2

我不确定我错了，在 Google Map v2 示例中nullPointerException使用。googlemap.setMyLocationEnabled(true)

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

顺便说一句，对于那些试图玩的人来说，源代码是一个很好的例子，google map v2并且得到了很好的评论。

任何有关该错误的帮助表示赞赏。

提前致谢。

4

2 回答 2

5

由于设备中缺少 Google Play Services API，我得到了一些类似的东西。如果您使用：

GooglePlayServicesUtil.isGooglePlayServicesAvailable(Context)

如果可用，它应该返回 ConnectionResult.SUCCESS。如果它返回

ConnectionResult.SERVICE_MISSING
ConnectionResult.SERVICE_VERSION_UPDATE_REQUIRED
ConnectionResult.SERVICE_DISABLED

您可以提示用户下载它使用

GooglePlayServicesUtil.getErrorDialog()
于 2013-01-11T16:24:11.283 回答
4

getmap()正在返回 null。这意味着地图还没有准备好。要么是因为片段尚未准备好，要么是您在没有可用 Google Play 服务的设备上运行。有关详细信息，请参阅getMap。

于 2013-01-11T16:18:59.780 回答