connect watching wallet with blockchain
i have done this by overriding methods of WalletAppkit and its working fine now,
here is code sample for this. 

  kit = new WalletAppKit(params, walletFile, APP_NAME) {
            @Override
            protected Wallet createWallet() {
                System.out.println("I am here");
                Wallet wallet = Wallet.fromWatchingKeyB58(params, tPub, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
                return wallet;
            }
@Override
        protected void onSetupCompleted() {
            super.onSetupCompleted();
            System.out.println(kit.wallet().currentReceiveAddress());
            System.out.println(kit.wallet().getTotalReceived().toFriendlyString());
            txHistory();

            kit.wallet().addEventListener(new AbstractWalletEventListener() {
                @Override
                public void onWalletChanged(Wallet wallet) {
                    System.out.println(kit.wallet().getTotalReceived());
                }
            });
        }