ADICIONANDO O CONTROLE PARA INICIAR A PARTIDA

android:enabled="flase"

<Button
    android:layout_width="150dp"
    android:layout_height="40dp"
    android:layout_marginLeft="30dp"
    android:onClick="newGame"
    android:text="Play" />

package com.example.jogo;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class Main extends Activity {

    //CONST DE CADA BOTAO
    private final String QUADRADO = "quadrado";
    private final String BOLA = "O";
    private final String XIS = "X";

    private String lastPlay = "X";

    private View view;


@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setView(getLayoutInflater().inflate(R.layout.main, null));
        setContentView( getView());
    }
    public void clickquadrado(View v){

        if(getLastPlay().equals(XIS)){
            ((Button)v).setText( BOLA );
            setLastPlay(BOLA);
        }else{
            ((Button)v).setText( XIS );
            setLastPlay(XIS);
        }

        ((Button)v).setText( XIS );

        Toast.makeText( getView().getContext(), v.getTag().toString(), Toast.LENGTH_LONG).show();
    }


    public Button getQuadrado(int tagNum){
        return (Button)getView().findViewWithTag("QUADRADO"+tagNum);
    }

    public void newGame(View v){

        setEnableQuadrado(true);

        for(int i=1; i<=9; ++i){
            if(getQuadrado(i)!=null){
                getQuadrado(i).setText("");
            }
        }
    }

    public void setEnableQuadrado(boolean b){
        for(int i=1; i<=9; ++i){
            if(getQuadrado(i)!=null){
                getQuadrado(i).setEnabled( b );
            }
        }
    }

    public String getLastPlay() {
        return lastPlay;
    }
    public void setLastPlay(String lastPlay) {
        this.lastPlay = lastPlay;
    }

    public View getView() {
        return view;
    }

    public void setView(View view) {
        this.view = view;
    }




}