make use of AndroidX implementation due to deprecated standard sdk implementation

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

src/main/java/com/owncloud/android/ui/activity/DrawerActivity.java

@@ -456,7 +456,7 @@ public abstract class DrawerActivity extends ToolbarActivity implements DisplayU
             case R.id.nav_logout:
                 mCheckedMenuItem = -1;
                 menuItem.setChecked(false);
-                UserInfoActivity.openAccountRemovalConfirmationDialog(getAccount(), getFragmentManager(), true);
+                UserInfoActivity.openAccountRemovalConfirmationDialog(getAccount(), getSupportFragmentManager(), true);
                 break;
             case R.id.drawer_menu_account_add:
                 boolean isProviderOrOwnInstallationVisible = getResources()

src/main/java/com/owncloud/android/ui/activity/StorageMigration.java

@@ -22,7 +22,6 @@ package com.owncloud.android.ui.activity;
 
 import android.accounts.Account;
 import android.accounts.AccountManager;
-import android.app.AlertDialog;
 import android.app.ProgressDialog;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -39,6 +38,8 @@ import com.owncloud.android.utils.FileStorageUtils;
 
 import java.io.File;
 
+import androidx.appcompat.app.AlertDialog;
+
 /**
  * @author Bartosz Przybylski
  */

src/main/java/com/owncloud/android/ui/activity/UserInfoActivity.java

@@ -27,8 +27,6 @@ import android.accounts.Account;
 import android.accounts.AccountManager;
 import android.app.AlertDialog;
 import android.app.Dialog;
-import android.app.DialogFragment;
-import android.app.FragmentManager;
 import android.content.ContentResolver;
 import android.content.Intent;
 import android.graphics.PorterDuff;
@@ -81,6 +79,8 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import androidx.core.graphics.drawable.DrawableCompat;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.FragmentManager;
 import androidx.recyclerview.widget.RecyclerView;
 import butterknife.BindString;
 import butterknife.BindView;
@@ -174,7 +174,7 @@ public class UserInfoActivity extends FileActivity {
                 onBackPressed();
                 break;
             case R.id.delete_account:
-                openAccountRemovalConfirmationDialog(account, getFragmentManager(), false);
+                openAccountRemovalConfirmationDialog(account, getSupportFragmentManager(), false);
                 break;
             default:
                 retval = super.onOptionsItemSelected(item);

src/main/java/com/owncloud/android/ui/dialog/RemoveFilesDialogFragment.java

@@ -19,7 +19,6 @@
 
 package com.owncloud.android.ui.dialog;
 
-import android.app.AlertDialog;
 import android.app.Dialog;
 import android.os.Bundle;
 import android.view.ActionMode;
@@ -34,6 +33,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 
 import androidx.annotation.NonNull;
+import androidx.appcompat.app.AlertDialog;
 
 /**
  *  Dialog requiring confirmation before removing a collection of given OCFiles.
@@ -133,7 +133,7 @@ public class RemoveFilesDialogFragment extends ConfirmationDialogFragment implem
 
         int color = ThemeUtils.primaryAccentColor(getActivity());
 
-        androidx.appcompat.app.AlertDialog alertDialog = (androidx.appcompat.app.AlertDialog) getDialog();
+        AlertDialog alertDialog = (AlertDialog) getDialog();
 
         alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setTextColor(color);
         alertDialog.getButton(AlertDialog.BUTTON_NEGATIVE).setTextColor(color);