Event Handlers
69
NetLinx Programming Language Reference Guide
In this example, the event will not perform as the previous one did. When the code is compiled, the
event parameters are dvTp, which is already assigned, and nMyChannel, which has a value of 0.
nMyChannel does not get assigned a value of 1 until DEFINE_START, at which time the event has
already been added to the event table. If you were to run this code, you would discover that it did in fact
run when button 1 was pushed, leading us to one of the "shortcuts":
<bold>
A value of 0 for a Channel or Level Number in a BUTTON_EVENT, CHANNEL_EVENT or LEVEL_EVENT
will be interpreted as an event handler for all events of that type from the given device number(s).
</bold>
So, the reason the above example runs when button 1 was pushed is that the above example runs when
any button on
dvTp is pushed. This "shortcut" was added so you could define an event handler for all
buttons, channel or levels of a device without having to define a
DEVCHAN of DEVLEV containing every
value you may want to handle.
To make the example 2 behave like the example 1, we simply need to make sure the value of
nMyChannel contains a value of 1 at compile time. This is simply done by initializing nMyChannel a
value of 1 in the
DEFINE_VARIABLE section. The new example reads:
Example 3:
DEFINE_DEVICE
dvTp = 128:1:0
DEFINE_VARIABLE
Integer nMyChannel = 1
DEFINE_EVENT
BUTTON_EVENT[dvTp,nMyChannel]
{
PUSH:
Send_String 0,"'Button ',ITOA(nMyChannel),' of dvTp was pushed'"
}
You may be tempted to use a more traditional variable as the channel number, mainly PUSH_CHANNEL
or
RELEASE_CHANNEL. It is important to realize that the identifiers are nothing more than global
(system) variable. At compile time, the values are defined and contain a value of 0. So the following
code:
Example 4:
DEFINE_EVENT
BUTTON_EVENT[dvTp,PUSH_CHANNEL]
{
PUSH:
Send_String 0,"'Button ',ITOA(BUTTON.INPUT.CHANNEL),' of dvTp was pushed'"
RELEASE:
Send_String 0,"'Button ',ITOA(BUTTON.INPUT.CHANNEL),' of dvTp was released'"
}
To Next Page
Loading...
Need help?
General
