Convert to Kotlin

Signed-off-by: alperozturk <alper_ozturk@proton.me>

app/src/main/java/com/owncloud/android/ui/preview/PreviewImageActivity.kt

@@ -11,396 +11,358 @@
  * SPDX-FileCopyrightText: 2013 David A. Velasco <dvelasco@solidgear.es>
  * SPDX-License-Identifier: GPL-2.0-only AND (AGPL-3.0-or-later OR GPL-2.0-only)
  */
-package com.owncloud.android.ui.preview;
-
-import android.annotation.SuppressLint;
-import android.content.BroadcastReceiver;
-import android.content.Context;
-import android.content.Intent;
-import android.content.IntentFilter;
-import android.os.Bundle;
-import android.view.MenuItem;
-import android.view.View;
-
-import com.nextcloud.client.account.User;
-import com.nextcloud.client.di.Injectable;
-import com.nextcloud.client.editimage.EditImageActivity;
-import com.nextcloud.client.jobs.download.FileDownloadHelper;
-import com.nextcloud.client.jobs.download.FileDownloadWorker;
-import com.nextcloud.client.jobs.upload.FileUploadWorker;
-import com.nextcloud.client.preferences.AppPreferences;
-import com.nextcloud.model.WorkerState;
-import com.nextcloud.model.WorkerStateLiveData;
-import com.nextcloud.utils.extensions.IntentExtensionsKt;
-import com.owncloud.android.MainApp;
-import com.owncloud.android.R;
-import com.owncloud.android.datamodel.FileDataStorageManager;
-import com.owncloud.android.datamodel.OCFile;
-import com.owncloud.android.datamodel.VirtualFolderType;
-import com.owncloud.android.lib.common.operations.OnRemoteOperationListener;
-import com.owncloud.android.lib.common.operations.RemoteOperation;
-import com.owncloud.android.lib.common.operations.RemoteOperationResult;
-import com.owncloud.android.lib.common.utils.Log_OC;
-import com.owncloud.android.operations.RemoveFileOperation;
-import com.owncloud.android.operations.SynchronizeFileOperation;
-import com.owncloud.android.ui.activity.FileActivity;
-import com.owncloud.android.ui.activity.FileDisplayActivity;
-import com.owncloud.android.ui.fragment.FileFragment;
-import com.owncloud.android.ui.fragment.GalleryFragment;
-import com.owncloud.android.ui.fragment.OCFileListFragment;
-import com.owncloud.android.utils.MimeTypeUtil;
-
-import java.io.Serializable;
-import java.util.Optional;
-
-import javax.inject.Inject;
-
-import androidx.annotation.NonNull;
-import androidx.appcompat.app.ActionBar;
-import androidx.drawerlayout.widget.DrawerLayout;
-import androidx.localbroadcastmanager.content.LocalBroadcastManager;
-import androidx.viewpager2.widget.ViewPager2;
-import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+package com.owncloud.android.ui.preview
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.os.Build
+import android.os.Bundle
+import android.view.MenuItem
+import android.view.View
+import android.view.WindowInsets
+import android.view.WindowInsetsController
+import androidx.appcompat.app.ActionBar
+import androidx.drawerlayout.widget.DrawerLayout
+import androidx.localbroadcastmanager.content.LocalBroadcastManager
+import androidx.viewpager2.widget.ViewPager2
+import androidx.viewpager2.widget.ViewPager2.OnPageChangeCallback
+import com.nextcloud.client.account.User
+import com.nextcloud.client.di.Injectable
+import com.nextcloud.client.editimage.EditImageActivity
+import com.nextcloud.client.jobs.download.FileDownloadHelper
+import com.nextcloud.client.jobs.download.FileDownloadWorker
+import com.nextcloud.client.jobs.download.FileDownloadWorker.Companion.getDownloadFinishMessage
+import com.nextcloud.client.jobs.upload.FileUploadWorker.Companion.getUploadFinishMessage
+import com.nextcloud.client.preferences.AppPreferences
+import com.nextcloud.model.WorkerState
+import com.nextcloud.model.WorkerStateLiveData
+import com.nextcloud.utils.extensions.getParcelableArgument
+import com.nextcloud.utils.extensions.getSerializableArgument
+import com.owncloud.android.MainApp
+import com.owncloud.android.R
+import com.owncloud.android.datamodel.FileDataStorageManager
+import com.owncloud.android.datamodel.OCFile
+import com.owncloud.android.datamodel.VirtualFolderType
+import com.owncloud.android.lib.common.operations.OnRemoteOperationListener
+import com.owncloud.android.lib.common.operations.RemoteOperation
+import com.owncloud.android.lib.common.operations.RemoteOperationResult
+import com.owncloud.android.lib.common.utils.Log_OC
+import com.owncloud.android.operations.RemoveFileOperation
+import com.owncloud.android.operations.SynchronizeFileOperation
+import com.owncloud.android.ui.activity.FileActivity
+import com.owncloud.android.ui.activity.FileDisplayActivity
+import com.owncloud.android.ui.fragment.FileFragment
+import com.owncloud.android.ui.fragment.GalleryFragment
+import com.owncloud.android.ui.fragment.OCFileListFragment
+import com.owncloud.android.utils.MimeTypeUtil
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings
+import java.io.Serializable
+import javax.inject.Inject
+import kotlin.math.max
 
