/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.example.android.networkusage;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.webkit.WebView;
import android.widget.Toast;
import com.example.android.networkusage.R;
import com.example.android.networkusage.StackOverflowXmlParser.Entry;
import org.xmlpull.v1.XmlPullParserException;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;
/**
* Main Activity for the sample application.
*
* This activity does the following:
*
* o Presents a WebView screen to users. This WebView has a list of HTML links to the latest
* questions tagged 'android' on stackoverflow.com.
*
* o Parses the StackOverflow XML feed using XMLPullParser.
*
* o Uses AsyncTask to download and process the XML feed.
*
* o Monitors preferences and the device's network connection to determine whether
* to refresh the WebView content.
*/
public class NetworkActivity extends Activity {
public static final String WIFI = "Wi-Fi";
public static final String ANY = "Any";
private static final String URL =
"http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest";
// Whether there is a Wi-Fi connection.
private static boolean wifiConnected = false;
// Whether there is a mobile connection.
private static boolean mobileConnected = false;
// Whether the display should be refreshed.
public static boolean refreshDisplay = true;
// The user's current network preference setting.
public static String sPref = null;
// The BroadcastReceiver that tracks network connectivity changes.
private NetworkReceiver receiver = new NetworkReceiver();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Register BroadcastReceiver to track connection changes.
IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
receiver = new NetworkReceiver();
this.registerReceiver(receiver, filter);
}
// Refreshes the display if the network connection and the
// pref settings allow it.
@Override
public void onStart() {
super.onStart();
// Gets the user's network preference settings
SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
// Retrieves a string value for the preferences. The second parameter
// is the default value to use if a preference value is not found.
sPref = sharedPrefs.getString("listPref", "Wi-Fi");
updateConnectedFlags();
// Only loads the page if refreshDisplay is true. Otherwise, keeps previous
// display. For example, if the user has set "Wi-Fi only" in prefs and the
// device loses its Wi-Fi connection midway through the user using the app,
// you don't want to refresh the display--this would force the display of
// an error page instead of stackoverflow.com content.
if (refreshDisplay) {
loadPage();
}
}
@Override
public void onDestroy() {
super.onDestroy();
if (receiver != null) {
this.unregisterReceiver(receiver);
}
}
// Checks the network connection and sets the wifiConnected and mobileConnected
// variables accordingly.
private void updateConnectedFlags() {
ConnectivityManager connMgr =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
if (activeInfo != null && activeInfo.isConnected()) {
wifiConnected = activeInfo.getType() == ConnectivityManager.TYPE_WIFI;
mobileConnected = activeInfo.getType() == ConnectivityManager.TYPE_MOBILE;
} else {
wifiConnected = false;
mobileConnected = false;
}
}
// Uses AsyncTask subclass to download the XML feed from stackoverflow.com.
// This avoids UI lock up. To prevent network operations from
// causing a delay that results in a poor user experience, always perform
// network operations on a separate thread from the UI.
private void loadPage() {
if (((sPref.equals(ANY)) && (wifiConnected || mobileConnected))
|| ((sPref.equals(WIFI)) && (wifiConnected))) {
// AsyncTask subclass
new DownloadXmlTask().execute(URL);
} else {
showErrorPage();
}
}
// Displays an error if the app is unable to load content.
private void showErrorPage() {
setContentView(R.layout.main);
// The specified network connection is not available. Displays error message.
WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.loadData(getResources().getString(R.string.connection_error),
"text/html", null);
}
// Populates the activity's options menu.
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.mainmenu, menu);
return true;
}
// Handles the user's menu selection.
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.settings:
Intent settingsActivity = new Intent(getBaseContext(), SettingsActivity.class);
startActivity(settingsActivity);
return true;
case R.id.refresh:
loadPage();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
// Implementation of AsyncTask used to download XML feed from stackoverflow.com.
private class DownloadXmlTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... urls) {
try {
return loadXmlFromNetwork(urls[0]);
} catch (IOException e) {
return getResources().getString(R.string.connection_error);
} catch (XmlPullParserException e) {
return getResources().getString(R.string.xml_error);
}
}
@Override
protected void onPostExecute(String result) {
setContentView(R.layout.main);
// Displays the HTML string in the UI via a WebView
WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.loadData(result, "text/html", null);
}
}
// Uploads XML from stackoverflow.com, parses it, and combines it with
// HTML markup. Returns HTML string.
private String loadXmlFromNetwork(String urlString) throws XmlPullParserException, IOException {
InputStream stream = null;
StackOverflowXmlParser stackOverflowXmlParser = new StackOverflowXmlParser();
List<Entry> entries = null;
String title = null;
String url = null;
String summary = null;
Calendar rightNow = Calendar.getInstance();
DateFormat formatter = new SimpleDateFormat("MMM dd h:mmaa");
// Checks whether the user set the preference to include summary text
SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
boolean pref = sharedPrefs.getBoolean("summaryPref", false);
StringBuilder htmlString = new StringBuilder();
htmlString.append("<h3>" + getResources().getString(R.string.page_title) + "</h3>");
htmlString.append("<em>" + getResources().getString(R.string.updated) + " " +
formatter.format(rightNow.getTime()) + "</em>");
try {
stream = downloadUrl(urlString);
entries = stackOverflowXmlParser.parse(stream);
// Makes sure that the InputStream is closed after the app is
// finished using it.
} finally {
if (stream != null) {
stream.close();
}
}
// StackOverflowXmlParser returns a List (called "entries") of Entry objects.
// Each Entry object represents a single post in the XML feed.
// This section processes the entries list to combine each entry with HTML markup.
// Each entry is displayed in the UI as a link that optionally includes
// a text summary.
for (Entry entry : entries) {
htmlString.append("<p><a href='");
htmlString.append(entry.link);
htmlString.append("'>" + entry.title + "</a></p>");
// If the user set the preference to include summary text,
// adds it to the display.
if (pref) {
htmlString.append(entry.summary);
}
}
return htmlString.toString();
}
// Given a string representation of a URL, sets up a connection and gets
// an input stream.
private InputStream downloadUrl(String urlString) throws IOException {
URL url = new URL(urlString);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000 /* milliseconds */);
conn.setConnectTimeout(15000 /* milliseconds */);
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query
conn.connect();
InputStream stream = conn.getInputStream();
return stream;
}
/**
*
* This BroadcastReceiver intercepts the android.net.ConnectivityManager.CONNECTIVITY_ACTION,
* which indicates a connection change. It checks whether the type is TYPE_WIFI.
* If it is, it checks whether Wi-Fi is connected and sets the wifiConnected flag in the
* main activity accordingly.
*
*/
public class NetworkReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager connMgr =
(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
// Checks the user prefs and the network connection. Based on the result, decides
// whether
// to refresh the display or keep the current display.
// If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection.
if (WIFI.equals(sPref) && networkInfo != null
&& networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
// If device has its Wi-Fi connection, sets refreshDisplay
// to true. This causes the display to be refreshed when the user
// returns to the app.
refreshDisplay = true;
Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show();
// If the setting is ANY network and there is a network connection
// (which by process of elimination would be mobile), sets refreshDisplay to true.
} else if (ANY.equals(sPref) && networkInfo != null) {
refreshDisplay = true;
// Otherwise, the app can't download content--either because there is no network
// connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there
// is no Wi-Fi connection.
// Sets refreshDisplay to false.
} else {
refreshDisplay = false;
Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show();
}
}
}
}
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