Add exception listener to Log class (#481)

Author: hborisoff

AndroidSDKCore/src/main/java/com/leanplum/Leanplum.java

@@ -754,7 +754,7 @@ public void response(JSONObject response) {
     request.onError(new Request.ErrorCallback() {
       @Override
       public void error(Exception e) {
-        Log.i("Failed to receive start response");
+        Log.e("Failed to receive start response", e);
         handleStartResponse(null);
       }
     });

AndroidSDKCore/src/main/java/com/leanplum/internal/Log.java

@@ -51,6 +51,9 @@ public static void e(String msg, Object... args) {
   }
 
   public static void e(String msg, Throwable throwable) {
+    if (exceptionListener != null) {
+      exceptionListener.onException(throwable);
+    }
     if (msg != null && msg.contains("%s")) {
       log(LogType.ERROR, msg, getStackTraceString(throwable));
     } else {
@@ -71,6 +74,9 @@ public static void d(String msg, Object... args) {
    * @param throwable to log
    */
   public static void exception(Throwable throwable) {
+    if (exceptionListener != null) {
+      exceptionListener.onException(throwable);
+    }
     ExceptionHandler.getInstance().reportException(throwable);
 
     if (throwable instanceof OutOfMemoryError) {
@@ -222,4 +228,19 @@ public static class Level {
      */
     public static final int DEBUG = 3;
   }
+
+  public interface ExceptionListener {
+    void onException(Throwable t);
+  }
+
+  private static ExceptionListener exceptionListener;
+
+  /**
+   * Sets listener for all logged exceptions.
+   *
+   * @param listener The listener that will receive all logged exceptions.
+   */
+  public static void setExceptionListener(ExceptionListener listener) {
+    exceptionListener = listener;
+  }
 }