Kotlin. Doesn't show files in the directory - kotlin

Question

Good evening! I can't output files in a specific directory on an android device, and I can't solve it.
Here is the program code
package com.example.nt_music
import android.os.Bundle
import android.os.Environment
import androidx.appcompat.app.AppCompatActivity
import java.io.File
import java.util.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
println()
//readSongs(dir, ext)
val gpath: String = Environment.getExternalStorageDirectory().absolutePath
val spath = "Music"
val fullpath = File(gpath + File.separator + spath)
println("fullpath")
println(fullpath)
imageReaderNew(fullpath)
}
fun imageReaderNew(root: File) {
val fileList: ArrayList<File> = ArrayList()
val listAllFiles = root.listFiles()
if (listAllFiles == null) println("null")
if (listAllFiles != null && listAllFiles.size > 0) {
for (currentFile in listAllFiles) {
if (currentFile.name.endsWith(".mp3")) {
// File absolute path
println("downloadFilePath")
println( currentFile.getAbsolutePath())
// File Name
println("downloadFileName")
println(currentFile.getName())
fileList.add(currentFile.absoluteFile)
}
}
println("fileList")
println(fileList.size)
}
}
}
in the AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.nt_music">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:launchMode="singleTop"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
Perhaps I put something wrong in it or something needs to be added
output:
I/System.out: fullpath
/storage/emulated/0/Music
I/System.out: null
But why null!?
maybe it has something to do with these errors that appear in the console
E/libc: Access denied finding property "ro.vendor.df.effect.conflict"
E/Perf: Fail to get file list com.example.nt_music
E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array
Fail to get file list com.example.nt_music
getFolderSize() : Exception_1 = java.lang.NullPointerException: Attempt to get length of null array

Answer 1

You can check the required permissions programmatically by calling this method
fun checkPermissions()
{
this.onPermissionGranted = onPermissionGranted
val ungrantedPermissions = requiredPermissionsStillNeeded()
if (ungrantedPermissions.isEmpty()) {
// All permission granted, you can list your files...
} else {
ActivityCompat.requestPermissions(activity, ungrantedPermissions, 1)
}
}
This function calls this method
private fun requiredPermissionsStillNeeded(): Array<String>
{
val permissions = HashSet<String>()
for (permission in getRequiredPermissions()) {
permissions.add(permission)
}
val i = permissions.iterator()
while (i.hasNext()) {
val permission = i.next()
if (ContextCompat.checkSelfPermission(activity, permission) == PackageManager.PERMISSION_GRANTED) {
i.remove()
}
}
return permissions.toTypedArray()
}
private fun getRequiredPermissions(): Array<String>
{
var permissions: Array<String>? = null
try {
permissions = activity.packageManager.getPackageInfo(activity.packageName, PackageManager.GET_PERMISSIONS).requestedPermissions
} catch (e: PackageManager.NameNotFoundException) {
e.printStackTrace()
}
return permissions?.clone() ?: arrayOf()
}
Lastly, you'll need to override this method in your activity. It is called recursively until your user has granted all the permissions needed by the app.
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
checkPermissions()
}
After that, your app should be able to list the files in the folder.
EDIT
These are all functions that check whether the users have granted you the required permissions.
You should add them to your MainActivity class and edit your onCreate method like this
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
println()
//readSongs(dir, ext)
checkPermissions()
}
And then call your list file function in checkPermissions() like this
fun checkPermissions()
{
this.onPermissionGranted = onPermissionGranted
val ungrantedPermissions = requiredPermissionsStillNeeded()
if (ungrantedPermissions.isEmpty()) {
val gpath: String = Environment.getExternalStorageDirectory().absolutePath
val spath = "Music"
val fullpath = File(gpath + File.separator + spath)
println("fullpath")
println(fullpath)
imageReaderNew(fullpath)
} else {
ActivityCompat.requestPermissions(activity, ungrantedPermissions, 1)
}
}