Blockchain-Android

in blog on blockchain

  1. Learning Site Address
  2. Source Code
    1. Build Gradle (module)
  3. Layouts (Activity Main)
  4. Main Activity
  5. Manifest
  6. Using Infura Endpoint

Learning Site Address

https://gitlab.com/teameverywhere-public/voteapp
https://gitlab.com/teameverywhere-public/android/tree/final
https://steemit.com/kr/@wonsama/kr-dev-ipfs
https://github.com/maheshmurthy/ethereum_voting_dapp

Source Code

Build Gradle (module)

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

// dependencies
implementation 'org.web3j:core:4.1.0-android'


web3 = Web3j.build(new HttpService("https://ropsten.infura.io/v3/a083e681e1df47fcafb3c448f6bd4ec1"));
    try {
        Web3ClientVersion clientVersion = web3.web3ClientVersion().sendAsync().get();
        if(!clientVersion.hasError()){
        //  toastAsync("Connected!");
        }
        else {
        //  toastAsync(clientVersion.getError().getMessage());
        }
    } catch (Exception e) {
        //  toastAsync(e.getMessage());
    }
Toast.makeText(MainActivity.this, "Connected", Toast.LENGTH_LONG).show();

public void toastAsync(String message) {
    runOnUiThread(() -> {
        Toast.makeText(this, message, Toast.LENGTH_LONG).show();
        Log.d(TAG, "toastAsync: "+message);
    });
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical"

   tools:context=".MainActivity">

   <Button
       android:id="@+id/btnConnect"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:text="Connect Ethereum Network"
        />

   <Button
       android:id="@+id/btnGetAddress"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:text="Get Adress"
       />
</LinearLayout>

public class MainActivity extends AppCompatActivity {
   private static final String TAG = "MainActivity";

   Web3j web3;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);


       Button btnConnect = (Button)findViewById(R.id.btnConnect);
       btnConnect.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               // 함수 호출
               Log.d(TAG, "btnConnect onClicked");
               web3 = Web3j.build(new HttpService("https://ropsten.infura.io/v3/a083e681e1df47fcafb3c448f6bd4ec1"));
               try {
                   Web3ClientVersion clientVersion = web3.web3ClientVersion().sendAsync().get();
                   if(!clientVersion.hasError()){
                       toastAsync("Connected!");
                   }
                   else {
                       toastAsync(clientVersion.getError().getMessage());
                   }
               } catch (Exception e) {
//                    toastAsync(e.getMessage());
               }
           }
       });
   }


   public void toastAsync(String message) {
       runOnUiThread(() -> {
           Toast.makeText(this, message, Toast.LENGTH_LONG).show();
           Log.d(TAG, "toastAsync: "+message);
       });
   }
}

public class MainActivity extends AppCompatActivity {
   private static final String TAG = "MainActivity";

   Web3j web3;
   Credentials credentials;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);


       Button btnConnect = (Button)findViewById(R.id.btnConnect);
       btnConnect.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               // 함수 호출
               Log.d(TAG, "btnConnect onClicked");
               web3 = Web3j.build(new HttpService("https://ropsten.infura.io/v3/a083e681e1df47fcafb3c448f6bd4ec1"));
               try {
                   Web3ClientVersion clientVersion = web3.web3ClientVersion().sendAsync().get();
                   if(!clientVersion.hasError()){
                       toastAsync("Connected!");
                   }
                   else {
                       toastAsync(clientVersion.getError().getMessage());
                   }
               } catch (Exception e) {
//                    toastAsync(e.getMessage());
               }
           }
       });

       Button btnGetAddress = (Button) findViewById(R.id.btnGetAddress);
       btnGetAddress.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               Log.d(TAG, "btnGetAddress onClicked");
               try {
//            Credentials credentials = WalletUtils.loadCredentials(password, new File(walletPath+"/"+fileName));
                   credentials = getCredentailFromPrivteKey("D581A513DBB0E0755E10FEFEB8B327DEA393A87EC500A51AC8EE34755DF87D4F");

                   toastAsync("Your address is " + credentials.getAddress());
                   Log.d(TAG, "getAddress: "+ credentials.getAddress());
                   Log.d(TAG, "getAddress: 0xA80c982364EF3f146266bec9d7E2F2b30CD94aF9");


