我的地图活动加载速度太慢，我希望有更快的地图活动。我怎样才能做到这一点？我听说预加载地图是有效的，但我不知道该怎么做。我不会发布我的整个地图活动，因为它有点令人困惑，但我会发布一个基本样本（来自Github），我使用相同的方式来加载地图。
import android.app.ProgressDialog;
import android.graphics.Color;
import android.location.Location;
import android.net.Uri;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationServices;
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.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.Polyline;
import com.google.android.gms.maps.model.PolylineOptions;
import com.google.maps.android.SphericalUtil;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class MapsActivity extends FragmentActivity implements
OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
GoogleMap.OnMarkerDragListener,
GoogleMap.OnMapLongClickListener,
View.OnClickListener{
//Our Map
private GoogleMap mMap;
//To store longitude and latitude from map
private double longitude;
private double latitude;
//From -> the first coordinate from where we need to calculate the distance
private double fromLongitude;
private double fromLatitude;
//To -> the second coordinate to where we need to calculate the distance
private double toLongitude;
private double toLatitude;
//Google ApiClient
private GoogleApiClient googleApiClient;
//Our buttons
private Button buttonSetTo;
private Button buttonSetFrom;
private Button buttonCalcDistance;
@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);
//Initializing googleapi client
// ATTENTION: This "addApi(AppIndex.API)"was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
googleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.addApi(AppIndex.API).build();
buttonSetTo = (Button) findViewById(R.id.buttonSetTo);
buttonSetFrom = (Button) findViewById(R.id.buttonSetFrom);
buttonCalcDistance = (Button) findViewById(R.id.buttonCalcDistance);
buttonSetTo.setOnClickListener(this);
buttonSetFrom.setOnClickListener(this);
buttonCalcDistance.setOnClickListener(this);
}
@Override
protected void onStart() {
googleApiClient.connect();
super.onStart();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Maps Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app deep link URI is correct.
Uri.parse("android-app://net.simplifiedcoding.googlemapsdistancecalc/http/host/path")
);
AppIndex.AppIndexApi.start(googleApiClient, viewAction);
}
@Override
protected void onStop() {
googleApiClient.disconnect();
super.onStop();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Maps Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app deep link URI is correct.
Uri.parse("android-app://net.simplifiedcoding.googlemapsdistancecalc/http/host/path")
);
AppIndex.AppIndexApi.end(googleApiClient, viewAction);
}
//Getting current location
private void getCurrentLocation() {
mMap.clear();
//Creating a location object
Location location = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
if (location != null) {
//Getting longitude and latitude
longitude = location.getLongitude();
latitude = location.getLatitude();
//moving the map to location
moveMap();
}
}
//Function to move the map
private void moveMap() {
//Creating a LatLng Object to store Coordinates
LatLng latLng = new LatLng(latitude, longitude);
//Adding marker to map
mMap.addMarker(new MarkerOptions()
.position(latLng) //setting position
.draggable(true) //Making the marker draggable
.title("Current Location")); //Adding a title
//Moving the camera
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
//Animating the camera
mMap.animateCamera(CameraUpdateFactory.zoomTo(15));
}
public String makeURL (double sourcelat, double sourcelog, double destlat, double destlog ){
StringBuilder urlString = new StringBuilder();
urlString.append("https://maps.googleapis.com/maps/api/directions/json");
urlString.append("?origin=");// from
urlString.append(Double.toString(sourcelat));
urlString.append(",");
urlString
.append(Double.toString( sourcelog));
urlString.append("&destination=");// to
urlString
.append(Double.toString( destlat));
urlString.append(",");
urlString.append(Double.toString(destlog));
urlString.append("&sensor=false&mode=driving&alternatives=true");
urlString.append("&key=AIzaSyCJVpM7-ayGMraxFRzq4U8Dt1uRNsmiaws");
return urlString.toString();
}
private void getDirection(){
//Getting the URL
String url = makeURL(fromLatitude, fromLongitude, toLatitude, toLongitude);
//Showing a dialog till we get the route
final ProgressDialog loading = ProgressDialog.show(this, "Getting Route", "Please wait...", false, false);
//Creating a string request
StringRequest stringRequest = new StringRequest(url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
loading.dismiss();
//Calling the method drawPath to draw the path
drawPath(response);
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
loading.dismiss();
}
});
//Adding the request to request queue
RequestQueue requestQueue = Volley.newRequestQueue(this);
requestQueue.add(stringRequest);
}
//The parameter is the server response
public void drawPath(String result) {
//Getting both the coordinates
LatLng from = new LatLng(fromLatitude,fromLongitude);
LatLng to = new LatLng(toLatitude,toLongitude);
//Calculating the distance in meters
Double distance = SphericalUtil.computeDistanceBetween(from, to);
//Displaying the distance
Toast.makeText(this,String.valueOf(distance+" Meters"),Toast.LENGTH_SHORT).show();
try {
//Parsing json
final JSONObject json = new JSONObject(result);
JSONArray routeArray = json.getJSONArray("routes");
JSONObject routes = routeArray.getJSONObject(0);
JSONObject overviewPolylines = routes.getJSONObject("overview_polyline");
String encodedString = overviewPolylines.getString("points");
List<LatLng> list = decodePoly(encodedString);
Polyline line = mMap.addPolyline(new PolylineOptions()
.addAll(list)
.width(20)
.color(Color.RED)
.geodesic(true)
);
}
catch (JSONException e) {
}
}
private List<LatLng> decodePoly(String encoded) {
List<LatLng> poly = new ArrayList<LatLng>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng p = new LatLng( (((double) lat / 1E5)),
(((double) lng / 1E5) ));
poly.add(p);
}
return poly;
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
LatLng latLng = new LatLng(-34, 151);
mMap.addMarker(new MarkerOptions().position(latLng).draggable(true));
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.setOnMarkerDragListener(this);
mMap.setOnMapLongClickListener(this);
}
@Override
public void onConnected(Bundle bundle) {
getCurrentLocation();
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
@Override
public void onMapLongClick(LatLng latLng) {
//Clearing all the markers
mMap.clear();
//Adding a new marker to the current pressed position
mMap.addMarker(new MarkerOptions()
.position(latLng)
.draggable(true));
latitude = latLng.latitude;
longitude = latLng.longitude;
}
@Override
public void onMarkerDragStart(Marker marker) {
}
@Override
public void onMarkerDrag(Marker marker) {
}
@Override
public void onMarkerDragEnd(Marker marker) {
//Getting the coordinates
latitude = marker.getPosition().latitude;
longitude = marker.getPosition().longitude;
//Moving the map
moveMap();
}
@Override
public void onClick(View v) {
if(v == buttonSetFrom){
fromLatitude = latitude;
fromLongitude = longitude;
Toast.makeText(this,"From set",Toast.LENGTH_SHORT).show();
}
if(v == buttonSetTo){
toLatitude = latitude;
toLongitude = longitude;
Toast.makeText(this,"To set",Toast.LENGTH_SHORT).show();
}
if(v == buttonCalcDistance){
getDirection();
}
}
}
提前谢谢。
答案 0 :(得分：-1)
我找到了一个问题的答案，但我知道这不是最佳答案，因为我不会将其标记为真正的答案，以便为其他人找到更好的答案。我在onMapReady中添加了以下代码：
googleMap.setMapType(GoogleMap.MAP_TYPE_TERRAIN);
我将地图类型从普通更改为地形，此解决方案导致地图加载速度更快。