Google has recently released the Android platform for developing mobile applications. The language used for developing Android programs is Java, but it is not Java Micro Edition. No wireless application developer can ignore Android. Google is the best known brand name, among the users of the web and Android comes from Google.
I am presenting this hands-on tutorial, as a sequel to my j2me series. Adequate knowledge of core-java ,especially Event-handling, Swing and inner-classes is assumed. Though Android does not make use of Swing, it uses similar ideas.
We can develop Android lessons and applications in Eclipse environment. Google have provided an Eclipse-plugin for Android. This is the popular method. Google has not given direct support to Netbeans. But some Netbeans users have developed a method for running Android in Netbeans . It is available at http://undroid.nolimit.cz/. You can find more screenshots and guidance in http://eppleton.com/blog/.
We can develop Android lessons without using either Eclipse or Netbeans. The necessary command-line tools have been provided by Google. I found that using these command-line tools is easier than either Eclipse or Netbeans method. So, I am basing all the following lessons on these tools. I think, most readers will agree with my view, after they try this method as well as Eclipse method. The Android site at 'code.google.com/android' has already given step-by-step instructions about Android in Eclipse. You can also get more details with screen shots from a wonderful website at www.tanguay.info/web/welcome.php titled 'Edward's Web Developer site'. He gives excellent guidance with plenty of screen shots
The Android site lacks clarity about the command-line method. Hence, I think I am adding something useful by writing on the command-line method instead of simply repeating the material in Android site.
Let us start from the beginning. The first step is downloading the Android SDK (version m5-rc14, Feb-12, 2008). Android was released in November, 2007 . It has been revised in the Feb-2008 version.Some of the earlier examples may not work in the newer version.
I am working in Windows-2000 and so I downloaded the windows version. The supported platform in Windows is either Windows-XP or Vista.(Mac OS 10 & Ubuntu Linux are the other platforms mentioned). However, it works well in my Win-2000. It is advisable to have at least 512MB memory. The android SDK is a zip file. I unzipped it to C:\unzipped\android and later, I copied that folder to D:\android. If you want, you can simply copy it to another drive like G:\android also. In the following lessons D:\android is used.
If you want to develop using Eclipse, you must have installed either Eclipse3.2 or Eclipse3.3(Europa). I have tested with Eclipse3.2. No problem.It works. But, we require ADT (ie) Android Development Tools plugin for Eclipse, if you are using Eclipse.You can get this plugin from http://code.google.com/android/adt_download. You have to be careful about the ADT version number.It is ADT-0.3.3.
As my present focus is on command-line method, let me begin straight away and give a simple demo.The procedure given here is common for all our experiments and so I will not be repeating it in each demo. So, please note it down carefully.
Demo 1 - TextBox
In my first demo, I will have a customary button and textbox ( called EditField in Android). When I click the button, I want the message "SUCCESS!" to be displayed in textbox. Just as an exercise, I am using two buttons and two textboxes.
The first step is to start the Emulator
cd to d:\android\tools
It will take a long time to get started. Do not be in a hurry. Wait till it gets fully started. And do not close that window carelessly by mistake. In that case, you will have to start it again and wait for a long time again. Finally, we get the emulator screen
The second step is to give the following command, from another command window.
activityCreator --out demo mypack.mydemos.demo
This means that my project is 'demo' and my package is 'mypack.mydemos'. A number of folders are created automatically by this command:
We need to note the src and res folders carefully. We will place the java source file in src folder and main.xml file in res\layout, overwriting any files that are generated automatically. For the moment, we can think of the res\layout folder as the one which decides the gui design. As in asp.net, flex etc, the gui details are specified in xml file. But how shall we write the XML file? by hand? Not too difficult .But....luckily, there is an open-source gui designer named 'DroidDraw' available in http://www.droiddraw.org/ .It is a nice tool and if you like it, you can send your appreciation to firstname.lastname@example.org. He has given a simple tutorial too, on how to use this gui tool.
I downloaded this software from the above site. I unzipped it. ( any folder). When we click on the icon, we get the screen as given below.
Thus we get a window, showing the drawing canvas on leftside and toolbox and a blank area in the rightside. ( for printing purpose, I have split them into two screens) as above.