android - 为什么我的可组合不会在更改 HashMap 的 MutableState 值时重新组合？

Question

为什么我的可组合不会在更改 HashMap 的 MutableState 的值时重新组合。
View 模型

 val imageList: MutableState<HashMap<Int, Uri>> = mutableStateOf(HashMap())
    fun setImage(imageUri: Uri) {
        imageList.value[imagePosition] = imageUri
    }

分段

if (viewModel.imageList.value[stepNo] != null && !TextUtils.isEmpty(
                                            viewModel.imageList.value[stepNo].toString()
                                        )
                                    ) {
                                        Image(
                                            contentDescription = "Recipe",
                                            painter = painterResource(R.drawable.ic_baseline_fastfood_24),
                                            modifier = Modifier
                                                .padding(8.dp)
                                        )
                                    }

fun permissionCallbacks() {
        imagePickerListener =
            registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
                if (result.resultCode == Activity.RESULT_OK) {
                    // There are no request codes
                    val data: Intent? = result.data
                    val selectedImageUri = data?.data
                    selectedImageUri?.let { viewModel.setImage(it) }
                }
            }
        requestPermissionLauncher =
            registerForActivityResult(
                ActivityResultContracts.RequestPermission()
            ) { isGranted: Boolean ->
                if (isGranted) {
                    val galleryIntent = Intent(
                        Intent.ACTION_PICK,
                        MediaStore.Images.Media.EXTERNAL_CONTENT_URI
                    )
                    galleryIntent.type = "image/*"
                    imagePickerListener?.launch(galleryIntent)
                } else {
                   
                }
            }
    }

我通过调试在 setImage() 中正确设置的值看到了方法但 if 条件为 viewModel.imageList.value[stepNo]当 hashmap 的值改变时不会再次调用。

Answer 1

mutableStateOf只能在您将一个值替换为另一个值时进行跟踪。如果您更改当前值的状态，它无法处理它
您可以使用 mutableStateMapOf而不是 mutableStateOf(HashMap()) :

val imageList = mutableStateMapOf<Int, Uri>()
---
fun setImage(imageUri: Uri) {
    imageList[imagePosition] = imageUri
}