 /**
- *  Holds a swiping gallery where image files contained in an Nextcloud directory are shown.
+ * Holds a swiping gallery where image files contained in an Nextcloud directory are shown.
  */
-@SuppressWarnings("PMD.AvoidDuplicateLiterals")
-public class PreviewImageActivity extends FileActivity implements
-    FileFragment.ContainerActivity,
-    OnRemoteOperationListener,
-    Injectable {
-
-    public static final String TAG = PreviewImageActivity.class.getSimpleName();
-    public static final String EXTRA_VIRTUAL_TYPE = "EXTRA_VIRTUAL_TYPE";
-    private static final String KEY_WAITING_FOR_BINDER = "WAITING_FOR_BINDER";
-    private static final String KEY_SYSTEM_VISIBLE = "TRUE";
-
-    private OCFile livePhotoFile;
-    private ViewPager2 viewPager;
-    private PreviewImagePagerAdapter previewImagePagerAdapter;
-    private int savedPosition;
-    private boolean hasSavedPosition;
-    private boolean requestWaitingForBinder;
-    private DownloadFinishReceiver downloadFinishReceiver;
-    private View fullScreenAnchorView;
-    private boolean isDownloadWorkStarted = false;
-
-    @Inject AppPreferences preferences;
-    @Inject LocalBroadcastManager localBroadcastManager;
-
-    private ActionBar actionBar;
-
-    public static Intent previewFileIntent(Context context, User user, OCFile file) {
-        final Intent intent = new Intent(context, PreviewImageActivity.class);
-        intent.putExtra(FileActivity.EXTRA_FILE, file);
-        intent.putExtra(FileActivity.EXTRA_USER, user);
-        return intent;
-    }
-
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
-        actionBar = getSupportActionBar();
-
-        if (savedInstanceState != null && !savedInstanceState.getBoolean(KEY_SYSTEM_VISIBLE, true) &&
-            actionBar != null) {
-            actionBar.hide();
+class PreviewImageActivity : FileActivity(), FileFragment.ContainerActivity, OnRemoteOperationListener, Injectable {
+    private var livePhotoFile: OCFile? = null
+    private var viewPager: ViewPager2? = null
+    private var previewImagePagerAdapter: PreviewImagePagerAdapter? = null
+    private var savedPosition = 0
+    private var hasSavedPosition = false
+    private var requestWaitingForBinder = false
+    private var downloadFinishReceiver: DownloadFinishReceiver? = null
+    private var fullScreenAnchorView: View? = null
+    private var isDownloadWorkStarted = false
+
+    @Inject
+    lateinit var preferences: AppPreferences
+
+    @Inject
+    lateinit var localBroadcastManager: LocalBroadcastManager
+
+    private var actionBar: ActionBar? = null
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        actionBar = supportActionBar
+
+        if (savedInstanceState != null && !savedInstanceState.getBoolean(
+                KEY_SYSTEM_VISIBLE,
+                true
+            ) && actionBar != null
+        ) {
+            actionBar?.hide()
         }
 
-        setContentView(R.layout.preview_image_activity);
+        setContentView(R.layout.preview_image_activity)
 
-        livePhotoFile = IntentExtensionsKt.getParcelableArgument(getIntent(), EXTRA_LIVE_PHOTO_FILE, OCFile.class);
+        livePhotoFile = intent.getParcelableArgument(EXTRA_LIVE_PHOTO_FILE, OCFile::class.java)
 
-        // Navigation Drawer
-        setupDrawer();
+        setupDrawer()
 
