Java tutorial
/* * Aegis Bitcoin Wallet - The secure Bitcoin wallet for Android * Copyright 2014 Bojan Simic and specularX.co, designed by Reuven Yamrom * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package com.aegiswallet.tasks; import android.content.Context; import android.content.SharedPreferences; import android.os.AsyncTask; import android.preference.PreferenceManager; import android.util.Log; import com.aegiswallet.utils.Constants; import org.json.JSONObject; import org.json.JSONTokener; import java.io.BufferedReader; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.URL; import java.util.Date; import java.util.concurrent.TimeUnit; /** * Created by bsimic on 3/17/14. */ public class GetCurrencyInfoTask extends AsyncTask<String, Void, Void> { private Context context; private String urlString = Constants.BLOCKCHAIN_CURRENCY_CALL; private JSONObject jsonObject; private SharedPreferences sharedPreferences; private String TAG = this.getClass().getName(); public GetCurrencyInfoTask(Context context) { this.context = context; this.sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context); } @Override protected Void doInBackground(String... strings) { Log.d(TAG, "inside currency info task..."); if (fileExistance(Constants.BLOCKCHAIN_CURRENCY_FILE_NAME) && !shouldRefreshFile(Constants.BLOCKCHAIN_CURRENCY_FILE_NAME)) { return null; } HttpURLConnection urlConnection = null; URL url = null; jsonObject = null; InputStream inStream = null; try { url = new URL(urlString.toString()); urlConnection = (HttpURLConnection) url.openConnection(); urlConnection.setRequestMethod("GET"); urlConnection.setDoOutput(true); urlConnection.setDoInput(true); urlConnection.connect(); inStream = urlConnection.getInputStream(); BufferedReader bReader = new BufferedReader(new InputStreamReader(inStream)); String temp, response = ""; while ((temp = bReader.readLine()) != null) { response += temp; } jsonObject = (JSONObject) new JSONTokener(response).nextValue(); } catch (Exception e) { } finally { if (inStream != null) { try { // this will close the bReader as well inStream.close(); } catch (IOException ignored) { Log.e("Currency Task", "File Close IO Exception: " + ignored.getMessage()); } } if (urlConnection != null) { urlConnection.disconnect(); } } if (jsonObject != null) { try { FileOutputStream fos = context.getApplicationContext() .openFileOutput(Constants.BLOCKCHAIN_CURRENCY_FILE_NAME, Context.MODE_PRIVATE); fos.write(jsonObject.toString().getBytes()); fos.close(); } catch (IOException e) { Log.e("Currency Task", "Cannot save or create file " + e.getMessage()); } } return null; } @Override protected void onPostExecute(Void aVoid) { super.onPostExecute(aVoid); //UPDATE views } public boolean fileExistance(String fname) { File file = context.getApplicationContext().getFileStreamPath(fname); return file.exists(); } public boolean shouldRefreshFile(String fname) { File file = context.getApplicationContext().getFileStreamPath(fname); long msBetweenDates = new Date().getTime() - file.lastModified(); long minutes = TimeUnit.MILLISECONDS.toMinutes(msBetweenDates); if (minutes > 15) return true; else return false; } }