Question

美好的一天。我不确定我的地图应用程序有什么问题，但是当我运行它时它会一直崩溃。消息是“不幸的”，应用程序名称“已经停止。我不确定它是我的片段还是我如何加载地图。这是我的代码：

MainActivity类：

package com.apress.gerber.wbcgapplication;

import android.app.Dialog;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;

public class MainActivity extends AppCompatActivity {

private static final String TAG = "MainActivity";
private static final int ERROR_DIALOG_REQUEST = 9001;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if(checkPlayServices())
    {
        Intent intent = new 
        Intent(MainActivity.this,MapsActivity.class);
        startActivity(intent);

    }
}

//check for google play services
 public boolean checkPlayServices(){
    Log.d(TAG, "checkPlayServices: checking google services 
    version");
    int available = 
    GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable
    (MainActivity.this);


    if(available == ConnectionResult.SUCCESS)
    {
        //everything is fine and the user can make map requests
        Log.d(TAG, "checkPlayServices:Google Play Services is 
        Working");
        return true;
    }
    else if
    (GoogleApiAvailability.getInstance().isUserResolvableError
    (available))
    {
        //an error occured but we cn resolve it
        Log.d(TAG, "checkPlayServices: Error Occured but Can Be 
              Fixed");
        Dialog dialog = 
        GoogleApiAvailability.getInstance().getErrorDialog
        (MainActivity.this,available,ERROR_DIALOG_REQUEST);
        dialog.show();
    }
    else
    {
        Toast.makeText(this, "We cannot connect, please check google 
        play services version", Toast.LENGTH_SHORT).show();
    }

    return false;
}

}

MapsActivityClass：

package com.apress.gerber.wbcgapplication;

import android.Manifest;
import android.app.Dialog;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;


public class MapsActivity extends AppCompatActivity implements 
OnMapReadyCallback {


private static final String TAG = "MapsActivity";

private static final String FINE_LOCATION = 
Manifest.permission.ACCESS_FINE_LOCATION;
private static final String COARSE_LOCATION = 
Manifest.permission.ACCESS_COARSE_LOCATION;
private static final int LOCATION_PERMISSION_REQUEST_CODE = 1234;
private Boolean mLocationPermissionGranted = false;
private GoogleMap mMap;
private FusedLocationProviderClient mFusedLocationProviderClient;
private static final float DEFAULT_ZOOM = 15f;



@Override
public void onMapReady(GoogleMap googleMap) {
    Toast.makeText(this, "MAP IS READY", Toast.LENGTH_SHORT).show();
    Log.d(TAG, "onMapReady: MAP IS READY");
    mMap = googleMap;

    if (mLocationPermissionGranted) {
        getDeviceLocation();

        if (ActivityCompat.checkSelfPermission(this, 
        Manifest.permission.ACCESS_FINE_LOCATION) != 
        PackageManager.PERMISSION_GRANTED && 
        ActivityCompat.checkSelfPermission(this, 
        Manifest.permission.ACCESS_COARSE_LOCATION) != 
        PackageManager.PERMISSION_GRANTED) {

            return;
        }
        mMap.setMyLocationEnabled(true);
        mMap.getUiSettings().setMyLocationButtonEnabled(false);

    }


  }



@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_map);

    getLocationPermission();

}

//initialize the map
private void initMap(){

    Log.d(TAG,"initMap: INITIALIZING MAP");
    SupportMapFragment mapFragment = (SupportMapFragment) 
    getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(MapsActivity.this);
}

//Getting device location
private void getDeviceLocation(){
    Log.d(TAG, "getDeviceLocation: GETTING THE DEVICE LOCATION");
    mFusedLocationProviderClient = 
    LocationServices.getFusedLocationProviderClient(this);

    try
    {
        if(mLocationPermissionGranted)
        {
            final Task location = 
            mFusedLocationProviderClient.getLastLocation();
            location.addOnCompleteListener(new OnCompleteListener() {
                @Override
                public void onComplete(@NonNull Task task) {
                    if (task.isSuccessful())
                    {
                        Log.d(TAG, "onComplete: FOUND LOCATION");
                        Location currentLocation = (Location) 
                        task.getResult();
                        moveCamera(new 
                        LatLng(currentLocation.getLatitude(),
                        currentLocation.getLongitude()),
                        DEFAULT_ZOOM);

