NetInventory Pro

01 Overview & Features

NetInventory Pro is a fully network-authoritative inventory system built for Unity with the Mirror networking library. Every item transaction — adding, removing, swapping, splitting, merging, dropping, and picking up — runs through the server, making it safe for multiplayer games where client authority would be a cheat risk.

Feature Highlights

• 40-slot inventory (8 hotbar + 32 grid), fully synced via Mirror SyncLists
• Stackable and non-stackable items with configurable per-item stack limits
• Drag & drop slots — left-drag to swap, right-drag to distribute a stack across multiple slots
• Right-click to split one unit; double right-click to merge all stacks of the same item
• Drag outside the inventory panel to drop items into the world
• Q key to drop the selected hotbar item (hold Ctrl to drop the full stack)
• Scroll wheel and number keys 1–8 for hotbar selection
• Item tooltip with name, description, type label (colour-coded), and max stack
• Colour-coded category dots on each slot indicating item type at a glance
• Automatic proximity pickup with a configurable radius and interval
• Server-authoritative JSON save/load with per-player files
• Held item display synced across all clients
• ScriptableObject-based item definitions — no code required to add new items
• Extensible item type and tool type enums

02 Requirements

03 Installation

Step 1 — Install Mirror

Open the Unity Asset Store window and import Mirror into your project. Alternatively, install it via the Package Manager using the Mirror GitHub URL.

Step 2 — Import NetInventory Pro

In the Unity Editor, go to Assets → Import Package → Custom Package and select the NetInventoryPro.unitypackage file. Import all assets.

Step 3 — Verify TextMeshPro

If prompted, click Import TMP Essentials in the TextMeshPro setup window. The UI prefabs require TMP to display item names and stack counts.

Step 4 — Open the Demo Scene

Navigate to Assets/Scenes/ and open DEMO.unity. Press Play to verify everything is working before integrating into your own project.

04 Project Structure

After import, the following folders will be present in your project:

05 Quick Start

The fastest way to get started is to use the pre-configured Player prefab:

Step 1 — Add a Network Manager

Drag a Mirror NetworkManager into your scene if you do not already have one.

Step 2 — Register the Player prefab

Open Resources/Player.prefab and assign it as the Player Prefab in your NetworkManager's Registered Spawnable Prefabs list, and in the Player Prefab field.

Step 3 — Add the InventoryUI to your scene

Drag the Prefabs/InventoryUI prefab into your scene. Assign the references (gridParent, hotbarParent, tooltipPanel, etc.) if not already set.

Step 4 — Register the DroppedItem prefab

Add Prefabs/DroppedItem to the NetworkManager's Registered Spawnable Prefabs list.

Step 5 — Press Play

Start a host from the NetworkManager HUD. Your player will spawn with a fully functional inventory.

06 Creating Items

Items are defined as ScriptableObject assets. Each asset represents one item type (e.g. Wood, Iron Sword, Health Potion). You do not need to write any code to add new items.

Creating a New Item Asset

• In the Project window, navigate to Resources/Items/ (or a subfolder inside it).
• Right-click and choose Create → Inventory → Item.
• Name the asset exactly as you want the item id to be (e.g. IronSword). The asset filename is the item id.
• Fill in the fields in the Inspector (see table below).
• Assign a Sprite to the Icon field.

ItemData Fields

Supported Item Subfolders

The system searches the following paths inside Resources/ when loading items at runtime:

• Items/
• Items/Resource/
• Items/Food/
• Items/Consumable/
• Items/Tool/
• Items/Weapon/
• Items/Station/

07 Integrating into Your Player

If you are using your own player prefab instead of the provided one, add the following components to your player GameObject:

InventoryLinker

InventoryLinker connects the local player's Inventory component to the singleton InventoryUI when the player object starts on the client. Without this component the UI will not display the correct inventory.

Blocking Movement from External UI

If you have UI panels outside of the inventory system, you can block player movement while they are open by assigning a delegate to PlayerMovement.IsUIOpen:

// In your UI script or game manager:
PlayerMovement.IsUIOpen = () => MyCustomUI.Instance.IsOpen;

08 Inventory System Reference

The Inventory component is the central authority for all item data. It runs on the player GameObject and all public methods that modify state are server-only. Clients interact with it exclusively through Commands.