-        // ActionBar
-        OCFile chosenFile = IntentExtensionsKt.getParcelableArgument(getIntent(), FileActivity.EXTRA_FILE, OCFile.class);
-        updateActionBarTitleAndHomeButton(chosenFile);
+        val chosenFile = intent.getParcelableArgument(EXTRA_FILE, OCFile::class.java)
+        updateActionBarTitleAndHomeButton(chosenFile)
 
         if (actionBar != null) {
-            viewThemeUtils.files.setWhiteBackButton(this, actionBar);
-            actionBar.setDisplayHomeAsUpEnabled(true);
+            viewThemeUtils.files.setWhiteBackButton(this, actionBar!!)
+            actionBar?.setDisplayHomeAsUpEnabled(true)
         }
 
-        fullScreenAnchorView = getWindow().getDecorView();
+        fullScreenAnchorView = window.decorView
         // to keep our UI controls visibility in line with system bars visibility
-        setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);
+        setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
 
-        if (savedInstanceState != null) {
-            requestWaitingForBinder = savedInstanceState.getBoolean(KEY_WAITING_FOR_BINDER);
-        } else {
-            requestWaitingForBinder = false;
-        }
+        requestWaitingForBinder = savedInstanceState?.getBoolean(KEY_WAITING_FOR_BINDER) ?: false
 
-        observeWorkerState();
+        observeWorkerState()
     }
 
-    public void toggleActionBarVisibility(boolean hide) {
+    fun toggleActionBarVisibility(hide: Boolean) {
         if (actionBar == null) {
-            return;
+            return
         }
 
         if (hide) {
-            actionBar.hide();
+            actionBar?.hide()
         } else {
-            actionBar.show();
+            actionBar?.show()
         }
     }
 
-    private void initViewPager(User user) {
-        // virtual folder
-        final Serializable virtualFolderType = IntentExtensionsKt.getSerializableArgument(getIntent(), EXTRA_VIRTUAL_TYPE, Serializable.class);
-        if (virtualFolderType != null && virtualFolderType != VirtualFolderType.NONE) {
-            VirtualFolderType type = (VirtualFolderType) virtualFolderType;
+    private fun initViewPager(user: User) {
+        val virtualFolderType = intent.getSerializableArgument(EXTRA_VIRTUAL_TYPE, Serializable::class.java)
+        if (virtualFolderType != null && virtualFolderType !== VirtualFolderType.NONE) {
+            val type = virtualFolderType as VirtualFolderType
 
-            previewImagePagerAdapter = new PreviewImagePagerAdapter(this,
-                                                                    type,
-                                                                    user,
-                                                                    getStorageManager());
+            previewImagePagerAdapter = PreviewImagePagerAdapter(
+                this,
+                type,
+                user,
+                storageManager
+            )
         } else {
             // get parent from path
-            OCFile parentFolder = getStorageManager().getFileById(getFile().getParentId());
+            var parentFolder = storageManager.getFileById(file.parentId)
 
             if (parentFolder == null) {
                 // should not be necessary
-                parentFolder = getStorageManager().getFileByEncryptedRemotePath(OCFile.ROOT_PATH);
+                parentFolder = storageManager.getFileByEncryptedRemotePath(OCFile.ROOT_PATH)
             }
 
-            previewImagePagerAdapter = new PreviewImagePagerAdapter(
+            previewImagePagerAdapter = PreviewImagePagerAdapter(
                 this,
                 livePhotoFile,
                 parentFolder,
                 user,
-                getStorageManager(),
+                storageManager,
                 MainApp.isOnlyOnDevice(),
                 preferences
-            );
+            )
         }
 
-        viewPager = findViewById(R.id.fragmentPager);
+        viewPager = findViewById(R.id.fragmentPager)
 
-        int position = hasSavedPosition ? savedPosition : previewImagePagerAdapter.getFilePosition(getFile());
-        position = Math.max(position, 0);
+        var position = if (hasSavedPosition) savedPosition else previewImagePagerAdapter?.getFilePosition(file)
+        position = position?.toDouble()?.let { max(it, 0.0).toInt() }
 
-        viewPager.setAdapter(previewImagePagerAdapter);
-        viewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
-            @Override
-            public void onPageSelected(int position) {
-                selectPage(position);
+        viewPager?.setAdapter(previewImagePagerAdapter)
+        viewPager?.registerOnPageChangeCallback(object : OnPageChangeCallback() {
+            override fun onPageSelected(position: Int) {
+                selectPage(position)
             }
-        });
-        viewPager.setCurrentItem(position, false);
+        })
+        if (position != null) {
+            viewPager?.setCurrentItem(position, false)
+        }
 
