Use reqireContext(), requireActivity() instead of getters

app/src/main/java/org/schabi/newpipe/local/subscription/ImportConfirmationDialog.java

@@ -40,7 +40,7 @@ public class ImportConfirmationDialog extends DialogFragment {
     @Override
     public Dialog onCreateDialog(@Nullable final Bundle savedInstanceState) {
         assureCorrectAppLanguage(getContext());
-        return new AlertDialog.Builder(getContext())
+        return new AlertDialog.Builder(requireContext())
                 .setMessage(R.string.import_network_expensive_warning)
                 .setCancelable(true)
                 .setNegativeButton(R.string.cancel, null)

app/src/main/java/org/schabi/newpipe/util/StreamDialogEntry.java

@@ -26,7 +26,8 @@ public enum StreamDialogEntry {
 
     show_channel_details(R.string.show_channel_details, (fragment, item) ->
         // For some reason `getParentFragmentManager()` doesn't work, but this does.
-        NavigationHelper.openChannelFragment(fragment.getActivity().getSupportFragmentManager(),
+        NavigationHelper.openChannelFragment(
+                fragment.requireActivity().getSupportFragmentManager(),
                 item.getServiceId(), item.getUploaderUrl(), item.getUploaderName())
     ),
 
@@ -80,7 +81,7 @@ public enum StreamDialogEntry {
     play_with_kodi(R.string.play_with_kodi_title, (fragment, item) -> {
         final Uri videoUrl = Uri.parse(item.getUrl());
         try {
-            NavigationHelper.playWithKore(fragment.getContext(), videoUrl);
+            NavigationHelper.playWithKore(fragment.requireContext(), videoUrl);
         } catch (final Exception e) {
             KoreUtil.showInstallKoreDialog(fragment.getActivity());
         }

app/src/main/java/us/shandian/giga/io/StoredFileHelper.java

@@ -275,7 +275,7 @@ public class StoredFileHelper implements Serializable {
             if (!docTree.canRead() || !docTree.canWrite()) return false;
             try {
                 docFile = createSAF(context, srcType, srcName);
-                if (docFile == null || docFile.getName() == null) return false;
+                if (docFile.getName() == null) return false;
                 result = true;
             } catch (IOException e) {
                 return false;

app/src/test/java/org/schabi/newpipe/local/subscription/services/ImportExportJsonHelperTest.java

@@ -91,7 +91,7 @@ public class ImportExportJsonHelperTest {
         final List<SubscriptionItem> itemsFromFile = ImportExportJsonHelper.readFrom(
                 inputStream, null);
 
-        if (itemsFromFile == null || itemsFromFile.isEmpty()) {
+        if (itemsFromFile.isEmpty()) {
             fail("ImportExportJsonHelper.readFrom(input) returned a null or empty list");
         }
 
@@ -116,7 +116,7 @@ public class ImportExportJsonHelperTest {
         final List<SubscriptionItem> secondReadItems = ImportExportJsonHelper.readFrom(
                 inputStream, null);
 
-        if (secondReadItems == null || secondReadItems.isEmpty()) {
+        if (secondReadItems.isEmpty()) {
             fail("second call to readFrom returned an empty list");
         }