Technical details

FILES

Your wallet contains your private keys and various transaction related metadata. It is stored in app-private storage:

Mainnet: /data/data/de.schildbach.wallet/files/wallet-protobuf
Testnet: /data/data/de.schildbach.wallet_test/files/wallet-protobuf-testnet

The wallet file format is not compatible to wallet.dat (Satoshi client). Rather, it uses a custom protobuf format which should be compatible between clients using dimecoinj.

Certain actions cause automatic rolling backups of your wallet to app-private storage:

Mainnet: /data/data/de.schildbach.wallet/files/key-backup-protobuf
Testnet: /data/data/de.schildbach.wallet_test/files/key-backup-protobuf-testnet

Your wallet can be manually backed up to and restored from a share of the storage access framework (likely Google Drive):

Mainnet: dimecoin-wallet-backup-<yyyy-MM-dd>
Testnet: dimecoin-wallet-backup-testnet-<yyyy-MM-dd>

If you want to recover coins from manual backups and for whatever reason you cannot use the app itself to restore from the backup, refer to the separate guide for instruction.

The current fee rate for each of the fee categories (economic, normal, priority) is cached in app-private storage:

Mainnet: /data/data/de.schildbach.wallet/files/fees.txt
Testnet: /data/data/de.schildbach.wallet_test/files/fees-testnet.txt

DEBUGGING

Wallet file for Testnet can be pulled from an (even un-rooted) device using:

adb pull /data/data/de.schildbach.wallet_test/files/wallet-protobuf-testnet

Log messages can be viewed by:

adb logcat

The app can send extensive debug information. Use Options > Settings > Report Issue and follow the dialog. In the generated e-mail, replace the support address with yours.

BUILDING THE DEVELOPMENT VERSION

It's important to know that the development version uses Testnet, is debuggable and the wallet file is world readable/writeable. The goal is to be able to debug easily.

You can probably skip some steps, especially if you built Android apps before.

You'll need git, a Java SDK 6 (or later) and Gradle 2.10 (or later) for this. I'll assume Ubuntu Xenial Linux for the package installs, which comes with slightly more recent versions.

# first time only
sudo apt install git gradle openjdk-8-jdk libstdc++6:i386 zlib1g:i386

Download the Android SDK Tools and unpack to your workspace directory. Point your ANDROID_HOME variable to the unpacked Android SDK directory and switch to it.

Download and install the required Android dependencies:

tools/android update sdk --no-ui --force --all --filter tool,platform-tool,build-tools-27.0.3,android-15,android-27

Download the Android NDK, then unpack it to your workspace directory. Point your ANDROID_NDK_HOME variable to the unpacked Android NDK directory.

Finally, you can build Dimecoin Wallet and sign it with your development key. Again in your workspace, use:

# first time only
git clone -b master https://github.com/dime-coin/android-wallet.git android-wallet

# each time
cd android-wallet
git pull
gradle clean :native-scrypt:copy test build

To install the app on your Android device, use:

# first time only
sudo apt install android-tools-adb

# each time
adb install wallet/build/outputs/apk/android-wallet-debug.apk

If installation fails, make sure "Developer options" and "USB debugging" are enabled on your Android device, and an ADB connection is established.

BUILDING THE PRODUCTIVE VERSION

At this point I'd like to remind that you continue on your own risk. According to the license, there is basically no warranty and liability. It's your responsibility to audit the source code for security issues and build, install and run the application in a secure way.

The production version uses Mainnet, is built non-debuggable, space-optimized with ProGuard and the wallet file is protected against access from non-root users. In the code repository, it lives in a separate 'prod' branch that gets rebased against master with each released version.

# each time
cd android-wallet
git fetch origin
git checkout origin/prod
gradle clean :native-scrypt:copy test build

SETTING UP FOR DEVELOPMENT

You should be able to import the project into Android Studio, as it uses Gradle for building.

TRANSLATIONS

The source language is English. Translations for all languages except German happened on Transifex.

The English resources are pushed to Transifex. Changes are pulled and committed to the git repository from time to time. It can be done by manually downloading the files, but using the tx command line client is more convenient:

# first time only
sudo apt install transifex-client

If strings resources are added or changed, the source language files need to be pushed to Transifex. This step will probably only be executed by the maintainer of the project, as special permission is needed:

# push source files to Transifex
tx push -s

As soon as a translation is ready, it can be pulled:

# pull translation from Transifex
tx pull -f -l <language code>

Note that after pulling, any bugs introduced by either translators or Transifex itself need to be corrected manually.

NFC (Near field communication)

Dimecoin Wallet supports reading Dimecoin requests via NFC, either from a passive NFC tag or from another NFC capable Android device that is requesting coins.

For this to work, just enable NFC in your phone and hold your phone to the tag or device (with the "Request coins" dialog open). The "Send coins" dialog will open with fields populated.

Instructions for preparing an NFC tag with your address:

• We have successfully tested this NFC tag writer. Other writers should work as well, let us know if you succeed.

• Some tags have less than 50 bytes capacity, those won't work. 1 KB tags recommended.

• The tag needs to contain a Dimecoin URI. You can construct one with the "Request coins" dialog, then share with messaging or email. You can also construct the URI manually. Mainnet example: dimecoin:1G2Y2jP5YFZ5RGk2PXaeWwbeA5y1ZtFhoL

• The type of the message needs to be URI or URL (not Text).

• If you put your tag at a public place, don't forget to enable write protect. Otherwise, someone could overwrite the tag with his own Dimecoin address.

DIMECOINJ

Dimecoin Wallet uses dimecoinj for Dimecoin specific logic.

EXCHANGE RATES

Dimecoin Wallet reads this feed from "DimecoinAverage" for getting exchange rates:

https://apiv2.bitcoinaverage.com/indices/global/ticker/short?crypto=BTC

We chose this feed because it is not dependent on a single exchange. However, you should keep in mind it's always a 24h average. This feature can be disabled with the compile-time flag

Constants.ENABLE_EXCHANGE_RATES