我的应用程序中不断获得NullPointerException行中定义的GoogleMap对象：
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
我在我的xml文件中定义了map，如下所示：
<fragment
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.SupportMapFragment"/>
我还拥有AndroidManifest.xml中的所有相应权限以及API。
以下是我的完整源代码：
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.location.LocationClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
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.MapFragment;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.provider.Settings;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.widget.Toast;
public class PlaceMarker extends FragmentActivity
implements GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener,
LocationListener {
private final static int CONNECTION_FAILURE_RESOLUTION_REQUEST = 9000;
private LocationClient mLocationClient = null;
private LocationRequest mLocationRequest = null;
private GoogleMap mMap;
private static final int UPDATE_INTERVAL_IN_SECONDS = 5;
private static final int MILLISECONDS_PER_SECOND = 1000;
private static final long UPDATE_INTERVAL = MILLISECONDS_PER_SECOND * UPDATE_INTERVAL_IN_SECONDS;
private static final int FASTEST_INTERVAL_IN_SECONDS = 1;
private static final long FASTEST_INTERVAL = MILLISECONDS_PER_SECOND * FASTEST_INTERVAL_IN_SECONDS;
private LocationManager locationManager;
private Location location = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_place_marker);
// mCurrentLocation = mLocationClient.getLastLocation();
// Double myLatitude = mCurrentLocation.getLatitude();
// Double myLongitude = mCurrentLocation.getLongitude();
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
mMap.setMyLocationEnabled(true);
// mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(myLatitude, myLongitude), 16));
mLocationClient = new LocationClient(this, this, this);
if (servicesConnected()) {
mLocationRequest = LocationRequest.create();
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setInterval(UPDATE_INTERVAL);
mLocationRequest.setFastestInterval(FASTEST_INTERVAL);
}
else {
Toast.makeText(this, "Position unavailable", Toast.LENGTH_SHORT).show();
}
// Marker marker = mMap.addMarker(new MarkerOptions()
// .position(new LatLng(myLatitude, myLongitude))
// .title("San Francisco")
// .snippet("Population: 776733"));
}
@Override
protected void onStart() {
super.onStart();
mLocationClient.connect();
}
@Override
protected void onStop() {
if (mLocationClient.isConnected()) {
mLocationClient.removeLocationUpdates(this);
}
mLocationClient.disconnect();
super.onStop();
}
private Location getCurrentLocation() {
Location location = mLocationClient.getLastLocation();
if (location != null) {
return location;
}
else {
Toast.makeText(this, "Current Location Unavailable", Toast.LENGTH_SHORT).show();
checkforGPSAndPromptOpen();
return null;
}
}
private void checkforGPSAndPromptOpen() {
boolean enabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!enabled) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
}
// Handle results returned to the FragmentActivity by Google Play services
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// Decide what to do based on the original request code
switch (requestCode) {
case CONNECTION_FAILURE_RESOLUTION_REQUEST :
// If the result code is Activity.RESULT_OK, try to connect again
switch (resultCode) {
case Activity.RESULT_OK :
// Try the request again
break;
}
}
}
private boolean servicesConnected() {
// Check that Google Play services is available
int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
// If Google Play services is available
if (ConnectionResult.SUCCESS == resultCode) {
// In debug mode, log the status
Log.d("Location Updates", "Google Play services is available.");
// Continue
return true;
// Google Play services was not available for some reason
} else {
// Get the error code
// Get the error dialog from Google Play services
Dialog errorDialog = GooglePlayServicesUtil.getErrorDialog(resultCode, this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
// If Google Play services can provide an error dialog
if (errorDialog != null) {
errorDialog.show();
}
return false;
}
}
/*
* Called by Location Services when the request to connect the client finishes successfully.
* At this point, you can request the current location or start periodic updates
*/
@Override
public void onConnected(Bundle dataBundle) {
// Display the connection status
Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show();
mLocationClient.requestLocationUpdates(mLocationRequest, this);
location = getCurrentLocation();
takeToLocation(convertLocationtoLatLong(location));
}
/*
* Called by Location Services if the connection to the location client drops because of an error.
