Why can not I capture KeyEvent in my program? Problems is not the main?

#include<QApplication>
#include<tabuleiro.h>
#include<jogador.h>
#include<QWidget>

int main(int argc, char* argv[]){

QApplication app(argc, argv);

QWidget window;
Tabuleiro t(&window);
Jogador j(&window);

window.show();



return app.exec();
return 0;
}

Classes:

#include<tabuleiro.h>
#include<QPainter>
#include<iostream>

using namespace std;

Tabuleiro::Tabuleiro(QWidget* parent)
: QWidget(parent){


layout = new QVBoxLayout();


gerarTabuleiro(1);
repaint();
setFixedSize(960,560);
setLayout(layout);

show();

}

void Tabuleiro::gerarTabuleiro(int modo){

x=0;
y=0;
w=40;
h=40;

switch(modo){

case 1 :

 for(int x = 0;  x<14 ; x++){
        for(int y = 0 ; y<12 ; y++){
            tabuleiro[x][y] ='1';
        }
    }

 for(int x = 0;  x<14 ; x++){
        for(int y = 12 ; y<24 ; y++){
            tabuleiro[x][y] ='0';
        }
    }

 break;


}




}

void Tabuleiro::draw(){
repaint();
}

void Tabuleiro::paintEvent(QPaintEvent *event){
QWidget::paintEvent(event);
QPainter painter(this);
painter.setPen(Qt::gray);

for(int c = 0 ; c<14 ; c++){


    for(int l = 0 ; l<24 ; l++){

        if(tabuleiro[c][l]=='1'){
            painter.setBrush(Qt::black);

        }
        else{
         painter.setBrush(Qt::white);
        }



        painter.drawRect(x,y,w,h);

        x+=40;



    }
    x=0;
    y+=40;
 }
y=0;

}

My problem is that I'm not able to capture the keyboard event.