Refactor: Fix some lint errors

- Use weak reference to LocalFileTransferActivity in async tasks to prevent leaks
- Add 'default' case in switch

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/FileListAdapter.java

@@ -58,6 +58,8 @@ public class FileListAdapter extends RecyclerView.Adapter<FileListAdapter.FileVi
         case ERROR:
           holder.statusImage.setImageResource(R.drawable.ic_baseline_error_24px);
           break;
+        default:
+          break;
       }
 
       holder.statusImage.setVisibility(View.VISIBLE);

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/PeerGroupHandshakeAsyncTask.java

@@ -5,6 +5,7 @@ import android.net.wifi.p2p.WifiP2pInfo;
 import android.os.AsyncTask;
 import android.util.Log;
 
+import java.lang.ref.WeakReference;
 import org.kiwix.kiwixmobile.BuildConfig;
 
 import java.io.InputStream;
@@ -39,11 +40,11 @@ class PeerGroupHandshakeAsyncTask extends AsyncTask<Void, Void, InetAddress> {
   private static final String TAG = "PeerGrpHndshakeAsyncTsk";
   private final String HANDSHAKE_MESSAGE = "Request Kiwix File Sharing";
 
-  private LocalFileTransferActivity localFileTransferActivity;
+  private WeakReference<LocalFileTransferActivity> weakReferenceToActivity;
   private WifiP2pInfo groupInfo;
 
   public PeerGroupHandshakeAsyncTask(LocalFileTransferActivity localFileTransferActivity, WifiP2pInfo groupInfo) {
-    this.localFileTransferActivity = localFileTransferActivity;
+    this.weakReferenceToActivity = new WeakReference<>(localFileTransferActivity);
     this.groupInfo = groupInfo;
   }
 
@@ -103,6 +104,8 @@ class PeerGroupHandshakeAsyncTask extends AsyncTask<Void, Void, InetAddress> {
   }
 
   private void exchangeFileTransferMetadata(OutputStream outputStream, InputStream inputStream) {
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
+
     if (localFileTransferActivity.isFileSender()) {
       try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream)) {
         // Send total number of files which will be transferred
@@ -149,6 +152,7 @@ class PeerGroupHandshakeAsyncTask extends AsyncTask<Void, Void, InetAddress> {
 
   @Override
   protected void onPostExecute(InetAddress inetAddress) {
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     localFileTransferActivity.setClientAddress(inetAddress);
   }
 }

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/ReceiverDeviceAsyncTask.java

@@ -4,6 +4,7 @@ import android.os.AsyncTask;
 import android.util.Log;
 import android.widget.Toast;
 
+import java.lang.ref.WeakReference;
 import org.kiwix.kiwixmobile.BuildConfig;
 import org.kiwix.kiwixmobile.R;
 
@@ -34,11 +35,11 @@ class ReceiverDeviceAsyncTask extends AsyncTask<Void, Integer, Boolean> {
 
   private static final String TAG = "ReceiverDeviceAsyncTask";
 
-  private LocalFileTransferActivity localFileTransferActivity;
+  private WeakReference<LocalFileTransferActivity> weakReferenceToActivity;
   private int fileItemIndex;
 
   public ReceiverDeviceAsyncTask(LocalFileTransferActivity localFileTransferActivity) {
-    this.localFileTransferActivity = localFileTransferActivity;
+    this.weakReferenceToActivity = new WeakReference<>(localFileTransferActivity);
   }
 
   @Override
@@ -46,6 +47,7 @@ class ReceiverDeviceAsyncTask extends AsyncTask<Void, Integer, Boolean> {
     try (ServerSocket serverSocket = new ServerSocket(FILE_TRANSFER_PORT)) {
       if (BuildConfig.DEBUG) Log.d(TAG, "Server: Socket opened at " + FILE_TRANSFER_PORT);
 
+      final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
       final String KIWIX_ROOT = localFileTransferActivity.getZimStorageRootPath();
 
       int totalFileCount = localFileTransferActivity.getTotalFilesForTransfer();
@@ -90,6 +92,7 @@ class ReceiverDeviceAsyncTask extends AsyncTask<Void, Integer, Boolean> {
   @Override
   protected void onProgressUpdate(Integer... values) {
     int fileStatus = values[0];
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     localFileTransferActivity.changeStatus(fileItemIndex, fileStatus);
   }
 
@@ -101,6 +104,7 @@ class ReceiverDeviceAsyncTask extends AsyncTask<Void, Integer, Boolean> {
   protected void onPostExecute(Boolean allFilesReceived) {
     if (BuildConfig.DEBUG) Log.d(TAG, "File transfer complete");
 
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     if (allFilesReceived) {
       showToast(localFileTransferActivity, R.string.file_transfer_complete,
           Toast.LENGTH_LONG);

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/SenderDeviceAsyncTask.java

@@ -1,12 +1,12 @@
 package org.kiwix.kiwixmobile.zim_manager.local_file_transfer;
 
-import android.app.Activity;
 import android.content.ContentResolver;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.util.Log;
 import android.widget.Toast;
 
+import java.lang.ref.WeakReference;
 import org.kiwix.kiwixmobile.BuildConfig;
 import org.kiwix.kiwixmobile.R;
 
@@ -38,22 +38,24 @@ class SenderDeviceAsyncTask extends AsyncTask<Uri, Void, Boolean> {
 
   private static final String TAG = "SenderDeviceAsyncTask";
 
-  private LocalFileTransferActivity localFileTransferActivity;
+  private WeakReference<LocalFileTransferActivity> weakReferenceToActivity;
   private int fileItemIndex;
 
   public SenderDeviceAsyncTask(LocalFileTransferActivity localFileTransferActivity, int fileItemIndex) {
-    this.localFileTransferActivity = localFileTransferActivity;
+    this.weakReferenceToActivity = new WeakReference<>(localFileTransferActivity);
     this.fileItemIndex = fileItemIndex;
   }
 
   @Override
   protected void onPreExecute() {
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     localFileTransferActivity.changeStatus(fileItemIndex, SENDING);
   }
 
   @Override
   protected Boolean doInBackground(Uri... fileUris) {
     Uri fileUri = fileUris[0];    // Uri of file to be transferred
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     ContentResolver contentResolver = localFileTransferActivity.getContentResolver();
 
     try (Socket socket = new Socket();
@@ -88,6 +90,7 @@ class SenderDeviceAsyncTask extends AsyncTask<Uri, Void, Boolean> {
 
   @Override
   protected void onPostExecute(Boolean fileSendSuccessful) {
+    final LocalFileTransferActivity localFileTransferActivity = weakReferenceToActivity.get();
     localFileTransferActivity.incrementTotalFilesSent();
 
     if (fileSendSuccessful) { // Whether this task was successful in sending the file

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/WifiPeerListAdapter.java

@@ -22,8 +22,7 @@ import static org.kiwix.kiwixmobile.zim_manager.local_file_transfer.LocalFileTra
 /**
  * Helper class, part of the local file sharing module.
  *
- * Defines the Adapter for the list of wifi peer-device items displayed in {
+ * Defines the Adapter for the list of wifi peer-device items displayed.
- * DeviceListFragment}
  */
 public class WifiPeerListAdapter extends ArrayAdapter<WifiP2pDevice> {