Android + Kotlin: Find Folders And Store Their Names As String Array

I have a PHP script which has the ability to automatically find folders and send their names to the client as string so that they can be used in innerHTML buttons. I'd like to do E

Solution 1:

In Android you should strictly specify the path of the folder you want to view. Start point could be Environment.getExternalStorageDirectory() - the primary shared/external storage directory.

Then you could get list of files with method dir.listFiles(). If you need to filter it somehow (for example have only directories) you could add a FileFilter: dir.listFiles(FileFilter { it.isDirectory })

Another important thing is that you have to have a permission for reading external storange. Thus you should add to your Manifest.xml:

<uses-permissionandroid:name="android.permission.READ_EXTERNAL_STORAGE"/>

Starting from Android 6.0 you should additionally ask for this permission:

Fragment.requestPermissions(arrayOf(Manifest.permission.READ_EXTERNAL_STORAGE), READ_STORAGE_RC)

And handle results in Fragment.onRequestPermissionsResult method.

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I created example of how it could be used together. You need to create activity and add a Fragment inside: DirListFragment

classDirListFragment : Fragment() {

    privateval adapter by lazy { DirListAdapter { dir = it } }
    privatevar dir: File by observable(Environment.getExternalStorageDirectory()) { _, _, _ -> onNewParent() }

    overridefunonCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View =
        inflater.inflate(R.layout.fragment_dir_list, container, false)

    overridefunonViewCreated(view: View, savedInstanceState: Bundle?) {
        checkPermissionReadStorage(requireActivity())
        list.adapter = adapter
        up.setOnClickListener { dir = dir.parentFile }
        onNewParent()
    }

    privatefunonNewParent() {
        parent.text = dir.absolutePath
        adapter.items = dir.listFiles(FileFilter { it.isDirectory })?.toList() ?: emptyList()
    }

    overridefunonRequestPermissionsResult(requestCode: Int, permissions: Array<outString>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == READ_STORAGE_RC && permissionGranted(requireActivity())) onNewParent()
    }

    privatefuncheckPermissionReadStorage(activity: Activity) {
        if (!permissionGranted(activity)) {
            requestPermissions(arrayOf(Manifest.permission.READ_EXTERNAL_STORAGE), READ_STORAGE_RC)
        }
    }

    privatefunpermissionGranted(activity: Activity) =
        ContextCompat.checkSelfPermission(activity, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED

    privatecompanionobject {
        constval READ_STORAGE_RC = 123
    }
}

DirListAdapter

classDirListAdapter(privateval clickListener: (file: File) -> Unit) :
    RecyclerView.Adapter<DirListAdapter.ViewHolder>() {

    var items by Delegates.observable(listOf<File>()) { _, _, _ -> notifyDataSetChanged() }

    overridefunonCreateViewHolder(parent: ViewGroup, viewType: Int) = ViewHolder(parent)

    overridefungetItemCount() = items.size

    overridefunonBindViewHolder(holder: ViewHolder, position: Int) {
        holder.caption.text = items[position].name
        holder.caption.setOnClickListener { clickListener(items[position]) }
    }

    classViewHolder(parent: ViewGroup) : RecyclerView.ViewHolder
        (LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false)) {

        val caption: TextView = itemView.findViewById(android.R.id.text1)
    }
}

fragment_dir_list.xml

<RelativeLayoutxmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"xmlns:app="http://schemas.android.com/apk/res-auto"android:padding="8dp"android:layout_width="match_parent"android:layout_height="match_parent"><Buttonandroid:id="@+id/up"android:text="UP"android:layout_width="wrap_content"android:layout_height="wrap_content"/><TextViewandroid:id="@+id/parent"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@id/up"android:layout_marginBottom="8dp"android:singleLine="true"android:ellipsize="start"tools:text="Parent dir"/><androidx.recyclerview.widget.RecyclerViewandroid:id="@+id/list"android:layout_below="@id/parent"android:layout_width="match_parent"android:layout_height="match_parent"app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/></RelativeLayout>

Hope this will help to understand the basis.