The task interface now contains a method to retrieve its cancel callback. Use case: adding a confirmation dialog before cancelling.

Author: NicoKiaru

src/main/java/org/scijava/task/DefaultTask.java

@@ -6,13 +6,13 @@
  * %%
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
- * 
+ *
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
- * 
+ *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
@@ -84,18 +84,19 @@ public class DefaultTask implements Task {
 
 	/**
 	 * Creates a new task.
-	 * 
+	 *
 	 * @param threadService Service to use for launching the task in its own
 	 *          thread. Required.
 	 * @param eventService Service to use for reporting status updates as
 	 *          {@link TaskEvent}s. May be null, in which case no events are
 	 *          reported.
 	 */
 	public DefaultTask(final ThreadService threadService,
-		final EventService eventService)
+					   final EventService eventService)
 	{
 		this.threadService = threadService;
 		this.eventService = eventService;
+		cancelCallBack = this::defaultCancelCallback;
 	}
 
 	// -- Task methods --
@@ -176,17 +177,25 @@ public void cancel(final String reason) {
 		canceled = true;
 		cancelReason = reason;
 		if (cancelCallBack!=null) cancelCallBack.run();
+		fireTaskEvent();
+	}
+
+	void defaultCancelCallback() {
 		if (future!=null) {
 			isDone = future.cancel(true);
 		}
-		fireTaskEvent();
 	}
 
 	@Override
 	public void setCancelCallBack(Runnable r) {
 		this.cancelCallBack = r;
 	}
 
+	@Override
+	public Runnable getCancelCallBack() {
+		return this.cancelCallBack;
+	}
+
 	@Override
 	public String getCancelReason() {
 		return cancelReason;

src/main/java/org/scijava/task/Task.java

@@ -6,13 +6,13 @@
  * %%
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
- * 
+ *
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
- * 
+ *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
@@ -140,4 +140,12 @@ default void finish() {}
 	 * @param runnable : should be executed if this task is cancelled through {@link Task#cancel(String)}
 	 */
 	default void setCancelCallBack(Runnable runnable) {}
+
+	/**
+	 * Returns the current cancel callback runnable,
+	 * This can be used to concatenate callbacks in order,
+	 * for instance, to ask for a user confirmation before cancelling the task
+	 */
+	default Runnable getCancelCallBack() { return () -> {}; }
+
 }