android - 在运行时获取权限 (ACCESS_FINE_LOCATION) 的问题

Question

我编写了以下代码来获取用户位置，但应用程序不断崩溃。这可能与我使用的 Android Studio 版本有关。

package com.example.userlocationmap;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    LocationManager locationManager;
    LocationListener locationListener;

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (grantResults.length >= 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
            }
        }
    }

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

        locationManager = (LocationManager) this.getSystemService(LOCATION_SERVICE);//get the location locater service running
        locationListener = new LocationListener() {//listening in on your current location
            @Override
            public void onLocationChanged(Location location) {
                //when location is changed
                Log.i("location", location.toString());//printing location to logs
                Toast.makeText(MainActivity.this, location.toString(), Toast.LENGTH_LONG).show();
            }

            @Override
            public void onStatusChanged(String provider, int status, Bundle extras) {

            }

            @Override
            public void onProviderEnabled(String provider) {
                //when location is enabled on mobile
            }

            @Override
            public void onProviderDisabled(String provider) {
                //when location is disabled on mobile
            }
        };

        //checking if the version of android is before marshmellow (SDK version 23)
        if (Build.VERSION.SDK_INT < 23) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
        } else {
            //checking whether we have permission to access the user location
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_DENIED) {
                //checking if permission is not granted. if not granted then ask for it.
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
                //this asks for permission which is stored in an array String
            } else {
                //if we already have permission
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);

            }
        }
    }
}

请帮我解决这个问题。请告诉我需要进行哪些更改才能使代码可以在模拟器上运行。

标签： androidruntime-permissions

Answer 1

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (grantResults.length >= 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED) {
                locationManager = (LocationManager) this.getSystemService(LOCATION_SERVICE);//after getting permission get locationManager
                if(locationManager != null)// prevent NullPointerException
                   locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
            }
        }
}