Exception when calling a Thread from another class

You must keep your Time_Stop class in your Menu_activity class example:

static Time_stop tim= new Time_Stop()

and have it called in your Cls_logeo class this way:

Menu_Main.tim.conectar()

Or instantiate your Time_Stop class in the Csl_Login activity: in this way you can have the methods of that class called. since the exception is telling you that the object tim is null.

My code is as follows in the Main Activity (Menu_Main): its thread structure:

1.- Variables:

// <editor-fold defaultstate="collapsed" desc="Variables">
        int Nro=-1,Puerto=0,NumSer=0;
        Socket Client;
        ObjectOutputStream Enviar;
        ObjectInputStream Recibir;
        Clas_ArrayList Cls_Get_Obj;
        Clas_ArrayList Cls_Ret_Tip;
        boolean Ini_Hilo=true,Corriendo=false,DatEnv=false;
        String Server="";
        int Num_Conect=0;//num con quien se conecta
        int Num_Env=-1; //num proceso pedido
        // </editor-fold>

2.-Connect

// <editor-fold defaultstate="collapsed" desc="Conectar">
        public void Conectar(String Serv,int Puert){
            Server=Serv;
            Puerto=Puert;
        }
        // </editor-fold>

3.- Time_Stop_Ini (initialize the socket):

// <editor-fold defaultstate="collapsed" desc="Time_Stop_Init">
        public void Time_Stop_Init(int Nro){
            this.Nro=Nro;
            Corriendo=true;
            Num_Env++;
        }
        // </editor-fold>

4.- Run (important (I only put the important thing because it is very very big indeed)):

public void run(){
            do {
                if(Corriendo){
                    // <editor-fold defaultstate="collapsed" desc="Switch">
                    System.out.println ("siiiiiiiiiiiiiiiiiiiiiiiiiiiiiii "+Cls_Met.CargarHoraReal ());
                    switch(Nro){
                        // <editor-fold defaultstate="collapsed" desc="0 Conexion">
                        case(0):
                            System.out.println ("Acceso S:"+Server+" : P:"+Puerto);
                            try {
                                Client = new Socket ( InetAddress.getByName ( Server ), Puerto);
                                Enviar = new ObjectOutputStream ( Client.getOutputStream () );
                                Enviar.flush ();
                                Recibir = new ObjectInputStream ( Client.getInputStream () );
                                Nro = 1;
                            } catch (IOException e) {
                                Nro = 3;
                                Log.e ( "Socket Iniciando !!!", "SI: 1B1B1B1B1B1B1B1B1B1B1B1B1B1B1B1B1B1B1B " + Cls_Met.CargarHoraReal () );
                                e.printStackTrace ();
                            } catch (Exception e) {
                                Nro = 3;
                                Log.e ( "Socket Iniciando !!!", "SI: 2C2C2C2C2C2C2C2C2C2C2C2C2C2C2C2C2C2C2C " + Cls_Met.CargarHoraReal () );
                                e.printStackTrace ();
                            }
                            break;
}
                    }else{
                        System.out.println ("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb "+Cls_Met.CargarHoraReal ());
                    }
                    // </editor-fold>
                    // <editor-fold defaultstate="collapsed" desc="Temporalizador">
                    try {
                        sleep ( 3000 );
                    } catch (InterruptedException e) {
                        Log.e("TCP SI client", "SI: InterruptedException No corriennnnndoooooo "+Cls_Met.CargarHoraReal ());
                        e.printStackTrace ();
                    }

                    // </editor-fold>
            }while (Ini_Hilo);
        }
        // </editor-fold>