[android] How to Lock Android App's Orientation to Portrait in Phones and Landscape in Tablets?

You have to add the android:screenOrientation="portrait" directive in your AndroidManifest.xml. This is to be done in your <activity> tag.

In addition, the Android Developers guide states that :

[...] you should also explicitly declare that your application requires either portrait or landscape orientation with the element. For example, <uses-feature android:name="android.hardware.screen.portrait" />.