JetpackCompose从入门到实战学习笔记13——Compose中实现简单瀑布流

1.简介：

LazyGrid包含两种控件：LazyVerticalStaggeredGrid和LazyHorizontalStaggeredGrid。两者内部均由LazyLayout实现（包括LazyColumn和LazyRow也是由LazyLayout实现的）。今天先以LazyVerticalStaggeredGrid为例。

2.竖向的StaggeredGrid参数：

@ExperimentalFoundationApi
@Composable
fun LazyVerticalStaggeredGrid(
    columns: StaggeredGridCells,
    modifier: Modifier = Modifier,
    state: LazyStaggeredGridState = rememberLazyStaggeredGridState(),
    contentPadding: PaddingValues = PaddingValues(0.dp),
    verticalArrangement: Arrangement.Vertical = Arrangement.spacedBy(0.dp),
    horizontalArrangement: Arrangement.Horizontal = Arrangement.spacedBy(0.dp),
    flingBehavior: FlingBehavior = ScrollableDefaults.flingBehavior(),
    userScrollEnabled: Boolean = true,
    content: LazyStaggeredGridScope.() -> Unit
) {
    LazyStaggeredGrid(
        modifier = modifier,
        orientation = Orientation.Vertical,
        state = state,
        verticalArrangement = verticalArrangement,
        horizontalArrangement = horizontalArrangement,
        contentPadding = contentPadding,
        flingBehavior = flingBehavior,
        userScrollEnabled = userScrollEnabled,
        slotSizesSums = rememberColumnWidthSums(columns, horizontalArrangement, contentPadding),
        content = content
    )
}

3.简单使用如下：

    @OptIn(ExperimentalFoundationApi::class)
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent() {
            LazyStaggeredGridComposeTheme() {
                LazyVerticalStaggeredGrid(
                    columns = StaggeredGridCells.Adaptive(110.dp),
                    modifier = Modifier.fillMaxSize(),
                    state = rememberLazyStaggeredGridState(),
                    contentPadding = PaddingValues(16.dp),
                    horizontalArrangement = Arrangement.spacedBy(16.dp),
                    verticalArrangement = Arrangement.spacedBy(16.dp),
                    flingBehavior = ScrollableDefaults.flingBehavior(),
                ) {
                    items(items) { item ->
                        RandomColorBox(item = item)
                    }
                }
            }
        }
    }

4.竖向瀑布流效果如下：

竖屏下的效果：

横屏下的效果：

5.横向的StaggeredGrid参数：

@ExperimentalFoundationApi
@Composable
fun LazyHorizontalStaggeredGrid(
    rows: StaggeredGridCells,
    modifier: Modifier = Modifier,
    state: LazyStaggeredGridState = rememberLazyStaggeredGridState(),
    contentPadding: PaddingValues = PaddingValues(0.dp),
    verticalArrangement: Arrangement.Vertical = Arrangement.spacedBy(0.dp),
    horizontalArrangement: Arrangement.Horizontal = Arrangement.spacedBy(0.dp),
    flingBehavior: FlingBehavior = ScrollableDefaults.flingBehavior(),
    userScrollEnabled: Boolean = true,
    content: LazyStaggeredGridScope.() -> Unit
) {
    LazyStaggeredGrid(
        modifier = modifier,
        orientation = Orientation.Horizontal,
        state = state,
        contentPadding = contentPadding,
        verticalArrangement = verticalArrangement,
        horizontalArrangement = horizontalArrangement,
        flingBehavior = flingBehavior,
        userScrollEnabled = userScrollEnabled,
        slotSizesSums = rememberRowHeightSums(rows, verticalArrangement, contentPadding),
        content = content
    )
}

6.简单使用如下：

@Preview
@OptIn(ExperimentalFoundationApi::class)
@Composable
fun LazyHorizontalStaggeredGridDemo() {
    LazyHorizontalStaggeredGrid(
        rows = StaggeredGridCells.Adaptive(110.dp),
        modifier = Modifier.fillMaxSize(),
        state = rememberLazyStaggeredGridState(),
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        flingBehavior = ScrollableDefaults.flingBehavior(),
        userScrollEnabled = true,//瀑布流是否可滑动
    )
    {
        items(items) { item ->
            HorizontalRandomColorBox(item = item)
        }
    }
}

7.横向瀑布流效果如下：

横屏效果：

竖向效果：

8.完整代码如下：

package com.example.lazystaggedgrildcompose

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.background
import androidx.compose.foundation.gestures.ScrollableDefaults
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.lazy.staggeredgrid.*
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
import com.example.lazystaggedgrildcompose.ui.theme.LazyStaggeredGridComposeTheme
import kotlin.random.Random

class MainActivity : ComponentActivity() {


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent() {
            LazyStaggeredGridComposeTheme {
                //竖向瀑布流
               // LazyVerticalStaggeredGridDemo()
                //横向瀑布流
                LazyHorizontalStaggeredGridDemo()
            }
        }
    }
}

@Preview
@OptIn(ExperimentalFoundationApi::class)
@Composable
fun LazyVerticalStaggeredGridDemo() {
    LazyVerticalStaggeredGrid(
        columns = StaggeredGridCells.Adaptive(110.dp),
        modifier = Modifier.fillMaxSize(),
        state = rememberLazyStaggeredGridState(),
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        flingBehavior = ScrollableDefaults.flingBehavior(),
        userScrollEnabled = true,//瀑布流是否可滑动
    ) {
        items(items) { item ->
            VerticalRandomColorBox(item = item)
        }
    }
}

@Preview
@OptIn(ExperimentalFoundationApi::class)
@Composable
fun LazyHorizontalStaggeredGridDemo() {
    LazyHorizontalStaggeredGrid(
        rows = StaggeredGridCells.Adaptive(110.dp),
        modifier = Modifier.fillMaxSize(),
        state = rememberLazyStaggeredGridState(),
        contentPadding = PaddingValues(16.dp),
        horizontalArrangement = Arrangement.spacedBy(16.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp),
        flingBehavior = ScrollableDefaults.flingBehavior(),
        userScrollEnabled = true,//瀑布流是否可滑动
    )
    {
        items(items) { item ->
            HorizontalRandomColorBox(item = item)
        }
    }
}

data class ListItem(
    val height: Dp,
    val color: Color
)

var items = (1..100).map {
    ListItem(
        height = Random.nextInt(100, 300).dp,
        color = Color(Random.nextLong(0XFFFFFF))
            .copy(alpha = 1f)
    )
}

@Composable
fun VerticalRandomColorBox(item: ListItem) {
    Box(
        modifier = Modifier
            .fillMaxWidth()
            .height(item.height)
            .clip(RoundedCornerShape(10.dp))
            .background(item.color)
    )
}

@Composable
fun HorizontalRandomColorBox(item: ListItem) {
    Box(
        modifier = Modifier
            .width(200.dp)//宽度可以随意调整
            .fillMaxHeight()
            .clip(RoundedCornerShape(10.dp))
            .background(item.color)
    )
}

9.项目demo的源码地址如下：

https://gitee.com/jackning_admin/lazy-stagged-grid-compose-demo

10.总结：

从上面的例子中可以看出:compose实现一个瀑布流demo非常简单方便，横向和竖向代码都是20行左右，道险且长，仍需奋勇前行！！！休息了，各位大侠！！