Localhost Access in Android Emulator

This is a small tit-bit I discovered today:


If you want to access your localhost through the Android Emulator - you need to use the IP Address 10.0.2.2 unlike how we do on the web browsers on our desktops where we access the local host as 127.0.0.1 or 'localhost' itself.


This information is useful if for testing purposes you have locally installed a webserver and put a few HTML pages or if you have locally hosted web services - say REST Services that need to be invoked through a URL like this: http://localhost:8080/rest/hello, then, use the above mentioned IP address and you will be able to access your service or webpage through the emulator.


Or you could simple use your own IP address like 192.168.3.233 - whatever yours is. If you do a "ipconfig" in a windows command prompt, you will know what your IP address is. (one of the ways to find it out). However, there is one disadvantage with this method if your IP is allocated to you dynamically on your network. This will keep changing. In such a case, using 10.0.2.2 will be the equivalent of 127.0.0.1 which will not change for the localhost.


Hope this helps.

Delete / Remove Android Applications deployed on Emulator

First, make sure the emulator is running. Then follow below steps:

1. Go to the tools directory in command prompt – c:\>android\tools
2. Type adb shell
3. #cd /data/app (this takes you to the folder where all apk files are installed)
4. #ls (It will display all the .apk installed in your emulator)
5. #rm ***.apk (which you want to remove, all apk files)
6.#exit (exits from the adb shell)

NOTE: to start the emulator, you can start it from eclipse by right clicking an android project and “run as” an “application” or by going to tools directory at command prompt and typing “emulator –avd <avd_name>”

Location Manager | Android Developer Tutorial (Part 15)

Location-based service is another key functionality that gets used by mobile applications. IT is often combined with maps to give a good user experience. We have already see how to use the external Google Maps API in tutorial Part 14. Here I will build upon the same to show how changes in location can be displayed on the map.

The location services are provided in the android.location package.

In order to use location services, our activity needs to implement the LocationManager Interface.

What does a LocationManager provide?

It is through this interface that an application can access the system’s location services. These services basically allow the application to obtain periodic updates of the device’s geographical location. It also helps in firing an application specific intent when the device comes within the proximity of a specified location.

Since in my example I want to simulate a location change and make my activity respond to the same, I am implementing this interface.

In order to make it an effective application, I have shown my location (hard-coded) on the google map. Then, I have used the location manager to handle any change in the location. The change in location needs to be simulated on the emulator by connecting through telnet. How to simulate location change is given at the end of this tutorial.

Now, dive into the code.

NOTE: I am adding the LocationManager implementation to the same MapActivity class created in the earlier tutorial (Part 14) and hence will not be explaining anything related to the maps API here.

Step 1: Obtain the LocationManager instance:

LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000L, 500.0f, this);

After getting the location manager, I am setting default GPS provider and asking to be notified if the location changes by more than 500 meters from the current location, the frequency of updation being 1 sec.

Step 2: Override the onLocationChanged() method in order to respond to changes in location.

      public void onLocationChanged(Location location) {

            if (location != null) {

                  double lat = location.getLatitude();

                  double lng = location.getLongitude();

                  String currentLocation = "The location is changed to Lat: " + lat + " Lng: " + lng;

                  myLoc.setText(currentLocation);

                  geoPoint = new GeoPoint((int) lat * 1000000, (int) lng * 1000000);

                  myMC.animateTo(geoPoint);

            }

      }

This method gets invoked when we change the location through the telnet connection to the emulator as described at the end of the tutorial. Based on the latitude and the longitude settings sent, the GeoPoint is changed to display the new location.

That is it. I have not overridden any of the other methods provided by the locationManager. Complete code is downloadable here.

How to simulate location change in the emulator?

Start the Emulator from eclipse

Start a command prompt

Start telnet

Then, type, o localhost 5554

This connects the telnet client to the android emulator (assuming emulator is running locally listening on port 5554. Else this connection fails)

Now type

geo fix 79.000000 13.000000 (or your latitude and longitude)

This sends the location change signal to the emulator.

Simulate Location Change in Android Emulator

Start the Emulator

Start a command prompt

Start telnet

Then, type, o localhost 5554

This connects the telnet client to the android emulator (assuming emulator is running locally listening on port 5554. Else this connection fails)

Now type

geo fix 79.000000 13.000000 (or your latitude and longitude)

This sends the location change signal to the emulator.

NOTE: This is useful for applications built using Location APIs in Android and need to work with changes in location