【區塊鏈】以太坊 web3j for java 使用
阿新 • • 發佈:2019-01-04
為使用者建立憑證credentials <2>
環境:mac os & android studio
參考:here
一、初始工作
檢視上一篇文章:here
二、建立credentials
String filePath = Environment.getExternalStorageDirectory().toString() + "/Pictures";
String fileName = WalletUtils.generateNewWalletFile("password",new File(filePath),false);
Credentials credentials = WalletUtils.loadCredentials("password" , filePath+"/"+fileName);
//"password" -> 輸入你的密碼
//這樣就可以建立一個憑證
但是你會遇到問題:
/storage/emulated/0/Pictures/UTC--2017--11-28....json(Permission denied)"
解決辦法:
加上許可權: <!-- SDCard中建立與刪除檔案許可權 --> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> <!-- 向SDCard寫入資料許可權 --> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
但可能還是失敗,不要慌,在建立憑證前加上一段:
int REQUEST_EXTERNAL_STORAGE = 1;
String[] PERMISSIONS_STORAGE = {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE
};
int permission = ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
f (permission != PackageManager.PERMISSION_GRANTED) {
// We don't have permission so prompt the user
ActivityCompat.requestPermissions(
MainActivity.this,
PERMISSIONS_STORAGE,
REQUEST_EXTERNAL_STORAGE
);
}
就可以成功啦:
三、主程式碼
package com.example.pro.blockchain1;
import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import org.web3j.crypto.CipherException;
import org.web3j.crypto.Credentials;
import org.web3j.crypto.WalletUtils;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.Web3jFactory;
import org.web3j.protocol.core.methods.response.Web3ClientVersion;
import org.web3j.protocol.http.HttpService;
import java.io.File;
import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.util.concurrent.ExecutionException;
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private Button showButton;
private TextView textview;
public static final int SHOW = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textview=(TextView)findViewById(R.id.textview);
showButton = (Button) findViewById(R.id.showView);
showButton.setOnClickListener(this);
}
@Override
public void onClick(View v) {
if(v.getId() == R.id.showView) {
show();
}
}
private void show() {
new Thread(new Runnable() {
@Override
public void run() {
try {
String url = "http://10.0.2.2:8545";
Web3j web3 = Web3jFactory.build(new HttpService(url));
Web3ClientVersion web3ClientVersion = web3.web3ClientVersion().sendAsync().get();
String clientVersion = web3ClientVersion.getWeb3ClientVersion();
// 獲取憑證
int REQUEST_EXTERNAL_STORAGE = 1;
String[] PERMISSIONS_STORAGE = {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE
};
int permission = ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
if (permission != PackageManager.PERMISSION_GRANTED) {
// We don't have permission so prompt the user
ActivityCompat.requestPermissions(
MainActivity.this,
PERMISSIONS_STORAGE,
REQUEST_EXTERNAL_STORAGE
);
}
String filePath = Environment.getExternalStorageDirectory().toString() + "/Pictures";
String fileName = WalletUtils.generateNewWalletFile("123456",new File(filePath),false);
Credentials credentials = WalletUtils.loadCredentials("123456", filePath+"/"+fileName);
String myAddress = credentials.getAddress();
textview.setText(myAddress);
} catch (ExecutionException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}catch (IOException e){
e.printStackTrace();
}catch (CipherException e){
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchProviderException e) {
e.printStackTrace();
} catch (InvalidAlgorithmParameterException e) {
e.printStackTrace();
}
}
}).start();
}
}
四、使用私有鏈建立的憑證
這裡我暫時沒有好解決的方法,希望有大佬能解答。以下給出我的方法:
1.開啟本地私有鏈資料夾找到keystore檔案
隨便選取一個,比如:UTC--2017-11-16T08-22-03.297518621Z--ea7cb6058aaf6369c3a97c4a5203364c8c4ff7fa
2.開啟monitor
工具欄: Tools -> Android -> Android Device Monitor
3.把keystore檔案放入sdcard/目錄下
- 安卓端程式碼
/* 使用已存在憑證 */
String filePath = "sdcard/";
String fileName = "UTC--2017-11-16T08-22-03.297518621Z--ea7cb6058aaf6369c3a97c4a5203364c8c4ff7fa";
Credentials credentials = WalletUtils.loadCredentials("123456", filePath + "/" + fileName);
String myAddress = credentials.getAddress();
textview.setText(myAddress);
可以檢視到ea7cb6058aaf6369c3a97c4a5203364c8c4ff7fa的地址