public boolean refreshData(String json, String courseID) {
   getDatabase();
   ContentValues value = new ContentValues();
   value.put("course_data", json);
   value.put("course_id", courseID);
   value.put("time", System.currentTimeMillis());
   int num =
       db.update(ConstantUtils.T_COURSE_DATA, value, "course_id = ?", new String[] {courseID});
   if (num == 0) {
     long num2 = db.insert(ConstantUtils.T_COURSE_DATA, null, value);
     if (num2 == -1) {
       return false;
     } else {
       return true;
     }
   }
   return true;
 }
 @Override
 public void handleMessage(Message msg) {
   if (progressBar.VISIBLE == View.VISIBLE) {
     progressBar.setVisibility(View.GONE);
   }
   if (msg.what == 0) {
     // success
     CourseDBManager db = new CourseDBManager(LoginActivity.this);
     db.getDatabase();
     List<HashMap<String, String>> data = db.queryEnrollment(Utils.getUserName());
     Intent intent = new Intent(LoginActivity.this, MainActivity.class);
     intent.putExtra("data", (ArrayList) data);
     startActivity(intent);
     db.closeDB();
     LoginActivity.this.finish();
   }
   if (msg.what == -1) {
     Toast.makeText(LoginActivity.this, msg.obj.toString(), Toast.LENGTH_LONG).show();
   }
 }
 private boolean refresh(List<HashMap<String, Object>> data, String table) {
   getDatabase();
   db.beginTransaction();
   try {
     db.execSQL("delete from " + table);
     for (HashMap<String, Object> item : data) {
       ContentValues values = new ContentValues();
       Iterator iter = item.entrySet().iterator();
       while (iter.hasNext()) {
         Map.Entry entry = (Map.Entry) iter.next();
         values.put(entry.getKey().toString(), entry.getValue().toString());
       }
       db.insert(table, null, values);
     }
     db.setTransactionSuccessful();
     return true;
   } catch (Exception e) {
     return false;
   } finally {
     db.endTransaction();
   }
 }