Monday, December 30, 2013

Measure geodesic distances on Google Maps

As the name suggests, this Measure Geodesic Distance mapplet allows users to measure the geodesic distance between two or more points on the earth's surface using the Haversine formula. The mapplet uses the formulas from this site The measurement points and lines are displayed on a Google Maps backdrop. Users have the option to choose the measurement units of meters, kilometers or miles: the line color can also be set by the user.

Run the mapplet from this site

Using the mapplet is easy, just do the following:

  1. Click two or more points on the map.

    Vertex markers are displayed, and geodetic lines are displayed between the vertex markers.
    Note I : the segment distance value is displayed at the mid point of the line(s).
    Note II: the total distance value is displayed at the last vertex marker. 

  2. Drag a vertex marker to another location on the map.

    The geodetic lines and vertex markers are updated to show the new distances.

  3. Click on a vertex marker.

    The latitude and longitude values are displayed in an Info Window.
  4. In the Info Window, click Delete to delete the vertex marker.

    The vertex marker is removed and the lines and markers are updated to show the new distances.
  5. To adjust a vertex marker by precision key-in, click on a vertex marker.

    The latitude and longitude values are displayed in an Info Window.
  6. In the Info Window, type in the new latitude and/or longitude values. Click Save.

    The vertex marker is moved to the new location and the lines and markers are updated to show the new distances.
  7. To clear all the markers and lines from the map, click the Clear button in the right pane

Monday, December 23, 2013

Seattle 911 incidents monitoring WebApp

This WebApp allows users to monitor the City of Seattle's Fire Department's real time 911 dispatches (updated every five minutes) and the Seattle Police Department's 911 dispatch incident responses that are non-confidential (updated every 4 hours) on a Google Maps backdrop. Simply choose the appropriate feed on the 911 feed drop down menu on the right pane.

The 911 incidents are shown as clickable icons with tool tips on Google Maps. Clicking on an icon will bring up more details about the incident. Users can utilize additional built-in Google Maps features such as Street View, or 3-D oblique 45 degrees views to immerse themselves into the incident environment.

The 911 incidents are also shown as a list on the right pane. The list can be sorted by incident category, date-time and address - either in ascending or descending order. Clicking the Maps hyperlink will automatically locate, zoom, and center the incident in the Map view.

The WebApp can be launched from this link

Monday, December 16, 2013

How to obfuscate an Android APK file using ProGuard in the Eclipse ADT

The classes in the Android APK can be obfuscated using the ProGuard tool in the Android Development Toolkit (ADT) in Eclipse. The following shows how to enable to source code obfuscation.
  1. In Eclipse, open up an Android project e.g. androidgames.
  2. Open up the file in the Eclipse text editor.

  3. Uncomment the following line by removing the # symbol in the first column.

  4. Optional. If there are any classes that you do not want to obfuscate, then the class must be added to the proguard-project.txt file, e.g. com.dom925.trains.manila.SvgInterface, as shown below.
# If your project uses WebView with JS, uncomment the following
# and specify the fully qualified class name to the JavaScript interface
# class:
#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
#   public *;
-keepclassmembers class com.dom925.trains.manila.SvgInterface {
public *;

An example of a decompiled obfuscated Android APK is shown below.

Monday, December 9, 2013

How to decompile an Android APK file

I was wondering how easy it is to decompile my Android APK files into source code files. So I did some searching using Google Search and found a few decompilers, some free and some commercial stuff. It seems that the process can be done in two steps: (1) convert the APK file to a JAR file, and (2) convert the JAR file to JAVA files.

The first step can be done using open source program dex2jar from The second part can be done using a Java decompiler from The Java decompiler will decompile the JAR file into the Java source code files. Using these two programs, it was very easy to reverse engineer the Android APK file as shown below:
  1. Open up a Command Prompt.
  2. Type in the d2j-dex2jar.bat command (assuming it is in the system path, otherwise you need to type in the whole command path) to convert an apk file e.g. androidgames.apk.

    C:\> d2j-dex2jar.bat androidgames.apk

    The apk file is converted to a jar file androidgames-dex2jar.jar.

    Note: the suffix "-dex2jar.jar" is appended to the file name.
  3. Now run the Java decompiler jd-gui.exe by double clicking the executable from the Windows Explorer.

    The Java Decompiler application appears.

  4. Click File | Open File. Browse and select the jar file created previously.

  5. Click Open.

    The classes and source code files are displayed in the application.

Monday, December 2, 2013

Find your way around Kuala Lumpur with this Android App: Trainsity Kuala Lumpur

Find your way around the city of Kuala Lumpur using the high resolution vector maps of the KTM Komuter lines, RapidKL lines, and KLIA Express Rail Link lines. The maps have small file size footprints but with many levels of zoom and can work offline without connecting to the Internet. Users can click the train station labels to open Google Maps, where they can use all the functions of the Google app to visualize the surrounding area and/or perform routing for directions.

On a mobile handset, the app will display a list of train maps, which when tapped will open up a detail view of the metro transit map, as shown below.

Tapping the station boxes will bring up an option menu where users can choose to display the station in Google Maps.

The app is also optimized for tablet sized devices. Both the list and the vector map are displayed at the same time, as shown below.

The user can toggle the map to full screen mode by tapping the action bar icon at the top.

The app can be downloaded from the Google Play Store 
Get it on Google Play