--- a/playlist/Playlist.cpp
+++ b/playlist/Playlist.cpp
@@ -41,6 +41,7 @@
 #include <QDir>
 
 #include <iostream>
+using namespace std;
 #include <ctime>
 
 using namespace std;
@@ -166,6 +167,7 @@
     if(!Helper::checkTrack(_v_meta_data[i])) return;
 
     emit sig_selected_file_changed(i);
+    cerr <<  "void Playlist::send_cur_playing_signal" << endl;
     emit sig_selected_file_changed_md(_v_meta_data[i]);
     _cur_play_idx = i;
 }