Android开发求助：实现点击按钮在Google Map Fragment显示当前位置

Hey there! Great job getting the location coordinates working already—let's get that Google Map Fragment set up to show your current position. Here's a step-by-step guide to make this happen:

Step 1: Add Google Maps Dependencies & Permissions #

First, make sure your project is set up to use Google Maps:

1. Open your module-level build.gradle file and add these dependencies:

dependencies {
    implementation 'com.google.android.gms:play-services-maps:18.1.0'
    implementation 'com.google.android.gms:play-services-location:21.0.1'
}

2. Update your AndroidManifest.xml to include required permissions and your Google Maps API key (replace YOUR_GOOGLE_MAPS_API_KEY with your actual key from the Google Cloud Console):

<!-- Internet access for map loading -->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<meta-data
    android:name="com.google.android.geo.API_KEY"
    android:value="YOUR_GOOGLE_MAPS_API_KEY" />

Step 2: Update Your Layout to Include the Map Fragment #

Replace your activity_main.xml with this layout to add a Google Map Fragment (we'll remove the TextView since we're showing the location on the map):

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button_location"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="13dp"
        android:text="Show My Location" />

    <!-- Google Map Fragment -->
    <fragment
        android:id="@+id/map_fragment"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/button_location" />

</RelativeLayout>

Step 3: Modify MainActivity to Integrate the Map #

Update your MainActivity.java to implement map initialization, and display your location on the map once retrieved:

package com.example.hello.sampleapp;

import android.Manifest;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.provider.Settings;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

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;

public class MainActivity extends AppCompatActivity implements View.OnClickListener, OnMapReadyCallback {

    private static final int REQUEST_LOCATION = 1;

    Button button;
    LocationManager locationManager;
    private GoogleMap mMap;

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

        // Request location permission on launch
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_LOCATION);

        button = findViewById(R.id.button_location);
        button.setOnClickListener(this);

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

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        // Enable the built-in "My Location" layer if permission is granted
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            mMap.setMyLocationEnabled(true);
        }
    }

    @Override
    public void onClick(View view) {
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
            buildAlertMessageNoGps();
        } else {
            getLocation();
        }
    }

    private void getLocation() {
        if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission
                (MainActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_LOCATION);
            return;
        }

        // Prioritize GPS location over network/passive
        Location currentLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (currentLocation == null) currentLocation = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        if (currentLocation == null) currentLocation = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

        if (currentLocation != null && mMap != null) {
            LatLng myLocation = new LatLng(currentLocation.getLatitude(), currentLocation.getLongitude());
            // Add a marker for your current position
            mMap.addMarker(new MarkerOptions().position(myLocation).title("My Current Location"));
            // Move the camera to your location with a zoom level of 15
            mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(myLocation, 15));
            Toast.makeText(this, "Location loaded on map!", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "Unable to trace your location", Toast.LENGTH_SHORT).show();
        }
    }

    protected void buildAlertMessageNoGps() {
        final AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Please Turn ON your GPS Connection")
                .setCancelable(false)
                .setPositiveButton("Yes", (dialog, id) -> startActivity(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)))
                .setNegativeButton("No", (dialog, id) -> dialog.cancel());
        final AlertDialog alert = builder.create();
        alert.show();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_LOCATION) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                if (mMap != null) {
                    try {
                        mMap.setMyLocationEnabled(true);
                    } catch (SecurityException e) {
                        e.printStackTrace();
                    }
                }
            } else {
                Toast.makeText(this, "Location permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

Quick Notes for Improvement #

• getLastKnownLocation might return null if no recent location data exists. For better reliability, you can add a LocationListener to receive real-time location updates.
• Make sure you've enabled the Maps SDK for Android in your Google Cloud Console project, otherwise the map won't load.

内容的提问来源于stack exchange，提问作者Madhumitha