ui: address new databinding requirements

Layouts in differing configurations must agree on their root tags, so we give
both copies of main_activity the same root ID, and adjust the check for
two-pane layout to simply test for nullability. This also changes the inset
dispatch code to use ViewCompat and WindowInsetsCompat since they will adjust
insets based on the SDK level allowing us to abstract away that concern.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/src/main/java/com/wireguard/android/activity/MainActivity.kt

@@ -9,8 +9,9 @@ import android.os.Bundle
 import android.view.Menu
 import android.view.MenuItem
 import android.view.View
-import android.widget.LinearLayout
 import androidx.appcompat.app.ActionBar
+import androidx.core.view.ViewCompat
+import androidx.core.view.WindowInsetsCompat
 import androidx.fragment.app.FragmentManager
 import androidx.fragment.app.FragmentTransaction
 import com.wireguard.android.R
@@ -55,16 +56,15 @@ class MainActivity : BaseActivity(), FragmentManager.OnBackStackChangedListener
         super.onCreate(savedInstanceState)
         setContentView(R.layout.main_activity)
         actionBar = supportActionBar
-        isTwoPaneLayout = findViewById<View>(R.id.master_detail_wrapper) is LinearLayout
+        isTwoPaneLayout = findViewById<View?>(R.id.master_detail_wrapper) != null
         supportFragmentManager.addOnBackStackChangedListener(this)
         onBackStackChanged()
         // Dispatch insets on back stack change
         // This is required to ensure replaced fragments are also able to consume insets
-        findViewById<View>(R.id.master_detail_wrapper).setOnApplyWindowInsetsListener { _, insets ->
-            val fragmentManager = supportFragmentManager
-            fragmentManager.addOnBackStackChangedListener {
-                fragmentManager.fragments.forEach {
-                    it.requireView().dispatchApplyWindowInsets(insets)
+        findViewById<View>(R.id.main_activity_container).setOnApplyWindowInsetsListener { _, insets ->
+            supportFragmentManager.addOnBackStackChangedListener {
+                supportFragmentManager.fragments.forEach {
+                    ViewCompat.dispatchApplyWindowInsets(it.requireView(), WindowInsetsCompat.toWindowInsetsCompat(insets))
                 }
             }
             insets