【Unity】问题记录"SetDestination" can only be called on an active agent that has been placed on a NavMesh

问题："SetDestination" can only be called on an active agent that has been placed on a NavMesh.

原因：导航NavMeshAgent组件所在物体距离Navmesh导航网格太远，'NavMeshAgent.SetDestination'设置导航目标点失败

解决：在设置导航目标点之前，可以用‘ NavMeshAgent.isOnNavMesh’判断，在返回值为Ture后再'NavMeshAgent.SetDestination'，如果返回值为False，说明当前NavMeshAgent不在导航网格上，可用‘NavMeshAgent.Warp’纠正位置。

此外，还可以用‘NavMesh.SamplePosition’检测地图内某点是否在导航网格NavMesh内

    public bool TestNavigation()
    {
        if (navMeshAgent.isOnNavMesh)
        {
            NavMeshHit navigationHit;
            if (NavMesh.SamplePosition(targetPosition, out navigationHit, 15, navMeshAgent.areaMask))
                return navMeshAgent.SetDestination(navigationHit.position);
            return false;
        }
        else
        {
            return navMeshAgent.Warp(warpPosition);
        }
    }