fix: record isn't stopped when volume down

refactor: recorder

common/src/main/java/com/stardust/event/EventDispatcher.java

@@ -0,0 +1,32 @@
+package com.stardust.event;
+
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * Created by Stardust on 2017/8/6.
+ */
+
+public class EventDispatcher<Listener> {
+
+    public interface Event<Listener> {
+        void notify(Listener l);
+    }
+
+    private CopyOnWriteArrayList<Listener> mListeners = new CopyOnWriteArrayList<>();
+
+    public void addListener(Listener l) {
+        mListeners.add(l);
+    }
+
+
+    public boolean removeListener(Listener l) {
+        return mListeners.remove(l);
+    }
+
+    public void dispatchEvent(Event<Listener> event) {
+        for (Listener listener : mListeners) {
+            event.notify(listener);
+        }
+    }
+
+}