I have this code:
// allocate one mesh
pScene.mNumMeshes = 1
pScene.mMeshes = mutableListOf(AiMesh())
val pMesh = pScene.mMeshes[0]
其中mMeshes是类型为的参数
var mMeshes: MutableList<AiMesh>? = null,
Compilers complains on the last row, where I try to declare pMesh
智能转换为
MutableList<AiMesh>是不可能的，因为pScene.mMeshes是一个复杂的表达式
What's the problem?
Since mMeshes is a var property, it can change between the assignment of mutableListOf(AiMesh()) and the usage in pScene.mMeshes[0], meaning that it is not guaranteed to be not-null at the use site.
编译器强制执行null-safety，将pScene.mMeshes视为可为null的MutableList<AiMesh>?，不允许将其用作MutableList<AiMesh>(即，它不能安全地执行smart cast).
To fix that, you can simply make a non-null assertion:
val pMesh = pScene.mMeshes!![0]
或者只重用您放入列表中的值:
val pMesh = AiMesh()
pScene.mMeshes = mutableListOf(mesh)
// use `pMesh` below