srcmini本文概述
在之前的Android Google Map教程中，我们仅显示了MapsActivity.java类文件设置的默认坐标（位置）。
现在，在本教程中，我们将显示标记并将其放置在用户当前位置。为此，我们需要生成Google Map API密钥。 Android Google Map教程中介绍了生成Google Map API的过程。
为了显示用户当前位置，我们需要实现一些接口以及那里的回调方法。
Google Map中的回调方法
- OnMapRreadyCallback：当在MapFragment对象上设置实例时，将调用此回调接口。准备使用地图时，将调用OnMapReadyCallback接口的onMapReady（GoogleMap）方法。在onMapReady（GoogleMap）方法中，我们可以添加标记，侦听器和其他属性。
- LocationListener：当设备位置更改时，此接口用于接收通知。位置更改后，将调用LocationListener的抽象方法onLocationChanged（Location）。
- GoogleApiClient.ConnectionCallbacks：此接口提供了onConnected（Bundle）和onConnectionSuspended（int）回调方法，这些方法将在设备连接和断开连接时被调用。
- GoogleApiClient.OnConnectionFailedListener：此接口提供回调方法onConnectionFailed（ConnectionResult），当将设备连接到服务时发生错误时将调用该方法。
GoogleMap的setMyLocationEnabled（）方法用于启用位置图层，该图层允许设备与当前位置进行交互。
显示当前位置的Google地图示例
让我们看一个显示设备当前位置的Google Map示例。
activity_maps.xml
在activity_maps.xml文件的片段中添加一个SupportMapFragment。
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:map="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/map"
android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="example.com.mapexample.MapsActivity" />build.gradel
在build.gradel文件中添加以下依赖项。
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.google.android.gms:play-services-maps:11.8.0'
compile 'com.google.android.gms:play-services-location:11.8.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}MapsActivity.java
在MapsActivity.java文件中添加以下代码。
package example.com.mapexample;
import android.os.Build;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import com.google.android.gms.common.api.GoogleApiClient;
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.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.location.LocationServices;
import android.location.Location;
import android.Manifest;
import android.content.pm.PackageManager;
import android.support.v4.content.ContextCompat;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener{
private GoogleMap mMap;
Location mLastLocation;
Marker mCurrLocationMarker;
GoogleApiClient mGoogleApiClient;
LocationRequest mLocationRequest;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
}
else {
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
}
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API).build();
mGoogleApiClient.connect();
}
@Override
public void onConnected(Bundle bundle) {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(1000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
mLastLocation = location;
if (mCurrLocationMarker != null) {
mCurrLocationMarker.remove();
}
//Place current location marker
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
MarkerOptions markerOptions = new MarkerOptions();
markerOptions.position(latLng);
markerOptions.title("Current Position");
markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
mCurrLocationMarker = mMap.addMarker(markerOptions);
//move map camera
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.animateCamera(CameraUpdateFactory.zoomTo(11));
//stop location updates
if (mGoogleApiClient != null) {
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
}
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
}请求运行时权限
具有Android 6.0（棉花糖）或更高版本的Android设备在运行时需要获得某些权限才能访问设备功能。
在上面的MapsActivity.java文件中，我们添加了运行时权限Manifest.permission.ACCESS_FINE_LOCATION，该访问权限请求访问设备位置。使用checkSelfPermission（）方法检查运行时权限，并返回PackageManager.PERMISSION_GRANTED或PackageManager.PERMISSION_DENIED。如果授予许可，则应用继续进行操作。
AndroidManifest.xml中的必需权限
在AndroidManifest.xml文件中添加以下用户权限。
<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" />AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="example.com.mapexample">
<!--
The ACCESS_COARSE/FINE_LOCATION permissions are not required to use
Google Maps Android API v2, but you must specify either coarse or fine
location permissions for the 'MyLocation' functionality.
-->
<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">
<!--
The API key for Google Maps-based APIs is defined as a string resource.
(See the file "res/values/google_maps_api.xml").
Note that the API key is linked to the encryption key used to sign the APK.
You need a different API key for each encryption key, including the release key that is used to
sign the APK for publishing.
You can define the keys for the debug and release targets in src/debug/ and src/release/.
-->
<meta-data
android:name="com.google.android.geo.API_KEY"
android:value="@string/google_maps_key" />
<activity
android:name=".MapsActivity"
android:label="@string/title_activity_maps">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>输出量
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