Google Maps Android API v2-- Android 新版地圖導航路徑開發方法

繼上一篇的"Android 新版地圖開發方法"，最近參考了一些網站後透過Google Directions API擷取了JSON做了個比較實用的導航路徑，如下圖:

本篇主要是在Android下解析Google Directions API 所傳回的JSON資料後再繪製導航路徑，程式碼如下:
(記得程式要匯入google-play-services_lib 以及申請Map API Key，詳見 "Android 新版地圖開發方法")

Layout部分:
activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <fragment
        android:id="@+id/map"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        class="com.google.android.gms.maps.SupportMapFragment" />

</RelativeLayout>

程式1:
MainActivity.java
package edu.nkut.myroutemap;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.json.JSONObject;

import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMap.OnMapClickListener;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;

public class MainActivity extends FragmentActivity {

static final LatLng NKUT = new LatLng(23.979548, 120.696745);
GoogleMap map;
ArrayList<LatLng> markerPoints;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// Initializing
markerPoints = new ArrayList<LatLng>();

// Getting reference to SupportMapFragment of the activity_main
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);

// Getting Map for the SupportMapFragment
map = fm.getMap();
Marker nkut = map.addMarker(new MarkerOptions().position(NKUT).title("南開科技大學").snippet("數位生活創意系"));
// Move the camera instantly to NKUT with a zoom of 16.
map.moveCamera(CameraUpdateFactory.newLatLngZoom(NKUT, 16));

if (map != null) {

// Enable MyLocation Button in the Map
map.setMyLocationEnabled(true);

// Setting onclick event listener for the map
map.setOnMapClickListener(new OnMapClickListener() {

@Override
public void onMapClick(LatLng point) {

// Already two locations
if (markerPoints.size() > 1) {
markerPoints.clear();
map.clear();
}

// Adding new item to the ArrayList
markerPoints.add(point);

// Creating MarkerOptions
MarkerOptions options = new MarkerOptions();

// Setting the position of the marker
options.position(point);

/**
* 起始及終點位置符號顏色
*/
if (markerPoints.size() == 1) {
options.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_GREEN)); //起點符號顏色
} else if (markerPoints.size() == 2) {
options.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_RED)); //終點符號顏色
}

// Add new marker to the Google Map Android API V2
map.addMarker(options);

// Checks, whether start and end locations are captured
if (markerPoints.size() >= 2) {
LatLng origin = markerPoints.get(0);
LatLng dest = markerPoints.get(1);

// Getting URL to the Google Directions API
String url = getDirectionsUrl(origin, dest);

DownloadTask downloadTask = new DownloadTask();

// Start downloading json data from Google Directions
// API
downloadTask.execute(url);
}

}
});
}
}

private String getDirectionsUrl(LatLng origin, LatLng dest) {

// Origin of route
String str_origin = "origin=" + origin.latitude + ","
+ origin.longitude;

// Destination of route
String str_dest = "destination=" + dest.latitude + "," + dest.longitude;

// Sensor enabled
String sensor = "sensor=false";

// Building the parameters to the web service
String parameters = str_origin + "&" + str_dest + "&" + sensor;

// Output format
String output = "json";

// Building the url to the web service
String url = "https://maps.googleapis.com/maps/api/directions/"
+ output + "?" + parameters;

return url;
}

/**從URL下載JSON資料的方法**/
private String downloadUrl(String strUrl) throws IOException {
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try {
URL url = new URL(strUrl);

// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();

// Connecting to url
urlConnection.connect();

// Reading data from url
iStream = urlConnection.getInputStream();

BufferedReader br = new BufferedReader(new InputStreamReader(
iStream));

StringBuffer sb = new StringBuffer();

String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}

data = sb.toString();

br.close();

} catch (Exception e) {
Log.d("Exception while downloading url", e.toString());
} finally {
iStream.close();
urlConnection.disconnect();
}
return data;
}

// Fetches data from url passed
private class DownloadTask extends AsyncTask<String, Void, String> {

// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {

// For storing data from web service
String data = "";

try {
// Fetching the data from web service
data = downloadUrl(url[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}

// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);

ParserTask parserTask = new ParserTask();

// Invokes the thread for parsing the JSON data
parserTask.execute(result);

}
}

/** 解析JSON格式 **/
private class ParserTask extends
AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {

// Parsing the data in non-ui thread
@Override
protected List<List<HashMap<String, String>>> doInBackground(
String... jsonData) {

JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;

try {
jObject = new JSONObject(jsonData[0]);
DirectionsJSONParser parser = new DirectionsJSONParser();

