I use some event system, to add some functions to the player death and player spawn.

 

If the player dies, it writes something to it's nbt.

Also, after checking it with .getKey, it IS there.

 

At spawn, I check again, if it's there.

But it isn't?!

 

 

Code:

@ForgeSubscribe
public void onEntitySpawn(EntityJoinWorldEvent event)
    {
	if(event.world.isRemote)
	{
		return;
	}
        if(event.entity instanceof EntityPlayer)
        {
        	EntityPlayer thePlayer = (EntityPlayer) event.entity;
        	
        	NBTTagCompound nbtTag = new NBTTagCompound();
        	thePlayer.writeToNBT(nbtTag);

        	System.out.println("Getting entity data...");
        	System.out.println("Has Key DI? : " + nbtTag.hasKey("DeathImprover"));
        	if(nbtTag.hasKey("DeathImprover"))
        	{
        		NBTTagCompound DI = nbtTag.getCompoundTag("DeathImprover");
        		System.out.println("Has DI Compound");
        		nbtTag.removeTag("DeathImprover");
        	}
        }
    }

@ForgeSubscribe
public void onEntityDeath(LivingDeathEvent event)
{
	if(event.entity.worldObj.isRemote)
	{
		return;
	}
	if(event.entity instanceof EntityPlayer)
	{
		EntityPlayer thePlayer = (EntityPlayer) event.entity;

		System.out.println("Player Died!");

		NBTTagCompound entityTempTag = new NBTTagCompound();
		thePlayer.writeToNBT(entityTempTag);

		entityTempTag.setBoolean("DeathImprover", true);
		System.out.println("Saved the Vars!");
		System.out.println("has DI: " + entityTempTag.hasKey("DeathImprover"));

		event.setCanceled(true);
	}
}

Still telling me on spawn, that the key doesn't exist...

 

Changed code:

@ForgeSubscribe
public void onEntitySpawn(EntityJoinWorldEvent event)
    {
	if(event.world.isRemote)
	{
		return;
	}
        if(event.entity instanceof EntityPlayer)
        {
        	EntityPlayer thePlayer = (EntityPlayer) event.entity;
        	
        	NBTTagCompound wholeTag = thePlayer.getEntityData();
        	
        	NBTTagCompound nbtTag = wholeTag.getCompoundTag(thePlayer.PERSISTED_NBT_TAG);

        	System.out.println("Getting entity data...");
        	System.out.println("Has Key DI? : " + nbtTag.hasKey("DeathImprover"));
        	if(nbtTag.hasKey("DeathImprover"))
        	{
        		NBTTagCompound DI = nbtTag.getCompoundTag("DeathImprover");
        		System.out.println("Has DI Compound");
                
        		nbtTag.removeTag("DeathImprover");
        	}
        }
    }

@ForgeSubscribe
public void onEntityDeath(LivingDeathEvent event)
{
	if(event.entity.worldObj.isRemote)
	{
		return;
	}
	if(event.entity instanceof EntityPlayer)
	{
		EntityPlayer thePlayer = (EntityPlayer) event.entity;

		System.out.println("Player Died!");
		NBTTagList tempTag = new NBTTagList();
		thePlayer.inventory.writeToNBT(tempTag);

		NBTTagCompound entityTempTag = thePlayer.getEntityData();
		thePlayer.writeToNBT(entityTempTag);

		NBTTagCompound persistTag = entityTempTag.getCompoundTag(thePlayer.PERSISTED_NBT_TAG);
		persistTag.setTag("DeathImprover", tempTag);

		System.out.println("Saved the Vars!");

		event.setCanceled(true);
	}
}

As test, I want to write an boolean variable and check it later.

 

What I actually want to do is, that if my inventory contains a special item (e.g. an egg) it should save my inventory and load it again on spawn, independent of how the gamerule keepInventory is.