你必须等到视图布置好

viewTreeObserver.addOnGlobalLayoutListener(object : OnGlobalLayoutListener {
            override fun onGlobalLayout() {
                val bitmap = graphicUtils.createBitmapFromView(view = view, width = width, height = height)
                onBitmapCreated(bitmap)
                viewTreeObserver.removeOnGlobalLayoutListener(this)
            }
        })

取自https://proandroiddev.com/create-bitmaps-from-jetpack-composables-bdb2c95db51

您缺少此代码：setContentView(composeView)

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val widthPx = 200
        val heightPx = 120

        val composeView = ComposeView(applicationContext)
        composeView.setContent {
            Text(
                text = "Hello",
                color = Color.Black,
                fontSize = 14.sp,
                modifier = Modifier
                    .wrapContentSize()
                    .background(Color.Green)
            )
        }
        // Without this code, you need to render to the activity to take a screenshot
        setContentView(composeView)

        val myBitmap: Bitmap = Bitmap.createBitmap(widthPx,heightPx,Bitmap.Config.ARGB_8888)

        val myCanvas = Canvas(myBitmap) 
        composeView.draw(myCanvas)
        val result = myBitmap /*<--- result is blank bitmap*/
    }
}