same script we can remove unneeded entries when the back button is used, as well as add new ones when we enter the frame via normal navigation. global gBack, gBackList on enterFrame me if gBack = void then gBack = false if gBackList = void then gBackList = [] howMany = gBackList.count if gBack = true then --came from back button gBack = false deleteAt gBackList, howMany else if howMany > 0 then if gBackList[howMany] <> the frame then --prevents the same frame from being added twice in a row add gBackList, the frame end if else add gBackList, the frame end if end if end Now, each time the user enters the frame the script checks to see how they got there and either adds or removes an entry from the list.  The extra if statement prevents the same frame from being added twice in a row.  We also need to check the variables and make sure that if they have never been used (if their value is "void") then we set them to their default states.  It is also a good idea to set theses in your startMovie script to clear them out during authoring so you don't start with the back list of a previous session while testing. If you want to customize this one you could make a next button list as well, or set different rollover and default graphic states for the button depending on if there are items in the back list or not, or add functionality for different movies to be tracked in the list as well. Here is an example of the code in action... As usual, you can also find all of these behaviors/scripts in the behavior database.