如何获取Jetpack Compose中Card组件视图并实现图片分享？

一、生成Card组件的Bitmap #

Compose没有传统Android View的概念，没法直接获取View实例，得通过绘制快照生成Bitmap：

1. 先捕获CardItem的实际尺寸：

var cardSize by remember { mutableStateOf(IntSize.Zero) }

CardItem(
    modifier = Modifier.onSizeChanged { cardSize = it },
    card = card,
    onClick = {}
)

2. 根据尺寸生成Bitmap并绘制Card内容：

val bitmap = remember(cardSize) {
    if (cardSize.width > 0 && cardSize.height > 0) {
        Bitmap.createBitmap(cardSize.width, cardSize.height, Bitmap.Config.ARGB_8888).apply {
            val composeView = ComposeView(LocalContext.current).apply {
                setContent { CardItem(card = card, onClick = {}) }
            }
            // 测量布局ComposeView
            composeView.measure(
                MeasureSpec.makeMeasureSpec(cardSize.width, MeasureSpec.EXACTLY),
                MeasureSpec.makeMeasureSpec(cardSize.height, MeasureSpec.EXACTLY)
            )
            composeView.layout(0, 0, cardSize.width, cardSize.height)
            // 绘制到Bitmap画布
            composeView.draw(Canvas(BitmapCanvas(this)))
        }
    } else {
        Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888)
    }
}

二、实现图片分享 #

拿到Bitmap后，转成可分享的文件，调用系统分享：

1. 保存Bitmap到临时文件：

private fun saveBitmapToFile(context: Context, bitmap: Bitmap): File {
    val cacheFile = File(context.externalCacheDir, "card_${System.currentTimeMillis()}.png")
    FileOutputStream(cacheFile).use {
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, it)
    }
    return cacheFile
}

2. 发起系统分享：

private fun shareCard(context: Context, bitmap: Bitmap) {
    val file = saveBitmapToFile(context, bitmap)
    val uri = FileProvider.getUriForFile(
        context,
        "${context.packageName}.fileprovider",
        file
    )

    val shareIntent = Intent(Intent.ACTION_SEND).apply {
        type = "image/png"
        putExtra(Intent.EXTRA_STREAM, uri)
        addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
    }

    context.startActivity(Intent.createChooser(shareIntent, "分享卡片"))
}

3. 在Compose里添加分享触发按钮：

Button(
    onClick = {
        if (cardSize.width > 0 && cardSize.height > 0) {
            shareCard(LocalContext.current, bitmap)
        }
    },
    enabled = cardSize.width > 0 && cardSize.height > 0
) {
    Text("分享卡片")
}

必要配置 #

• 在AndroidManifest.xml中注册FileProvider：

<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.fileprovider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_paths" />
</provider>

• 在res/xml下创建file_paths.xml：

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <external-cache-path name="card_share" path="." />
</paths>

内容的提问来源于stack exchange，提问作者abbasalim