                    }
                    else
                    {
                        Log.d(TAG, "onComplete: NO LOCATION FOUND");
                        Toast.makeText(MapsActivity.this, "UNABLE TO 
                        GET CURRENT LOCATION", 
                        Toast.LENGTH_SHORT).show();
                    }
                }
            });
        }
    }
    catch (SecurityException e)
    {
        Log.e(TAG, "getDeviceLocation: SecurityException " + e.getMessage());

    }
}

private void moveCamera(LatLng latLng, float zoom){

    Log.e(TAG, "moveCamera: MOVING CAMERA TO: LATITUDE: " + latLng.latitude + ", LONGITUDE: " + latLng.longitude);
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, zoom));


}

private void getLocationPermission(){

    Log.d(TAG,"getLocationPermission: GETTING LOCATION PERMISSION");
    String [] persmissons = {Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION};

    if(ContextCompat.checkSelfPermission(this.getApplicationContext(),FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
    {
        if(ContextCompat.checkSelfPermission(this.getApplicationContext(),COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED)
        {
            mLocationPermissionGranted = true;
            initMap();
        }
        else
        {
            ActivityCompat.requestPermissions(this,persmissons,LOCATION_PERMISSION_REQUEST_CODE);
        }
    }
    else
    {
        ActivityCompat.requestPermissions(this,persmissons,LOCATION_PERMISSION_REQUEST_CODE);
    }

}


@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    Log.d(TAG, "onRequestPermissionsResult: CALLED");
    mLocationPermissionGranted = false;

    switch (requestCode)
    {
        case LOCATION_PERMISSION_REQUEST_CODE:{
            if(grantResults.length > 0 )
            {
                for(int i = 0; i < grantResults.length; i++)
                {
                    if(grantResults[i] == PackageManager.PERMISSION_GRANTED)
                    {
                        mLocationPermissionGranted = false;
                        Log.d(TAG, "onRequestPermissionsResult: PERMISSION FAILED");
                        return;
                    }
                }
                Log.d(TAG, "onRequestPermissionsResult: PERMISSION GRANTED");
                mLocationPermissionGranted = true;

                //initialise the map
                initMap();

            }

        }

    }
}


}

activity_map.xml

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

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

</android.support.constraint.ConstraintLayout>

<!--<android.support.constraint.ConstraintLayout>

</android.support.constraint.ConstraintLayout>!-->

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.apress.gerber.wbcgapplication.MainActivity">


</android.support.constraint.ConstraintLayout>

这是错误

03-29 13:02:33.702 3053-3053/com.apress.gerber.wbcgapplication E/AndroidRuntime: FATAL EXCEPTION: main
                                                                             Process: com.apress.gerber.wbcgapplication, PID: 3053
                                                                             java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
                                                                                 at com.apress.gerber.wbcgapplication.MapsActivity$1.onComplete(MapsActivity.java:105)
                                                                                 at com.google.android.gms.tasks.zzf.run(Unknown Source)
                                                                                 at android.os.Handler.handleCallback(Handler.java:815)
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:104)
                                                                                 at android.os.Looper.loop(Looper.java:194)
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5624)
                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)

Answer 1

我认为您的currentLocation没有得到更新。它在这里是空的。

位置currentLocation =（位置） task.getResult（）;

因此，你得到的是NullPointerException，因为你试图在这里得到lat和long。

moveCamera（new LatLng（currentLocation.getLatitude（），currentLocation.getLongitude（））， DEFAULT_ZOOM）;

确保获取此变量中的当前位置。然后它会工作得很好。

谷歌地图应用程序崩溃

1 个答案: