I managed to do this today after some painful debugging. The result is here: https://github.com/zupzup/react-native-ethereum-wallet
It's not a full example yet, but it shows how to interact with the running geth node.
Here's what I did:
First step, add the geth dependency to build.gradle:
compile 'org.ethereum:geth:1.6.7'
Then, in MainActivity.java, try to get the node running. You'll see if it's running correctly in the Android Monitor.
This looks something like this:
NodeConfig nc = new NodeConfig();
Node node = Geth.newNode(getFilesDir() + "/.eth1", nc);
Then, you need some way to expose this node to your Wrapping module. I just used a Singleton for this, but I guess there are cleaner ways to share state in Android.
Regarding the wrapping, I just used the official docs at https://facebook.github.io/react-native/docs/native-modules-android.html.
Basically, I created a method test, which fetches the node from the singleton and executes something on it (in my case a simple getBalanceAt query).
And this test method can be called from React-Native with a callback, if you register the wrapping module correctly. Like this:
NativeModules.TestNative.test("tojavandback", (str) => {
Alert.alert(str);
})
This outputs, in my case, the amount of ether at the given address. It's just a simple example, but the whole end2end interaction works.
Hope this helps.
Best Answer
MyEtherWallet provides an offline signer for contract deployment here. You can use this to generate -and relay- your transaction.
Edit:
For the current version (v3.8.1), you need to click "Deploy contract" first. In that page it asks for the bytecode (yes, you cannot directly paste Solidity code), however, obtaining the bytecode from the source code is trivial. You can use Remix for that. Though I'm not sure if it will work with smartphones. If not, you need to find another Solidity compiler.