diff --git a/app/src/main/java/cchcc/learn/amu/e04/E04Activity.kt b/app/src/main/java/cchcc/learn/amu/e04/E04Activity.kt
index d01aa1c..509e203 100644
--- a/app/src/main/java/cchcc/learn/amu/e04/E04Activity.kt
+++ b/app/src/main/java/cchcc/learn/amu/e04/E04Activity.kt
@@ -28,27 +28,28 @@ class E04Activity : AppCompatActivity() {
             it.viewModel = viewModel
         }
 
-        viewModel.pickContactAction.observe(this, Observer {
-            permissionOf(Manifest.permission.READ_CONTACTS).checkOrRequest permissionIsGranted@{
-
-                val intent = Intent(Intent.ACTION_PICK, ContactsContract.CommonDataKinds.Phone.CONTENT_URI)
-                startActivityWithResult(intent) { resultCode, data ->
-                    if (resultCode == Activity.RESULT_OK && data?.data != null) {
+        val actionPermissionGrant: () -> Unit = {
+            val intent = Intent(Intent.ACTION_PICK, ContactsContract.CommonDataKinds.Phone.CONTENT_URI)
+            startActivityWithResult(intent) { resultCode, data ->
+                if (resultCode == Activity.RESULT_OK && data?.data != null) {
 
-                        val cursor = contentResolver.query(data.data!!, null, null, null, null)
-                        val nameAndPhone = cursor?.use {
-                            it.moveToFirst()
+                    val cursor = contentResolver.query(data.data!!, null, null, null, null)
+                    val nameAndPhone = cursor?.use {
+                        it.moveToFirst()
 
-                            val name = it.getString(it.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME))
-                            val phone = it.getString(it.getColumnIndexOrThrow(ContactsContract.CommonDataKinds.Phone.DATA))
+                        val name = it.getString(it.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME))
+                        val phone = it.getString(it.getColumnIndexOrThrow(ContactsContract.CommonDataKinds.Phone.DATA))
 
-                            name to phone
-                        } ?: "" to ""
+                        name to phone
+                    } ?: "" to ""
 
-                        viewModel.nameAndPhone.value = nameAndPhone
-                    }
+                    viewModel.nameAndPhone.value = nameAndPhone
                 }
             }
+        }
+
+        viewModel.pickContactAction.observe(this, Observer {
+                permissionOf(Manifest.permission.READ_CONTACTS).checkOrRequest(actionPermissionGrant) {}
         })
     }
 
diff --git a/app/src/main/java/cchcc/learn/amu/util/DialogUtil.kt b/app/src/main/java/cchcc/learn/amu/util/DialogUtil.kt
new file mode 100644
index 0000000..36f0b34
--- /dev/null
+++ b/app/src/main/java/cchcc/learn/amu/util/DialogUtil.kt
@@ -0,0 +1,15 @@
+package cchcc.learn.amu.util
+
+import android.app.Activity
+import android.content.DialogInterface
+import androidx.appcompat.app.AlertDialog
+
+
+fun Activity.showAlert() {
+    val alertDialog = AlertDialog.Builder(this).create()
+    alertDialog.setTitle("Permission Rationale")
+    alertDialog.setMessage("Show detail alert message about why this permission is needed.")
+    alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
+        DialogInterface.OnClickListener { dialog, which -> dialog.dismiss() })
+    alertDialog.show()
+}
\ No newline at end of file
diff --git a/app/src/main/java/cchcc/learn/amu/util/UserPermission.kt b/app/src/main/java/cchcc/learn/amu/util/UserPermission.kt
index 360be17..cbebb10 100644
--- a/app/src/main/java/cchcc/learn/amu/util/UserPermission.kt
+++ b/app/src/main/java/cchcc/learn/amu/util/UserPermission.kt
@@ -13,10 +13,6 @@ class UserPermission(private val activity: Activity, vararg permissions: String)
     lateinit var isGrantedCallback: () -> Unit
     lateinit var notGrantedCallback: () -> Unit
 
-    fun isGranted(): Boolean = perms.all { ContextCompat.checkSelfPermission(activity, it) == PackageManager.PERMISSION_GRANTED }
-
-    fun checkOrRequest(isGranted: () -> Unit) = checkOrRequest(isGranted) {}
-
     /**
      *  1. check if permission is granted
      *  2. if permission is granted, callback `isGranted`, or request permission
@@ -30,11 +26,15 @@ class UserPermission(private val activity: Activity, vararg permissions: String)
         if (permissionIsAllGranted) {
             isGranted()
         } else {
-            isGrantedCallback = isGranted
-            notGrantedCallback = notGranted
-            val requestCode = Math.abs((activity.hashCode() + isGranted.hashCode()).toShort().toInt())
-            activity.permissions.put(requestCode, this)
-            ActivityCompat.requestPermissions(activity, notGrantedPermissions, requestCode)
+            if(shouldShowRequestRational()) {
+                activity.showAlert()
+            } else {
+                isGrantedCallback = isGranted
+                notGrantedCallback = notGranted
+                val requestCode = Math.abs((activity.hashCode() + isGranted.hashCode()).toShort().toInt())
+                activity.permissions.put(requestCode, this)
+                ActivityCompat.requestPermissions(activity, notGrantedPermissions, requestCode)
+            }
         }
     }