No signer to authorize the transaction with

Question

When trying to make a transaction on a boundContract with geth-api through the library of @karalabe. I am missing a way to get the signer. I only see the interface for signer in the aar but no way to get a implementation of it.

java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
    Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 
    Caused by: java.lang.Exception: no signer to authorize the transaction with
        at go.Seq.throwException(Seq.java:52)
        at org.ethereum.geth.BoundContract.transfer(Native Method)
        at org.ligi.ewallet.MainActivity$onCreate$function$1.invoke(MainActivity.kt:68)
        at org.ligi.ewallet.MainActivity$onCreate$function$1.invoke(MainActivity.kt:27)
        at org.ligi.ewallet.MainActivityKt$sam$OnClickListener$af810d58.onClick(MainActivity.kt:0)
        at android.view.View.performClick(View.java:5697)
        at android.view.View$PerformClick.run(View.java:22526)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:158)
        at android.app.ActivityThread.main(ActivityThread.java:7225)
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

It happens when trying to trying to invoke transfer on a boundContract

Answer 1

You can create an implementation of Signer that uses an AccountManager to sign a transaction with.

Here's a sample which assumes your AccountManager contains already unlocked accounts:

final AccountManager am = new AccountManager(this.getFilesDir() + "/keystore", Geth.LightScryptN, Geth.LightScryptP);

Signer mySigner = new Signer() {
    @Override
    public Transaction sign(Address address, Transaction transaction) throws Exception {
        byte[] signature = am.sign(address, transaction.getSigHash().getBytes());
        return transaction.withSignature(signature);
    }
};

And this one uses password strings instead:

final AccountManager am = new AccountManager(this.getFilesDir() + "/keystore", Geth.LightScryptN, Geth.LightScryptP);

Signer mySigner = new Signer() {
    @Override
    public Transaction sign(Address address, Transaction transaction) throws Exception {
        byte[] signature = am.signWithPassphrase(address, "password", transaction.getSigHash().getBytes());
        return transaction.withSignature(signature);
    }
};