Compose开发桌面软件（二：图片与应用内图标）

前言

本文更多的是翻译官方的教程，并且代码自己也进行了编写运行，图标部分mac和win有部分差异，我这里是用的mac的例子。

官方地址：github.com/JetBrains/c…

本文中将展示如何使用Compose for Desktop处理图片

从资源文件加载图像

假设我们有一个 PNG 图片放在resources我们项目的目录中。图片示例：

代码：

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.singleWindowApplication

fun main() = singleWindowApplication {
    Image(
        painter = painterResource("sample.png"),
        contentDescription = "Sample",
        modifier = Modifier.fillMaxSize()
    )
}

painterResource支持（BMP、GIF、HEIF、ICO、JPEG、PNG、WBMP、WebP）和矢量格式（SVG、XML 矢量可绘制）

点击运行，结果如下：

从本地存储或网络异步加载图片

要加载存储在设备内存中（或来自网络）的图像，您可以使用loadImageBitmap,loadSvgPainter或loadXmlImageVector。如何使用它们异步加载图片代码如下：

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.width
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.produceState
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.painter.BitmapPainter
import androidx.compose.ui.graphics.painter.Painter
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.graphics.vector.rememberVectorPainter
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.res.loadImageBitmap
import androidx.compose.ui.res.loadSvgPainter
import androidx.compose.ui.res.loadXmlImageVector
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import org.xml.sax.InputSource
import java.io.File
import java.io.IOException
import java.net.URL

fun main() = singleWindowApplication {
    val density = LocalDensity.current
    Column {
        AsyncImage(
            load = { loadImageBitmap(File("sample.png")) },
            painterFor = { remember { BitmapPainter(it) } },
            contentDescription = "Sample",
            modifier = Modifier.width(200.dp)
        )
        AsyncImage(
            load = { loadSvgPainter("https://github.com/JetBrains/compose-multiplatform/raw/master/artwork/idea-logo.svg", density) },
            painterFor = { it },
            contentDescription = "Idea logo",
            contentScale = ContentScale.FillWidth,
            modifier = Modifier.width(200.dp)
        )
        AsyncImage(
            load = { loadXmlImageVector(File("compose-logo.xml"), density) },
            painterFor = { rememberVectorPainter(it) },
            contentDescription = "Compose logo",
            contentScale = ContentScale.FillWidth,
            modifier = Modifier.width(200.dp)
        )
    }
}

@Composable
fun <T> AsyncImage(
    load: suspend () -> T,
    painterFor: @Composable (T) -> Painter,
    contentDescription: String,
    modifier: Modifier = Modifier,
    contentScale: ContentScale = ContentScale.Fit,
) {
    val image: T? by produceState<T?>(null) {
        value = withContext(Dispatchers.IO) {
            try {
                load()
            } catch (e: IOException) {
                // instead of printing to console, you can also write this to log,
                // or show some error placeholder
                e.printStackTrace()
                null
            }
        }
    }

    if (image != null) {
        Image(
            painter = painterFor(image!!),
            contentDescription = contentDescription,
            contentScale = contentScale,
            modifier = modifier
        )
    }
}

/* Loading from file with java.io API */

fun loadImageBitmap(file: File): ImageBitmap =
    file.inputStream().buffered().use(::loadImageBitmap)

fun loadSvgPainter(file: File, density: Density): Painter =
    file.inputStream().buffered().use { loadSvgPainter(it, density) }

fun loadXmlImageVector(file: File, density: Density): ImageVector =
    file.inputStream().buffered().use { loadXmlImageVector(InputSource(it), density) }

/* Loading from network with java.net API */

fun loadImageBitmap(url: String): ImageBitmap =
    URL(url).openStream().buffered().use(::loadImageBitmap)

fun loadSvgPainter(url: String, density: Density): Painter =
    URL(url).openStream().buffered().use { loadSvgPainter(it, density) }

fun loadXmlImageVector(url: String, density: Density): ImageVector =
    URL(url).openStream().buffered().use { loadXmlImageVector(InputSource(it), density) }

