Android中实现实时经纬度存储至Firebase并支持后续检索

Hey there! Let's get your latitude and longitude saved to Firebase Realtime Database and set up a way to retrieve that data later. I'll walk you through modifying your existing code step by step.

Step 1: Firebase Setup (Prerequisite) #

First, make sure you've got Firebase configured in your project:

• Add Firebase Realtime Database dependencies to your app-level build.gradle file (use the latest available versions):

  implementation 'com.google.firebase:firebase-database:20.3.0'
  implementation 'com.google.firebase:firebase-core:21.1.1'
  

• Connect your app to Firebase via the Firebase Console, and adjust your Realtime Database rules (for testing, you can use temporary public rules, but lock them down for production).

Step 2: Modified MapsActivity Code #

Here's the updated code that handles saving location to Firebase and includes a method to retrieve stored data later:

import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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.LocationServices;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MapsActivity extends AppCompatActivity {
    private FusedLocationProviderClient client;
    private DatabaseReference mDatabase; // Firebase Database reference
    private EditText locationNameEt; // Renamed for better readability

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        
        // Initialize Firebase Database reference (points to a "user_locations" node)
        mDatabase = FirebaseDatabase.getInstance().getReference("user_locations");
        
        requestPermission();
        client = LocationServices.getFusedLocationProviderClient(this);
        
        Button saveLocBtn = findViewById(R.id.button);
        locationNameEt = findViewById(R.id.ed);
        
        // Save current location to Firebase when button is clicked
        saveLocBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ActivityCompat.checkSelfPermission(MapsActivity.this, 
                        Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED 
                        && ActivityCompat.checkSelfPermission(MapsActivity.this, 
                        Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                    requestPermission();
                    return;
                }
                
                client.getLastLocation().addOnSuccessListener(MapsActivity.this, new OnSuccessListener<Location>() {
                    @Override
                    public void onSuccess(Location location) {
                        if(location!=null) {
                            double latitude = location.getLatitude();
                            double longitude = location.getLongitude();
                            String locationName = locationNameEt.getText().toString().trim();
                            
                            // Create a structured object to store in Firebase
                            LocationData locationData = new LocationData(locationName, latitude, longitude);
                            
                            // Generate a unique key for this location entry (prevents overwrites)
                            String entryKey = mDatabase.push().getKey();
                            if (entryKey != null) {
                                mDatabase.child(entryKey).setValue(locationData)
                                        .addOnSuccessListener(aVoid -> {
                                            Toast.makeText(MapsActivity.this, "Location saved successfully!", Toast.LENGTH_SHORT).show();
                                            locationNameEt.setText("");
                                        })
                                        .addOnFailureListener(e -> {
                                            Toast.makeText(MapsActivity.this, "Save failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                                        });
                            }
                        } else {
                            Toast.makeText(MapsActivity.this, "Couldn't retrieve location. Try again.", Toast.LENGTH_SHORT).show();
                        }
                    }
                });
            }
        });

        // Optional: Uncomment this and add a "retrieve" button to your layout to fetch saved locations
        /*Button retrieveBtn = findViewById(R.id.retrieve_btn);
        retrieveBtn.setOnClickListener(v -> fetchSavedLocations());*/
    }

    // Model class to define the structure of location data for Firebase
    public static class LocationData {
        public String locationName;
        public double latitude;
        public double longitude;
        
        // Empty constructor required for Firebase deserialization
        public LocationData() {}
        
        public LocationData(String locationName, double latitude, double longitude) {
            this.locationName = locationName;
            this.latitude = latitude;
            this.longitude = longitude;
        }
    }

    // Method to retrieve all saved locations from Firebase
    private void fetchSavedLocations() {
        mDatabase.addValueEventListener(new com.google.firebase.database.ValueEventListener() {
            @Override
            public void onDataChange(@NonNull com.google.firebase.database.DataSnapshot snapshot) {
                StringBuilder locationList = new StringBuilder();
                for (com.google.firebase.database.DataSnapshot entrySnapshot : snapshot.getChildren()) {
                    LocationData locData = entrySnapshot.getValue(LocationData.class);
                    if (locData != null) {
                        locationList.append("Name: ").append(locData.locationName)
                                .append("\nLat: ").append(locData.latitude)
                                .append(" | Lng: ").append(locData.longitude)
                                .append("\n\n");
                    }
                }
                // Display retrieved data (you can replace this with a TextView/RecyclerView for better UI)
                Toast.makeText(MapsActivity.this, locationList.toString(), Toast.LENGTH_LONG).show();
            }

            @Override
            public void onCancelled(@NonNull com.google.firebase.database.DatabaseError error) {
                Toast.makeText(MapsActivity.this, "Retrieval failed: " + error.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
    }

    public void requestPermission() {
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
    }

    // Handle permission request results properly
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == 1) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Location permission granted!", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "Permission denied. Cannot access location.", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

Key Details to Note: #

• Firebase Node Structure: We use a user_locations node to store all location entries. The push() method generates a unique key for each entry, so you won't overwrite existing data.
• LocationData Class: This acts as a blueprint for the data saved to Firebase, making it easy to serialize/deserialize data.
• Retrieval Logic: The fetchSavedLocations() method listens for changes in the Firebase node and collects all stored locations. You can adapt this to display data in a RecyclerView or TextView for a better user experience.
• Permission Handling: Added onRequestPermissionsResult to properly respond when the user grants or denies location access.

内容的提问来源于stack exchange，提问作者M Hero