-        if (position == 0 && !getFile().isDown()) {
+        if (position == 0 && !file.isDown) {
             // this is necessary because mViewPager.setCurrentItem(0) just after setting the
             // adapter does not result in a call to #onPageSelected(0)
-            requestWaitingForBinder = true;
+            requestWaitingForBinder = true
         }
     }
 
-    @Override
-    public void onBackPressed() {
-        sendRefreshSearchEventBroadcast();
-        super.onBackPressed();
+    override fun onBackPressed() {
+        sendRefreshSearchEventBroadcast()
+        super.onBackPressed()
     }
 
-    @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
-        if (item.getItemId() == android.R.id.home) {
-            sendRefreshSearchEventBroadcast();
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        if (item.itemId != android.R.id.home) {
+            return super.onOptionsItemSelected(item)
+        }
+
+        sendRefreshSearchEventBroadcast()
 
-            if (isDrawerOpen()) {
-                closeDrawer();
-            } else {
-                backToDisplayActivity();
-            }
-            return true;
+        if (isDrawerOpen) {
+            closeDrawer()
         } else {
-            return super.onOptionsItemSelected(item);
+            backToDisplayActivity()
         }
+
+        return true
     }
 
-    private void sendRefreshSearchEventBroadcast() {
-        Intent intent = new Intent(GalleryFragment.REFRESH_SEARCH_EVENT_RECEIVER);
-        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
+    private fun sendRefreshSearchEventBroadcast() {
+        val intent = Intent(GalleryFragment.REFRESH_SEARCH_EVENT_RECEIVER)
+        LocalBroadcastManager.getInstance(this).sendBroadcast(intent)
     }
 
-    @Override
-    public void onStart() {
-        super.onStart();
-        Optional<User> optionalUser = getUser();
-        if (optionalUser.isPresent()) {
-            OCFile file = getFile();
-            /// Validate handled file (first image to preview)
-            if (file == null) {
-                throw new IllegalStateException("Instanced with a NULL OCFile");
-            }
-            if (!MimeTypeUtil.isImage(file)) {
-                throw new IllegalArgumentException("Non-image file passed as argument");
-            }
+    public override fun onStart() {
+        super.onStart()
+        val optionalUser = user
+        if (optionalUser.isPresent) {
+            var file: OCFile? = file ?: throw IllegalStateException("Instanced with a NULL OCFile")
+            // / Validate handled file (first image to preview)
+            require(MimeTypeUtil.isImage(file)) { "Non-image file passed as argument" }
 
             // Update file according to DB file, if it is possible
-            if (file.getFileId() > FileDataStorageManager.ROOT_PARENT_ID) {
-                file = getStorageManager().getFileById(file.getFileId());
+            if (file!!.fileId > FileDataStorageManager.ROOT_PARENT_ID) {
+                file = storageManager.getFileById(file.fileId)
             }
 
             if (file != null) {
-                /// Refresh the activity according to the Account and OCFile set
-                setFile(file);  // reset after getting it fresh from storageManager
-                updateActionBarTitle(getFile().getFileName());
-                //if (!stateWasRecovered) {
-                initViewPager(optionalUser.get());
-                //}
+                // / Refresh the activity according to the Account and OCFile set
+                setFile(file) // reset after getting it fresh from storageManager
+                updateActionBarTitle(getFile().fileName)
+                // if (!stateWasRecovered) {
+                initViewPager(optionalUser.get())
 
+                // }
             } else {
                 // handled file not in the current Account
-                finish();
+                finish()
             }
         }
     }
 
-    @Override
-    protected void onSaveInstanceState(@NonNull Bundle outState) {
-        super.onSaveInstanceState(outState);
-        outState.putBoolean(KEY_WAITING_FOR_BINDER, requestWaitingForBinder);
-        outState.putBoolean(KEY_SYSTEM_VISIBLE, isSystemUIVisible());
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        outState.putBoolean(KEY_WAITING_FOR_BINDER, requestWaitingForBinder)
+        outState.putBoolean(KEY_SYSTEM_VISIBLE, isSystemUIVisible)
     }
 
-    @Override
-    public void onRemoteOperationFinish(RemoteOperation operation, RemoteOperationResult result) {
-        super.onRemoteOperationFinish(operation, result);
+    override fun onRemoteOperationFinish(operation: RemoteOperation<*>?, result: RemoteOperationResult<*>) {
+        super.onRemoteOperationFinish(operation, result)
 