Constants

Server Methods

Commands (client → server)

Example: Adding an Item from External Code

// From a server-side script (e.g. a chest or resource node):
Inventory inv = player.GetComponent<Inventory>();
inv.AddItem("Wood", 5);

// From a client-side script:
Inventory inv = GetComponent<Inventory>();
inv.CmdAddItem("Stone", 3);

09 UI System Reference

InventoryUI

InventoryUI is a singleton MonoBehaviour that manages all UI elements. It instantiates slot prefabs, handles input for opening/closing, scroll wheel hotbar cycling, number key selection, tooltip display, and slot swapping.

SlotUI — Gesture Summary

10 Save & Load System

InventorySaveManager saves and loads each player's inventory as a JSON file on the server. Save files are stored in Application.persistentDataPath by default, with one file per player.

File Path

{saveFolderPath}/inventory_{playerId}.json

Default Behaviour

• On server start, the inventory is loaded automatically after a 0.3 s delay.
• If no save file exists, the player receives the default starter items (Wood ×10, Stone ×10).
• Call SaveInventory() manually to persist the inventory (e.g. on disconnect or at intervals).

Custom Configuration

To provide a custom save folder or player id (e.g. SteamID), call Configure() before OnStartServer runs:

InventorySaveManager saveManager = player.GetComponent<InventorySaveManager>();
saveManager.Configure("/path/to/saves", steamId.ToString());

Changing Starter Items

Edit the GiveStarterItems() method inside InventorySaveManager.cs:

void GiveStarterItems()
{
    inventory.AddItem("Wood", 10);
    inventory.AddItem("Stone", 10);
    // Add more items here
}

11 Input Reference

12 Extending the System

Adding a New Item Type

Open ItemData.cs and add a new value to the ItemType enum:

public enum ItemType
{
    Resource, Tool, Weapon, Consumable, Seed, Food,
    Quest // your new type
}

Then add a matching colour entry in InventoryUI.GetTypeColor() and SlotUI.GetCategoryColor().

Adding a New Tool Type

Add a new value to the ToolType enum in ItemData.cs:

public enum ToolType
{
    None, Axe, Pickaxe, Hoe, WateringCan, Sword,
    Shovel // your new tool
}

Changing the Inventory Size

Edit the constants at the top of Inventory.cs:

public const int TOTAL_SLOTS = 40; // hotbar + grid
public const int HOTBAR_SLOTS = 8;
public const int GRID_SLOTS = 32;

Spawning Items from External Systems

Any server-side script can drop items into the world using ItemDropper:

// e.g. a tree falls and drops logs:
ItemDropper dropper = player.GetComponent<ItemDropper>();
dropper.SpawnDroppedItem("Wood", 3, treePosition);

13 Troubleshooting

Compile errors after import

Mirror is not installed. Install Mirror first, then re-import the package.

Inventory slots are all empty after spawning

Make sure InventoryLinker is on the player prefab and that InventoryUI exists in the scene. Check that the player prefab is registered in the NetworkManager.

Item icons are not showing

Verify that each ItemData asset has a Sprite assigned to the Icon field. Also confirm the asset is inside a Resources/ subfolder.

"Item not found" warning in the console

The item id passed to AddItem or LoadItem does not match any asset filename. Item ids are case-sensitive and must match the asset filename exactly (e.g. "Wood" not "wood").

Inventory does not save between sessions

SaveInventory() must be called explicitly (e.g. on player disconnect). It is not called automatically on exit. Hook it to your disconnect event.

Dropped items are not visible to other players

Ensure the DroppedItem prefab is added to the NetworkManager's Registered Spawnable Prefabs list.

Player can still move while inventory is open

Check that InventoryUI.Instance is not null and that the IsOpen property returns true when the panel is visible.

Right-drag distribute does not work

Right-drag requires the source slot to have more than one unit. The drag threshold is 8 pixels — move the mouse further from the starting point.