Changing configuration at runtime

class DynamicConfigurationActivity : PdfActivity() {

    override fun onPrepareOptionsMenu(menu: Menu): Boolean {
        super.onPrepareOptionsMenu(menu)
        menuInflater.inflate(R.menu.dynamic_configuration_menu, menu)
        return true
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        var handled = false
        when (item.itemId) {
            R.id.toggle_scroll_direction -> {
                handled = true
                // Create the configuration builder with the configuration 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 will recreate the activity, similar to changing the orientation or language.
                configuration = newConfiguration
            }
        }
        return handled || super.onOptionsItemSelected(item)
    }
}

public class DynamicConfigurationActivity extends PdfActivity {

    @Override public boolean onPrepareOptionsMenu(Menu menu) {
        super.onPrepareOptionsMenu(menu);
        getMenuInflater().inflate(R.menu.dynamic_configuration_menu, menu);
        return true;
    }

    @Override public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        boolean handled = false;
        PdfActivityConfiguration configuration = getConfiguration();
        switch (item.getItemId()) {
            case R.id.toggle_scroll_direction: {
                handled = true;
                // Create the configuration builder with the configuration prefilled from the current configuration.
                PdfActivityConfiguration newConfiguration = new PdfActivityConfiguration.Builder(getConfiguration())
                        .scrollDirection(
                                configuration.getConfiguration().getScrollDirection() == PageScrollDirection.HORIZONTAL ?
                                        PageScrollDirection.VERTICAL :
                                        PageScrollDirection.HORIZONTAL)
                        .build();
                // Set the configuration on the activity. This will recreate the activity, similar to changing the orientation or language.
                setConfiguration(newConfiguration);
                break;
            }
        }
        return handled || super.onOptionsItemSelected(item);
    }
}

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) {
        PdfActivityConfigurations 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);
}