-        if (operation instanceof RemoveFileOperation) {
-            int deletePosition = viewPager.getCurrentItem();
-            int nextPosition = deletePosition > 0 ? deletePosition - 1 : 0;
+        if (operation is RemoveFileOperation) {
+            val deletePosition = viewPager?.currentItem ?: return
+            val nextPosition = if (deletePosition > 0) deletePosition - 1 else 0
 
-            if (previewImagePagerAdapter.getItemCount() <= 1) {
-                finish();
-                return;
+            previewImagePagerAdapter?.let {
+                if (it.itemCount <= 1) {
+                    finish()
+                    return
+                }
             }
 
-            viewPager.setCurrentItem(nextPosition, true);
-            previewImagePagerAdapter.delete(deletePosition);
-        } else if (operation instanceof SynchronizeFileOperation) {
-            onSynchronizeFileOperationFinish(result);
+            viewPager?.setCurrentItem(nextPosition, true)
+            previewImagePagerAdapter?.delete(deletePosition)
+        } else if (operation is SynchronizeFileOperation) {
+            onSynchronizeFileOperationFinish(result)
         }
     }
 
-    private void onSynchronizeFileOperationFinish(RemoteOperationResult result) {
-        if (result.isSuccess()) {
-            supportInvalidateOptionsMenu();
+    private fun onSynchronizeFileOperationFinish(result: RemoteOperationResult<*>) {
+        if (result.isSuccess) {
+            supportInvalidateOptionsMenu()
         }
     }
 
-    private void observeWorkerState() {
-        WorkerStateLiveData.Companion.instance().observe(this, state -> {
-            if (state instanceof WorkerState.Download) {
-                Log_OC.d(TAG, "Download worker started");
-                isDownloadWorkStarted = true;
+    private fun observeWorkerState() {
+        WorkerStateLiveData.instance().observe(this) { state: WorkerState? ->
+            if (state is WorkerState.Download) {
+                Log_OC.d(TAG, "Download worker started")
+                isDownloadWorkStarted = true
 
                 if (requestWaitingForBinder) {
-                    requestWaitingForBinder = false;
-                    Log_OC.d(TAG, "Simulating reselection of current page after connection " +
-                        "of download binder");
-                    selectPage(viewPager.getCurrentItem());
+                    requestWaitingForBinder = false
+                    Log_OC.d(
+                        TAG,
+                        "Simulating reselection of current page after connection " +
+                            "of download binder"
+                    )
+                    selectPage(viewPager?.currentItem)
                 }
             } else {
-                Log_OC.d(TAG, "Download worker stopped");
-                isDownloadWorkStarted = false;
+                Log_OC.d(TAG, "Download worker stopped")
+                isDownloadWorkStarted = false
             }
-        });
-    }
-
-    @Override
-    public void onStop() {
-        super.onStop();
-    }
-
-    @Override
-    public void onDestroy() {
-        super.onDestroy();
+        }
     }
 
-    @Override
-    protected void onResume() {
-        super.onResume();
+    override fun onResume() {
+        super.onResume()
 
-        downloadFinishReceiver = new DownloadFinishReceiver();
-        IntentFilter downloadIntentFilter = new IntentFilter(FileDownloadWorker.Companion.getDownloadFinishMessage());
-        localBroadcastManager.registerReceiver(downloadFinishReceiver, downloadIntentFilter);
+        downloadFinishReceiver = DownloadFinishReceiver()
+        val downloadIntentFilter = IntentFilter(getDownloadFinishMessage())
+        localBroadcastManager.registerReceiver(downloadFinishReceiver!!, downloadIntentFilter)
 
-        UploadFinishReceiver uploadFinishReceiver = new UploadFinishReceiver();
-        IntentFilter uploadIntentFilter = new IntentFilter(FileUploadWorker.Companion.getUploadFinishMessage());
-        localBroadcastManager.registerReceiver(uploadFinishReceiver, uploadIntentFilter);
+        val uploadFinishReceiver = UploadFinishReceiver()
+        val uploadIntentFilter = IntentFilter(getUploadFinishMessage())
+        localBroadcastManager.registerReceiver(uploadFinishReceiver, uploadIntentFilter)
     }
 
-    @Override
-    protected void onPostResume() {
-        super.onPostResume();
-    }
-
-    @Override
-    public void onPause() {
-        if (downloadFinishReceiver != null){
-            localBroadcastManager.unregisterReceiver(downloadFinishReceiver);
-            downloadFinishReceiver = null;
+    public override fun onPause() {
+        if (downloadFinishReceiver != null) {
+            localBroadcastManager.unregisterReceiver(downloadFinishReceiver!!)
+            downloadFinishReceiver = null
         }
 