/* Loading from network with Ktor client API (https://ktor.io/docs/client.html). */

/*

suspend fun loadImageBitmap(url: String): ImageBitmap =
    urlStream(url).use(::loadImageBitmap)

suspend fun loadSvgPainter(url: String, density: Density): Painter =
    urlStream(url).use { loadSvgPainter(it, density) }

suspend fun loadXmlImageVector(url: String, density: Density): ImageVector =
    urlStream(url).use { loadXmlImageVector(InputSource(it), density) }

@OptIn(KtorExperimentalAPI::class)
private suspend fun urlStream(url: String) = HttpClient(CIO).use {
    ByteArrayInputStream(it.get(url))
}

 */

运行结果如下：

图片资源如下：PNG 、 SVG 、 XML vector drawable

使用Canvas绘制图片

import androidx.compose.foundation.Canvas
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Paint
import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
import androidx.compose.ui.graphics.vector.rememberVectorPainter
import androidx.compose.ui.graphics.withSave
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.res.loadImageBitmap
import androidx.compose.ui.res.loadSvgPainter
import androidx.compose.ui.res.loadXmlImageVector
import androidx.compose.ui.res.useResource
import androidx.compose.ui.window.singleWindowApplication
import org.xml.sax.InputSource

fun main() = singleWindowApplication {
    val density = LocalDensity.current // to calculate the intrinsic size of vector images (SVG, XML)

    val sample = remember {
        useResource("sample.png", ::loadImageBitmap)
    }
    val ideaLogo = remember {
        useResource("idea-logo.svg") { loadSvgPainter(it, density) }
    }
    val composeLogo = rememberVectorPainter(
        remember {
            useResource("compose-logo.xml") { loadXmlImageVector(InputSource(it), density) }
        }
    )

    Canvas(
        modifier = Modifier.fillMaxSize()
    ) {
        drawIntoCanvas { canvas ->
            canvas.withSave {
                canvas.drawImage(sample, Offset.Zero, Paint())
                canvas.translate(sample.width.toFloat(), 0f)
                with(ideaLogo) {
                    draw(ideaLogo.intrinsicSize)
                }
                canvas.translate(ideaLogo.intrinsicSize.width, 0f)
                with(composeLogo) {
                    draw(Size(100f, 100f))
                }
            }
        }
    }
}

设置应用程序窗口图标

你可以通过函数中的参数设置窗口的图标Window。

注意：要在某些操作系统（macOs）上更改任务栏上的图标，应该在build.gradle中更改图标

import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.paint
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.Window
import androidx.compose.ui.window.application

fun main() = application {
    val icon = painterResource("sample.png")
    Window(
        onCloseRequest = ::exitApplication,
        icon = icon
    ) {
        Box(Modifier.paint(icon).fillMaxSize())
    }
}

在使用 singleWindowApplication 的情况下，可以使用以下方法：

import androidx.compose.material.Text
import androidx.compose.ui.graphics.painter.BitmapPainter
import androidx.compose.ui.res.loadImageBitmap
import androidx.compose.ui.res.useResource
import androidx.compose.ui.window.singleWindowApplication

fun main() {
    val icon = BitmapPainter(useResource("sample.png", ::loadImageBitmap))
    singleWindowApplication(icon = icon) {
        Text("Hello World!")
    }
}

设置应用程序托盘图标

可以为你的应用程序创建托盘图标：

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.Tray
import androidx.compose.ui.window.Window
import androidx.compose.ui.window.application

fun main() = application {
    val icon = painterResource("sample.png")

    Tray(
        icon = icon,
        menu = {
            Item("Quit App", onClick = ::exitApplication)
        }
    )

    Window(onCloseRequest = ::exitApplication, icon = icon) {
        Image(
            painter = icon,
            contentDescription = "Icon",
            modifier = Modifier.fillMaxSize()
        )
    }
}

以上就是用compose来编写准面项目时图片以及图标部分的内容。

感谢大家，如果有错误之处欢迎指出，共同进步！