import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    final int itemId = item.getItemId();

    if (itemId == R.id.action_info) {
        Intent intent = new Intent(this, InfoActivity.class);
        intent.putExtra(IssueActivity.MODAL_URL, getString(R.string.asset_url_info));
        startActivity(intent);
        return true;
    } else if (itemId == R.id.action_settings) {
        Intent settingsIntent = new Intent(this, SettingsActivity.class);
        startActivity(settingsIntent);
        return true;
    } else if (itemId == R.id.action_refresh) {
        swipeRefreshLayout.setRefreshing(true);
        if(!issueCollection.isLoading()) {
            issueCollection.reload();
        }
        return true;
    } else if (itemId == R.id.action_subscribe) {

        if(issueCollection.getSubscriptionSku() != null) {
            final ActivityCheckout checkout = this.getCheckout();
            checkout.whenReady(new Checkout.ListenerAdapter() {
                @Override
                public void onReady(@NonNull BillingRequests requests) {
                    requests.purchase(issueCollection.getSubscriptionSku(), null, checkout.getPurchaseFlow());
                }
            });
            return true;
        }else{
            Toast.makeText(this, "Subscriptions are currently not available!", Toast.LENGTH_LONG).show();
            return false;
        }
    } else {
        return super.onContextItemSelected(item);
    }
}
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
@Nullable
public ActivityCheckout getCheckout() {
    return mCheckout;
}
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
@NonNull
public ActivityCheckout getCheckout() {
    return checkout;
}
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
@Nullable
ActivityCheckout getCheckout();
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
/**
 * {@inheritDoc}
 */
@Nullable
@Override
public ActivityCheckout getCheckout() {
    return mCheckout;
}
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
/**
 * {@inheritDoc}
 */
@Nullable
@Override
public ActivityCheckout getCheckout() {
    return mAbs.getCheckout();
}
 

import org.solovyev.android.checkout.ActivityCheckout; //导入依赖的package包/类
public ActivityCheckout getShelfCheckout() {
    return shelfCheckout;
}