-        super.onPause();
+        super.onPause()
     }
 
-
-    private void backToDisplayActivity() {
-        finish();
+    private fun backToDisplayActivity() {
+        finish()
     }
 
     @SuppressFBWarnings("DLS")
-    @Override
-    public void showDetails(OCFile file) {
-        final Intent showDetailsIntent = new Intent(this, FileDisplayActivity.class);
-        showDetailsIntent.setAction(FileDisplayActivity.ACTION_DETAILS);
-        showDetailsIntent.putExtra(FileActivity.EXTRA_FILE, file);
-        showDetailsIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
-        startActivity(showDetailsIntent);
-        finish();
-    }
+    override fun showDetails(file: OCFile) {
+        val intent = Intent(this, FileDisplayActivity::class.java).apply {
+            setAction(FileDisplayActivity.ACTION_DETAILS)
+            putExtra(EXTRA_FILE, file)
+            addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
+        }
 
-    @Override
-    public void showDetails(OCFile file, int activeTab) {
-        showDetails(file);
+        startActivity(intent)
+        finish()
     }
 
-    public void requestForDownload(OCFile file) {
-        requestForDownload(file, null);
+    override fun showDetails(file: OCFile, activeTab: Int) {
+        showDetails(file)
     }
 
-    public void requestForDownload(OCFile file, String downloadBehaviour) {
-        final User user = getUser().orElseThrow(RuntimeException::new);
-        FileDownloadHelper.Companion.instance().downloadFileIfNotStartedBefore(user, file);
+    @JvmOverloads
+    fun requestForDownload(file: OCFile?, downloadBehaviour: String? = null) {
+        if (file == null) return
+        val user = user.orElseThrow { RuntimeException() }
+        FileDownloadHelper.instance().downloadFileIfNotStartedBefore(user, file)
     }
 
     /**
      * This method will be invoked when a new page becomes selected. Animation is not necessarily
      * complete.
      *
-     *  @param  position        Position index of the new selected page
+     * @param position        Position index of the new selected page
      */
-    public void selectPage(int position) {
-        savedPosition = position;
-        hasSavedPosition = true;
+    fun selectPage(position: Int?) {
+        if (position == null) return
+        savedPosition = position
+        hasSavedPosition = true
 
-        OCFile currentFile = previewImagePagerAdapter.getFileAt(position);
+        val currentFile = previewImagePagerAdapter?.getFileAt(position)
 
         if (!isDownloadWorkStarted) {
-            requestWaitingForBinder = true;
+            requestWaitingForBinder = true
         } else {
             if (currentFile != null) {
-                if (currentFile.isEncrypted() && !currentFile.isDown() &&
-                    !previewImagePagerAdapter.pendingErrorAt(position)) {
-                    requestForDownload(currentFile);
+                if (currentFile.isEncrypted && !currentFile.isDown &&
+                    previewImagePagerAdapter?.pendingErrorAt(position) == false
+                ) {
+                    requestForDownload(currentFile)
                 }
 
                 // Call to reset image zoom to initial state
@@ -409,128 +371,157 @@ public class PreviewImageActivity extends FileActivity implements
         }
 
         if (currentFile != null) {
-            updateActionBarTitle(currentFile.getFileName());
-            setDrawerIndicatorEnabled(false);
+            updateActionBarTitle(currentFile.fileName)
+            setDrawerIndicatorEnabled(false)
         }
     }
 
-    public void updateActionBarTitle(String title) {
-        if (getSupportActionBar() != null) {
-            getSupportActionBar().setTitle(title);
-        }
+    private fun updateActionBarTitle(title: String?) {
+        supportActionBar?.title = title
     }
 
     /**
-     * Class waiting for broadcast events from the {@link FileDownloadWorker} service.
-     * <p>
+     * Class waiting for broadcast events from the [FileDownloadWorker] service.
+     *
+     *
      * Updates the UI when a download is started or finished, provided that it is relevant for the
      * folder displayed in the gallery.
      */
-    private class DownloadFinishReceiver extends BroadcastReceiver {
-        @Override
-        public void onReceive(Context context, Intent intent) {
-            previewNewImage(intent);
+    private inner class DownloadFinishReceiver : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            previewNewImage(intent)
         }
     }
 
