Question

package com.example.getlocation;

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.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class LbsGeocodingActivity extends Activity {

    private static final long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 1; // in Meters
    private static final long MINIMUM_TIME_BETWEEN_UPDATES = 1000; // in Milliseconds
    private static final int MY_PERMISSION_ACCESS_COARSE_LOCATION = 11;

    protected LocationManager locationManager;

    protected Button retrieveLocationButton;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        retrieveLocationButton = (Button) findViewById(R.id.retrieve_location_button);


        if ( ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION ) != PackageManager.PERMISSION_GRANTED ) {

            ActivityCompat.requestPermissions( this, new String[] {  android.Manifest.permission.ACCESS_COARSE_LOCATION  },
                    LbsGeocodingActivity.MY_PERMISSION_ACCESS_COARSE_LOCATION );
        }

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        locationManager.requestLocationUpdates(
                LocationManager.GPS_PROVIDER,
                MINIMUM_TIME_BETWEEN_UPDATES,
                MINIMUM_DISTANCE_CHANGE_FOR_UPDATES,
                new MyLocationListener()
        );

        retrieveLocationButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                showCurrentLocation();
            }
        });

    }

    protected void showCurrentLocation() {

        if ( ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION ) != PackageManager.PERMISSION_GRANTED ) {

            ActivityCompat.requestPermissions( this, new String[] {  android.Manifest.permission.ACCESS_COARSE_LOCATION  },
                    LbsGeocodingActivity.MY_PERMISSION_ACCESS_COARSE_LOCATION );
        }


        Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        if (location != null) {
            String message = String.format(
                    "Current Location \n Longitude: %1$s \n Latitude: %2$s",
                    location.getLongitude(), location.getLatitude()
            );
            Toast.makeText(LbsGeocodingActivity.this, message,
                    Toast.LENGTH_LONG).show();
        }


    }

    private class MyLocationListener implements LocationListener {

        public void onLocationChanged(Location location) {
            String message = String.format(
                    "New Location \n Longitude: %1$s \n Latitude: %2$s",
                    location.getLongitude(), location.getLatitude()
            );
            Toast.makeText(LbsGeocodingActivity.this, message, Toast.LENGTH_LONG).show();
        }

        public void onStatusChanged(String s, int i, Bundle b) {
            Toast.makeText(LbsGeocodingActivity.this, "Provider status changed",
                    Toast.LENGTH_LONG).show();
        }

        public void onProviderDisabled(String s) {
            Toast.makeText(LbsGeocodingActivity.this,
                    "Provider disabled by the user. GPS turned off",
                    Toast.LENGTH_LONG).show();
        }

        public void onProviderEnabled(String s) {
            Toast.makeText(LbsGeocodingActivity.this,
                    "Provider enabled by the user. GPS turned on",
                    Toast.LENGTH_LONG).show();
        }

    }

}

我试图通过点击按钮获取当前位置。我尝试了上面的代码，但行Location location = locationManager.getLastKnownLocation（LocationManager.GPS_PROVIDER）总是给位置null。我抬头找出问题可能是由于getLastKnownLocation。由于LastKnownLocation不是cancehd，我得到null值。但是我如何修改此代码以提供当前位置而不是空值。

Answer 1

制作两个全局字符串，如：

public class LbsGeocodingActivity extends Activity {

private latVar;
private lonVar;

然后在您的位置监听器的onLocationChanged方法中：

public void onLocationChanged(Location location) {

double lat = location.getLatitude();
double lon = location.getLongitude();
latVar = Double.toString(lat);
lonVar = Double.toString(lon);

然后在按钮中点击：

protected void showCurrentLocation() {

    if ( ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION ) != PackageManager.PERMISSION_GRANTED ) {

        ActivityCompat.requestPermissions( this, new String[] {  android.Manifest.permission.ACCESS_COARSE_LOCATION  },
                LbsGeocodingActivity.MY_PERMISSION_ACCESS_COARSE_LOCATION );
    }
        String message = String.format(
                "Current Location \n Longitude: %1$s \n Latitude: %2$s",
                lonVar, latVar
        );
        Toast.makeText(LbsGeocodingActivity.this, message,
                Toast.LENGTH_LONG).show();
        }

还考虑将变量MINIMUM_DISTANCE_CHANGE_FOR_UPDATES更改为0

如何在启动应用程序时使用getLastKnownLocation获取非null值

1 个答案: