谷歌地图V2上使用的setMyLocationEnabled的错误 [英] Google Maps v2 Error on use of setMyLocationEnabled
本文介绍了谷歌地图V2上使用的setMyLocationEnabled的错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我不知道是我出了问题，使用 googlemap.setMyLocationEnabled（真）得到了一个 NullPointerException异常谷歌地图V2的例子。
I am not sure were I went wrong, getting a nullPointerException on using googlemap.setMyLocationEnabled(true) in Google Map v2 example.
MainActivity.java文件：
package com.example.locationgooglemapsv2;
import java.io.IOException;
import java.util.List;
import android.content.Context;
import android.location.Address;
import android.location.Criteria;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
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.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MainActivity extends FragmentActivity implements LocationListener {
GoogleMap googleMap;
MarkerOptions markerOptions;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Getting reference to the SupportMapFragment of activity_main.xml
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Getting GoogleMap object from the fragment
googleMap = fm.getMap();
// Enabling MyLocation Layer of Google Map
googleMap.setMyLocationEnabled(true);
/*======== MAP TYPE ==========*/
googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
RadioGroup rgViews = (RadioGroup) findViewById(R.id.rg_views);
rgViews.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
// TODO Auto-generated method stub
switch(checkedId){
case R.id.normal: googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
break;
case R.id.satellite:googleMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
break;
case R.id.terrain: googleMap.setMapType(GoogleMap.MAP_TYPE_TERRAIN);
break;
}
}
});
/*======== MARKER AND ONCLICK ==========*/
googleMap.setOnMapClickListener(new OnMapClickListener() {
@Override
public void onMapClick(LatLng latlng) {
// Creating a marker
MarkerOptions markerOption = new MarkerOptions();
// Setting the position for the marker
markerOption.position(latlng);
// Setting the title for the marker.
// This will be displayed on taping the marker
//markerOption.title(latlng.latitude + " : " + latlng.longitude);
// Clears the previously touched position
googleMap.clear();
// Animating to the touched position
googleMap.animateCamera(CameraUpdateFactory.newLatLng(latlng));
// Placing a marker on the touched position
googleMap.addMarker(markerOption);
// Adding Marker on the touched location with address
new ReverseGeocodingTask(getBaseContext()).execute(latlng);
}
});
/*======== LOCATION ==========*/
// Getting LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location
Location location = locationManager.getLastKnownLocation(provider);
if(location!=null){
onLocationChanged(location);
}
locationManager.requestLocationUpdates(provider, 20000, 0, this);
}
@Override
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
double lat = location.getLatitude();
double lng = location.getLongitude();
//--maps
LatLng latlng = new LatLng(lat, lng);
googleMap.moveCamera(CameraUpdateFactory.newLatLng(latlng));
googleMap.animateCamera(CameraUpdateFactory.zoomTo(10));
}
@Override
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
/*======== REVERSE GEO CODING ==========*/
class ReverseGeocodingTask extends AsyncTask<LatLng, Void, String>{
Context mContext;
public ReverseGeocodingTask( Context con) {
super();
this.mContext = con;
}
@Override
protected String doInBackground(LatLng... params) {
// TODO Auto-generated method stub
Geocoder geocoder = new Geocoder(mContext);
double lat = params[0].latitude;
double lng = params[0].longitude;
List<Address> addresses = null;
String actualAdress = "";
try {
addresses = geocoder.getFromLocation(lat, lng, 1);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(addresses != null && addresses.size() > 0){
Address address = addresses.get(0);
actualAdress = String.format("%s, %s, %s", address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "",
address.getLocality(), address.getCountryName());
}
return actualAdress;
}
@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
// Setting the title for the marker.
// This will be displayed on taping the marker
markerOptions.title(result);
// Placing a marker on the touched position
googleMap.addMarker(markerOptions);
}
}
}
清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.locationgooglemapsv2"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<permission
android:name="com.example.locationgooglemapsv2.permission.MAPS_RECIEVE"
android:protectionLevel="signature" >
</permission>
<uses-permission android:name="com.example.locationgooglemapsv2.permission.MAPS_RECIEVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<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="com.example.locationgooglemapsv2.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="API_KEY" />
</application>
</manifest>
错误日志：
01-11 21:11:56.282: E/AndroidRuntime(327): FATAL EXCEPTION: main
01-11 21:11:56.282: E/AndroidRuntime(327): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.locationgooglemapsv2/com.example.locationgooglemapsv2.MainActivity}: java.lang.NullPointerException
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.os.Handler.dispatchMessage(Handler.java:99)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.os.Looper.loop(Looper.java:123)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread.main(ActivityThread.java:4627)
01-11 21:11:56.282: E/AndroidRuntime(327): at java.lang.reflect.Method.invokeNative(Native Method)
01-11 21:11:56.282: E/AndroidRuntime(327): at java.lang.reflect.Method.invoke(Method.java:521)
01-11 21:11:56.282: E/AndroidRuntime(327): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
01-11 21:11:56.282: E/AndroidRuntime(327): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
01-11 21:11:56.282: E/AndroidRuntime(327): at dalvik.system.NativeStart.main(Native Method)
01-11 21:11:56.282: E/AndroidRuntime(327): Caused by: java.lang.NullPointerException
01-11 21:11:56.282: E/AndroidRuntime(327): at com.example.locationgooglemapsv2.MainActivity.onCreate(MainActivity.java:46)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-11 21:11:56.282: E/AndroidRuntime(327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
01-11 21:11:56.282: E/AndroidRuntime(327): ... 11 more
BTW源是一个很好的例子对于那些谁试图用谷歌地图V2 玩，有很好的注释。
BTW the source is a good example for those who are trying to play with google map v2 and is well commented.
任何关于此错误的帮助是AP preciated。
Any help regarding the error is appreciated.
在此先感谢。
推荐答案
的GetMap（）则返回null。这意味着，在地图还没有准备好。或者是因为片段没有准备好或者你有没有可用谷歌播放服务的设备上运行。请参阅<一href="https://developers.google.com/maps/documentation/android/reference/com/google/android/gms/maps/MapFragment#getMap%28%29"相对=nofollow>的GetMap 获取更多信息。
getmap() is returning null. That means the map is not ready. Either because the fragment is not ready or your are running on a device without Google Play services available. See getMap for more info.
这篇关于谷歌地图V2上使用的setMyLocationEnabled的错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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