Changing configuration at runtime

class DynamicConfigurationActivity : PdfActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Add a toolbar item that toggles the scroll direction.
        setToolbarItemsProvider { defaultItems ->
            defaultItems + ToolbarItem.Button(
                actionId = "my.app.toggle_scroll_direction",
                id = R.id.toggle_scroll_direction,
                contentDescription = "Toggle scroll direction",
                icon = ToolbarIcon.Resource(R.drawable.ic_swap),
            )
        }
        setOnToolbarItemClickListener { id ->
            if (id != R.id.toggle_scroll_direction) return@setOnToolbarItemClickListener false
            // Create the configuration builder prefilled from the current configuration.
            val newConfiguration = PdfActivityConfiguration.Builder(configuration)
                .scrollDirection(
                    if (configuration.configuration.scrollDirection == PageScrollDirection.HORIZONTAL)
                        PageScrollDirection.VERTICAL
                    else
                        PageScrollDirection.HORIZONTAL)
                .build()
            // Set the configuration on the activity. This recreates the activity, similar to changing the orientation or language.
            configuration = newConfiguration
            true
        }
    }
}

public class DynamicConfigurationActivity extends PdfActivity {

    @Override protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Add a toolbar item that toggles the scroll direction.
        setToolbarItemsProvider(defaultItems -> {
            final List<ToolbarItem> items = new ArrayList<>(defaultItems);
            items.add(new ToolbarItem.Button(
                    "my.app.toggle_scroll_direction",
                    R.id.toggle_scroll_direction,
                    "Toggle scroll direction",
                    new ToolbarIcon.Resource(R.drawable.ic_swap),
                    new ToolbarItemState(true, false, true),
                    ToolbarItem.ItemEdge.End,
                    ToolbarItem.OverflowBehavior.IfRoom));
            return items;
        });
        setOnToolbarItemClickListener(id -> {
            if (id != R.id.toggle_scroll_direction) return false;
            final PdfActivityConfiguration configuration = getConfiguration();
            // Create the configuration builder prefilled from the current configuration.
            final PdfActivityConfiguration newConfiguration = new PdfActivityConfiguration.Builder(configuration)
                    .scrollDirection(
                            configuration.getConfiguration().getScrollDirection() == PageScrollDirection.HORIZONTAL ?
                                    PageScrollDirection.VERTICAL :
                                    PageScrollDirection.HORIZONTAL)
                    .build();
            // Set the configuration on the activity. This recreates the activity, similar to changing the orientation or language.
            setConfiguration(newConfiguration);
            return true;
        });
    }
}

class StartupConfigurationChangeActivity : PdfActivity() {

    override fun onCreate(savedInstanceState: Bundle) {
        val newConfiguration = PdfActivityConfiguration.Builder(configuration)
            // Change your configuration.
            ...
            .build()

        // Set the new configuration.
        this.configuration = newConfiguration

        // Make sure to call `super.onCreate()` on the parent `PdfActivity`.
        super.onCreate(savedInstanceState)
    }
}

public class StartupConfigurationChangeActivity extends PdfActivity {

    @Override protected void onCreate(Bundle savedInstanceState) {
        PdfActivityConfiguration newConfiguration = PdfActivityConfiguration.Builder(configuration)
            // Change your configuration.
            ...
            .build();

        // Set the new configuration.
        setConfiguration(newConfiguration);

        // Make sure to call `super.onCreate()` on the parent `PdfActivity`.
        super.onCreate(savedInstanceState);
    }
}

/** The currently displayed `PdfFragment`. **/
private var fragment: PdfFragment? = null
    set(fragment) {
        // Remove the previous fragment.
        this.fragment?.let {
            it.removeDocumentListener(this)
        }
        field = fragment
        if (fragment != null) {
            // Replace the old fragment with a new one.
            supportFragmentManager
                .beginTransaction()
                .replace(R.id.fragmentContainer, fragment)
                .commit()
            // Register the activity to be notified when the document is loaded.
            fragment.addDocumentListener(this)
        }
    }

/** Switches between horizontal and vertical scrolling. */
private fun toggleScrollDirection() {
    val currentFragment = fragment
    val currentDocument = fragment?.document
    if (currentFragment == null || currentDocument == null || currentFragment.configuration == null) return

    val scrollDirection = currentFragment.configuration.scrollDirection

    // Copy the existing configuration to a new configuration builder.
    val configurationBuilder = PdfConfiguration.Builder(currentFragment.configuration)

    // Toggle the scroll direction.
    configurationBuilder.scrollDirection(
        if (scrollDirection == PageScrollDirection.HORIZONTAL)
            PageScrollDirection.VERTICAL
        else
            PageScrollDirection.HORIZONTAL)

    // Save the old fragment state.
    val state = currentFragment.state
    // Create the fragment with the already loaded document and the new configuration.
    val newFragment = PdfFragment.newInstance(currentDocument, configurationBuilder.build())
    fragment = newFragment
    // Restore the fragment state.
    newFragment.state = state
}

/** The currently displayed `PdfFragment`. **/
private PdfFragment fragment;

/** Replaces the currently displayed fragment. */
private void setFragment(@NonNull PdfFragment fragment) {
    // Remove the previous fragment.
    if (this.fragment != null) {
        this.fragment.removeDocumentListener(this);
    }
    this.fragment = fragment;

    // Replace the old fragment with a new one.
    getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.fragmentContainer, fragment)
            .commit();

    // Register the activity to be notified when the document is loaded.
    fragment.addDocumentListener(this);
}

/** Switches between horizontal and vertical scrolling. */
private void toggleScrollDirection() {
    if (fragment == null || fragment.getDocument() == null || fragment.getConfiguration() == null) return;

    PageScrollDirection scrollDirection = fragment.getConfiguration().getScrollDirection();

    // Copy the existing configuration to a new configuration builder.
    PdfConfiguration.Builder configurationBuilder = new PdfConfiguration.Builder(fragment.getConfiguration());

    // Toggle the scroll direction.
    configurationBuilder.scrollDirection(
            scrollDirection == PageScrollDirection.HORIZONTAL ?
                PageScrollDirection.VERTICAL :
                PageScrollDirection.HORIZONTAL);

    // Save the old fragment state.
    Bundle state = fragment.getState();
    // Create the fragment with the already loaded document and the new configuration.
    PdfFragment newFragment = PdfFragment.newInstance(fragment.getDocument(), configurationBuilder.build());
    setFragment(newFragment);
    // Restore the fragment state.
    newFragment.setState(state);
}