How to debug an android application in Eclipse?

Question

Android

Hello everybody. Need help: I ​​can't debug an android application: step-by-step tracing continues until it meets Java classes in the source code, namely in the following piece of code

try{
      Log.d(LOG, "opening testTask.json");
//в следующей строке получаю сообщение "Source not found"
      InputStreamReader istream = new InputStreamReader(aMngr.open("testTask.json"));
      BufferedReader br = new BufferedReader(istream);
      String line;
      while((line=br.readLine()) != null){
        sb.append(line);
      }
      Log.d(LOG, "After read file");
      br.close();	
      try{....

in the indicated line, debugging is interrupted with the message "Source not found"
In the project settings Project properties=>Java Build Path=>Libraries=>Add external JARs... I add src.zip from the folder where the JDK is installed, but nothing happens. How to be?