// Starts parsing data
routes = parser.parse(jObject);
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}

// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();

// Traversing through all the routes
for (int i = 0; i < result.size(); i++) {
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();

// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);

// Fetching all the points in i-th route
for (int j = 0; j < path.size(); j++) {
HashMap<String, String> point = path.get(j);

double lat = Double.parseDouble(point.get("lat"));
double lng = Double.parseDouble(point.get("lng"));
LatLng position = new LatLng(lat, lng);

points.add(position);
}

// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(5);  //導航路徑寬度
lineOptions.color(Color.BLUE); //導航路徑顏色

}

// Drawing polyline in the Google Map for the i-th route
map.addPolyline(lineOptions);
}
}
}

程式2: 
DirectionsJSONParser.java

package edu.nkut.myroutemap;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.google.android.gms.maps.model.LatLng;

public class DirectionsJSONParser {

/** 接收一個JSONObject並返回一個列表的列表，包含經緯度 */
public List<List<HashMap<String,String>>> parse(JSONObject jObject){

List<List<HashMap<String, String>>> routes = new ArrayList<List<HashMap<String,String>>>() ;
JSONArray jRoutes = null;
JSONArray jLegs = null;
JSONArray jSteps = null;

try {

jRoutes = jObject.getJSONArray("routes");

/** Traversing all routes */
for(int i=0;i<jRoutes.length();i++){
jLegs = ( (JSONObject)jRoutes.get(i)).getJSONArray("legs");
List path = new ArrayList<HashMap<String, String>>();

/** Traversing all legs */
for(int j=0;j<jLegs.length();j++){
jSteps = ( (JSONObject)jLegs.get(j)).getJSONArray("steps");

/** Traversing all steps */
for(int k=0;k<jSteps.length();k++){
String polyline = "";
polyline = (String)((JSONObject)((JSONObject)jSteps.get(k)).get("polyline")).get("points");
List<LatLng> list = decodePoly(polyline);

/** Traversing all points */
for(int l=0;l<list.size();l++){
HashMap<String, String> hm = new HashMap<String, String>();
hm.put("lat", Double.toString(((LatLng)list.get(l)).latitude) );
hm.put("lng", Double.toString(((LatLng)list.get(l)).longitude) );
path.add(hm);
}
}
routes.add(path);
}
}

} catch (JSONException e) {
e.printStackTrace();
}catch (Exception e){
}


return routes;
}


/**
* 解碼折線點的方法
* */
    private List<LatLng> decodePoly(String encoded) {

        List<LatLng> poly = new ArrayList<LatLng>();
        int index = 0, len = encoded.length();
        int lat = 0, lng = 0;

        while (index < len) {
            int b, shift = 0, result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lat += dlat;

            shift = 0;
            result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lng += dlng;

            LatLng p = new LatLng((((double) lat / 1E5)),
                    (((double) lng / 1E5)));
            poly.add(p);
        }

        return poly;
    }
}

AndroidManifest.xml 內容:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="edu.nkut.myroutemap"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <uses-permission android:name="android.permission.INTERNET" />

    <permission
        android:name="in.wptrafficanalyzer.locationroutedirectionmapv2.permission.MAPS_RECEIVE"
        android:protectionLevel="signature" />

    <uses-permission android:name="in.wptrafficanalyzer.locationroutedirectionmapv2.permission.MAPS_RECEIVE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="edu.nkut.myroutemap.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="你所申請的API Key" />
    </application>

</manifest>

執行結果:

上圖執行結果是點選地圖起點(南開科技大學)及終點(逢甲大學)，藍色的線就是程式所繪出的導航路徑。
(別忘了，預設模擬器不支援本程式執行，另外程式出處請看參考1項目。)



參考:
1.Showing current location using OnMyLocationChangeListener in Google Map Android API V2 (有提供程式碼，本篇參考出處)
http://goo.gl/3UEmPV

2.Google Directions API |  Maps API 網路服務
https://developers.google.com/maps/documentation/directions/?hl=zh-TW&csw=1

3.編碼折線演算法格式 | Google Maps API
https://developers.google.com/maps/documentation/utilities/polylinealgorithm?hl=zh-TW&csw=1

4.Android程式設計 - Google Maps API v2在地圖上繪圖
http://nkeegamedev.blogspot.tw/2013/05/android-google-map-v2.html

==============延伸閱讀=====================
1.Google Maps Android API v2-- Android 新版地圖開發方法
http://www.cheng-min-i-taiwan.blogspot.tw/2013/04/google-maps-android-api-v2-android.html