软件主页背景动画，存在两个问题：1.只有位置改变，没有图片索引改变；2.布局上下比例还要调整

app/src/main/java/com/aiosman/riderpro/ui/login/login.kt

@@ -3,11 +3,16 @@ package com.aiosman.riderpro.ui.login
 import android.content.ContentValues.TAG
 import android.util.Log
 import android.widget.Toast
+import androidx.compose.animation.core.LinearEasing
+import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.animation.core.infiniteRepeatable
+import androidx.compose.animation.core.tween
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
@@ -16,20 +21,39 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.layout.widthIn
+import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.mutableStateListOf
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.draw.scale
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleEventObserver
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.compose.LocalLifecycleOwner
 import com.aiosman.riderpro.AppState
 import com.aiosman.riderpro.AppStore
 import com.aiosman.riderpro.LocalNavController
@@ -42,6 +66,8 @@ import com.aiosman.riderpro.ui.modifiers.noRippleClickable
 import com.aiosman.riderpro.utils.GoogleLogin
 import com.google.accompanist.systemuicontroller.rememberSystemUiController
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 
 @Composable
@@ -112,46 +138,19 @@ fun LoginPage() {
         }
     }
     Box(
-        modifier = Modifier.fillMaxSize().background(Color.White)
+        modifier = Modifier
+            .fillMaxSize()
+            .background(Color.White)
     ) {
-        // bg image
         Box(
-            modifier = Modifier.fillMaxWidth().height(900.dp).offset(
+            modifier = Modifier
+                .fillMaxSize()
+                .offset(
                     y = (-72).dp
                 ),
         ) {
-            Image(
-                painter = painterResource(id = R.mipmap.rider_pro_login_bg),
-                contentDescription = "Login Background",
-                modifier = Modifier.fillMaxWidth().fillMaxHeight(),
-                contentScale = androidx.compose.ui.layout.ContentScale.Crop,
-            )
-            Box(
-                modifier = Modifier
-                    .fillMaxWidth()
-                    .fillMaxHeight()
-                    .background(Color.White.copy(alpha = 0.8f)),
-                contentAlignment = Alignment.BottomCenter
-            ) {
-                Box(
-                    modifier = Modifier
-                        .fillMaxWidth()
-                        .height(300.dp)
-                        .background(
-                            Brush.verticalGradient(
-                                colors = listOf(
-                                    Color.Transparent,
-                                    Color.White
-                                ),
-                                startY = 0f,
-                                endY = 300f
-                            )
-                        )
-                )
+            MovingImageWall()
         }
-        }
-
-
         Column(
             modifier = Modifier
                 .fillMaxSize()
@@ -230,7 +229,209 @@ fun LoginPage() {
             Spacer(modifier = Modifier.height(120.dp))
         }
     }
-
-
 }
 
