Android 从AssetManager以InputStream形式读取文件后发生java.lang.NullPointerException

AssetManager的定义和使用：

...
AssetManager mngr = getAssets();
try{
      encrypter.decrypt(mngr.open("sample.txt"),output_file);
}...(continued)

解密函数：

public void decrypt(InputStream in, OutputStream out)
    {
            try
            {
                    // Bytes read from in will be decrypted
                    in = new CipherInputStream(in, dcipher);
                    // Read in the decrypted bytes and write the cleartext to out
                    int numRead = 0;
                    while ((numRead = in.read(buf)) >= 0)
                    {
                      out.write(buf, 0, numRead);
                    }
                    out.close();
            ...(continued)

它给行out.write（buf，0，numRead）的错误作为java.lang.NullPointerException

此呼叫在用作以下用途时工作正常：

*encrypter.decrypt（新文件输入流（“sample.txt”），输出文件）*（即从android的本地资产目录读取文件时）

有什么原因吗

---

感谢您的帮助！谢谢

您的OutputStream未初始化。因此您将获得空指针异常。您可能需要 像这样的

 public void decrypt(InputStream in,String file)
        {
                try
                {
                 OutputStream out = new FileOutputStream(file);
                        // Bytes read from in will be decrypted
                        in = new CipherInputStream(in, dcipher);
                        // Read in the decrypted bytes and write the cleartext to out
                        int numRead = 0;
                        while ((numRead = in.read(buf)) >= 0)
                        {
                          out.write(buf, 0, numRead);
                        }
                        out.close();

---

您的OutputStream未初始化。因此您得到的是空指针异常。您可能需要 像这样的

 public void decrypt(InputStream in,String file)
        {
                try
                {
                 OutputStream out = new FileOutputStream(file);
                        // Bytes read from in will be decrypted
                        in = new CipherInputStream(in, dcipher);
                        // Read in the decrypted bytes and write the cleartext to out
                        int numRead = 0;
                        while ((numRead = in.read(buf)) >= 0)
                        {
                          out.write(buf, 0, numRead);
                        }
                        out.close();

---

显示完整代码，我的意思是声明哪部分的声明。。AssetManager？显示完整代码，我指的是声明哪部分的声明。。AssetManager？谢谢问题正是你说的。。非常感谢，谢谢问题正是你说的。。非常感谢。