Solana Flutter create transaction for phantom /signAndSendTransaction deeplink

Question

I want to fund another user's wallet (let's say I have their public wallet address in my code) from my phantom wallet using a Flutter app.

Now I can use the /connect deeplink of Phantom in a Flutter app, but how do I create a transaction for transferring funds to another wallet in Flutter and then execute it through Phantom's /signAndSendTransaction? I know I need to use the Cryptoplease package, but I don't know how to do it exactly.

Answer 1

You can use my package for flutter flutter_phantom

    Future<web3.Transaction> createTransactionTransfer() async {
  final transaction = web3.Transaction(
      feePayer: phantom.phantomWalletPublicKey,
      recentBlockhash: (await connection.getLatestBlockhash()).blockhash);
  transaction.add(
    SystemProgram.transfer(
      fromPublicKey: phantom.phantomWalletPublicKey,
      toPublicKey: phantom.phantomWalletPublicKey,
      lamports: web3.solToLamports(1),
    ),
  );
  return transaction;
}

 void signAndSendTransaction() async {
  try { 
    web3.Transaction transaction = await createTransactionTransfer();

    web3.Buffer transactionSerialize = transaction
        .serialize(const web3.SerializeConfig(requireAllSignatures: false));

    final url = phantom.generateSignAndSendTransactionUri(
        transaction: transactionSerialize,
        redirect: "onSignAndSendTransaction");
  
    launchUrl(
      url,
      mode: LaunchMode.externalNonBrowserApplication,
    );
  } catch (e) {
  print(e)
  }
}

full example of how to use this package (Android,Ios) flutter_phantom-demo.

Answer 2

I would recommend following the merigolabs's Solana DART API.

Here's an example how to create a transaction to transfer SOL from 1 wallet to another.

// Create a System Program instruction to transfer 1 SOL from [address1] to [address2].
final transaction = web3.Transaction();
transaction.add(
    SystemProgram.transfer(
        fromPublicKey: address1, 
        toPublicKey: address2, 
        lamports: web3.solToLamports(1),
    ),
);

You will additionally have to serialise this transaction and provide it as payload to the Phantom deeplink as a parameter, as mentioned here.

Hope this helps.