在按钮上单击动态更改整个应用程序的主题并存储它

我正在使用 Utills 类来更改单击按钮时的主题，有 8 个带有图像背景的按钮。这是我的实用程序类

public class Utills {

public static boolean isPurchsed =true;
private static int sTheme;
public final static int THEME_DEFAULT = 0;
public final static int THEME_ONE = 1;
public final static int THEME_TWO = 2;
public final static int THEME_THREE = 3;
public final static int THEME_FOUR = 4;
public final static int THEME_FIVE = 5;
public final static int THEME_SIX = 6;
public final static int THEME_SEVEN = 7;
/**
 * Set the theme of the Activity, and restart it by creating a new Activity of the same type.
 */
public static void changeToTheme(Activity activity, int theme)
{
    sTheme = theme;
    activity.finish();
    activity.startActivity(new Intent(activity, activity.getClass()));
}
/** Set the theme of the activity, according to the configuration. */
public static void onActivityCreateSetTheme(Activity activity)
{
    switch (sTheme)
    {
        default:
        case THEME_DEFAULT:
            activity.setTheme(R.style.MyTheme);
            break;
        case THEME_ONE:
            activity.setTheme(R.style.MySecondTheme);
            break;
        case THEME_TWO:
            activity.setTheme(R.style.MyThirdTheme);
            break;
        case THEME_THREE:
            activity.setTheme(R.style.MyFourthTheme);
            break;
        case THEME_FOUR:
            activity.setTheme(R.style.MyFifthTheme);
            break;
        case THEME_FIVE:
            activity.setTheme(R.style.MySixthTheme);
            break;
        case THEME_SIX:
            activity.setTheme(R.style.MySeventhTheme);
            break;
        case THEME_SEVEN:
            activity.setTheme(R.style.MyLastTheme);
            break;
    }
}

这是活动课

public class ChangeBackgroundActivity extends AppCompatActivity {


Button bck1, bck2, bck3, bck4, bck5, bck6,bck7,bck8;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Utills.onActivityCreateSetTheme(this);
    setContentView(R.layout.activity_change_background);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar_changebackground);
    setSupportActionBar(toolbar);


    bck1 = (Button)findViewById(R.id.btn_bck1);
    bck1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_DEFAULT);
        }
    });

    bck2 = (Button)findViewById(R.id.btn_bck2);
    bck2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_ONE);
        }
    });


    bck3 = (Button)findViewById(R.id.btn_bck3);
    bck3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_TWO);
        }
    });

    bck4 = (Button)findViewById(R.id.btn_bck4);
    bck4.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_THREE);
        }
    });
    bck5 = (Button)findViewById(R.id.btn_bck5);
    bck5.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_FOUR);
        }
    });
    bck6 = (Button)findViewById(R.id.btn_bck6);
    bck6.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_FIVE);
        }
    });
    bck7 = (Button)findViewById(R.id.btn_bck7);
    bck7.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this, Utills.THEME_SIX);
        }
    });
    bck8 = (Button)findViewById(R.id.btn_bck8);
    bck8.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Utills.changeToTheme(ChangeBackgroundActivity.this,Utills.THEME_SEVEN);
        }
    });

}

当我关闭我的应用程序并重新启动它时，整个应用程序上再次设置了默认主题。如何从 Utills 类存储应用程序的主题，所以每当我关闭我的应用程序并再次重新启动它时，所选主题将为整个应用程序设置。