android: Prevent crash when trying to change pages in setup fragment

Sometimes when we want to change the current setup page, the current view isn't available and we try to alter the current view. This adds a guard to prevent that issue.

src/android/app/src/main/java/org/yuzu/yuzu_emu/fragments/EmulationFragment.kt

@@ -17,6 +17,7 @@ import android.os.Handler
 import android.os.Looper
 import android.view.*
 import android.widget.TextView
+import android.widget.Toast
 import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.widget.PopupMenu
 import androidx.core.content.res.ResourcesCompat
@@ -53,6 +54,7 @@ import org.yuzu.yuzu_emu.model.Game
 import org.yuzu.yuzu_emu.model.EmulationViewModel
 import org.yuzu.yuzu_emu.overlay.InputOverlay
 import org.yuzu.yuzu_emu.utils.*
+import java.lang.NullPointerException
 
 class EmulationFragment : Fragment(), SurfaceHolder.Callback {
     private lateinit var preferences: SharedPreferences
@@ -104,10 +106,21 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                 null
             }
         }
-        game = if (args.game != null) {
-            args.game!!
-        } else {
-            intentGame ?: error("[EmulationFragment] No bootable game present!")
+
+        try {
+            game = if (args.game != null) {
+                args.game!!
+            } else {
+                intentGame!!
+            }
+        } catch (e: NullPointerException) {
+            Toast.makeText(
+                requireContext(),
+                R.string.no_game_present,
+                Toast.LENGTH_SHORT
+            ).show()
+            requireActivity().finish()
+            return
         }
 
         // So this fragment doesn't restart on configuration changes; i.e. rotation.
@@ -131,6 +144,11 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
     // This is using the correct scope, lint is just acting up
     @SuppressLint("UnsafeRepeatOnLifecycleDetector")
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        if (requireActivity().isFinishing) {
+            return
+        }
+
         binding.surfaceEmulation.holder.addCallback(this)
         binding.showFpsText.setTextColor(Color.YELLOW)
         binding.doneControlConfig.setOnClickListener { stopConfiguringControls() }
@@ -286,25 +304,23 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
 
     override fun onConfigurationChanged(newConfig: Configuration) {
         super.onConfigurationChanged(newConfig)
+        if (_binding == null) {
+            return
+        }
+
         updateScreenLayout()
         if (emulationActivity?.isInPictureInPictureMode == true) {
             if (binding.drawerLayout.isOpen) {
                 binding.drawerLayout.close()
             }
             if (EmulationMenuSettings.showOverlay) {
-                binding.surfaceInputOverlay.post {
-                    binding.surfaceInputOverlay.visibility = View.INVISIBLE
-                }
+                binding.surfaceInputOverlay.visibility = View.INVISIBLE
             }
         } else {
             if (EmulationMenuSettings.showOverlay && emulationViewModel.emulationStarted.value) {
-                binding.surfaceInputOverlay.post {
-                    binding.surfaceInputOverlay.visibility = View.VISIBLE
-                }
+                binding.surfaceInputOverlay.visibility = View.VISIBLE
             } else {
-                binding.surfaceInputOverlay.post {
-                    binding.surfaceInputOverlay.visibility = View.INVISIBLE
-                }
+                binding.surfaceInputOverlay.visibility = View.INVISIBLE
             }
             if (!isInFoldableLayout) {
                 if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT) {

src/android/app/src/main/java/org/yuzu/yuzu_emu/fragments/SetupFragment.kt

@@ -295,8 +295,10 @@ class SetupFragment : Fragment() {
 
     override fun onSaveInstanceState(outState: Bundle) {
         super.onSaveInstanceState(outState)
-        outState.putBoolean(KEY_NEXT_VISIBILITY, binding.buttonNext.isVisible)
-        outState.putBoolean(KEY_BACK_VISIBILITY, binding.buttonBack.isVisible)
+        if (_binding != null) {
+            outState.putBoolean(KEY_NEXT_VISIBILITY, binding.buttonNext.isVisible)
+            outState.putBoolean(KEY_BACK_VISIBILITY, binding.buttonBack.isVisible)
+        }
         outState.putBooleanArray(KEY_HAS_BEEN_WARNED, hasBeenWarned)
     }
 
@@ -353,11 +355,15 @@ class SetupFragment : Fragment() {
     }
 
     fun pageForward() {
-        binding.viewPager2.currentItem = binding.viewPager2.currentItem + 1
+        if (_binding != null) {
+            binding.viewPager2.currentItem += 1
+        }
     }
 
     fun pageBackward() {
-        binding.viewPager2.currentItem = binding.viewPager2.currentItem - 1
+        if (_binding != null) {
+            binding.viewPager2.currentItem -= 1
+        }
     }
 
     fun setPageWarned(page: Int) {

src/android/app/src/main/res/values/strings.xml

@@ -294,6 +294,7 @@
     <string name="performance_warning">Turning off this setting will significantly reduce emulation performance! For the best experience, it is recommended that you leave this setting enabled.</string>
     <string name="device_memory_inadequate">Device RAM: %1$s\nRecommended: %2$s</string>
     <string name="memory_formatted">%1$s %2$s</string>
+    <string name="no_game_present">No bootable game present!</string>
 
     <!-- Region Names -->
     <string name="region_japan">Japan</string>