Code to identify device is small(phone/handset) or large(Tablet) in Android

Here the difference between a tablet and a phone is the screen size which is why you want to use different layout files. These files are stored in the res/layout-<qualifiers> directories. You can create an XML file in the directoy res/values-<same qualifiers> for each of your layouts and put an int/bool/string resource into it to distinguish between the layouts you use.

Example:

File res/values/screen.xml (assuming res/layout/ contains your layout files for handsets)

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <string name="screen_type">phone</string>
</resources>

File res/values-sw600dp/screen.xml (assuming res/layout-sw600dp/ contains your layout files for small tablets like the Nexus 7)

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <string name="screen_type">7-inch-tablet</string>
</resources>

File res/values-sw720dp/screen.xml (assuming res/layout-sw720dp/ contains your layout files for large tablets like the Nexus 10):

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <string name="screen_type">10-inch-tablet</string>
</resources>

Now the screen type is accessible using the R.string.screen_type constant.

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Another easiest way of detecting device type is to put different values in strings.xml for a single key, let's call it "device_type". So in:

1. values -> strings.xml I will have <string name="device_type">smartphone</string>
2. values-large -> strings.xml I will have <string name="device_type">tablet</string>
3. values-small -> strings.xml I will have <string name="device_type">small</string>
4. values-xlarge -> strings.xml I will have <string name="device_type">xlarge</string>

Having a context, I will read this value and determine what type of device I have.

Please refer the folllowing URl's for more information:

http://developer.android.com/guide/practices/screens_support.html 

http://developer.android.com/training/multiscreen/screensizes.html#TaskUseSWQuali