Class JSignal

public class JSignal extends AbstractJSignal
A signal that may be triggered from the browser with a JavaScript call. For a usage example take a look the documentation of JSignal2.
  • Constructor Details

    • JSignal

      public JSignal(WObject sender, String name)
      Creates a signal.
      sender - the object that will be identified as the sender for this signal.
      name - the signal name (must be unique for each sender)
  • Method Details

    • addListener

      public AbstractSignal.Connection addListener(WObject receiver, Signal.Listener listener)
      Description copied from class: AbstractSignal
      Adds a listener for this signal.

      Each listener will be notified when the signal is triggered.

      An owner object may be passed when the listener is implemented using an (anonymous) inner class. In that case the owner object should be the enclosing object of the listener object, and this is used to bind the lifetime of the listener. To avoid the owner object from not being garbage collected when it is no longer used, only the owner object will add a reference to the listener, while the signal will use a weak reference.

      This avoids the most common reason for memory leaks in Java implementations of the Observer pattern: the owner object will not get garbage collected because of the (anonymous) listener object having a reference to it, even if the receiver object is no longer referenced from anywhere. When the owner object is not null, the listener is stored using a strong reference in the owner object, and using a weak reference in the signal.

      Specified by:
      addListener in class AbstractSignal
      receiver - if not null, the enclosing object for a listener implemented using an inner class
      listener - the listener
      a connection object that may be used to control the connection
    • getListenerCount

      protected int getListenerCount()
      Description copied from class: AbstractSignal
      Returns the number of connected listeners.
      getListenerCount in class AbstractEventSignal
      the number of connected listeners.
    • removeListener

      public void removeListener(Signal.Listener listener)
      Description copied from class: AbstractSignal
      Removes a listener.

      Specified by:
      removeListener in class AbstractSignal
      listener - a listener that was previously added.
    • trigger

      public void trigger()
      Triggers the signal.
    • createCall

      public String createCall()
      Returns a JavaScript statement that triggers this signal.

      You can use this to trigger the signal from within generated JavaScript code.

    • getArgumentCount

      protected int getArgumentCount()
      Description copied from class: AbstractSignal
      Returns the number of parameters (excluding an 'event').
      Specified by:
      getArgumentCount in class AbstractSignal