Toying with Android apps


As the title suggests this is my first encounter with Android. This post is not meant for those who are intending to develop serious android apps. This article shows how to get started with Android App development. Recently I acquired my first Samsung smartphone and I can’t seem to get enough of it. I am now fully hooked on to Android and hope to play around with it in the days to come. Fortunately the initial encounter has been fairly pleasant.

To get started download the SDK from http://developer.android.com/sdk/index.html#ExistingIDE assuming you already have Eclipse like I did. Unpack and install the SDK at a suitable location for e.g. /android. You will also have to install the Eclipse plugin for Android from http://developer.android.com/sdk/installing/installing-adt.html. Alternatively you can directly download the comple ADT bundle which includes the SDK,Eclipse along with plugin etc.

Once you have Android installed on in the plugin start Eclipse. Select File->New->Project-> Android Application Project and click next. In the Application Name enter My Test and let eclipse fill the names for Project name and Package name. Click next. Allow default values in New Android Application and Configure Launcher icon screens. In the Create Activity choose Blank Activity and choose default values for New Blank Activity and finally choose Finish.

This will create the Android Project. The files and folders that are created
/src – Source folder. This contains the java source files
/res – Resource folder. This is the resource which specifies the Layout, UI and also has the Android Manifest File indicating permissions.

For the 1st Android app under res/layout open activity_main.xml. There are 2 tabs in the eclipse Window namely Graphical Layout and activity_main.xml. The Palette can be used to drag and drop widgets like textfield, buttons, radio buttons etc. For my example I placed a text field with a text “My first Android Hello World App”. You can modify the text after dragging from the palette by right clicking and entering the text string. Similarly I also dragged and dropped a button and named it “Submit”. Right click the button choose Other properties->Inherited from View and select onClick and enter “print” for New OnClickValue. Now the function print will be invoked when the Submit button is clicked.

The activity_main.xml will contain the following contents
<RelativeLayout xmlns:android=http://schemas.android.com/apk/res/android&#8221;
xmlns:tools=http://schemas.android.com/tools&#8221;
android:layout_width=“match_parent”
android:layout_height=“match_parent”
tools:context=“.MainActivity” >
<Button
android:id=“@+id/button1”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:layout_alignLeft=“@+id/textView1”
android:layout_below=“@+id/textView1”
android:layout_marginTop=“32dp”
android:onClick=“print”
android:text=“Submit” />
<TextView
android:id=“@+id/textView1”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:layout_alignParentTop=“true”
android:layout_centerHorizontal=“true”
android:layout_marginTop=“22dp”
android:text=“My First Android Hello World App”
android:textAppearance=“?android:attr/textAppearanceMedium” />
</RelativeLayout>

Now under src open MainActivity.java and add the following code
public void print(View view) {
Toast.makeText(this, “Hello World, Hello Android!”,
Toast.LENGTH_LONG).show();
return;
}

Before you build your application click Windows->Android SDK Manager. Select Tools, Android 4.2 and the necessary Extras. This will update your SDK with the latest version of teh SDK and associated libraries. Now click Windows-> Android Virtual Device Manager. This is Android’s emulator and needs to be setup. The simplest way is to select the Device Definitions tab and choose one of the devices mentioned there as your AVD. Alternatively you can select New and create a custom AVD.

Now build the project by selecting Project->Build All. Once the build is successful run the project. This will bring the AVD you selected above.

This will take a few minutes. Finally the screen will appear with a lock. Drag the lock to unlock it. To see a list of apps click the rectange wih six squares inside it. You show now see this in the AVD.

Finally double click your My Test app. When you click the Submit button it show print “Hello world, Hello Android as show below.

The SDK also comes with several sample Android projects to play around with. To build a sample project click New->Project-Android Sample Project and choose any one among them. Play around with other AVDs.

I hope to do some more serious stuff with Android in the days to come. Watch this space

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