Permissions

Android applications are isolated from the operating system. Because of this they need to request permission to perform and accesss certain operations and actions.

Andriod Manifest

Defines the permissions needed

  <manifest xmlns:android=
     "http://schemas.android.com/apk/res/android" 
     package="com.journaler"> 

      <uses-permission android:name="android.permission.INTERNET" /> 
      <uses-permission android:name=
       "android.permission.RECEIVE_BOOT_COMPLETED" /> 
      <uses-permission android:name=
       "android.permission.READ_EXTERNAL_STORAGE" /> 
      <uses-permission android:name=
       "android.permission.WRITE_EXTERNAL_STORAGE" /> 
      <uses-permission android:name=
       "android.permission.ACCESS_NETWORK_STATE" /> 
      <uses-permission android:name=
       "android.permission.ACCESS_FINE_LOCATION" /> 
      <uses-permission android:name=
       "android.permission.ACCESS_COARSE_LOCATION" /> 
      <uses-permission android:name="android.permission.VIBRATE" /> 
       <application ... > 
         ... 
       </application 

       ... 

     </manifest>

Runtime Permissions

Some permissions have to be requested at Runtime, with the ActivityCompat.requestPermissions method. The results are available in the onRequestPermissionsResult method.

    abstract class BaseActivity : AppCompatActivity() {
      companion object { 
      val REQUEST_GPS = 0 
      ... }
      ... 
      override fun onCreate(savedInstanceState: Bundle?) {   
        super.onCreate(savedInstanceState)
        ...
        requestGpsPermissions() } 
     ...
     private fun requestGpsPermissions() {   
       ActivityCompat.requestPermissions( 
         this@BaseActivity,
         arrayOf( 
           Manifest.permission.ACCESS_FINE_LOCATION,
           Manifest.permission.ACCESS_COARSE_LOCATION ),
           REQUEST_GPS ) }
            ... 
      override fun onRequestPermissionsResult(
        requestCode:
         Int, permissions: Array<String>, grantResults: IntArray ) {
           if (requestCode == REQUEST_GPS) { 
            for (grantResult in grantResults) 
            { if (grantResult == PackageManager.PERMISSION_GRANTED)
             { Log.i( tag, String.format( Locale.ENGLISH, "Permission 
              granted [ %d ]", requestCode ) ) 
             } 
             else {
               Log.e( tag, String.format( Locale.ENGLISH, "Permission
               not granted [ %d ]", requestCode ) )
             } } } } }

Kotlin simplifications

interface PermissionRequestCallback { 
       fun onPermissionGranted(permissions: List<String>) 
       fun onPermissionDenied(permissions: List<String>) 
     }

 abstract class PermissionCompatActivity : AppCompatActivity() { 

       private val tag = "Permissions extension" 
       private val latestPermissionRequest = AtomicInteger() 
       private val permissionRequests = ConcurrentHashMap<Int,
       List<String>>() 
       private val permissionCallbacks =  
        ConcurrentHashMap<List<String>, PermissionRequestCallback>() 

       private val defaultPermissionCallback = object :  
       PermissionRequestCallback { 
         override fun onPermissionGranted(permissions: List<String>) { 
            Log.i(tag, "Permission granted [ $permissions ]") 
         } 
         override fun onPermissionDenied(permissions: List<String>) { 
            Log.e(tag, "Permission denied [ $permissions ]") 
         } 
      } 

     fun requestPermissions( 
        vararg permissions: String,  
        callback: PermissionRequestCallback = defaultPermissionCallback 
     ) { 
        val id = latestPermissionRequest.incrementAndGet() 
        val items = mutableListOf<String>() 
        items.addAll(permissions) 
        permissionRequests[id] = items 
        permissionCallbacks[items] = callback 
        ActivityCompat.requestPermissions(this, permissions, id) 
     } 

     override fun onRequestPermissionsResult( 
        requestCode: Int,  
        permissions: Array<String>,  
        grantResults: IntArray 
     ) { 
        val items = permissionRequests[requestCode] 
        items?.let { 
           val callback = permissionCallbacks[items] 
           callback?.let { 
             var success = true 
              for (x in 0..grantResults.lastIndex) { 
                  val result = grantResults[x] 
                  if (result != PackageManager.PERMISSION_GRANTED) { 
                      success = false 
                      break 
                  } 
              } 
              if (success) { 
                 callback.onPermissionGranted(items) 
              } else { 
                  callback.onPermissionDenied(items) 
              } 
             } 
           } 
         } 
     }

use

 abstract class BaseActivity : PermissionCompatActivity() { 
     ... 
     override fun onCreate(savedInstanceState: Bundle?) { 
         ... 
         requestPermissions( 
            Manifest.permission.ACCESS_FINE_LOCATION, 
            Manifest.permission.ACCESS_COARSE_LOCATION 
         ) 
     } 
     ... 
    }