Question Detail

You can specify android:screenOrientation="portrait" for each activity in your manifest.xml file

I want to change it for the entire app in one go not activity by activity.

I don't think it can happen.
We need to change it from Manifest file

I don't think it can happen.
We need to change it from Manifest file

Check Out this https://stackoverflow.com/a/44890811/1640009

If anyone was wondering , how you could do this for your entire application without having to make all your activities extend a common base class in Kotlin , see the example below :

class InteractiveStoryApplication: Application() {
override fun onCreate() {
    super.onCreate()
    registerActivityLifecycleCallbacks(object: ActivityLifecycleCallbacks {
        override fun onActivityCreated(activity: Activity?, savedInstanceState: Bundle?) {
            activity?.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
        }

        override fun onActivityPaused(activity: Activity?) {
        }

        override fun onActivityResumed(activity: Activity?) {
        }

        override fun onActivityDestroyed(activity: Activity?) {
        }

        override fun onActivitySaveInstanceState(activity: Activity?, outState: Bundle?) {
        }

        override fun onActivityStarted(activity: Activity?) {
        }

        override fun onActivityStopped(activity: Activity?) {
        }
    })
}
}

and then you have to add your common base class in AndroidManifest like so:

<application android:allowBackup="true"
android:name=".InteractiveStoryApplication"