Jetpack Compose 中的图像渐变 [英] Gradient over image in Jetpack Compose

问题描述

这是我的组件:

@Composable有趣的封面(名称:字符串，imageRes: Int,修饰符:修饰符 = Modifier.padding(16.dp, 8.dp)){框(修饰符){卡片(形状 = RoundedCornerShape(4.dp),backgroundColor = MaterialTheme.colors.secondary，海拔 = 4.dp){堆 {图片(图像资源(图像资源)，修饰符 = 修饰符.gravity(Alignment.Center).纵横比(2f)，contentScale = ContentScale.Crop，)文本(文字 = 姓名，修饰符 = 修饰符.gravity(Alignment.BottomStart).填充(8.dp)，样式 = MaterialTheme.typography.h6)}}}}

这是它的样子:

我想在 Image 上方和 Text 后面显示深色渐变，以便文本易于阅读.我想我将不得不使用 LinearGradient 或 RadialGradient 但由于缺乏文档，我无法做到.

Here is my component:

@Composable
fun Cover(
    name: String,
    imageRes: Int,
    modifier: Modifier = Modifier.padding(16.dp, 8.dp)
) {
    Box(modifier) {
        Card(
            shape = RoundedCornerShape(4.dp),
            backgroundColor = MaterialTheme.colors.secondary,
            elevation = 4.dp
        ) {
            Stack {
                Image(
                    imageResource(imageRes),
                    modifier = Modifier
                        .gravity(Alignment.Center)
                        .aspectRatio(2f),
                    contentScale = ContentScale.Crop,
                )

                Text(
                    text = name,
                    modifier = Modifier
                        .gravity(Alignment.BottomStart)
                        .padding(8.dp),
                    style = MaterialTheme.typography.h6
                )
            }
        }
    }
}

This is how it looks:

I want to display a dark gradient over the Image and behind the Text so that the text is easy to read. I guess I'll have to use LinearGradient or RadialGradient but due to the lack of documentation I'm not able to do it.

Edit: This is what I'm trying to do but with Jetpack Compose.

解决方案

The updated answer of @vitor-ramos

1.0.0-alpha09

import androidx.annotation.DrawableRes
import androidx.compose.foundation.Image
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.material.Card
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Brush
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.layout.onGloballyPositioned
import androidx.compose.ui.platform.AmbientDensity
import androidx.compose.ui.res.imageResource
import androidx.compose.ui.unit.dp
import tech.abd3lraouf.learn.compose.kombose.ui.theme.typography

@Composable
fun Cover(
    name: String,
    @DrawableRes imageRes: Int,
    modifier: Modifier = Modifier
) {
    val image = imageResource(imageRes)
    val density = AmbientDensity.current.density
    val width = remember { mutableStateOf(0f) }
    val height = remember { mutableStateOf(0f) }
    Box(
        modifier
            .padding(16.dp, 8.dp)
    ) {
        Card(
            shape = RoundedCornerShape(4.dp),
            backgroundColor = MaterialTheme.colors.secondary,
            elevation = 4.dp
        ) {
            Box {
                Image(
                    image,
                    modifier = Modifier
                        .align(Alignment.Center)
                        .aspectRatio(2f)
                        .onGloballyPositioned {
                            width.value = it.size.width / density
                            height.value = it.size.height / density
                        },
                    contentScale = ContentScale.Crop,
                )
                Column(
                    Modifier
                        .size(width.value.dp, height.value.dp)
                        .background(
                            Brush.verticalGradient(
                                listOf(Color.Transparent, Color.Black),
                                image.height * 0.6F,
                                image.height * 1F
                            )
                        )
                ) {}
                Text(
                    text = name,
                    modifier = Modifier
                        .align(Alignment.BottomStart)
                        .padding(8.dp),
                    style = typography.body2,
                    color = Color.White
                )
            }
        }
    }
}

Also, notice the control of how the gradient draws its height.

The output

这篇关于Jetpack Compose 中的图像渐变的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！