segregated witness – Fail to sign the Segwit Transaction’s input in bitcoinj

I want to spend from a segwit address and it has a P2WPH script, I created this transaction just like creating a normal P2PKH transaction, but just changed the address of the input to the segwit address, I don’t know if this is correct, and signing this transaction in the following method, but it says script was NOT verified successfully…

Transaction signedtx = signInput(rawtx.getHashAsString(),privkey,rawtx);

    public static Transaction signInput(String hash, String prvKey,Transaction spendTx) {
        ECKey ecKey = ECKey.fromPrivate(Utils.HEX.decode(prvKey));
        ECKey.ECDSASignature signature = ecKey.sign(Sha256Hash.wrap(hash));
        TransactionSignature transactionSignature = new TransactionSignature(signature,Transaction.SigHash.ALL,true);
        TransactionWitness witness = TransactionWitness.redeemP2WPKH(transactionSignature,ecKey);
        TransactionInput input = spendTx.getInput(0);
        input.setWitness(witness);
        return spendTx;
    }

I am not very familiar with bitcoinj, and currently there is very little technical guidance related to segwit, I hope someone can help me！