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

1. 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