java - 谷歌地图错误；无法看到输出

Question

我是 Android Google map 新手。我按照一些教程在 map 上编写了一些代码，但是我看不到输出。我生成并使用了映射 key APIv2。请帮我解决代码。

Manifest.xml

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

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="18" />

<permission
    android:name="com.examp.nowmap.permission.MAPS_RECEIVE"
    android:protectionLevel="signature" />

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

<uses-permission android:name="com.examp.nowmap.package.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" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.examp.nowmap.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="AIzaSyBbMfnc3rVf89ie564M8VgKZpfpbLHKyKo" />
     </application>

</manifest>

MainActivity.java

package com.examp.nowmap;

@SuppressLint("NewApi")
public class MainActivity extends Fragment {

private Location currentLocation = null;
private LocationManager locationManager;
private GeoPoint currentPoint;

TextView location1;

ArrayList<LatLng> markerPoints;
GoogleMap map;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

getLastLocation();
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle  savedInstanceState) {
View view = inflater.inflate(R.layout.main, container, false);
//  ...some other stuff being done here...
// Return view
return view;
}

public void getLastLocation(){
String provider = getBestProvider();
currentLocation = locationManager.getLastKnownLocation(provider);

this.markerPoints = new ArrayList<LatLng>();

LatLng fromPosition = new LatLng(currentLocation.getLatitude(),   currentLocation.getLongitude());
LatLng toPosition = new LatLng(29.633289, -82.305838);

LatLng toPosition1 = new LatLng(40.044438,-106.197281);


MainActivity.this.markerPoints.add(fromPosition);
MainActivity.this.markerPoints.add(toPosition);

// Getting URL to the Google Directions API
String url = MainActivity.this.getDirectionsUrl(fromPosition, toPosition);

DownloadTask downloadTask = new DownloadTask();

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

if(currentLocation != null) {
    setCurrentLocation(currentLocation);
} else { 
    // do something
}
}

public String getBestProvider() {
locationManager = (LocationManager)    getActivity().getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
criteria.setPowerRequirement(Criteria.NO_REQUIREMENT);
criteria.setAccuracy(Criteria.NO_REQUIREMENT);
String bestProvider = locationManager.getBestProvider(criteria, true);
return bestProvider;
}

public void setCurrentLocation(Location location){
// Get current location
int currLatitude = (int) (location.getLatitude()*1E6);
int currLongitude = (int) (location.getLongitude()*1E6);
currentPoint = new GeoPoint(currLatitude,currLongitude); 
// Set current location
currentLocation = new Location("");
currentLocation.setLatitude(currentPoint.getLatitudeE6() / 1e6);
currentLocation.setLongitude(currentPoint.getLongitudeE6() / 1e6);
}

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;
}

/** A method to download json data from url */
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, ArrayList<String>> {
@Override
protected ArrayList<String> doInBackground(String... urlList) {
    try {
        ArrayList<String> returnList = new ArrayList<String>();
        for (String url : urlList) {
            // Fetching the data from web service
            String data = MainActivity.this.downloadUrl(url);
            returnList.add(data);
        }
        return returnList;
    } catch (Exception e) {
        Log.d("Background Task", e.toString());
        return null; // Failed, return null
    }
}

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

    ParserTask parserTask = new ParserTask();

    for (String url : results) {
        parserTask.execute(url);
    }

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

/** A class to parse the Google Places in JSON format */
private class ParserTask extends AsyncTask<String, Integer,    ArrayList<List<HashMap<String, String>>>> {
// Parsing the data in non-ui thread
@Override
protected ArrayList<List<HashMap<String, String>>> doInBackground(String... jsonData) {
    try {
        ArrayList<List<HashMap<String, String>>> routes = new  ArrayList<List<HashMap<String, String>>>();

        // for (String url : jsonData) {
        for (int i = 0; i < jsonData.length; i++) {
            JSONObject jObject = new JSONObject(jsonData[i]);

            DirectionsJSONParser parser = new DirectionsJSONParser();
            // Starts parsing data
            routes = (ArrayList<List<HashMap<String, String>>>) parser.parse(jObject);
        }
        return routes;
    } catch (Exception e) {
        Log.d("Background task", e.toString());
        return null; // Failed, return null
    }
}

// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result)  
{
    if (result.size() < 1) 
    {
        Toast.makeText(getActivity(), "No Points", Toast.LENGTH_SHORT).show();
        return;
    }

    TextView tv1 = (TextView) getActivity().findViewById(R.id.location1);
    TextView tv2 = (TextView) getActivity().findViewById(R.id.location2);
    TextView tv3 = (TextView) getActivity().findViewById(R.id.location3);
    TextView tv4 = (TextView) getActivity().findViewById(R.id.location4);

    TextView[] views = {tv1, tv2, tv3, tv4};


    // Traversing through all the routes
    for (int i = 0; i < result.size(); i++) 
    {
        // Fetching i-th route
        List<HashMap<String, String>> path = result.get(i);
        String distance = "No distance";

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

            if (j == 0)  
            {
                distance = point.get("distance");
                continue;
            }
        }

        // Set text
        views[i].setText(distance);
    }
}
}
}

ma​​in.xml

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<fragment
    android:name="com.google.android.gms.maps.SupportMapFragment"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</LinearLayout>

Answer 1

这是 Google map 的一个常见问题，很多人都会问这个问题，研究显示有很多主观问题...试试这个:

1. 检查您是否已在 Google API 控制台上启用 Google Maps Android API v2 服务。如果没有，请启用它，然后按生成新 key 重新创建 API key 。

2. 仔细检查所有必需的权限以及您复制并粘贴的 API key 。

3. 卸载您的设备或 AVD 上的应用，然后重新安装并尝试...有时需要完全刷新。

使用 LatLng 前往特定位置

这是我设计的一种易于使用的方法，用于前往特定位置。将其放入您的 Activity 中或创建一个新类并将数据传递给它:)

/** goToLocation
 * @param map - You GoogleMap reference
 * @param location - your LatLng value
 * @param zoom Float - ie. 15
 * @param b Boolean - Animate camera movement: true or false
 */
public void goToLocation(GoogleMap map, LatLng ll, float zoom, boolean b) {
    if (b == true) {
        map.animateCamera(CameraUpdateFactory.newLatLngZoom(ll, zoom));
    } else {
        map.moveCamera(CameraUpdateFactory.newLatLngZoom(ll, zoom));
    }
}