Animate image size on scroll

compose/snippets/src/main/java/com/example/compose/snippets/images/AnimateImageSnippets.kt

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+/*
+ * Copyright 2024 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.
+ */
+
+package com.example.compose.snippets.images
+
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.offset
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.graphics.painter.ColorPainter
+import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
+import androidx.compose.ui.input.nestedscroll.NestedScrollSource
+import androidx.compose.ui.input.nestedscroll.nestedScroll
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.IntOffset
+import androidx.compose.ui.unit.dp
+
+// [START android_compose_images_imageresizeonscrollexample]
+@Composable
+fun ImageResizeOnScrollExample(
+    modifier: Modifier = Modifier,
+    maxImageSize: Dp = 300.dp,
+    minImageSize: Dp = 100.dp
+) {
+    var currentImageSize by remember { mutableStateOf(maxImageSize) }
+    var imageScale by remember { mutableFloatStateOf(1f) }
+
+    val nestedScrollConnection = remember {
+        object : NestedScrollConnection {
+            override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
+                // Calculate the change in image size based on scroll delta
+                val delta = available.y
+                val newImageSize = currentImageSize + delta.dp
+                val previousImageSize = currentImageSize
+
+                // Constrain the image size within the allowed bounds
+                currentImageSize = newImageSize.coerceIn(minImageSize, maxImageSize)
+                val consumed = currentImageSize - previousImageSize
+
+                // Calculate the scale for the image
+                imageScale = currentImageSize / maxImageSize
+
+                // Return the consumed scroll amount
+                return Offset(0f, consumed.value)
+            }
+        }
+    }
+
+    Box(Modifier.nestedScroll(nestedScrollConnection)) {
+        LazyColumn(
+            Modifier
+                .fillMaxWidth()
+                .padding(15.dp)
+                .offset {
+                    IntOffset(0, currentImageSize.roundToPx())
+                }
+        ) {
+            // Placeholder list items
+            items(100, key = { it }) {
+                Text(
+                    text = "Item: $it",
+                    style = MaterialTheme.typography.bodyLarge
+                )
+            }
+        }
+
+        Image(
+            painter = ColorPainter(Color.Red),
+            contentDescription = "Red color image",
+            Modifier
+                .size(maxImageSize)
+                .align(Alignment.TopCenter)
+                .graphicsLayer {
+                    scaleX = imageScale
+                    scaleY = imageScale
+                    // Center the image vertically as it scales
+                    translationY = -(maxImageSize.toPx() - currentImageSize.toPx()) / 2f
+                }
+        )
+    }
+}
+// [END android_compose_images_imageresizeonscrollexample]
+
+@Preview(showBackground = true)
+@Composable
+private fun ImageSizeOnScrollScreenPreview() {
+    ImageResizeOnScrollExample()
+}