I added a button on the main menu. When player clicks that button, i want a certain world to be loaded.

Here is my code to load world:

    GuiButton playButton = new GuiButton(id, xPosition, yPosition, width, height, "play"){

    @Override

public void mouseReleased(int p_146118_1_, int p_146118_2_){

    String name = "My World";

    Settings.mc.launchIntegratedServer(name, name, null);    

    Settings.mc.setIngameFocus();

   

    }

    };

 

I got this error:

 

java.lang.NullPointerException: Unexpected error

at net.minecraft.client.network.NetHandlerPlayClient.handleJoinGame(NetHandlerPlayClient.java:275)

at net.minecraft.network.play.server.S01PacketJoinGame.processPacket(S01PacketJoinGame.java:84)

at net.minecraft.network.play.server.S01PacketJoinGame.processPacket(S01PacketJoinGame.java:142)

at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:241)

at net.minecraft.client.Minecraft.runTick(Minecraft.java:2152)

at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1039)

at net.minecraft.client.Minecraft.run(Minecraft.java:962)

at net.minecraft.client.main.Main.main(Main.java:164)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)

at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

at net.minecraftforge.gradle.GradleStartCommon.launch(Unknown Source)

at GradleStart.main(Unknown Source)

 

It seems i cannot simpily use launchIntegratedServer() to load a world successfully. What is the right way?

 

1.7.10 is old and not supported, update.