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Android example source code file (GpsXtraDownloader.java)

This example Android source code file (GpsXtraDownloader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

accept, android, androidhttpclient, context, datainputstream, downloading, gpsxtradownloader, http, httpentity, httphost, internet, io, ioexception, net, network, random, statusline, string, unexpected, util

The GpsXtraDownloader.java Android example source code

/*
 * Copyright (C) 2008 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.android.internal.location;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.conn.params.ConnRouteParams;

import java.io.DataInputStream;
import java.io.IOException;
import java.util.Properties;
import java.util.Random;

import android.content.Context;
import android.net.Proxy;
import android.net.http.AndroidHttpClient;
import android.util.Config;
import android.util.Log;



/**
 * A class for downloading GPS XTRA data.
 *
 * {@hide}
 */
public class GpsXtraDownloader {

    private static final String TAG = "GpsXtraDownloader";
    
    private Context mContext;
    private String[] mXtraServers;
    // to load balance our server requests
    private int mNextServerIndex;

    GpsXtraDownloader(Context context, Properties properties) {
        mContext = context;

        // read XTRA servers from the Properties object
        int count = 0;
        String server1 = properties.getProperty("XTRA_SERVER_1");
        String server2 = properties.getProperty("XTRA_SERVER_2");
        String server3 = properties.getProperty("XTRA_SERVER_3");
        if (server1 != null) count++;
        if (server2 != null) count++;
        if (server3 != null) count++;
        
        if (count == 0) {
            Log.e(TAG, "No XTRA servers were specified in the GPS configuration");
            return;
        } else {
            mXtraServers = new String[count];
            count = 0;
            if (server1 != null) mXtraServers[count++] = server1;
            if (server2 != null) mXtraServers[count++] = server2;
            if (server3 != null) mXtraServers[count++] = server3;

            // randomize first server
            Random random = new Random();
            mNextServerIndex = random.nextInt(count);
        }       
    }

    byte[] downloadXtraData() {
        String proxyHost = Proxy.getHost(mContext);
        int proxyPort = Proxy.getPort(mContext);
        boolean useProxy = (proxyHost != null && proxyPort != -1);
        byte[] result = null;
        int startIndex = mNextServerIndex;

        if (mXtraServers == null) {
            return null;
        }

        // load balance our requests among the available servers
        while (result == null) {
            result = doDownload(mXtraServers[mNextServerIndex], useProxy, proxyHost, proxyPort);
            
            // increment mNextServerIndex and wrap around if necessary
            mNextServerIndex++;
            if (mNextServerIndex == mXtraServers.length) {
                mNextServerIndex = 0;
            }
            // break if we have tried all the servers
            if (mNextServerIndex == startIndex) break;
        }
    
        return result;
    }

    protected static byte[] doDownload(String url, boolean isProxySet, 
            String proxyHost, int proxyPort) {
        if (Config.LOGD) Log.d(TAG, "Downloading XTRA data from " + url);

        AndroidHttpClient client = null;
        try {
            client = AndroidHttpClient.newInstance("Android");
            HttpUriRequest req = new HttpGet(url);

            if (isProxySet) {
                HttpHost proxy = new HttpHost(proxyHost, proxyPort);
                ConnRouteParams.setDefaultProxy(req.getParams(), proxy);
            }

            req.addHeader(
                    "Accept",
                    "*/*, application/vnd.wap.mms-message, application/vnd.wap.sic");

            req.addHeader(
                    "x-wap-profile",
                    "http://www.openmobilealliance.org/tech/profiles/UAPROF/ccppschema-20021212#");

            HttpResponse response = client.execute(req);
            StatusLine status = response.getStatusLine();
            if (status.getStatusCode() != 200) { // HTTP 200 is success.
                if (Config.LOGD) Log.d(TAG, "HTTP error: " + status.getReasonPhrase());
                return null;
            }

            HttpEntity entity = response.getEntity();
            byte[] body = null;
            if (entity != null) {
                try {
                    if (entity.getContentLength() > 0) {
                        body = new byte[(int) entity.getContentLength()];
                        DataInputStream dis = new DataInputStream(entity.getContent());
                        try {
                            dis.readFully(body);
                        } finally {
                            try {
                                dis.close();
                            } catch (IOException e) {
                                Log.e(TAG, "Unexpected IOException.", e);
                            }
                        }
                    }
                } finally {
                    if (entity != null) {
                        entity.consumeContent();
                    }
                }
            }
            return body;
        } catch (Exception e) {
            if (Config.LOGD) Log.d(TAG, "error " + e);
        } finally {
            if (client != null) {
                client.close();
            }
        }
        return null;
    }

}

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