title: How to get weather tile layer correctly?
body: <p>I am trying to get a precipitation weather layer to appear in my Google Maps activity, but cannot understand why it is not showing on the map. I have implemented my Google Maps Key in <code>app\src\debug\res\values\google_maps_api.xml</code>, have installed Google Play Services in Android SDK manager, and I have set up an account with OpenWeatherMap for their API (which is taken out below).</p>
  
  <p>The map loads fine, and when I search the layer in a separate browser with inputted zoom,x,y it shows up fine, but I cannot get the layer to appear on my Google Maps activity. </p>
  
  <p>Do I need to define x,y,zoom or are these pulled from the URL?</p>
  
  <p>Here is my java:</p>
  
  <pre><code>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 &lt; minZoom || zoom &gt; maxZoom);
  
              }
          };
  
          TileOverlay tileOverlay = mMap.addTileOverlay(new TileOverlayOptions()
                  .tileProvider(tileProvider));
      }
  }
  </code></pre>
  
  <p>Here is the Android Studio generated layout:</p>
  
  <pre><code>&lt;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"/&gt;
  </code></pre>
  
  <p>I have followed tutorials and documentation offered from OpenWeatherMap, Google Maps API, and Android Developers, but do not understand why this is not working.</p>
  
  <p>What am I missing?</p>