Mission Triggers can be used to trigger an action during the execution of a Timeline element if a set of criteria is met. The subclass of DJIMissionTrigger should implement the logic for collecting and judging the criteria, and then executing the action. Mission Triggers are used in the Timeline element DJIMissionControlTimelineElement.
Trigger actions can be listened to, so when subclassing this class, notifyListenersOfEvent:error should be used to notify listeners of trigger events.
Begins trigger activity including monitoring the criteria required to trigger the action. When subclassing, [super start] should be called on the first line.
Ends all trigger activities including monitoring the criteria required to trigger the action. When subclassing, [super stop] should be called at the end.
Method which checks whether the action block is not null and executes it. It also notifies the listeners about the success / failure (in the case of a null action block) of the action. When subclassing, [super triggerAction] should be called at the end.