-    private class UploadFinishReceiver extends BroadcastReceiver {
-        @Override
-        public void onReceive(Context context, Intent intent) {
-            previewNewImage(intent);
+    private inner class UploadFinishReceiver : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            previewNewImage(intent)
         }
     }
 
-    private void previewNewImage(Intent intent) {
-        String accountName = intent.getStringExtra(FileDownloadWorker.EXTRA_ACCOUNT_NAME);
-        String downloadedRemotePath = intent.getStringExtra(FileDownloadWorker.EXTRA_REMOTE_PATH);
-        String downloadBehaviour = intent.getStringExtra(OCFileListFragment.DOWNLOAD_BEHAVIOUR);
+    @Suppress("NestedBlockDepth", "ReturnCount")
+    private fun previewNewImage(intent: Intent) {
+        val accountName = intent.getStringExtra(FileDownloadWorker.EXTRA_ACCOUNT_NAME)
+        val downloadedRemotePath = intent.getStringExtra(FileDownloadWorker.EXTRA_REMOTE_PATH)
+        val downloadBehaviour = intent.getStringExtra(OCFileListFragment.DOWNLOAD_BEHAVIOUR)
 
-        if (getAccount().name.equals(accountName) && downloadedRemotePath != null) {
-            OCFile file = getStorageManager().getFileByEncryptedRemotePath(downloadedRemotePath);
-            boolean downloadWasFine = intent.getBooleanExtra(FileDownloadWorker.EXTRA_DOWNLOAD_RESULT, false);
+        if (account.name != accountName || downloadedRemotePath == null) {
+            return
+        }
 
-            if (EditImageActivity.OPEN_IMAGE_EDITOR.equals(downloadBehaviour)) {
-                startImageEditor(file);
-            } else {
-                int position = previewImagePagerAdapter.getFilePosition(file);
-                if (position >= 0) {
-                    if (downloadWasFine) {
-                        previewImagePagerAdapter.updateFile(position, file);
-                    } else {
-                        previewImagePagerAdapter.updateWithDownloadError(position);
-                    }
-                    previewImagePagerAdapter.notifyItemChanged(position);
-                } else if (downloadWasFine) {
-                    Optional<User> user = getUser();
-
-                    if (user.isPresent()) {
-                        initViewPager(user.get());
-                        int newPosition = previewImagePagerAdapter.getFilePosition(file);
-                        if (newPosition >= 0) {
-                            viewPager.setCurrentItem(newPosition);
-                        }
+        val file = storageManager.getFileByEncryptedRemotePath(downloadedRemotePath)
+        val downloadWasFine = intent.getBooleanExtra(FileDownloadWorker.EXTRA_DOWNLOAD_RESULT, false)
+
+        if (EditImageActivity.OPEN_IMAGE_EDITOR == downloadBehaviour) {
+            startImageEditor(file)
+        } else {
+            val position = previewImagePagerAdapter?.getFilePosition(file) ?: return
+
+            if (position >= 0) {
+                if (downloadWasFine) {
+                    previewImagePagerAdapter?.updateFile(position, file)
+                } else {
+                    previewImagePagerAdapter?.updateWithDownloadError(position)
+                }
+                previewImagePagerAdapter?.notifyItemChanged(position)
+            } else if (downloadWasFine) {
+                val user = user
+
+                if (user.isPresent) {
+                    initViewPager(user.get())
+                    val newPosition = previewImagePagerAdapter?.getFilePosition(file) ?: return
+                    if (newPosition >= 0) {
+                        viewPager?.currentItem = newPosition
                     }
                 }
             }
         }
     }
 
-    public boolean isSystemUIVisible() {
-        return getSupportActionBar() == null || getSupportActionBar().isShowing();
-    }
+    val isSystemUIVisible: Boolean
+        get() = supportActionBar == null || supportActionBar?.isShowing == true
 
-    public void toggleFullScreen() {
-        boolean visible = (fullScreenAnchorView.getSystemUiVisibility()
-            & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) == 0;
+    fun toggleFullScreen() {
+        if (fullScreenAnchorView == null) return
+        val visible = (
+            fullScreenAnchorView!!.systemUiVisibility
+                and View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
+            ) == 0
 
         if (visible) {
-            hideSystemUI(fullScreenAnchorView);
+            hideSystemUI(fullScreenAnchorView!!)
         } else {
-            showSystemUI(fullScreenAnchorView);
+            showSystemUI(fullScreenAnchorView!!)
         }
     }
 
