Help with PlayerInventory.setContents(ItemStack[] arg0)

Hello everybody. I have recently started to make some pretty basic plugins for my private server. I am currently working on a plugin that when you die to lava it stores the inventory of the player that died in a global variable of type ItemStack[]. However in the onPlayerRespawn() function I can not seem to get PlayerInventory.setContents() to work.

This is my onPlayerRespawn()

public void onPlayerRespawn(PlayerRespawnEvent event)
{
Player player = event.getPlayer();
//player.sendMessage("in respawn function");
//player.sendMessage(player.getName());
PlayerInventory pI = event.getPlayer().getInventory();
pI.setContents(tempStack);
tempStack = null;
}

I have a feeling it's because for some reason it will not let me register the event PLAYER_RESPAWN.
I would appreciate any help .