@Override protected JsonObject getChartData() { JsonObject data = new JsonObject(); JsonObject values = new JsonObject(); HashMap<String, Integer> map = getValues(new HashMap<String, Integer>()); if (map == null || map.isEmpty()) { // Null = skip the chart return null; } boolean allSkipped = true; for (Map.Entry<String, Integer> entry : map.entrySet()) { if (entry.getValue() == 0) { continue; // Skip this invalid } allSkipped = false; values.addProperty(entry.getKey(), entry.getValue()); } if (allSkipped) { // Null = skip the chart return null; } data.add("values", values); return data; }