Street Address

This app looks up the street address and zipcode of the Woolworth Building, given its latitude and longitude:
Latitude 40.712222° North
Longitude 74.008056° West
See the JavaScript Geocoding Service. Conversion from latitude and longitude to street address is called reverse geocoding.

The JavaScript function onFound in page.html is called when the Geocoder object finds the street address and zipcode of the given latitude and longitude. I named it onFound because it’s like an Android listener. The results argument of onFound is an array of GeocoderResult objects. We examine only the first element of this array. The element contains an array of GeocoderAddressComponents, each of which contains a type and long_name.

Source code in Address.zip

1. MainActivity.java
2. activity_main.xml contains a WebView.
3. page.html in the assets folder.
4. AndroidManifest.xml: a WebView requires uses-permission INTERNET.

Create the project

Create the assets folder

The page.html to which the URL refers must be in the assets folder in the Android Studio project view. Select the app folder at the top of the project view. Pull down
File → New… → Folder → Assets Folder
Finish

Remember to add the uses-permission to AndroidManifest.xml.

Create the page.html file

Select the assets folder in the Android Studio project view.
File → New… → File
Enter a new filename: page.html
OK

Things to try

1. We passed the latitude and longitude from the Android app to the JavaScript program. Now let’s pass the zipcode from the JavaScript program back to the Android app. We will create an object with dual citizenship: it will be a Java object in the Android app, and a JavaScript object in the JavaScript program.
   1. Insert the following nested class into class MainActivity.

          class DualCitizen {
              //This method, although written in Java, can be called in a JavaScript statement.
              @JavascriptInterface
              public void setZipcode(String z) {
                  int zipcode = Integer.parseInt(z);
                  Toast toast = Toast.makeText(MainActivity.this, "Zipcode is " + zipcode, Toast.LENGTH_LONG);
                  toast.show();
              }
          }
      

   2. Insert the following statement immediately before the loadURL at the end of onCreate.

              //Create a new Java object, and specify the name it will have when it
              //appears in the JavaScript program.
              webView.addJavascriptInterface(new DualCitizen(), "dualCitizen");
      

   3. In the JavaScript function onFound in page.html, insert the following statements immediately before the break.

                          var zipcode = results[0].address_components[i].long_name;
                          dualCitizen.setZipcode(zipcode);
      



2. In Location, we used the GPS to get our latitude and longitude. In Map, we took a latitude and longitude and displayed a Google map of that place. In the present app, we took a latitude and longitude and displayed the zipcode of that place. Write an app that displays a map of your current location, with a Toast displaying the zipcode of the location.