Android获取用户当前位置并在MapView添加标记问题求助

Hey Paul, let's break down why your current location marker isn't working and fix it properly.

a) Why Your Code Isn't Working #

Here are the key issues in your current implementation:

• Unused & Deprecated API: You declared GoogleApiClient but never initialized or used it. Worse, this API is deprecated—Google recommends using FusedLocationProviderClient for location updates now.
• Unconnected Location Callback: Your onLocationChanged method is custom, but you never registered it with the system. Android won't automatically call this method unless you set up a location listener.
• Incomplete Permission Handling: You request location permissions in onCreate, but you don't handle the user's response (allow/deny) with onRequestPermissionsResult. If the user grants permission after your initial request, your code won't trigger a location refresh.
• No Location Update Request: Even if permissions are granted, you never tell the system you want to receive location data. There's no code to request periodic or one-time location updates.
• Missing "My Location" Setup: You didn't enable the built-in "My Location" layer on the map (via mMap.setMyLocationEnabled(true)), which is the simplest way to show the user's current position, or implement logic to add a marker once you have location data.

b) Fixed Implementation #

Here's the revised code with all issues addressed. I've added comments to explain each change:

import android.Manifest;
import android.content.Intent;
import android.location.Location;
import android.net.Uri;
import android.os.Bundle;
import android.widget.Button;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;
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 static android.content.pm.PackageManager.PERMISSION_GRANTED;

public class fthactivity extends AppCompatActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
    private FusedLocationProviderClient fusedLocationClient;
    private LocationCallback locationCallback;
    private static final int LOCATION_PERMISSION_REQUEST_CODE = 3;

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

        // Initialize modern location API client
        fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);

        // Set up callback to handle incoming location updates
        locationCallback = new LocationCallback() {
            @Override
            public void onLocationResult(@NonNull LocationResult locationResult) {
                if (locationResult == null) {
                    return;
                }
                // Get latest location and update map if available
                Location location = locationResult.getLastLocation();
                if (location != null && mMap != null) {
                    updateUserLocationMarker(location);
                }
            }
        };

        // Initialize map fragment
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.fthmap);
        mapFragment.getMapAsync(this);

        // Phone dialer button logic (unchanged)
        findViewById(R.id.fthphone).setOnClickListener(v -> dialContactPhone("1234567890"));

        // Web link button logic (unchanged)
        Button btn = findViewById(R.id.fthweb);
        btn.setOnClickListener(v -> {
            Intent myWebLink = new Intent(Intent.ACTION_VIEW);
            myWebLink.setData(Uri.parse("http://google.ca/"));
            startActivity(myWebLink);
        });

        // Check location permissions on launch
        checkLocationPermissions();
    }

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

        // Add your fixed marker (unchanged)
        LatLng fthloc = new LatLng(51.036585, -114.066152);
        mMap.addMarker(new MarkerOptions().position(fthloc).title("Certain Location"));
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(fthloc, 18.0f));

        // Re-check permissions after map is ready to enable location features
        checkLocationPermissions();
    }

    private void checkLocationPermissions() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PERMISSION_GRANTED) {
            // Request permission if not granted
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                    LOCATION_PERMISSION_REQUEST_CODE);
        } else {
            // Permissions granted: enable built-in location dot and request updates
            if (mMap != null) {
                mMap.setMyLocationEnabled(true); // Shows blue dot for current location
            }
            startLocationUpdates();
        }
    }

    private void startLocationUpdates() {
        // Configure location update settings
        LocationRequest locationRequest = LocationRequest.create();
        locationRequest.setInterval(10000); // Update every 10 seconds
        locationRequest.setFastestInterval(5000); // Fastest allowed update interval
        locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);

        // Request location updates (only if permissions are granted)
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PERMISSION_GRANTED) {
            fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null);
        }
    }

    private void updateUserLocationMarker(Location location) {
        LatLng userLoc = new LatLng(location.getLatitude(), location.getLongitude());
        // Add custom marker for user's current location
        mMap.addMarker(new MarkerOptions().position(userLoc).title("Your Location"));
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userLoc, 18.0f));
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == LOCATION_PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PERMISSION_GRANTED) {
                // Permission granted: set up location features
                checkLocationPermissions();
            } else {
                // Permission denied: add logic here (e.g., show a toast explaining why permission is needed)
            }
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        // Stop location updates when activity is paused to save battery
        fusedLocationClient.removeLocationUpdates(locationCallback);
    }

    @Override
    protected void onResume() {
        super.onResume();
        // Resume location updates when activity is active again
        checkLocationPermissions();
    }

    private void dialContactPhone(final String phoneNumber) {
        startActivity(new Intent(Intent.ACTION_DIAL, Uri.fromParts("tel", phoneNumber, null)));
    }
}

Additional Required Step: Update AndroidManifest.xml #

Make sure you've added these permissions to your manifest file (inside the <manifest> tag, outside <application>):

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<!-- For Android 10+, add this if you need background location (optional for your use case) -->
<!-- <uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION" /> -->

Key Improvements Explained: #

• Modern Location API: Uses FusedLocationProviderClient instead of deprecated GoogleApiClient for reliable, optimized location data.
• Proper Callback Registration: The LocationCallback is connected to the system, so it will receive location updates automatically.
• Complete Permission Flow: onRequestPermissionsResult handles user choices and triggers location setup if permission is granted.
• Lifecycle-Aware Updates: Location updates stop when the activity is paused (saves battery) and resume when it's active again.
• Built-in Location Layer: Enables the default blue dot for current location (you can keep this or use only your custom marker, or both).

内容的提问来源于stack exchange，提问作者Paul Jonathan