联网demo:在线解析JSON+ AsyncTaskLoader

Posted 2021-02-15 neowu

demo效果：

 

获取并解析Json

package com.example.admin.quakereport;

import android.text.TextUtils;
import android.util.Log;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

public class QueryUtils {

    private static final String LOG_TAG = QueryUtils.class.getSimpleName();

    public static List<Earthquake> fetchEarthquakeData(String requestUrl){
        URL url = createUrl(requestUrl);
        String jsonResponse = null;
        try
        { jsonResponse = makehttpRequest(url);
        }catch (IOException e){
            Log.e(LOG_TAG,"Error in making http request",e); }
        List<Earthquake> result = extractEarthquakes(jsonResponse);
        return result;
    }


    private static URL createUrl(String mUrl) {
        URL url = null;
        try {
            url = new URL(mUrl);
        } catch (MalformedURLException e) {
            Log.e(LOG_TAG, "Problem building the URL ", e);
        }
        return url;
    }

    private static String makehttpRequest(URL url)throws IOException {
        String jsonResponse = "";
        if (url == null) {
            return jsonResponse;
        }

        HttpURLConnection urlConnection = null;
        InputStream inputStream = null;

        try {
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setReadTimeout(10000);
            urlConnection.setConnectTimeout(15000);
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();

            if (urlConnection.getResponseCode() == 200) {
                inputStream = urlConnection.getInputStream();
                jsonResponse = readFromStream(inputStream);
            } else {
                Log.e(LOG_TAG, "Error in connection!! Bad Response ");
            }

        } catch (IOException e) {
            Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
        } finally {
            {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (inputStream != null) {
                    inputStream.close();
                }
            }
        }
        return jsonResponse;
    }

    private static String readFromStream(InputStream inputStream)throws IOException{
        StringBuilder output = new StringBuilder();
        if (inputStream != null) {
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
            BufferedReader reader = new BufferedReader(inputStreamReader);
            String line = reader.readLine();

            while (line != null) {
                output.append(line);
                line = reader.readLine();
            }
        }

       return output.toString();
}

    private static List<Earthquake> extractEarthquakes(String earthquakeJSON){
        if (TextUtils.isEmpty(earthquakeJSON)) {
            return null;
        }
        List<Earthquake> earthquakes = new ArrayList<>();

        try {
            JSONObject baseJsonResponse = new JSONObject(earthquakeJSON);
            JSONArray featureArray = baseJsonResponse.getJSONArray("features");

            for (int i = 0; i < featureArray.length(); i++) {
                JSONObject currentEarthquake = featureArray.getJSONObject(i);
                JSONObject properties = currentEarthquake.getJSONObject("properties");
                double magnitude = properties.getDouble("mag");
                String location = properties.getString("place");
                long time = properties.getLong("time");
                String Url = properties.getString("url");
                Earthquake earthquake = new Earthquake(magnitude, location, time,Url);
                earthquakes.add(earthquake);
            }

        }catch (JSONException e){
            Log.e(LOG_TAG,"Error in fetching data",e);
        }
        return earthquakes;
    }


}

android 网络连接必须放在子线程中，不推荐用AsyncTask的原因：横屏时AsyncTask不会被回收到内存。

package com.example.admin.quakereport;

import android.content.AsyncTaskLoader;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;


import java.util.List;

public class EarthquakeLoader extends AsyncTaskLoader<List<Earthquake>> {
    private String mUrl;
    private List<Earthquake> itemlist;


    public EarthquakeLoader(@NonNull Context context,String mUrl) {
        super(context);
        this.mUrl=mUrl;
    }

    @Override
    protected void onStartLoading() {
        if (itemlist!=null){
            deliverResult(itemlist);
        }else {
            forceLoad();
        }
    }

    @Nullable
    @Override

    public List<Earthquake> loadInBackground(){
        if (mUrl == null) {
            return null; }
        List<Earthquake> earthquakes = QueryUtils.fetchEarthquakeData(mUrl);
        return earthquakes;
    }

    @Override
    public void deliverResult(@Nullable List<Earthquake> data) {
        itemlist=data;
        super.deliverResult(data);
    }
}

完整代码请看github: https://github.com/NeoWu55/Android-QuakeReport