如何正确获取天气图层？

Question

我想让降雪天气图层出现在我的Google地图活动中，但无法理解它为什么没有显示在地图上。我在app\src\debug\res\values\google_maps_api.xml中实施了我的Google地图密钥，已经在Android SDK管理器中安装了Google Play服务，并且我已经在OpenWeatherMap中为其API（在下面列出）中创建了一个帐户。

地图加载正常，当我在带有输入缩放的单独浏览器中搜索图层时，x，y显示正常，但我无法让图层出现在我的Google地图活动中。

我需要定义x，y，缩放还是这些从URL中拉出来？

这是我的java：

package com.example.user.project; 

import android.support.v4.app.FragmentActivity; 
import android.os.Bundle; 

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; 
import com.google.android.gms.maps.model.TileOverlay; 
import com.google.android.gms.maps.model.TileOverlayOptions; 
import com.google.android.gms.maps.model.TileProvider; 
import com.google.android.gms.maps.model.UrlTileProvider; 

import java.net.MalformedURLException; 
import java.net.URL; 
import java.util.Locale; 

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback { 

    private GoogleMap mMap; 

    @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); 
    } 

    /** 
    * Manipulates the map once available. 
    * This callback is triggered when the map is ready to be used. 
    * This is where we can add markers or lines, add listeners or move the camera. In this case, 
    * we just add a marker near Sydney, Australia. 
    * If Google Play services is not installed on the device, the user will be prompted to install 
    * it inside the SupportMapFragment. This method will only be triggered once the user has 
    * installed Google Play services and returned to the app. 
    */ 
    @Override 
    public void onMapReady(GoogleMap googleMap) { 
     mMap = googleMap; 

     // Move the camera 
     LatLng indy = new LatLng(39, -86.5); 
     mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(indy, 8)); 

     TileProvider tileProvider = new UrlTileProvider(256, 256) { 
      @Override 
      public URL getTileUrl(int x, int y, int zoom) { 

    /* Define the URL pattern for the tile images */ 
       String s = String.format(Locale.US, "http://tile.openweathermap.org/map/precipitation/%d/%d/%d.png?appid={my_key}", 
         zoom, x, y); 

       if (!checkTileExists(x, y, zoom)) { 
        return null; 
       } 

       try { 
        return new URL(s); 
       } catch (MalformedURLException e) { 
        throw new AssertionError(e); 
       } 
      } 

      /* 
      * Check that the tile server supports the requested x, y and zoom. 
      * Complete this stub according to the tile range you support. 
      * If you support a limited range of tiles at different zoom levels, then you 
      * need to define the supported x, y range at each zoom level. 
      */ 
      private boolean checkTileExists(int x, int y, int zoom) { 
       int minZoom = 12; 
       int maxZoom = 16; 

       return !(zoom < minZoom || zoom > maxZoom); 

      } 
     }; 

     TileOverlay tileOverlay = mMap.addTileOverlay(new TileOverlayOptions() 
       .tileProvider(tileProvider)); 
    } 
} 

下面是Android Studio生成布局：

<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="com.example.user.project.MapsActivity"/> 

我按照教程和文档从OpenWeatherMap，谷歌地图API和Android开发者提供的，但不明白为什么这不起作用。

我错过了什么？

Answer 1

您正在将级别8设置为地图的缩放级别，但您也将缩放级别限制在12和16之间，以使TileProvider可见。

删除此：

if (!checkTileExists(x, y, zoom)) { 
    return null; 
} 

如果您不需要任何规模的限制，你还可以去除checkTileExists方法。