Support predictive back design

app/src/main/AndroidManifest.xml

@@ -57,6 +57,7 @@
         android:theme="@style/Hydra.Material"
         android:localeConfig="@xml/locales_config"
         android:networkSecurityConfig="@xml/network_security_config"
+        android:enableOnBackInvokedCallback="true"
         tools:ignore="AllowBackup,GoogleAppIndexingWarning,UnusedAttribute"
         tools:replace="android:supportsRtl">
 

app/src/main/java/be/ugent/zeus/hydra/MainActivity.java

@@ -31,6 +31,7 @@
 import android.util.Log;
 import android.view.MenuItem;
 import android.view.View;
+import androidx.activity.OnBackPressedCallback;
 import androidx.annotation.*;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.core.view.GravityCompat;
@@ -58,14 +59,15 @@
 import be.ugent.zeus.hydra.resto.menu.RestoFragment;
 import be.ugent.zeus.hydra.schamper.SchamperFragment;
 import be.ugent.zeus.hydra.urgent.UrgentFragment;
+import be.ugent.zeus.hydra.wpi.EnableManager;
+import be.ugent.zeus.hydra.wpi.WpiActivity;
 import com.google.android.material.bottomnavigation.BottomNavigationView;
 import com.google.android.material.navigation.NavigationView;
 import com.google.android.material.shape.MaterialShapeDrawable;
 import com.google.android.material.tabs.TabLayout;
-import be.ugent.zeus.hydra.wpi.EnableManager;
-import be.ugent.zeus.hydra.wpi.WpiActivity;
 import dev.chrisbanes.insetter.Insetter;
 import jonathanfinerty.once.Once;
+import org.jetbrains.annotations.NotNull;
 
 import static be.ugent.zeus.hydra.common.utils.FragmentUtils.requireArguments;
 
@@ -260,6 +262,37 @@ private void initialize(@Nullable Bundle savedInstanceState) {
         // Register the listener for navigation events from the drawer.
         binding.navigationView.setNavigationItemSelectedListener(this);
 
+        OnBackPressedCallback drawerCloser = new OnBackPressedCallback(false) {
+
+            @Override
+            public void handleOnBackPressed() {
+                binding.drawerLayout.closeDrawer(GravityCompat.START);
+            }
+        };
+        getOnBackPressedDispatcher().addCallback(this, drawerCloser);
+
+        binding.drawerLayout.addDrawerListener(new DrawerLayout.DrawerListener() {
+            @Override
+            public void onDrawerSlide(@NonNull @NotNull View drawerView, float slideOffset) {
+                // Do nothing.
+            }
+
+            @Override
+            public void onDrawerOpened(@NonNull @NotNull View drawerView) {
+                drawerCloser.setEnabled(true);
+            }
+
+            @Override
+            public void onDrawerClosed(@NonNull @NotNull View drawerView) {
+                drawerCloser.setEnabled(false);
+            }
+
+            @Override
+            public void onDrawerStateChanged(int newState) {
+                // Do nothing.
+            }
+        });
+
         toggle = new ActionBarDrawerToggle(this, binding.drawerLayout, binding.toolbar, R.string.action_drawer_open, R.string.action_drawer_close) {
             @Override
             public void onDrawerSlide(View drawerView, float slideOffset) {
@@ -498,44 +531,6 @@ private void setFragment(Fragment fragment, MenuItem menuItem, @NavigationSource
         binding.progressBar.progressBar.setVisibility(View.GONE);
     }
 
-    /**
-     * Implements the correct back-button behaviour for the drawer. If the drawer does not consume the back press,
-     * the parent method is called.
-     */
-    @Override
-    public void onBackPressed() {
-        // If the drawer is open, close it.
-        if (binding.drawerLayout.isDrawerOpen(GravityCompat.START)) {
-            binding.drawerLayout.closeDrawer(GravityCompat.START);
-            return;
-        }
-
-        // The super method handles both the fragment back stack and finishing the activity. To know what was executed,
-        // we need to add a listener.
-        FragmentManager.OnBackStackChangedListener listener = () -> {
-            Fragment current = getSupportFragmentManager().findFragmentById(R.id.content);
-            Log.w(TAG, "onBackPressed: current fragment is somehow null? Ignoring update for now.");
-            if (current == null) {
-                return;
-            }
-            MenuItem item = binding.navigationView.getMenu().findItem(getFragmentMenuId(current));
-            updateDrawer(current, item);
-        };
-
-        // Allow the current fragment to intercept the back press.
-        Fragment current = getSupportFragmentManager().findFragmentById(R.id.content);
-        if (current instanceof OnBackPressed && (((OnBackPressed) current).onBackPressed())) {
-            // The fragment has handled it.
-            return;
-        }
-
-        // We need to listen to the back stack to update the drawer.
-        getSupportFragmentManager().addOnBackStackChangedListener(listener);
-        super.onBackPressed();
-        // The drawer has been updated, so we abandon the listener.
-        getSupportFragmentManager().removeOnBackStackChangedListener(listener);
-    }
-
     /**
      * Set the menu ID as argument for a fragment.
      *
@@ -665,21 +660,6 @@ public interface ScheduledRemovalListener {
         void onRemovalScheduled();
     }
 
