要触发Android围栏，必须在应用程序中请求位置更新。一种常见的方法是在位置服务中注入LocationListener并使用PendingIntent将其与围栏关联。以下是代码示例：

// 注入位置服务
LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

// 创建围栏
Geofence geofence = new Geofence.Builder()
        .setRequestId("myGeofence") // 给围栏一个ID
        .setCircularRegion(latitude, longitude, radius) // 指定围栏中心点和半径
        .setExpirationDuration(Geofence.NEVER_EXPIRE) // 指的是围栏有效期,这样指定代表永久存在
        .setNotificationResponsiveness(1000)// 指定回调时间
        .setTransitionTypes(Geofence.GEOFENCE_TRANSITION_ENTER | Geofence.GEOFENCE_TRANSITION_EXIT) // 监听进出事件
        .build();

// 创建PendingIntent
Intent intent = new Intent(context, GeofenceIntentService.class);
intent.putExtra(GeofenceUtils.EXTRA_GEOFENCE_ID, geofence.getRequestId());
PendingIntent pendingIntent = PendingIntent.getService(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

// 注入位置监听器
locationManager.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 1000, 0, new LocationListener() {
    @Override
    public void onLocationChanged(Location location) {
        // 添加围栏
        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        geofencingClient.addGeofences(getGeofencingRequest(geofence), pendingIntent);
    }
});