将字节数组转换为pdf文件，然后保存它

Question

我正在用Kotlin Android应用程序访问API端点。在此API调用中，我返回一个字节数组。我想看到的是一种将字节数组转换为pdf文件并将其保存在手机下载文件夹中的方法。

    private suspend fun getIDCard(sessionID: String?, carriermemid: String?): ByteArray? {
        var results: String = ""

        val postData = "{\"sessionid\": \" $sessionID\"}"
        val outputStreamWriter: OutputStreamWriter

        var byteArray: ByteArray? = null
        val url: URL = URL(idURL + carriermemid)
        val conn: HttpURLConnection = url.openConnection() as HttpURLConnection

        try {
            conn.setRequestProperty(apiConfig.typeKey, apiConfig.typeValueJSON)
            conn.setRequestProperty("Accept", "application/json")
            conn.setRequestProperty("sessionid", sessionID)
            conn.requestMethod = apiConfig.methodGet


            val responseCode: Int = conn.responseCode
            println("Response Code :: $responseCode")
            //returning 404
            return if (responseCode == HttpURLConnection.HTTP_OK) {// connection ok
                var out: ByteArrayOutputStream? = ByteArrayOutputStream()
                val `in`: InputStream = conn.inputStream
                var bytesRead: Int
                val buffer = ByteArray(1024)
                while (`in`.read(buffer).also { bytesRead = it } > 0) {
                    out!!.write(buffer, 0, bytesRead)
                }
                out!!.close()
                byteArray = out.toByteArray()
                return byteArray

            } else {
                return byteArray
            }

        } catch (ex: Exception) {
            ex.printStackTrace()
        } finally {
            conn.disconnect()
        }
        return byteArray
    }

Answer 1

这将获得Android下载目录，并将字节数组写为PDF文件（假设字节数组包含PDF）。将File.createTempFile更改为您喜欢的任何文件（无需创建临时文件）：

fun writeBytesAsPdf(bytes : ByteArray) {
   val path = requireContext().getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)
    var file = File.createTempFile("my_file",".pdf", path)
    var os = FileOutputStream(file);
    os.write(bytes);
    os.close();
}

您还必须将android.permission.WRITE_EXTERNAL_STORAGE添加到清单中。

Answer 2

查看How to download PDF file with Retrofit and Kotlin coroutines?，您可以使用：

private const val BUFFER_SIZE = 4 * 1024

private fun copyStreamToFile(inputStream: InputStream, outputFile: File) {
    inputStream.use { input ->
        val outputStream = FileOutputStream(outputFile)
        outputStream.use { output ->
            val buffer = ByteArray(BUFFER_SIZE)
            while (true) {
                val byteCount = input.read(buffer)
                if (byteCount < 0) break
                output.write(buffer, 0, byteCount)
            }
            output.flush()
        }
    }
}

或

private fun InputStream.saveToFile(file: String) = use { input ->
    File(file).outputStream().use { output ->
        input.copyTo(output)
    }
}

还应该创建文件。

private fun createFile(context: Context, name: String): File? {
    val storageDir = context.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)?.path
    var file = File("$storageDir/$name.pdf")
    return storageDir?.let { file }
}