fix clear remote view issue

Author: xianing

Android/APIExample/app/src/main/java/io/agora/api/example/examples/basic/JoinChannelVideo.java

@@ -192,6 +192,7 @@ public void onClick(View v)
                  *      2:If you call the leaveChannel method during CDN live streaming, the SDK
                  *          triggers the removeInjectStreamUrl method.*/
                 engine.leaveChannel();
+                clearRemoteViews();
                 join.setText(getString(R.string.join));
             }
         }
@@ -513,6 +514,15 @@ public void onRtcStats(io.agora.rtc.IRtcEngineEventHandler.RtcStats rtcStats) {
         }
     };
 
+    private void clearRemoteViews() {
+        remoteViews.clear();
+        fl_remote.removeAllViews();
+        fl_remote_2.removeAllViews();
+        fl_remote_3.removeAllViews();
+        fl_remote_4.removeAllViews();
+        fl_remote_5.removeAllViews();
+    }
+
     private ViewGroup getAvailableView() {
         if(fl_remote.getChildCount() == 0){
             return fl_remote;