在 onCreate 方法之前调用 onLocationChanged - Android

Question

    import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Color;

import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.example.rajitha.model.Point;
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.CircleOptions;
import com.google.android.gms.maps.model.LatLng;


public class CurrentLocationActivity extends AppCompatActivity implements
        OnMapReadyCallback, LocationListener {

    private static final int LOCATION_PERMISSION_REQUEST_CODE = 1;

    private GoogleMap mMap;
    ImageView share;
   TextView logitude,latitude;

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

        Toolbar tb = findViewById(R.id.toolbar);
        share=(ImageView)findViewById(R.id.share);
        logitude=(TextView)findViewById(R.id.logitude);
        latitude=(TextView)findViewById(R.id.latitude);
        setSupportActionBar(tb);
        tb.setSubtitle("Your Point");

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.current_location);
        mapFragment.getMapAsync(this);

        LocationManager mLocManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        LocationListener mLocListener = new CurrentLocationActivity();
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            return;
        }
        mLocManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, mLocListener);

        share.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.e("Test share",logitude.getText().toString());
            }
        });
    }


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

        mMap.setOnMyLocationButtonClickListener(onMyLocationButtonClickListener);
        mMap.setOnMyLocationClickListener(onMyLocationClickListener);
        enableMyLocationIfPermitted();

        mMap.getUiSettings().setZoomControlsEnabled(true);
        mMap.setMinZoomPreference(5);
    }

    private void enableMyLocationIfPermitted() {
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION,
                            Manifest.permission.ACCESS_FINE_LOCATION},
                    LOCATION_PERMISSION_REQUEST_CODE);
        } else if (mMap != null) {
            mMap.setMyLocationEnabled(true);
        }
    }

    private void showDefaultLocation() {
        Toast.makeText(this, "Point permission not granted, " +
                        "showing default location",
                Toast.LENGTH_SHORT).show();
        LatLng redmond = new LatLng(7.8731, 80.7718);
        mMap.moveCamera(CameraUpdateFactory.newLatLng(redmond));
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        switch (requestCode) {
            case LOCATION_PERMISSION_REQUEST_CODE: {
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    enableMyLocationIfPermitted();
                } else {
                    showDefaultLocation();
                }
                return;
            }

        }
    }

    private GoogleMap.OnMyLocationButtonClickListener onMyLocationButtonClickListener =
            new GoogleMap.OnMyLocationButtonClickListener() {
                @Override
                public boolean onMyLocationButtonClick() {
                    mMap.setMinZoomPreference(5);
                    return false;
                }
            };

    private GoogleMap.OnMyLocationClickListener onMyLocationClickListener =
            new GoogleMap.OnMyLocationClickListener() {
                @Override
                public void onMyLocationClick(@NonNull Location location) {

                    mMap.setMinZoomPreference(4);

                    CircleOptions circleOptions = new CircleOptions();
                    circleOptions.center(new LatLng(location.getLatitude(),
                            location.getLongitude()));

                    circleOptions.radius(200);
                    circleOptions.fillColor(Color.RED);
                    circleOptions.strokeWidth(6);

                    mMap.addCircle(circleOptions);
                }
            };

    @Override
    public void onLocationChanged(Location location) {

      logitude.setText(String.valueOf(location.getLongitude()));
     latitude.setText(String.valueOf(location.getLatitude()));
        String message = String.format(
                "New Point \n Longitude: %1$s \n Latitude: %2$s",
                location.getLongitude(), location.getLatitude()
        );
        Log.e("Test",message);

    }

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

    }

    @Override
    public void onProviderEnabled(String s) {

    }

    @Override
    public void onProviderDisabled(String s) {

    }

}

这里我只需要更新文本中当前的经纬度值。但是在运行这段代码后我得到了一个空异常。由于 onLocationChanged 方法之后的 onCreate 调用，logitude 和 latitude TextViews 似乎变得空了。我需要在单击按钮后共享这些值。我怎样才能从 avove 代码中完成这些任务。提前致谢。

Answer 1

你注意到你的 mLocListener 是什么了吗？

删除LocationListener mLocListener = new CurrentLocationActivity();

在任何地方都使用 this 而不是 mLocListener。

喜欢改变

mLocManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, mLocListener);

到

mLocManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);