public class BoxScreenHandler extends ScreenHandler {
    private final Inventory inventory;

    // 服务器想要客户端开启 screenHandler 时，客户端调用这个构造器。
    // 如有空的物品栏，客户端会调用其他构造器，screenHandler 将会自动
    // 在客户端将空白物品栏同步给物品栏。
    public BoxScreenHandler(int syncId, PlayerInventory playerInventory) {
        this(syncId, playerInventory, new SimpleInventory(9));
    }

    // 这个构造器是在服务器的 BlockEntity 中被调用的，无需线调用其他构造器，服务器知道容器的物品栏
    // 并直接将其作为参数传入。然后物品栏在客户端完成同步。
    public BoxScreenHandler(int syncId, PlayerInventory playerInventory, Inventory inventory) {
        super(ExampleMod.BOX_SCREEN_HANDLER, syncId);
        checkSize(inventory, 9);
        this.inventory = inventory;
        // 玩家开启时，一些物品栏有自定义的逻辑。
        inventory.onOpen(playerInventory.player);

        // 这会将槽位放置在 3×3 网格的正确位置中。这些槽位在客户端和服务器中都存在！
        // 但是这不会渲染槽位的背景，这是 Screens 类的工作
        int m;
        int l;
        //Our inventory
        for (m = 0; m < 3; ++m) {
            for (l = 0; l < 3; ++l) {
                this.addSlot(new Slot(inventory, l + m * 3, 62 + l * 18, 17 + m * 18));
            }
        }
        // 玩家物品栏
        for (m = 0; m < 3; ++m) {
            for (l = 0; l < 9; ++l) {
                this.addSlot(new Slot(playerInventory, l + m * 9 + 9, 8 + l * 18, 84 + m * 18));
            }
        }
        // 玩家快捷栏
        for (m = 0; m < 9; ++m) {
            this.addSlot(new Slot(playerInventory, m, 8 + m * 18, 142));
        }

    }

    @Override
    public boolean canUse(PlayerEntity player) {
        return this.inventory.canPlayerUse(player);
    }

    // Shift + 玩家物品栏槽位
    @Override
    public ItemStack transferSlot(PlayerEntity player, int invSlot) {
        ItemStack newStack = ItemStack.EMPTY;
        Slot slot = this.slots.get(invSlot);
        if (slot != null && slot.hasStack()) {
            ItemStack originalStack = slot.getStack();
            newStack = originalStack.copy();
            if (invSlot < this.inventory.size()) {
                if (!this.insertItem(originalStack, this.inventory.size(), this.slots.size(), true)) {
                    return ItemStack.EMPTY;
                }
            } else if (!this.insertItem(originalStack, 0, this.inventory.size(), false)) {
                return ItemStack.EMPTY;
            }

            if (originalStack.isEmpty()) {
                slot.setStack(ItemStack.EMPTY);
            } else {
                slot.markDirty();
            }
        }

        return newStack;
    }
}