+
+@Composable
+fun MovingImageWall() {
+    val imageList1 = remember { mutableStateListOf(R.drawable.wall_1_1, R.drawable.wall_1_2, R.drawable.wall_1_3) }
+    val imageList2 = remember { mutableStateListOf(R.drawable.wall_2_1, R.drawable.wall_2_2, R.drawable.wall_2_3) }
+    val imageList3 = remember { mutableStateListOf(R.drawable.wall_3_1, R.drawable.wall_3_2, R.drawable.wall_3_3) }
+
+    var offset1 by remember { mutableFloatStateOf(0f) }
+    var offset2 by remember { mutableFloatStateOf(0f) }
+    var offset3 by remember { mutableFloatStateOf(0f) }
+
+    val lifecycleOwner = LocalLifecycleOwner.current
+    val coroutineScope = rememberCoroutineScope() // 使用 rememberCoroutineScope
+    LaunchedEffect(key1 = lifecycleOwner) {
+        lifecycleOwner.lifecycle.addObserver(object : LifecycleEventObserver {
+            override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
+                when (event) {
+                    Lifecycle.Event.ON_RESUME -> {
+                    coroutineScope.launch { // 在 coroutineScope 中启动协程
+                        animateImageWall(imageList1, offset1, speed = 1f) { offset1 = it }
+                    }
+                    coroutineScope.launch {
+                        animateImageWall(imageList2, offset2, speed = 1.5f, reverse = true) { offset2 = it }
+                    }
+                    coroutineScope.launch {
+                        animateImageWall(imageList3, offset3, speed = 2f) { offset3 = it }
+                    }
+                }
+                    Lifecycle.Event.ON_PAUSE -> {
+                        // 可选： 在Composable暂停时取消协程
+                        coroutineScope.cancel()
+                    }
+                    else -> {}
+                }
+            }
+        })
+    }
+
+    Box(
+        modifier = Modifier
+            .fillMaxSize()
+            .offset(y = (-72).dp)
+    ) {
+
+        Row (modifier = Modifier
+            .fillMaxWidth()
+            .height(700.dp)){
+            // 第1列
+            ImageColumn(imageList1, offset1,
+                Modifier
+                    .fillMaxHeight()
+                    .weight(1f))
+            // 第2列
+            ImageColumn(imageList2, offset2,
+                Modifier
+                    .fillMaxHeight()
+                    .weight(1f), reverse = true)
+            // 第3列
+            ImageColumn(imageList3, offset3,
+                Modifier
+                    .fillMaxHeight()
+                    .weight(1f))
+        }
+
+        // 白色叠加层
+        Box(
+            modifier = Modifier
+                .fillMaxWidth()
+                .fillMaxHeight()
+                .background(Color.White.copy(alpha = 0.5f)),
+            contentAlignment = Alignment.BottomCenter
+        ) {
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(650.dp)
+                    .background(
+                        Brush.verticalGradient(
+                            colors = listOf(
+                                Color.Transparent,
+                                Color.White
+                            ),
+                            startY = 0f,
+                            endY = 650f
+                        )
+                    )
+            )
+        }
+    }
+}
+
+@Composable
+fun ImageColumn(
+    imageList: List<Int>,
+    offset: Float,
+    modifier: Modifier,
+    reverse: Boolean = false
+) {
+    val imageCount = imageList.size
+    val imageHeight = 208.dp
+    var currentImage by remember { mutableStateOf(0) }
+    val totalHeight = imageHeight.value * imageCount // 计算总高度
+    Column(modifier = modifier) {
+        for (i in 0 until imageCount) {
+            Box(modifier = Modifier
+                .width(156.dp)
+                .height(208.dp)
+                .scale(1f)
+                .graphicsLayer {
+                    var translation = if (reverse) {
+                        offset
+                    } else {
+                        offset
+                    }
+                    // 检查是否超出屏幕范围
+                    if (translation < -imageHeight.value) { // 移出屏幕底部
+                        translation += totalHeight
+                    } else if (translation > totalHeight) { // 移出屏幕顶部
+                        translation -= totalHeight
+                    }
+                    translationY = translation
+                }
+                .clip(RoundedCornerShape(16.dp)),
+                contentAlignment = Alignment.Center){
+                Image(
+                    painter = painterResource(id = imageList[(currentImage + i) % imageCount]),
+                    contentDescription = "背景图片",
+                    modifier = Modifier
+                        .width(156.dp)
+                        .height(208.dp)
+                        .scale(0.9f)
+                        .clip(RoundedCornerShape(16.dp)),
+                    contentScale = ContentScale.Crop
+                )
+            }
+
+        }
+    }
+}
+
+suspend fun animateImageWall(
+    imageList: MutableList<Int>,
+    initialOffset: Float,
+    speed: Float,
+    reverse: Boolean = false,
+    onUpdate: (Float) -> Unit,
+) {
+    var currentOffset = initialOffset
+    val imageCount = imageList.size
+    val imageHeight = 208.dp
+    var currentIndex = 0 // 添加一个变量来跟踪当前显示的图片索引
+    while (true) {
+        onUpdate(currentOffset)
+        if (reverse) {
+            currentOffset -= speed
+            if (currentOffset < -imageHeight.value * (imageCount - 1)) {
+//                val firstImage = imageList.first() // 将第一个元素移除
+//                imageList.add(firstImage) // 将第一个元素添加到末尾
+                currentOffset += imageHeight.value * imageCount // 将图片移动到末尾
+//                currentIndex = (currentIndex - 1 + imageCount) % imageCount // 反向旋转
+            }
+        } else {
+            currentOffset += speed
+            if (currentOffset > imageHeight.value * (imageCount - 1)) {
+//                val lastImage = imageList.last() // 将最后一个元素移除
+//                imageList.add(0, lastImage) // 将最后一个元素添加到开头
+                currentOffset -= imageHeight.value * imageCount // 将图片移动到开头
+//                currentIndex = (currentIndex + 1) % imageCount // 正向旋转
+            }
+        }
+        // 更新 ImageColumn 中的 currentImage
+//        onUpdate(currentIndex.toFloat()) // 将当前索引传递给 onUpdate
+        delay(16)
+    }
+}
+
+// 计算图片的透明度
+private fun calculateAlpha(
+    offset: Float,
+    index: Int,
+    imageHeight: Float,
+    totalHeight: Float,
+    reverse: Boolean
+): Float {
+    val offsetDp = if (reverse) {
+        -offset
+    } else {
+        offset
+    }
+    val imageTop = index * imageHeight
+    val imageBottom = imageTop + imageHeight
+    return when {
+        offsetDp in imageTop..imageBottom -> {
+            (offsetDp - imageTop) / imageHeight
+        }
+        (offsetDp + totalHeight) in imageTop..imageBottom -> { // 考虑循环滚动的情况
+            (offsetDp + totalHeight - imageTop) / imageHeight
+        }
+        (offsetDp - totalHeight) in imageTop..imageBottom -> { // 考虑循环滚动的情况
+            (offsetDp - totalHeight - imageTop) / imageHeight
+        }
+        else -> 0f
+    }
+}