pretty cool

app/src/main/java/common/Signal0.java

@@ -0,0 +1,26 @@
+package common;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Signal0 {
+	private final List<Runnable> handlers;
+
+	public Signal0() {
+		this.handlers = new ArrayList<>();
+	}
+
+	public void connect(Runnable handler) {
+		this.handlers.add(handler);
+	}
+
+	public void disconnect(Runnable handler) {
+		this.handlers.remove(handler);
+	}
+
+	public void emit() {
+		for (Runnable handler : this.handlers) {
+			handler.run();
+		}
+	}
+}