在 Android N 中调用位置时出现空点异常

Question

我正在尝试构建一个获取设备当前位置的应用程序。但它抛出 nullPointException 在：- lat.setText（location.getLatitude（）+"）;因为位置对象始终为空。请解决此问题，以下代码已在Android-7.1.1中进行测试

package in.technomenia.user.test;
import android.Manifest;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
    LocationManager locationManager;
    Location location;
    TextView lat, lng;
    Button getlocation;
    private boolean permission_granted = false;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lat = (TextView) findViewById(R.id.lati);
        lng = (TextView) findViewById(R.id.longi);
        getlocation = (Button) findViewById(R.id.get_latlng);

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        locations();
    }
    public void locations() {
        Toast.makeText(getApplicationContext(), "permissions-> "+permission_granted, Toast.LENGTH_SHORT).show();
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
                    if (permission_granted == false) {
                        requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 19);
                        Toast.makeText(getApplicationContext(), "Requires GPS Permission", Toast.LENGTH_SHORT).show();
                    }else{
                        if(locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) || locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER))
                            location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        else
                            Toast.makeText(getApplicationContext(), "Enable Locaion", Toast.LENGTH_SHORT).show();
                    }
                }
            } else {
                permission_granted= true;
                Toast.makeText(getApplicationContext(), "less than android m", Toast.LENGTH_SHORT).show();
            }

        getlocation.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (permission_granted == true) {
                    Toast.makeText(getApplicationContext(), "permission granted", Toast.LENGTH_SHORT).show();
                    lat.setText(location.getLatitude()+"");
                    lng.setText(location.getLongitude()+"");
                }
            }
        });
    }


    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode ==19){
            if(grantResults[0] == PackageManager.PERMISSION_GRANTED){
                permission_granted = true;
                locations();
            }else{
                permission_granted= false;
            }
        }
    }
}

Answer 1

getLastKnownLocation() 方法返回调用 requestLocationUpdates() 方法后收集的位置值。如果您尝试在没有请求位置更新的情况下获取最后一个位置，则返回将始终null。

有关实现示例
，请参阅此处如果您的位置信息在收到位置信息更新请求后仍返回null，请参阅此项