GT's Blog

My first Android project in Eclipse: Multiplication Table Generator App using TextWatcher and OnClickListener

After removing the configuration errors that came during running the auto generated Hello World project, I decided to write a Multiplication Table Generator App on Android platform. This is my first android app other than HelloWorld. In this article, I am going to explain how I created the App. It describes the use of TextWatcher and OnClickListener interfaces for event handling.

Multiplication Table Generator contains the EditText-ipNumberTxt component for reading user input – a number. It contains two Buttons '+' and '–' to increment/decrement the number in EditText. The generated output is displayed in TextView-outputTXT. The multiplication table is generated on afterTextChanged event of EditText field.

The download link for complete project is given at end of article.

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Error Free Android Hello World Project on Eclipse

Removal of two common errors that may arise when running the android project on eclipse.
[ PANIC: Could not open: C:\Users\gTiwari\.android/avd/MyAndAVD.ini ]
and
[ invalid command-line parameter: Files ]

Today I tried to setup the essentials and test a demo project on Eclipse.I installed required tools (Android SDK, ADT, etc) and created a empty project successfully.

I was following these articles :
Installing Android SDK and ADT in eclipse.
Android First HelloWorld App in Eclipse.
But I got the few errors when I tried run the Hello World project that eclipse created for me.

In this Blog, I am describing the errors and how I solved them that may be useful for Android beginners like you.

[My System Details : Windows 7(64-bit). Eclipse 3.7 (Indigo).The MyFirstEmul is the name of emulator I created.]

Error #1
When i created a hello world project and tried to run it. I got the following error.
[2011-08-27 18:05:22 - Emulator] PANIC: Could not open: C:\Users\gTiwari\.android/avd/MyAndAVD.ini
Cause :
The emulator could not found in location "C:\Users\gTiwari\". I searched over my HDD for the emulator I created earlier. And I found it in the E:\ .android folder. This might be due to I had moved my system folders such as Documents, Desktop, Downloads to E:\.
Solution :
I simply moved the E:\.android folder to C:\Users\gTiwari\ and solved it.

Error #2
After I solved the Error #1, and tried to run the project, I got the following error :
[2011-08-27 18:24:39 - Emulator] invalid command-line parameter: Files.
[2011-08-27 18:24:39 - Emulator] Hint: use '@foo' to launch a virtual device named 'foo'.
[2011-08-27 18:24:39 - Emulator] please use -help for more information
Cause :
The default installation location is: C:\Programme Files(x86)\Android\android-sdk. But the SDK location cannot contain any spaces.
Solution :
Should I reinstall the Android SDK to new location with no space in folder names ?
Well, that may be a solution. But i found easy solution for this.
I make use of mklink command line utility of NTFS in Windows 7 (in previous versions of the command may be different). I pointed C:\AndroidSDK to the actual C:\Program Files (x86)\Android\android-sdk by using following command.
MKLINK /J C:\AndroidSDK "C:\Program Files (x86)\Android\android-sdk\"
This command created special junction folder C:\AndroidSDK helped me in redirection.

And I configured this new path(C:\AndroidSDK) to AndroidSDK in Eclipse IDE settings - from
Windows -> Preferences -> Android
And run the Hello World project successfully.

See my other posts on android from : http://ganeshtiwaridotcomdotnp.blogspot.com/search/label/Android

android get current screen orientation

The current configuration ( orientation as well) can be available from the Resources' Configuration object as:
The return parameter may be one of ORIENTATION_LANDSCAPE, ORIENTATION_PORTRAIT, or ORIENTATION_SQUARE.

public static int getScreenOrientation(){    
    return getResources().getConfiguration().orientation;
}

check http://developer.android.com/reference/android/content/res/Configuration.html#orientation for details

java android write to sd card

You can access to sd card by File sdCard = Environment.getExternalStorageDirectory();

Note : Hard coding the /sdcard/ folder is not good.

Write to sd card

File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdcard.getAbsolutePath() + "/dir1/dir2");
dir.mkdirs();
File file = new File(dir, "filename");
FileOutputStream f = new FileOutputStream(file);
...

And read/write to file by using FileOutputStream f .

Mouse Gesture Recognition with Hidden Markov Model.

Understanding gestures can be posed as a pattern recognition problem. These patterns(gestures) are variable but distinct and have an associated meaning. Since gesture consists of continuous motion in sequential time, an HMM is an effective recognition tool.

My work is a demonstration of a mouse motion gesture recognition system using Dynamic HMM. It is developed in Java.

Code Available @ : https://github.com/gtiwari333/mouse-gesture-recognition-java-hidden-markov-model

Main References were :

DEMO VIDEO

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Redirecting JAVA IO to GUI by Redirecting IO Streams

Here is a small utility program for fun (but useful). It is written in Java by redirecting IO Streams to GUI.
Its features are:

Reading console input from GUI --> No need of Black Screen.
Displaying console output (including exceptions) to GUI.
Easy to use.
Useful for Java Beginners

First lets see the code of test application.

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Java Map Comparison- hashmap, linkedhashmap, treemap

Java Map Comparison :

HashMap is the fastest map with O(1) search and insertion times.
LinkedHashMap is a little slower for inserts, but maintains the insertion order.
TreeMap is the slowest map, but lets you iterate over the keys in a sorted order.