問題描述

我需要實現下面這段代碼，但是應該是耗時太長放在主界面會卡，所以希望異步處理

JsonReader jsonReader = new JsonReader();cityObject = jsonReader.jsonObject();try { cityArray = cityObject.getJSONArray('city_info'); for (int i=0;i<cityArray.length();i++) {Gson gson = new Gson();JSONObject city = (JSONObject) cityArray.get(i);cityDataList.add(gson.fromJson(city.toString(), CityData.class)); }} catch (JSONException e) { e.printStackTrace();}provinceList = getProvinceList();cityMap = getCityMap();

public class JsonReader { public JSONObject jsonObject(){InputStream inputStream = getClass().getClassLoader().getResourceAsStream('assets/cityList.json');InputStreamReader streamReader = new InputStreamReader(inputStream);BufferedReader reader = new BufferedReader(streamReader);String line;StringBuilder stringBuilder = new StringBuilder();try { while ((line = reader.readLine()) != null) {stringBuilder.append(line); } reader.close(); reader.close(); inputStream.close();} catch (IOException e) { e.printStackTrace();}try { JSONObject cityJson = new JSONObject(stringBuilder.toString()); return cityJson;} catch (JSONException e) { e.printStackTrace();}return null; }}

private List<String> getProvinceList() {List<String> list = new ArrayList<>();for (int i = 0; i < cityDataList.size(); i++) { CityData cityData = cityDataList.get(i); boolean isProvince = false; for (int j = 0; j < list.size(); j++) {if (list.get(j).equals(cityData.getProv())) { isProvince = true; break;} } if (isProvince) continue; else list.add(cityData.getProv());}return list; } private HashMap<String, List<String>> getCityMap() {HashMap<String, List<String>> map = new HashMap<>();for (int i = 0; i < provinceList.size(); i++) { String prov = provinceList.get(i); List<String> list = new ArrayList<>(); for (int j = 0; j < cityDataList.size(); j++) {if (cityDataList.get(j).getProv().equals(prov)) list.add(cityDataList.get(j).getCity()); } map.put(prov, list);}return map; }

這幾個操作循環比較多，比較耗時，我想用rxjava處理，但是對observable的使用還是不太清楚，有人能介紹一下像我這樣observable怎么寫嗎？我想要改進的是用observable通過flatmap等這些操作符來返回provinceList和cityMap,并且把線程轉到后臺，在前臺接收到這兩個數據就好了

問題解答

幫樓主寫了下示例代碼，像樓主這種需求，其實無須操作符進行變換的。

Observable.create(new Observable.OnSubscribe<Pair>() { @Override public void call(Subscriber<? super Pair> subscriber) {JsonReader jsonReader = new JsonReader();cityObject = jsonReader.jsonObject();try { cityArray = cityObject.getJSONArray('city_info'); for (int i=0;i<cityArray.length();i++) {Gson gson = new Gson();JSONObject city = (JSONObject) cityArray.get(i);cityDataList.add(gson.fromJson(city.toString(), CityData.class)); }} catch (JSONException e) { e.printStackTrace();}provinceList = getProvinceList();cityMap = getCityMap();Pair pair = new Pair(provinceList, cityMap); }}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Subscriber<Pair>() { @Override public void onCompleted() { } @Override public void onError(Throwable e) { } @Override public void onNext(Pair pair) {//pair.first -> provinceList//pair.second -> cityMap }});回答2：

你需要的是cityDataList這個list吧？那么就可以使用Observable.create來新建一個Observable，把所有操作放在OnSubscribe對象中的call方法中，在最后數據準備完成后調用subscriber相應的onNext就行了。同時處理一下對應的onCompleted和onError