NavEventSnippets as per the Doc

compose/snippets/src/main/java/com/example/compose/snippets/predictiveback/Nav3Snippets.kt

@@ -0,0 +1,133 @@
+/*
+ * Copyright 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@file:Suppress("unused", "UNUSED_VARIABLE")
+
+package com.example.compose.snippets.predictiveback
+
+import android.annotation.SuppressLint
+import android.os.Bundle
+import android.util.Log
+import android.view.MotionEvent.EDGE_LEFT
+import android.view.MotionEvent.EDGE_RIGHT
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.offset
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.scale
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.unit.dp
+import androidx.navigationevent.NavigationEventInfo
+import androidx.navigationevent.NavigationEventTransitionState
+import androidx.navigationevent.compose.NavigationEventState
+import androidx.navigationevent.compose.rememberNavigationEventState
+
+
+// [START android_compose_predictiveback_navevent_animation]
+object Routes {
+    const val SCREEN_A = "Screen A"
+    const val SCREEN_B = "Screen B"
+}
+
+class MainActivity : ComponentActivity() {
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        setContent {
+            var state by remember { mutableStateOf(Routes.SCREEN_A) }
+            val backEventState = rememberNavigationEventState<NavigationEventInfo>(currentInfo = NavigationEventInfo.None)
+
+            when (state) {
+                Routes.SCREEN_A -> {
+                    ScreenA { state = Routes.SCREEN_B }
+                }
+                else -> {
+                    if (backEventState.transitionState is NavigationEventTransitionState.InProgress) {
+                        ScreenA { }
+                    }
+                    ScreenB(
+                        backEventState = backEventState,
+                        onBackCompleted = { state = Routes.SCREEN_A }
+                    )
+                }
+            }
+        }
+    }
+}
+
+@SuppressLint("ConfigurationScreenWidthHeight")
+@Composable
+fun ScreenB(
+    backEventState: NavigationEventState<NavigationEventInfo>,
+    onBackCompleted: () -> Unit = {},
+) {
+    val transitionState = backEventState.transitionState
+    val latestEvent =
+        (transitionState as? NavigationEventTransitionState.InProgress)
+            ?.latestEvent
+    val backProgress = latestEvent?.progress ?: 0f
+    val swipeEdge = latestEvent?.swipeEdge ?: 0
+
+    if (transitionState is NavigationEventTransitionState.InProgress) {
+        Log.d("BackGesture", "Progress: ${transitionState.latestEvent.progress}")
+    } else if (transitionState is NavigationEventTransitionState.Idle) {
+        Log.d("BackGesture", "Idle")
+    }
+
+    val animatedScale by animateFloatAsState(
+        targetValue = 1f - (backProgress * 0.1f),
+        label = "ScaleAnimation"
+    )
+
+    val configuration = LocalConfiguration.current
+    val maxShift = remember(configuration) {
+        (configuration.screenWidthDp / 20f) - 8
+    }
+
+    val offsetX = when (swipeEdge) {
+        EDGE_LEFT -> (backProgress * maxShift).dp
+        EDGE_RIGHT -> (-backProgress * maxShift).dp
+        else -> 0.dp
+    }
+
+    NavigationBackHandler(
+        state = backEventState,
+        onBackCompleted = onBackCompleted,
+        isBackEnabled = true
+    )
+    Box(
+        modifier = Modifier
+            .offset(x = offsetX)
+            .scale(animatedScale)
+    ){
+        // Rest of UI
+    }
+}
+// [END android_compose_predictiveback_navevent_animation]
+
+@Composable
+fun ScreenA(onNavigate: () -> Unit) {
+    // Basic ScreenA implementation for snippet
+}
+