Fetch PDF content and open in the app — Android with Kotlin

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Another solution to fetch PDF content and open it on your android device.

I was struggling to find a better solution on the internet to fetch a PDF file content like in a Stream and then display it in a PDF application on my android device. I couldn’t find a good and neat solution. Here I will explain how you can fetch and display a PDF file.

Firstly, I am using the Retrofit HTTP client. Example:

@GET("files/{id}/pdf")
suspend fun getPDF(
    @Path("id") id: String
): Response<ResponseBody>

You can see response type is ResponseBody. Then, get InputStream from responseBody like response.byteStream() and pass it to your method to parse, save and display file. Example:

fun openPDFContent(context: Context, inputStream: InputStream, fileName: String) {
//saving in cache directory
val filePath = context.externalCacheDir?.absolutePath ?: context.cacheDir.absolutePath
    val fileNameExtension =
        if (fileName.isNotNullOrEmpty()) fileName else context.getString(R.string.app_name) + ".pdf"
    val file = inputStream.saveToFile(filePath, fileNameExtension)

    val uri = FileProvider.getUriForFile(
        context,
        BuildConfig.APPLICATION_ID + ".provider", file
    )
    val intent = Intent(Intent.ACTION_VIEW).apply {
        addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
        addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
        setDataAndType(uri, "application/pdf")
    }
    context.startActivity(Intent.createChooser(intent, "Select app"))
}

I am saving the file in the application cache temporarily because I don’t need to ask for any permission from the user to save the file and when a user view in a PDF application then user can download or share: context.externalCacheDir?.absolutePath but if you want, you can download in external directory but then you would have to ask for read/write permission: Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).absolutePath

You must have noticed the saveToFile extension function. I have used a very neat and short form of kotlin extension function to create and write a PDF file:

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

Are we missing anything?

Yes, we are missing Provider in manifest.xml inside application tag:

<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/provider_paths" />
</provider>

Define provider_paths in res->xml->provider_paths.xml:

<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path
        name="external"
        path="." />
    <external-files-path
        name="external_files"
        path="." />
    <cache-path
        name="cache"
        path="." />
    <external-cache-path
        name="external_cache"
        path="." />
    <files-path
        name="files"
        path="." />
</paths>

I have defined all paths so you can get an idea.

I hope it will work fine for you. Happy coding 😊

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