X-Git-Url: http://source.jalview.org/gitweb/?a=blobdiff_plain;f=src%2Fjalview%2Fws2%2Factions%2Fapi%2FTaskEventListener.java;h=9dee10ca117bb152a028c12f58289f3fad75047e;hb=c6bce37c6553e40f0d3149546a8c96916cf04e21;hp=94de9d0822d8f135e4658b9a667a41870c1e4f3f;hpb=5f4f772b4ce40f2ea987cb03dd2c06ec1f48ba67;p=jalview.git

diff --git a/src/jalview/ws2/actions/api/TaskEventListener.java b/src/jalview/ws2/actions/api/TaskEventListener.java
index 94de9d0..9dee10c 100644
--- a/src/jalview/ws2/actions/api/TaskEventListener.java
+++ b/src/jalview/ws2/actions/api/TaskEventListener.java
@@ -108,4 +108,55 @@ public interface TaskEventListener<T>
    *          new log string
    */
   void subJobErrorLogChanged(TaskI<T> source, JobI job, String log);
+
+  @SuppressWarnings("rawtypes")
+  static final TaskEventListener NULL_LISTENER = new TaskEventListener()
+  {
+    @Override
+    public void taskStarted(TaskI source, List subJobs)
+    {
+    }
+
+    @Override
+    public void taskStatusChanged(TaskI source, JobStatus status)
+    {
+    }
+
+    @Override
+    public void taskCompleted(TaskI source, Object result)
+    {
+    }
+
+    @Override
+    public void taskException(TaskI source, Exception e)
+    {
+    }
+
+    @Override
+    public void taskRestarted(TaskI source)
+    {
+    }
+
+    @Override
+    public void subJobStatusChanged(TaskI source, JobI job,
+            JobStatus status)
+    {
+    }
+
+    @Override
+    public void subJobLogChanged(TaskI source, JobI job, String log)
+    {
+    }
+
+    @Override
+    public void subJobErrorLogChanged(TaskI source, JobI job, String log)
+    {
+    }
+  };
+
+  @SuppressWarnings("unchecked")
+  static <T> TaskEventListener<T> nullListener()
+  {
+    return (TaskEventListener<T>) NULL_LISTENER;
+  }
 }