这里使用bitcoinj库，来实现生成bip39的12个助记词，引用库

implementation ‘org.bitcoinj:bitcoinj-core:0.14.7’

填坑1

如果你直接引用库之后，直接安装运行apk，会造成app崩溃，这是因为这个库里面有一个libscrypt.dylib，这个库是针对x86_64平台的，并且没有其他平台的这个库，所以在arm cpu平台的手机app会崩溃，解决方案就是在gradle的android节点下，加上以下配置

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packagingOptions {
       exclude 'lib/x86_64/darwin/libscrypt.dylib'
       exclude 'com/google/thirdparty/publicsuffix/PublicSuffixPatterns.gwt.xml'
       exclude 'com/google/thirdparty/publicsuffix/PublicSuffixType.gwt.xml'
       exclude 'org/bitcoinj/crypto/mnemonic/wordlist/english.txt'
       exclude 'org/bitcoinj/crypto/cacerts'
   }

填坑2

我们要得到12个随机的单词，就要用到里面的MnemonicCode类，但是这个类，默认会new一个实例出来，并且默认加载的单词库路径方式是不支持android的，官方代码如下

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static {
     try {
         INSTANCE = new MnemonicCode();
     } catch (FileNotFoundException e) {
         // We expect failure on Android. The developer has to set INSTANCE themselves.
         if (!Utils.isAndroidRuntime())
             log.error("Could not find word list", e);
     } catch (IOException e) {
         log.error("Failed to load word list", e);
     }
 }

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/** Initialise from the included word list. Won't work on Android. */
   public MnemonicCode() throws IOException {
       this(openDefaultWords(), BIP39_ENGLISH_SHA256);
   }

   private static InputStream openDefaultWords() throws IOException {
       InputStream stream = MnemonicCode.class.getResourceAsStream(BIP39_ENGLISH_RESOURCE_NAME);
       if (stream == null)
           throw new FileNotFoundException(BIP39_ENGLISH_RESOURCE_NAME);
       return stream;
   }

可以从代码中看出来，在android平台此路径是绝对不可用的，所以我们要手动自己new这个对象，使用public MnemonicCode(InputStream wordstream, String wordListDigest) throws IOException, IllegalArgumentException这个构造函数

具体实现代码

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public static void generateMnemonic(Context context) throws Exception {
    MnemonicCode mnemonicCode = new MnemonicCode(context.getAssets().open("english.txt"), null);

    SecureRandom secureRandom = SecureRandomUtils.secureRandom();
    byte[] initialEntropy = new byte[16];//算法需要，必须是被4整除
    secureRandom.nextBytes(initialEntropy);
    List<String> wd = mnemonicCode.toMnemonic(initialEntropy);
    if (wd == null || wd.size() != 12)
        throw new RuntimeException("generate word error");
    else {
        words.clear();
        words.addAll(wd);
        LogUtils.d(words.toString());
    }
}