               }
               catch (Exception e){

                   toastAsync("getAddress error "+e.getMessage());
               }

           }
       });
   }

   private Credentials getCredentailFromPrivteKey(String privateKeyInHex) {
       BigInteger privateKeyInBT = new BigInteger(privateKeyInHex, 16);
       ECKeyPair aPair = ECKeyPair.create(privateKeyInBT);
       Credentials aCredential = Credentials.create(aPair);
       return aCredential;
   }

   public void toastAsync(String message) {
       runOnUiThread(() -> {
           Toast.makeText(this, message, Toast.LENGTH_LONG).show();
           Log.d(TAG, "toastAsync: "+message);
       });
   }
}

Layouts (Activity Main)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical"

   tools:context=".MainActivity">

   <Button
       android:id="@+id/btnConnect"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:text="Connect Ethereum Network"
        />

   <Button
       android:id="@+id/btnGetAddress"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:text="Get Adress"
       />
</LinearLayout>

Main Activity

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.kenai.jffi.Main;

import org.web3j.crypto.Credentials;
import org.web3j.crypto.ECKeyPair;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.methods.response.Web3ClientVersion;
import org.web3j.protocol.http.HttpService;

import java.math.BigInteger;


public class MainActivity extends AppCompatActivity {
   private static final String TAG = "MainActivity";

   Web3j web3;
   Credentials credentials;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);


       Button btnConnect = (Button)findViewById(R.id.btnConnect);
       btnConnect.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               // 함수 호출
               Log.d(TAG, "btnConnect onClicked");
               web3 = Web3j.build(new HttpService("https://ropsten.infura.io/v3/a083e681e1df47fcafb3c448f6bd4ec1"));
               try {
                   Web3ClientVersion clientVersion = web3.web3ClientVersion().sendAsync().get();
                   if(!clientVersion.hasError()){
                       toastAsync("Connected!");
                   }
                   else {
                       toastAsync(clientVersion.getError().getMessage());
                   }
               } catch (Exception e) {
//                    toastAsync(e.getMessage());
               }
           }
       });

       Button btnGetAddress = (Button) findViewById(R.id.btnGetAddress);
       btnGetAddress.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               Log.d(TAG, "btnGetAddress onClicked");
               try {
//            Credentials credentials = WalletUtils.loadCredentials(password, new File(walletPath+"/"+fileName));
                   credentials = getCredentailFromPrivteKey("D581A513DBB0E0755E10FEFEB8B327DEA393A87EC500A51AC8EE34755DF87D4F");

                   toastAsync("Your address is " + credentials.getAddress());
                   Log.d(TAG, "getAddress: "+ credentials.getAddress());
                   Log.d(TAG, "getAddress: 0xA80c982364EF3f146266bec9d7E2F2b30CD94aF9");


               }
               catch (Exception e){

                   toastAsync("getAddress error "+e.getMessage());
               }

           }
       });
   }

   private Credentials getCredentailFromPrivteKey(String privateKeyInHex) {
       BigInteger privateKeyInBT = new BigInteger(privateKeyInHex, 16);
       ECKeyPair aPair = ECKeyPair.create(privateKeyInBT);
       Credentials aCredential = Credentials.create(aPair);
       return aCredential;
   }



   public void toastAsync(String message) {
       runOnUiThread(() -> {
           Toast.makeText(this, message, Toast.LENGTH_LONG).show();
           Log.d(TAG, "toastAsync: "+message);
       });
   }
}

backup

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

Manifest

<uses-permission android:name="android.permission.INTERNET"/>

Using Infura Endpoint

https://infura.io/

web3 = ... HtpServer(...)

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