-    /**
-     * Allows fragments to listen to and intercept back button presses.
-     */
-    @FunctionalInterface
-    public interface OnBackPressed {
-
-        /**
-         * Called when the back button is pressed. This function provides the fragment
-         * with an opportunity to intercept the back press.
-         *
-         * @return True if consumed, false otherwise. Consumed events are not propagated.
-         */
-        boolean onBackPressed();
-    }
-
     private static final class TutorialEndEvent implements Event {
         @Nullable
         @Override

app/src/main/java/be/ugent/zeus/hydra/association/list/EventFragment.java

@@ -28,6 +28,7 @@
 import android.widget.Button;
 import android.widget.FrameLayout;
 import android.widget.LinearLayout;
+import androidx.activity.OnBackPressedCallback;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.appcompat.widget.Toolbar;
@@ -68,7 +69,7 @@
  * @author ellen
  * @author Niko Strijbol
  */
-public class EventFragment extends Fragment implements MainActivity.ScheduledRemovalListener, MainActivity.OnBackPressed {
+public class EventFragment extends Fragment implements MainActivity.ScheduledRemovalListener {
 
     private static final String TAG = "EventFragment";
 
@@ -194,6 +195,30 @@ protected void onSuccess(@NonNull AssociationRequest.EventItemsAndAssociations d
                 .setOnClickListener(v -> viewModel.onRefresh());
         view.<Button>findViewById(R.id.events_no_data_button_filters)
                 .setOnClickListener(v -> showSheet());
+
+        var callback = new OnBackPressedCallback(false) {
+            @Override
+            public void handleOnBackPressed() {
+                hideSheet();
+            }
+        };
+        var behavior = BottomSheetBehavior.from(bottomSheet);
+        behavior.addBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
+            @Override
+            public void onStateChanged(@NonNull @NotNull View bottomSheet, int newState) {
+                if (newState == BottomSheetBehavior.STATE_HIDDEN || newState == BottomSheetBehavior.STATE_COLLAPSED) {
+                    callback.setEnabled(false);
+                } else if (newState == BottomSheetBehavior.STATE_EXPANDED || newState == BottomSheetBehavior.STATE_HALF_EXPANDED) {
+                    callback.setEnabled(true);
+                }
+            }
+
+            @Override
+            public void onSlide(@NonNull @NotNull View bottomSheet, float slideOffset) {
+                // Do nothing.
+            }
+        });
+        requireActivity().getOnBackPressedDispatcher().addCallback(getViewLifecycleOwner(), callback);
     }
 
     private void setupBottomSheet() {
@@ -262,14 +287,4 @@ private void hideSheet() {
     private void showSheet() {
         behavior.setState(BottomSheetBehavior.STATE_EXPANDED);
     }
-
-    @Override
-    public boolean onBackPressed() {
-        if (behavior.getState() != BottomSheetBehavior.STATE_HIDDEN) {
-            Log.d(TAG, "onBackPressed: hiding sheet");
-            hideSheet();
-            return true;
-        }
-        return false;
-    }
 }

app/src/main/java/be/ugent/zeus/hydra/wpi/account/ApiKeyManagementActivity.java

@@ -26,7 +26,6 @@
 import android.os.Bundle;
 import android.text.Editable;
 import android.text.TextWatcher;
-import android.view.MenuItem;
 import androidx.annotation.Nullable;
 
 import java.util.Objects;
@@ -53,6 +52,7 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
         binding.apiTap.setText(AccountManager.getTapKey(this));
         binding.apiUsername.setText(AccountManager.getUsername(this));
         binding.doorApiKey.setText(AccountManager.getDoorKey(this));
+        setResult(RESULT_OK, new Intent());
     }
 
     @Override
@@ -73,22 +73,6 @@ protected void onStop() {
         binding.doorApiKey.removeTextChangedListener(this);
     }
 
-    @Override
-    public void onBackPressed() {
-        Intent intent = new Intent();
-        setResult(RESULT_OK, intent);
-        super.onBackPressed();
-    }
-
-    @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
-        if (item.getItemId() == android.R.id.home) {
-            Intent intent = new Intent();
-            setResult(RESULT_OK, intent);
-        }
-        return super.onOptionsItemSelected(item);
-    }
-
     @Override
     public void beforeTextChanged(CharSequence s, int start, int count, int after) {
         // Do nothing.