*/
@Override
public void onDisconnected() {
// Display the connection status
Toast.makeText(this, "Disconnected. Please re-connect.", Toast.LENGTH_SHORT).show();
}
public void onLocationChanged(Location location) {
// Report to the UI that the location was updated
String msg = "Updated location: " + Double.toString(location.getLatitude()) + "," + Double.toString(location.getLongitude());
Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
}
/*
* Called by Location Services if the attempt to Location Services fails.
*/
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
private void takeToLocation(LatLng newLocation) {
if (newLocation != null) {
CameraUpdate update = CameraUpdateFactory.newLatLngZoom(newLocation, 16);
mMap.animateCamera(update);
}
else {
Toast.makeText(this, "Position unavailable", Toast.LENGTH_SHORT).show();
}
}
private LatLng convertLocationtoLatLong(Location location) {
LatLng currentLatLong = new LatLng(location.getLatitude(), location.getLongitude());
return currentLatLong;
}
}
我不确定导致异常的原因。我初始化mMap错了吗？
这里有完整的logcat：
02-05 01:08:49.122: E/AndroidRuntime(14029): FATAL EXCEPTION: main
02-05 01:08:49.122: E/AndroidRuntime(14029): Process: com.example.MyApp, PID: 14029
02-05 01:08:49.122: E/AndroidRuntime(14029): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.p1/com.example.p1.PlaceMarker}: java.lang.NullPointerException
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread.access$800(ActivityThread.java:145)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.os.Handler.dispatchMessage(Handler.java:102)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.os.Looper.loop(Looper.java:136)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread.main(ActivityThread.java:5081)
02-05 01:08:49.122: E/AndroidRuntime(14029): at java.lang.reflect.Method.invokeNative(Native Method)
02-05 01:08:49.122: E/AndroidRuntime(14029): at java.lang.reflect.Method.invoke(Method.java:515)
02-05 01:08:49.122: E/AndroidRuntime(14029): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
02-05 01:08:49.122: E/AndroidRuntime(14029): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-05 01:08:49.122: E/AndroidRuntime(14029): at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:126)
02-05 01:08:49.122: E/AndroidRuntime(14029): at dalvik.system.NativeStart.main(Native Method)
02-05 01:08:49.122: E/AndroidRuntime(14029): Caused by: java.lang.NullPointerException
02-05 01:08:49.122: E/AndroidRuntime(14029): at com.example.MyApp.PlaceMarker.onCreate(PlaceMarker.java:52)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.Activity.performCreate(Activity.java:5231)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-05 01:08:49.122: E/AndroidRuntime(14029): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
02-05 01:08:49.122: E/AndroidRuntime(14029): ... 12 more
答案 0 :(得分：3)
在我的情况下，谷歌地图对象调用像这些＆amp;这样的片段。完美无缺：
private GoogleMap mGoogleMap = null;
int sdk = Build.VERSION.SDK_INT;
if(sdk >= Build.VERSION_CODES.LOLLIPOP) {
mGoogleMap = ((MapFragment) getChildFragmentManager().findFragmentById(R.id.map)).getMap();
}
else {
mGoogleMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
}
答案 1 :(得分：2)
你应该替换这个
mMap=((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
使用
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(
R.id.map)).getMap();
试试这个。
答案 2 :(得分：0)
注意：Google Maps Android API需要API等级12或更高版本才能支持 MapFragment 对象。如果您的目标是 API级别12 之前的应用程序，则可以通过 SupportMapFragment 类访问相同的功能。您还必须包含 Android支持库。
除了使用MapFragment之外，您还需要使用SupportMapFragment，因为您正在开发API级别11以下的Google地图。
写如下：
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
相反
mMap=((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
答案 3 :(得分：0)
尝试以下方法，
替换
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
带
FragmentManager myFM = getActivity().getSupportFragmentManager();
final SupportMapFragment myMAPF = (SupportMapFragment) myFM
.findFragmentById(R.id.map);