I have a recyclerview that uses Glide to show images from Firebase Realtime database. I have a download button in this recyclerview and I want users to be able to download these images once the click the download button. I heard you can use Glide to download images to device internal storage, but I'm unfamiliar with this, so I would like your assistance.

Adapter class

class AbstractAdapter(private val mContext: Context, private val abstractList: ArrayList<Abstract>) :
RecyclerView.Adapter<AbstractAdapter.ViewHolder>() {


override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    val view = LayoutInflater.from(parent.context).inflate(R.layout.abstract_image_view, parent, false)
    return ViewHolder(view)

}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {

    holder.imageView.setOnClickListener {
        val intent = Intent(mContext, AbstractPreview::class.java)
        intent.putExtra("abstract", abstractList[position].abstract.toString())
        Toast.makeText(mContext, "Fullscreen view", Toast.LENGTH_SHORT).show()
        mContext.startActivity(intent)

    }

    holder.downloadBtn.setOnClickListener {
        
    }

    Glide.with(mContext)
        .load(abstractList[position].abstract)
        .into(holder.imageView)
}

override fun getItemCount(): Int {
    return abstractList.size
}

class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    val imageView: ImageView = itemView.findViewById(R.id.abstractImageView)
    val downloadBtn: Button = itemView.findViewById(R.id.abstractDownloadBtn)

}

companion object {
    private const val Tag = "RecyclerView"
}

This is the onClickLister for the download button.

holder.downloadBtn.setOnClickListener {

        }

As you can see, I know how to show images using Glide. All I need to know is how to download those images into the device internal storage.

CodePudding user response：

1. Add Okhttp dependency

First of all you need to have okhttp dependency on your app gradle:

implementation("com.squareup.okhttp3:okhttp:4.10.0")

Note: if you are having retrofit no need to add okhttp dependency

2. Create download function

Ok now we are going to add the download logic in your view model, add okhttp instance declaration and download function to your view model:

Note: you can move download logic to a repository or anywhere you want, it's up to you.

class YourViewModel : ViewModel() {

    // add okhttp instance to your view model or you inject it with hilt if your using dependency injection
    private val okHttpClient = OkHttpClient.Builder().build()

    // add this function to your view model
    fun downloadImage(imageUrl: String) {
        val request = Request.Builder()
            .url(imageUrl)
            .build()

        okHttpClient.newCall(request).enqueue(object : Callback {
            override fun onFailure(call: Call, e: IOException) {
                // Download Failed, you can show error to the user
            }

            override fun onResponse(call: Call, response: Response) {
                if (!response.isSuccessful) {
                    // Download Failed, you can show error to the user
                    return
                }

                response.body?.let { responseBody ->
                    try {
                        // Convert response body to byte array
                        val imageByteArray = responseBody.byteStream().readBytes()

                        // Split image url so we can get the image name
                        val words = imageUrl.split("/").toTypedArray()

                        // Get the image name
                        val imageName = words.last()

                        // Init pathName (Downloads Directory)
                        val pathName = "${Environment.getExternalStorageDirectory()}/${Environment.DIRECTORY_DOWNLOADS}"

                        // Create New file for the image
                        val file = File(pathName, imageName)

                        // Set byteArray To Image File
                        file.writeBytes(imageByteArray)
                    } catch(e: IOException) {
                        // Saving Image Failed, you can show error to the user
                        e.printStackTrace()
                    }
                }
            }
        })
    }

}

3. Pass download function from your fragment to your adapter

Now you need to pass your download function to your adapter inside a lambda function, adapter creation in your fragment should look like this:

val adapter = AbstractAdapter(
    context = requireContext(),
    abstractList = abstractList, // your list here
    downloadImage = { imageUrl ->
        viewModel.downloadImage(imageUrl)
    }
)

Your adapter constructor will look like this:

class AbstractAdapter(
    private val mContext: Context, 
    private val abstractList: ArrayList<Abstract>,
    private val downloadImage: (imageUrl: String) -> Unit
): RecyclerView.Adapter<AbstractAdapter.ViewHolder>()

4. Call downloadImage lambda inside downloadBtn click listener

now we will add downloadImage call inside the click listener

holder.downloadBtn.setOnClickListener {
    val imageUrl = abstractList[position].abstract
    downloadImage(imageUrl)
}

5. Add write external storage permission to AndroidManifest.xml

add this permission to your AndroidManifest.xml file to be able to add files to phone storage

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
        android:maxSdkVersion="28" />

Note: This permission is only required for sqk version <= 28 that's why we added android:maxSdkVersion="28"

I hope that everything is clear. This code should give you the result that you want, try it and tell me if there is anything wrong.