-    public void startImageEditor(OCFile file) {
-        if (file.isDown()) {
-            Intent editImageIntent = new Intent(this, EditImageActivity.class);
-            editImageIntent.putExtra(EditImageActivity.EXTRA_FILE, file);
-            startActivity(editImageIntent);
+    fun startImageEditor(file: OCFile) {
+        if (file.isDown) {
+            val editImageIntent = Intent(this, EditImageActivity::class.java)
+            editImageIntent.putExtra(EditImageActivity.EXTRA_FILE, file)
+            startActivity(editImageIntent)
         } else {
-            requestForDownload(file, EditImageActivity.OPEN_IMAGE_EDITOR);
+            requestForDownload(file, EditImageActivity.OPEN_IMAGE_EDITOR)
         }
     }
 
-    @Override
-    public void onBrowsedDownTo(OCFile folder) {
+    override fun onBrowsedDownTo(folder: OCFile) {
         // TODO Auto-generated method stub
-
     }
 
-    @Override
-    public void onTransferStateChanged(OCFile file, boolean downloading, boolean uploading) {
+    override fun onTransferStateChanged(file: OCFile, downloading: Boolean, uploading: Boolean) {
         // TODO Auto-generated method stub
+    }
 
+    private fun hideSystemUI(anchorView: View) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+            window.insetsController?.let { controller ->
+                controller.hide(WindowInsets.Type.systemBars())
+                controller.systemBarsBehavior = WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
+            }
+        } else {
+            @Suppress("DEPRECATION")
+            anchorView.systemUiVisibility = (
+                View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hides NAVIGATION BAR; Android >= 4.0
+                    or View.SYSTEM_UI_FLAG_FULLSCREEN // hides STATUS BAR;     Android >= 4.1
+                    or View.SYSTEM_UI_FLAG_IMMERSIVE // stays interactive;    Android >= 4.4
+                    or View.SYSTEM_UI_FLAG_LAYOUT_STABLE // draw full window;     Android >= 4.1
+                    or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN // draw full window;     Android >= 4.1
+                    or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                )
+        }
     }
 
+    private fun showSystemUI(anchorView: View) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+            window.insetsController?.let { controller ->
+                controller.show(WindowInsets.Type.systemBars())
 
-    @SuppressLint("InlinedApi")
-    private void hideSystemUI(View anchorView) {
-        anchorView.setSystemUiVisibility(
-            View.SYSTEM_UI_FLAG_HIDE_NAVIGATION         // hides NAVIGATION BAR; Android >= 4.0
-                |   View.SYSTEM_UI_FLAG_FULLSCREEN              // hides STATUS BAR;     Android >= 4.1
-                |   View.SYSTEM_UI_FLAG_IMMERSIVE               // stays interactive;    Android >= 4.4
-                |   View.SYSTEM_UI_FLAG_LAYOUT_STABLE           // draw full window;     Android >= 4.1
-                |   View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN       // draw full window;     Android >= 4.1
-                |   View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION  // draw full window;     Android >= 4.1
-                                        );
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+                    controller.systemBarsBehavior = WindowInsetsController.BEHAVIOR_DEFAULT
+                }
+            }
+        } else {
+            @Suppress("DEPRECATION")
+            anchorView.systemUiVisibility = (
+                View.SYSTEM_UI_FLAG_LAYOUT_STABLE // draw full window;     Android >= 4.1
+                    or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN // draw full window;     Android >= 4.1
+                    or View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                )
+        }
     }
 
-    @SuppressLint("InlinedApi")
-    private void showSystemUI(View anchorView) {
-        anchorView.setSystemUiVisibility(
-            View.SYSTEM_UI_FLAG_LAYOUT_STABLE           // draw full window;     Android >= 4.1
-                |   View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN       // draw full window;     Android >= 4.1
-                |   View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION  // draw full window;     Android >= 4.
-                                        );
+    companion object {
+        val TAG: String = PreviewImageActivity::class.java.simpleName
+        const val EXTRA_VIRTUAL_TYPE: String = "EXTRA_VIRTUAL_TYPE"
+        private const val KEY_WAITING_FOR_BINDER = "WAITING_FOR_BINDER"
+        private const val KEY_SYSTEM_VISIBLE = "TRUE"
+
+        fun previewFileIntent(context: Context?, user: User?, file: OCFile?): Intent {
+            return Intent(context, PreviewImageActivity::class.java).apply {
+                putExtra(EXTRA_FILE, file)
+                putExtra(EXTRA_USER, user)
+            }
+        }
     }
 }