fix: back press trigger the discard dialog

Author: criticalAY

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

@@ -24,6 +24,7 @@ import android.graphics.Color
 import android.net.Uri
 import android.os.Bundle
 import android.view.View
+import androidx.activity.OnBackPressedCallback
 import androidx.core.graphics.createBitmap
 import androidx.fragment.app.Fragment
 import com.ichi2.anki.common.time.TimeManager
@@ -47,17 +48,7 @@ class DrawingFragment : Fragment(R.layout.fragment_drawing) {
     ) {
         super.onViewCreated(view, savedInstanceState)
         binding.toolbar.apply {
-            setNavigationOnClickListener {
-                // avoid showing the discard changes dialog only if the user hasn't drawn anything,
-                // even if is is erased or undone, since they may want to undo/redo something.
-                if (whiteboardFragment?.isEmpty() == true) {
-                    requireActivity().onBackPressedDispatcher.onBackPressed()
-                } else {
-                    DiscardChangesDialog.showDialog(requireContext()) {
-                        requireActivity().onBackPressedDispatcher.onBackPressed()
-                    }
-                }
-            }
+            setNavigationOnClickListener { handleBackNavigation() }
             setOnMenuItemClickListener { item ->
                 when (item.itemId) {
                     R.id.action_save -> onSaveDrawing()
@@ -66,6 +57,25 @@ class DrawingFragment : Fragment(R.layout.fragment_drawing) {
                 true
             }
         }
+
+        requireActivity().onBackPressedDispatcher.addCallback(
+            viewLifecycleOwner,
+            object : OnBackPressedCallback(true) {
+                override fun handleOnBackPressed() {
+                    handleBackNavigation()
+                }
+            },
+        )
+    }
+
+    private fun handleBackNavigation() {
+        if (whiteboardFragment?.isEmpty() == true) {
+            requireActivity().finish()
+        } else {
+            DiscardChangesDialog.showDialog(requireContext()) {
+                requireActivity().finish()
+            }
+        }
     }
 
     private fun onSaveDrawing() {

AnkiDroid/src/test/java/com/ichi2/anki/DrawingFragmentTest.kt

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2026 Ashish Yadav <mailtoashish693@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.ichi2.anki
+
+import android.graphics.Path
+import androidx.appcompat.app.AlertDialog
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.ichi2.anki.ui.windows.reviewer.whiteboard.WhiteboardFragment
+import org.hamcrest.MatcherAssert.assertThat
+import org.hamcrest.Matchers.equalTo
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.shadows.ShadowDialog
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+
+/** Tests for [DrawingFragment] */
+@RunWith(AndroidJUnit4::class)
+class DrawingFragmentTest : RobolectricTest() {
+    @Test
+    fun `back press finishes the activity when the whiteboard is empty`() {
+        val (activity, _) = launchDrawingActivity()
+
+        activity.onBackPressedDispatcher.onBackPressed()
+        advanceRobolectricLooper()
+
+        assertNull(ShadowDialog.getLatestDialog(), "no discard dialog should be shown for an empty whiteboard")
+        assertThat("activity finishes immediately", activity.isFinishing, equalTo(true))
+    }
+
+    @Test
+    fun `back press shows the discard dialog when the whiteboard has content`() {
+        val (activity, whiteboard) = launchDrawingActivity()
+        whiteboard.binding.whiteboardView.onNewPath
+            ?.invoke(samplePath())
+        advanceRobolectricLooper()
+
+        activity.onBackPressedDispatcher.onBackPressed()
+        advanceRobolectricLooper()
+
+        val dialog =
+            assertNotNull(
+                ShadowDialog.getLatestDialog() as? AlertDialog,
+                "discard dialog should be shown",
+            )
+        assertThat("activity is not finishing while dialog is open", activity.isFinishing, equalTo(false))
+
+        dialog.getButton(AlertDialog.BUTTON_POSITIVE).performClick()
+        advanceRobolectricLooper()
+        assertThat("activity finishes after discard is confirmed", activity.isFinishing, equalTo(true))
+    }
+
+    private fun launchDrawingActivity(): Pair<SingleFragmentActivity, WhiteboardFragment> {
+        val activity = startRegularActivity<SingleFragmentActivity>(DrawingFragment.getIntent(targetContext))
+        val drawingFragment =
+            activity.supportFragmentManager.findFragmentByTag(SingleFragmentActivity.FRAGMENT_TAG) as DrawingFragment
+        val whiteboardFragment =
+            drawingFragment.childFragmentManager.findFragmentById(R.id.fragment_container) as WhiteboardFragment
+        return activity to whiteboardFragment
+    }
+
+    private fun samplePath(): Path =
+        Path().apply {
+            moveTo(0f, 0f)
+            lineTo(10f, 10f)
+        }
+}