While I think the Android development examples are not really good and straight forward perhaps some of you come along with them. However, I would like to provide you a very very simple example here on how to write your own first Android program.

This is technically very easy. Once you got Eclipse and Android installed and running on your computer (I use a Mac OS Leopard powered MacBook but you can use a Microsoft Windows XP/Vista/etc. PC as well) you just start Eclipse. Now you just go to “New » Project... » Android » Android Project...” and enter the required data. Once you are done the result might look like this:

Now you can start writing and customize the default “Hello World” a.k.a. “Hello Android” app which just shows a text field. If you are really really lazy you could also copy/paste the following code:

I have just found a very good android tutorial for beginners and want to share with you:

PDF version: android tutorial for beginners

PPT version: android tutorial for beginners

Introduction

[This post is by Gilles Debunne, an engineer in the Android group who loves to get multitasked. — Tim Bray]

A good practice in creating responsive applications is to make sure your main UI thread does the minimum amount of work. Any potentially long task that may hang your application should be handled in a different thread. Typical examples of such tasks are network operations, which involve unpredictable delays. Users will tolerate some pauses, especially if you provide feedback that something is in progress, but a frozen application gives them no clue.

In this article, we will create a simple image downloader that illustrates this pattern. We will populate a ListView with thumbnail images downloaded from the internet. Creating an asynchronous task that downloads in the background will keep our application fast.

To generate a skewed bitmap, Matrix.postSkew() can be used.



Extend the last exercisse "Rotate bitmap image, using Matrix".

Modify main.xml to add two SeekBar to set the skew for x and y.

Here Rotating function is going to be added on the last exercise "Scale bitmap image, using Matrix". It's a SeekBar on the screen to change the degree to rotate the bitmap, by using of Matrix.postRotate().

Modify the last exercise "Load bitmap file from SD Card", to implement function to post-scale the bitmap image using Matrix.



In order to create a new bitmap with selected scale: A new Matrix object have to be created, with postScale. Then create a new bitmap from the image in SD Card, using the matrix.

In last exercise "Save file to SD Card", a file have been saved in SD Card. In this exercise, the bitmap file in SD Card will be loaded, using BitmapFactory.

In the previous exercises "Load ImageView with bitmap from internet" and "Generate QR code using Google Chart API", images were downloaded from internet for display only. Here, we are going to save the download image to SD Card.