Fix onBackPressed() deprecation for CardTemplateBrowserAppearanceEditor

The previous code was showing a discard dialog if there were any
changes, meaning that the user entered something different in the
input boxed than what text was the screen initialized with.

The fix introduces two listeners for the input boxes to use them as a
dynamic listener for when there's change and implicitly could be BACK
changes as well.

The code still shows the discard changes dialog for the UP button in
the toolbar like before.

AnkiDroid/src/main/java/com/ichi2/anki/CardTemplateBrowserAppearanceEditor.kt

@@ -21,8 +21,11 @@ import android.os.Bundle
 import android.view.Menu
 import android.view.MenuItem
 import android.widget.EditText
+import androidx.activity.OnBackPressedCallback
+import androidx.activity.addCallback
 import androidx.annotation.CheckResult
 import androidx.appcompat.app.AlertDialog
+import androidx.core.widget.doAfterTextChanged
 import com.ichi2.anki.dialogs.DiscardChangesDialog
 import com.ichi2.utils.message
 import com.ichi2.utils.negativeButton
@@ -40,6 +43,14 @@ import timber.log.Timber
 class CardTemplateBrowserAppearanceEditor : AnkiActivity() {
     private lateinit var questionEditText: EditText
     private lateinit var answerEditText: EditText
+
+    // start with the callback disabled as there aren't any changes yet
+    private val discardChangesCallback = object : OnBackPressedCallback(false) {
+        override fun handleOnBackPressed() {
+            showDiscardChangesDialog()
+        }
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         if (showedActivityFailedScreen(savedInstanceState)) {
             return
@@ -52,6 +63,15 @@ class CardTemplateBrowserAppearanceEditor : AnkiActivity() {
             return
         }
         initializeUiFromBundle(bundle)
+        // default result, only changed to RESULT_OK if actually saving changes
+        setResult(RESULT_CANCELED)
+        onBackPressedDispatcher.addCallback(discardChangesCallback)
+        questionEditText.doAfterTextChanged { _ ->
+            discardChangesCallback.isEnabled = hasChanges()
+        }
+        answerEditText.doAfterTextChanged { _ ->
+            discardChangesCallback.isEnabled = hasChanges()
+        }
     }
 
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
@@ -73,34 +93,22 @@ class CardTemplateBrowserAppearanceEditor : AnkiActivity() {
             }
             android.R.id.home -> {
                 Timber.i("Back Pressed")
-                closeWithDiscardWarning()
+                if (hasChanges()) {
+                    showDiscardChangesDialog()
+                } else {
+                    finish() // the result was already set to RESULT_CANCELLED
+                }
                 return true
             }
             else -> {}
         }
         return super.onOptionsItemSelected(item)
     }
 
-    @Suppress("DEPRECATION", "Deprecated in API34+dependencies for predictive back feature")
-    @Deprecated("Deprecated in Java")
-    override fun onBackPressed() {
-        Timber.i("Back Button Pressed")
-        super.onBackPressed()
-        closeWithDiscardWarning()
-    }
-
-    private fun closeWithDiscardWarning() {
-        if (hasChanges()) {
-            Timber.i("Changes detected - displaying discard warning dialog")
-            showDiscardChangesDialog()
-        } else {
-            discardChangesAndClose()
-        }
-    }
-
     private fun showDiscardChangesDialog() {
         DiscardChangesDialog.showDialog(this) {
-            discardChangesAndClose()
+            Timber.i("Changes discarded, finishing...")
+            finish()
         }
     }
 
@@ -129,6 +137,8 @@ class CardTemplateBrowserAppearanceEditor : AnkiActivity() {
         answerEditText = findViewById(R.id.answer_format)
         answerEditText.setText(bundle.getString(INTENT_ANSWER_FORMAT))
 
+        discardChangesCallback.isEnabled = hasChanges()
+
         enableToolbar()
         setTitle(R.string.card_template_browser_appearance_title)
     }
@@ -157,12 +167,6 @@ class CardTemplateBrowserAppearanceEditor : AnkiActivity() {
         saveAndExit()
     }
 
-    private fun discardChangesAndClose() {
-        Timber.i("Closing and discarding changes")
-        setResult(RESULT_CANCELED)
-        finish()
-    }
-
     private fun saveAndExit() {
         Timber.i("Save and Exit")
         val data = Intent().apply {