NullPointerException but it isn't null!

[Ablaze]

I send a message for the GUI on my screen to update (IExtendedEntityProperties), but it crashes with an NPE. But it isn't null!

 

Stacktrace:

http://pastebin.com/zsMV5K7A

 

Code:

 

Main file: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/main/LetsMod.java

Class implementing ExtendedProperties (called manaplayer):  https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/extendedproperty/ManaPlayer.java

ExtendedPropertyMessage: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/message/ExtendedPropertyMessage.java

ExtendedPropertyMessageHandler: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/message/ExtendedPropertyMessageHandler.java

 

The two places where I send a message:

FirstBlock: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/block/FirstBlock.java#L50

FirstItem: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/item/FirstItem.java#L34

 

Okay so, I want to consume mana when I place a block. (Look at consumeMana() in ManaPlayer.java). This works fine. But now I have a gui (a bar at the top) so I have to send values to the client as well. So in the onBlockPlacedBy() method of FirstBlock.java I send a message. But it gives me an NPE (NullPointerException) (see the stacktrace) on ManaPlayer.java line 28. So I go there and add a few checks - "Player is null" and "Mana is null". It outputs Player is null. But it can't be! I have proof that it isn't null!:

 

The first two lines of the stacktrace are Yay! and Mana:35/50. This shows that 15 mana has been taken out. I initialize the ManaPlayer object on this line: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/block/FirstBlock.java#L48 . Over there you see I pass it an entity? Well, how could I have initialized the object if my player was null?

 

P.S. If you want to see where the Yay! and Mana:35/50 lines are coming from, it is over here: https://github.com/greatblitz982/LetsMod_1.7/blob/master/src/main/java/com/github/greatblitz982/extendedproperty/ManaPlayer.java#L58

 

Please help me.

 

This thread was a bit hard to explain so if you don't understand, or need some code, just tell me and I'll explain that bit of code or provide you with that code.

 

All my code is available on that github.

 

Regards,

Ablaze.

[TheGreyGhost]

Hi

 

The crash is occurring on the client.

Looks to me like you have populated the player field on the server but not on the client.  When the client receives the packet it creates ExtendedPropertyMessage using the default constructor so everything in it is null.  Presumably you then use fromBytes to copy the currentMana and maxMana, but player stays null.

 

You can access the player on the client using Minecraft.getMinecraft().thePlayer.

 

-TGG

 

[Ablaze]

  On 6/15/2014 at 10:35 AM, TheGreyGhost said:

Hi

 

The crash is occurring on the client.

Looks to me like you have populated the player field on the server but not on the client.  When the client receives the packet it creates ExtendedPropertyMessage using the default constructor so everything in it is null.  Presumably you then use fromBytes to copy the currentMana and maxMana, but player stays null.

 

You can access the player on the client using Minecraft.getMinecraft().thePlayer.

 

-TGG

 

Cazzar and I came to the same exact conclusion on IRC. Sadly there is no ByteBuf.writePlayer() haha . Just one more thing - will this work on multiplayer? thePlayer sounds more 'single-player-ish' due to the usage of the word 'the'.

[TheGreyGhost]

Hi

 

Yes it will work on both single player and multiplayer.

 

client side always has only one player.

server side may have lots.

 

-TGG

[Ablaze]

  On 6/15/2014 at 12:54 PM, TheGreyGhost said:

Hi

 

Yes it will work on both single player and multiplayer.

 

client side always has only one player.

server side may have lots.

 

-TGG

 

But if it is on multiplayer how does Minecraft know which player 'thePlayer' is referring to?

[Kwibble]

Umm.. I am pretty sure that Minecraft.getMinecraft().thePlayer is the client side player. And since there is only one player per client, thePlayer is the player for that client.

[TheGreyGhost]

Hi

 

Kwibble is right.

 

some more background information

http://greyminecraftcoder.blogspot.com.au/2013/10/client-side-class-linkage-map.html

http://greyminecraftcoder.blogspot.com.au/2013/10/server-side-class-linkage-map.html

 

-TGG