Cách lấy địa chỉ đầy đủ từ vĩ độ/kinh độ trên Android Kotlin

Giới thiệu

Hướng dẫn này trình bày cách chuyển đổi tọa độ địa lý (latitude, longitude) thành địa chỉ đọc được (Reverse Geocoding) trên Android sử dụng Geocoder và Kotlin. Kết quả trả về qua Handler để cập nhật UI từ background thread.

Các bước thực hiện

Bước 1: Tạo dự án mới

Tạo project: File → New Project.

Bước 2: Thiết kế giao diện (res/layout/activity_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16sp"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:text="Tutorials Point"
        android:textAlignment="center"
        android:textColor="@android:color/holo_green_dark"
        android:textSize="32sp"
        android:textStyle="bold" />

    <Button
        android:id="@+id/btnShowAddress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Show Address" />

    <TextView
        android:id="@+id/tvAddress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/btnShowAddress"
        android:layout_centerInParent="true"
        android:textColor="@android:color/background_dark"
        android:textSize="12sp"
        android:textStyle="bold" />

</RelativeLayout>

Bước 3: MainActivity.kt

import android.Manifest
import android.content.Intent
import android.content.pm.PackageManager
import android.location.Location
import android.location.LocationManager
import android.os.Bundle
import android.os.Handler
import android.os.Message
import android.provider.Settings
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat

class MainActivity : AppCompatActivity() {
    private lateinit var btnShowAddress: Button
    private lateinit var tvAddress: TextView
    private lateinit var location: Location
    private lateinit var appLocationService: AppLocationService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        title = "KotlinApp"

        tvAddress = findViewById(R.id.tvAddress)
        appLocationService = AppLocationService(this)
        btnShowAddress = findViewById(R.id.btnShowAddress)

        // Yêu cầu quyền vị trí
        requestLocationPermission()

        btnShowAddress.setOnClickListener {
            // Lấy vị trí hiện tại (hoặc dùng tọa độ cố định để test)
            location = appLocationService.getLocation(LocationManager.GPS_PROVIDER)!!
            
            // Tọa độ mẫu (Hanoi, Vietnam)
            val latitude = 21.0285
            val longitude = 105.8542

            val locationAddress = LocationAddress()
            locationAddress.getAddressFromLocation(
                latitude, longitude, applicationContext, GeoCodeHandler()
            )
        }
    }

    private fun requestLocationPermission() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) 
            != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(
                this, 
                arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), 
                1
            )
        }
    }

    private fun showSettingsAlert() {
        AlertDialog.Builder(this).apply {
            setTitle("SETTINGS")
            setMessage("Enable Location Provider! Go to settings menu?")
            setPositiveButton("Settings") { _, _ ->
                startActivity(Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS))
            }
            setNegativeButton("Cancel") { dialog, _ -> dialog.cancel() }
            show()
        }
    }

    inner class GeoCodeHandler : Handler() {
        override fun handleMessage(message: Message) {
            val locationAddress = when (message.what) {
                1 -> message.data.getString("address") ?: ""
                else -> ""
            }
            tvAddress.text = locationAddress
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array,
        grantResults: IntArray
    ) {
        if (requestCode == 1) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission Granted", Toast.LENGTH_SHORT).show()
            } else {
                Toast.makeText(this, "Permission Denied", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

Bước 4: AppLocationService.kt

import android.annotation.SuppressLint
import android.app.Service
import android.content.Context
import android.content.Intent
import android.location.Location
import android.location.LocationListener
import android.location.LocationManager
import android.os.Bundle
import android.os.IBinder

open class AppLocationService(context: Context) : Service(), LocationListener {
    private var locationManager: LocationManager? = context.getSystemService(Context.LOCATION_SERVICE) as LocationManager
    private lateinit var location: Location

    companion object {
        private const val MIN_DISTANCE_FOR_UPDATE: Long = 10
        private const val MIN_TIME_FOR_UPDATE = 1000 * 60 * 2L
    }

    @SuppressLint("MissingPermission")
    fun getLocation(provider: String?): Location? {
        if (locationManager!!.isProviderEnabled(provider)) {
            locationManager!!.requestLocationUpdates(
                provider,
                MIN_TIME_FOR_UPDATE,
                MIN_DISTANCE_FOR_UPDATE.toFloat(),
                this
            )
            if (locationManager != null) {
                location = locationManager!!.getLastKnownLocation(provider)
                return location
            }
        }
        return null
    }

    override fun onLocationChanged(location: Location) {}
    override fun onProviderDisabled(provider: String) {}
    override fun onProviderEnabled(provider: String) {}
    override fun onStatusChanged(provider: String, status: Int, extras: Bundle) {}
    override fun onBind(arg0: Intent): IBinder? = null
}

Bước 5: LocationAddress.kt

import android.content.Context
import android.location.Geocoder
import android.os.Bundle
import android.os.Handler
import android.os.Message
import android.util.Log
import java.io.IOException
import java.util.Locale

class LocationAddress {
    private val tag = "LocationAddress"

    fun getAddressFromLocation(
        latitude: Double,
        longitude: Double,
        context: Context,
        handler: Handler
    ) {
        Thread {
            val geoCoder = Geocoder(context, Locale.getDefault())
            var result: String = ""

            try {
                val addressList = geoCoder.getFromLocation(latitude, longitude, 1)
                if (addressList != null && addressList.isNotEmpty()) {
                    val address = addressList[0]
                    val sb = StringBuilder()
                    
                    for (i in 0 until address.maxAddressLineIndex) {
                        sb.append(address.getAddressLine(i)).append("\n")
                    }
                    sb.append(address.locality).append("\n")
                    sb.append(address.postalCode).append("\n")
                    sb.append(address.countryName)
                    
                    result = sb.toString()
                }
            } catch (e: IOException) {
                Log.e(tag, "Unable connect to GeoCoder", e)
            } finally {
                val message = Message.obtain().apply {
                    target = handler
                    what = 1
                    data = Bundle().apply {
                        putString("address", "Latitude: $latitude Longitude: $longitude\n\nAddress:\n$result")
                    }
                    sendToTarget()
                }
            }
        }.start()
    }
}

Bước 6: Cấu hình Manifest (androidManifest.xml)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
    package="app.com.q11">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
</manifest>

Chạy ứng dụng

Cấp quyền vị trí, nhấn "Show Address". Ứng dụng sẽ hiển thị địa chỉ đầy đủ tương ứng với tọa độ (mặc định là Hanoi).

Lưu ý quan trọng

• Geocoder cần Internet để truy vấn server Google.
• Rate limit: Không gọi quá nhiều lần trong thời gian ngắn.
• Locale ảnh hưởng đến ngôn ngữ kết quả (mặc định Locale.getDefault()).
• Android 10+: Cần quyền ACCESS_BACKGROUND_LOCATION nếu lấy vị trí khi app background.
• Thay thế AppLocationService bằng FusedLocationProviderClient (Google Play Services) để chính xác và tiết kiệm pin hơn.

// build.gradle
implementation "com.google.android.gms:play-services-location:21.0.1"

// Trong Activity
val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation.addOnSuccessListener { location ->
    location?.let { 
        getAddressFromLocation(it.latitude, it.longitude, ...) 
    }
}