How to create transaction with API then sign a transaction offline and then broadcast using API

[CoticiGabi]

I want to create a transaction by using api call https://api.nile.trongrid.io/wallet/createtransaction , which gives me this response for example :

{"visible":false,"txID":"ca3d16a01baa0cc7506d1ce08d6f741b1b085c7f597d6f518758c5cd1ebe9355","raw_data":{"contract":[{"parameter":{"value":{"amount":1,"owner_address":"4120a913a920deb99f6e3a98724712e2c0447db89f","to_address":"41e2a881d0c71612624ba204ebb9a559a751e2852a"},"type_url":"type.googleapis.com/protocol.TransferContract"},"type":"TransferContract"}],"ref_block_bytes":"38f2","ref_block_hash":"97436e309100ba8c","expiration":1722934221000,"timestamp":1722934163579},"raw_data_hex":"0a0238f2220897436e309100ba8c40c8b187b792325a65080112610a2d747970652e676f6f676c65617069732e636f6d2f70726f746f636f6c2e5472616e73666572436f6e747261637412300a154120a913a920deb99f6e3a98724712e2c0447db89f121541e2a881d0c71612624ba204ebb9a559a751e2852a180170fbf083b79232"}

Then I want to sign the transaction offline using the trident library. From what I saw in other closed issues, you recommend to use this :
public Chain.Transaction signTransaction(Response.TransactionExtention txnExt, KeyPair keyPair) {
byte[] txid = txnExt.getTxid().toByteArray();
byte[] signature = KeyPair.signTransaction(txid, keyPair);
Chain.Transaction signedTxn = txnExt.getTransaction().toBuilder().addSignature(ByteString.copyFrom(signature)).build();
return signedTxn;
}
Which uses a TransactionExtension object, that i do not get from the /createtransaction API response, and I didn't find a way to construct it from the API response.

My question is : How can I create a trasnaction using the API , then sign it using the trident sdk and then broadcast it using the API ?

[endiaoekoe]

How can I create a trasnaction using the API , then sign it using the trident sdk and then broadcast it using the API ?

@CoticiGabi
basically, you can refer to this doc which detailed a normal routine for sending a transaction(including:Create -> Sign -> Broadcast -> (wait) -> Lookup and get receipt)
byw, TransactionExtension struct is the newer version of Transaction struct which contains more response infos ,and it is preferred to use TransactionExtension struct.

[CoticiGabi]

Hello @endiaoekoe ,

I tried following the doc that you gave me, i created and signed the transaction using ApiWrapper class. But the signature is in ByteString format, when i transform it in hex and then call the Trongrid API to broadcast with the provided signature I keep getting the following error :

{"code":"SIGERROR","txid":"e8b4c08c29a1a19d10c39511aeca2f68c67be6b0f24de5d6a165a58eb9dd210a","message":"Validate signature error: 53db352cee757e299d2cd851a9cc31b99b7fe471162e5aa66bbc952a6938fc9960845838bd2fcaf7b31305a36158f29d097471b77989b3dcb8c5534556feec7400 is signed by random_trx_address but it is not contained of permission."}
But when I broadcast the transaction using the ApiWrapper method broadcastTransaction() it works, so the address that signs the transactions is my address, the correct one, not a random trx address like the error message form the API.

Can I use ApiWrapper with an API like Trongrid ? I see that it has constructors only for grpc full nodes.
And how can I use trident SDK with the API ? I see that the objects in the sdk (Transaction, TransactionExtention etc.) are not compatible with the responses given by the API.

[endiaoekoe]

@CoticiGabi
here is a code example for sending tx;
if you want to use trongrid API , try 'grpc.shasta.trongrid.io:50051' in shata testnet and 'grpc.trongrid.io:50051' in mainnet and 'grpc.nile.trongrid.io:50051' in nile testnet which configed in this file.
by the way,make sure to configure the right API endpoint ;
hope it helps.