Web3j-Android-Solidity-example

• This is more than a simple web3j project using solidity.
• What we are trying to acheive here is to make a dapp game just like cryptokitties but on android which is supposed to be harder since you have to consider many things like wallet and user interface.

Quick Overview

SolidityAndWeb3js

• The folder contains solidity contracts

  • solidity source code which tells how a Fish( actually, i prefer to call it CryptoFancyCarp ) is made with pieces.
  • Also it is a genetic game which means you can let your fish to mate with others and have baby fish. This, i implemented a genetic algorithm for it. You can also see it here:GeneticConsoleWithSolidity.
  • and other contract using soldity. I put many files together to FishContracts.

• The folder contains Web3js implementation

  • I already deployed the contract and made a simple web3js file for you to call the functions. I have deployed a webpage just for you. FishDApp

• Deployment

  • When you deploy the contract, use this FishContracts file. And remember to deploy two contracts: FishCore & GeneticConsole and rememeber to set the address of geneticConsole to fishcore.

PHPServerAPI

• The folder contains secret fomula of a fish's gene.

  • Gene Quality

    • There are several qualities about genes i created.
    • Start from normal to rare,superior,Godlike, and even to MasterOfUniverse.
    • $names = ['普通','稀有','卓越','史诗','神话','传说','超神','宇宙之主'];
    • Try it yourself here: FishAlphaGene

  • Image

    • There are nearly 200 million possibilities of the outlook of our fishes.
    • Here are some exaples:
    • See more in images folder. Or Try the combination yourself here: FishAlphaImage

AndroidAndWeb3j

• The folder contains android code & generated contract code
  • Wallet: How to use/create/import Ethereum wallet.
  • FishAPI: How to call,send transaction to a deployed contract
  • Utils: Some useful functions waiting to be explored
  • Others.

Others

• This file includes everything that i need about my deplyed contract and how i can connect to blockchain.
  • Infura. It has my own Infura API token. You are welcome to use it by any means.
  • Contract address, contract ABI, contract owner.
  • Web3j simple code to call or send transaction of functions of a contract. You can use them in the chrome console. I deployed my web3j front-end here. Try it out. FishDApp

The processes of Making Your Own Android DAPP

##Soidity First
1. You need to write your own solidity source code.
2. Compile and Deploy your source code using `remix`
(Don't forget to record your contract address! )
##Autogenerate file 
3. Now use your source code( contract.sol )to use `solc` and `web3j` command tool to generate a java file.
##Android
###dependencies
4. Add `compile ('org.web3j:core:3.3.1-android')` to app/build.gradle
###Testing
5. Write and run simple code like creating a wallet
##Done

Tools:

remix

solc (Remeber to use npm install solc to get solc):

Example: solc MetaCoin.sol --bin --abi --optimize -o /Users/pro/Desktop

Format: solc <contract>.sol --bin --abi --optimize -o <output-dir>/

web3j:

Format: web3j solidity generate [--javaTypes|--solidityTypes] /path/to/<smart-contract>.bin /path/to/<smart-contract>.abi -o /path/to/src/main/java -p com.your.organisation.name

Erros during Android development

This is a list a possible error you might encounter, and i may have dealt with them already. So I am gonna share my experience here.

• Error: Execution failed for task ': app: packageAllDebugClassesForMultiDex'. > Java.util.zip.ZipException: duplicate entry: bolts / AggregateException.class

• Solution: 1.add multiDexEnabled true to defaultConfig in app/build.gradle. 2.add compile 'com.android.support:multidex:1.0.3' to dependecies in app/build.gradle.

• java.lang.OutOfMemoryError: Failed to allocate a 268435468 byte allocation with 8050708 free bytes and 244MB until OOM

• Solution:

1. When you are trying to create a new wallet. Try String filename = WalletUtils.generateLightNewWalletFile(password,new File(filepath)); 👍 instead of String filename = WalletUtils.generateFullNewWalletFile(password,new File(filepath));
2. And when you import an old wallet from ECKeyPair, Try String filename = WalletUtils.generateWalletFile(password,ecKeyPair,new File(filepath),false);👍 instead of String filename = WalletUtils.generateWalletFile(password,ecKeyPair,new File(filepath),true);

• javax.net.ssl.SSLException: Connection closed by peer
• Solution: Try using higher version of Android devices. I tried Android 7.0 on Genymotion and it works well. See more about this issue here: ERROR with infura & web3j on Android 4.x : javax.net.ssl.SSLException: Connection closed by peer

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Ethereum : 0x94cba7B70800575a3A4BfFd3B195bE4CcF5f7AAd