setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);

<activity android:name="MyActivity"
android:screenOrientation="landscape"
android:configChanges="keyboardHidden|orientation|screenSize">
...
</activity>

<activity android:name="MyActivity" android:screenOrientation="landscape"></activity>

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

android:screenOrientation="landscape"

android:screenOrientation="portrait"