java - 出现错误 java.lang.NullPointerException : Attempt to invoke virtual method 'double android.location.Location.getLatitude()'

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 3 年前。

这是来自日志猫的错误消息；

我收到以下错误:java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“double android.location.Location.getLatitude()”

进程:com.marktech.myrider，PID:20905

java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
    at com.marktech.myrider.CustomerMapActivity$2.onClick(CustomerMapActivity.java:94)
    at android.view.View.performClick(View.java:6291)
    at android.view.View$PerformClick.run(View.java:24931)
    at android.os.Handler.handleCallback(Handler.java:808)
    at android.os.Handler.dispatchMessage(Handler.java:101)
    at android.os.Looper.loop(Looper.java:166)
    at android.app.ActivityThread.main(ActivityThread.java:7425)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)

这是我的代码

错误就在这一行；

geoFire.setLocation( userId, new GeoLocation( mLastLocation.getLatitude(), mLastLocation.getLongitude() ), new GeoFire.CompletionListener() {

private GoogleMap mMap;
GoogleApiClient mGoogleApiClient;
Location mLastLocation;
LocationRequest mLocationRequest;

private Button btnLogout, btnRequest;
private LatLng pickupLocation;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_customer_map );
    // Obtain the SupportMapFragment and get notified when the map is ready to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById( R.id.map );
    assert mapFragment != null;
    mapFragment.getMapAsync( this );

    btnLogout = (Button) findViewById( R.id.btnLogout );
    btnRequest = (Button) findViewById( R.id.btnRequest );

    btnLogout.setOnClickListener( new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            FirebaseAuth.getInstance().signOut();
            Intent intent = new Intent( CustomerMapActivity.this, MainActivity.class);
            startActivity( intent );
            finish();
            return;

        }
    } );

    btnRequest.setOnClickListener( new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            if(mLastLocation!= null){
                double latitude = mLastLocation.getLatitude();
                double longitude = mLastLocation.getLongitude();
            }
            String userId = FirebaseAuth.getInstance().getUid();

            DatabaseReference ref = FirebaseDatabase.getInstance().getReference("customerRequest");
            GeoFire geoFire = new GeoFire( ref );
            geoFire.setLocation( userId, new GeoLocation( mLastLocation.getLatitude(), mLastLocation.getLongitude() ), new GeoFire.CompletionListener() {
                @Override
                public void onComplete(String key, DatabaseError error) {


            }
            });
            pickupLocation = new LatLng( mLastLocation.getLatitude(), mLastLocation.getLongitude() );
            mMap.addMarker( new MarkerOptions().position( pickupLocation ).title( "Pickup Here" ) );
            btnRequest.setText( "Getting your rider..." );

        }
    } );


}


@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    if((ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)&&
            (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)&&
            (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED))
    {
        return;
    }

    buildGoogleApiClient();

    // mMap.setMyLocationEnabled( true );

}

private synchronized void buildGoogleApiClient(){
    mGoogleApiClient = new GoogleApiClient.Builder(this)
            .addConnectionCallbacks( this )
            .addOnConnectionFailedListener( this )
            .addApi( LocationServices.API )
            .build();
    mGoogleApiClient.connect();
}

@Override
public void onLocationChanged(Location location) {
    mLastLocation = location;

    mMap.setMyLocationEnabled( true );
    mMap.getUiSettings().setMyLocationButtonEnabled(true);

    LatLng latlng = new LatLng( location.getLatitude(),location.getLongitude() );
    //moving the camera with the user
    mMap.moveCamera( CameraUpdateFactory.newLatLng( latlng  ) );
    mMap.animateCamera( CameraUpdateFactory.zoomTo( 11 ) );

}

@Override
public void onStatusChanged(String s, int i, Bundle bundle) {

}

@Override
public void onProviderEnabled(String s) {

}

@Override
public void onProviderDisabled(String s) {

}

@Override
public void onConnected(@Nullable Bundle bundle) {
    mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval( 1000 );
    mLocationRequest.setFastestInterval( 1000 );
    mLocationRequest.setPriority( LocationRequest.PRIORITY_HIGH_ACCURACY );

    if((ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)&&
            (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)&&
            (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED))
    {
        return;
    }

    if (mGoogleApiClient != null) {
        LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
    }

    //LocationServices.FusedLocationApi.requestLocationUpdates( mGoogleApiClient, mLocationRequest, this );
}

@Override
public void onConnectionSuspended(int i) {

}

@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {

}

@Override
protected void onStop() {
    super.onStop();
}

}

Answer 1

mLastLocation 实际上可以为 null。您已经在方法的顶部进行了检查，但没有在...之后进行检查

试试这个:

btnRequest.setOnClickListener(new View.OnClickListener() {@
    Override
    public void onClick(View view) {
        if (mLastLocation != null) {
            double latitude = mLastLocation.getLatitude();
            double longitude = mLastLocation.getLongitude();
            String userId = FirebaseAuth.getInstance().getUid();
            DatabaseReference ref = FirebaseDatabase.getInstance().getReference("customerRequest");
            GeoFire geoFire = new GeoFire(ref);
            geoFire.setLocation(userId, new GeoLocation(latitude, longitude), new GeoFire.CompletionListener() {@
                Override
                public void onComplete(String key, DatabaseError error) {}
            });
            pickupLocation = new LatLng(latitude, longitude);
            mMap.addMarker(new MarkerOptions()
                .position(pickupLocation)
                .title("Pickup Here"));
            btnRequest.setText("Getting your rider...");
        }
    }
});