# Customize Navigation View UI elements

Navigation View is the UI provided to show the navigation route process. In this example we will show how to do customization on Navigation View, including:

-   Add a new UI element by customizing the activity layout

-   Show or hide existing Navigation View UI elements


As is shown in the above image, we customized the Navigation View app bar and added a switch button to it. A user tapping the switch button will change the visibility of two UI elements (Recenter Button and Sound button), which are originally existing in Navigation View.

For all code examples, refer to [Navigation Code Examples](https://github.com/nextbillion-ai/nb-navigation-android-demo)

![documentation image](https://static.nextbillion.io/docs-next/docs/navigation/android/customize-navigation-view-ui-elements.webp)

**activity_custom_element_visibility.xml [view source](https://github.com/nextbillion-ai/nb-navigation-android-demo/blob/main/app/src/main/res/layout/activity_custom_element_visibility.xml)**

```xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.CustomElementVisibilityActivity">

    <ai.nextbillion.navigation.ui.NavigationView
        android:id="@+id/custom_element_navigation_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>
```

**CustomElementVisibilityActivity [view source](https://github.com/nextbillion-ai/nb-navigation-android-demo/blob/main/app/src/main/java/ai/nextbillion/navigation/demo/activity/CustomElementVisibilityActivity.java)**

```java
package ai.nextbillion.navigation.demo.activity;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import ai.nextbillion.kits.directions.models.DirectionsResponse;
import ai.nextbillion.kits.directions.models.RouteRequestParams;
import ai.nextbillion.navigation.core.routefetcher.RequestParamsWrapper;
import ai.nextbillion.navigation.demo.R;
import ai.nextbillion.navigation.ui.NavViewConfig;
import ai.nextbillion.navigation.ui.NavigationView;
import ai.nextbillion.navigation.ui.OnNavigationReadyCallback;
import ai.nextbillion.navigation.ui.listeners.NavigationListener;

import android.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.SwitchCompat;

import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;

/***
 * This class demonstrates how to add an extra switch button on Appbar
 * and use the switch button to control the display of UI elements in Navigation view
 */

public class CustomElementVisibilityActivity extends AppCompatActivity implements OnNavigationReadyCallback, NavigationListener {
    private NavigationView navigationView;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_custom_element_visibility);
        navigationView = findViewById(R.id.custom_element_navigation_view);
        navigationView.onCreate(savedInstanceState);
        navigationView.initialize(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.mainmenu, menu);
        MenuItem item = menu.findItem(R.id.myswitch);
        SwitchCompat mySwitch = (SwitchCompat) item.getActionView();

        // adding this here to keep the initial display consistency of the UI elements
        controlDisplayOfElements(mySwitch.isChecked());
        // The on-click event will be triggered each time user clicks the switch button on the App bar
        mySwitch.setOnCheckedChangeListener((buttonView, isChecked) -> {
            controlDisplayOfElements(isChecked);
        });
        return true;
    }

    private void controlDisplayOfElements(boolean shouldDisplay) {
        if (shouldDisplay) {
            navigationView.showRecenterBtn();
            navigationView.retrieveSoundButton().show();
        } else {
            navigationView.hideRecenterBtn();
            navigationView.retrieveSoundButton().hide();
        }
    }

    @Override
    public void onNavigationReady(boolean b) {
        // read original backend response from file
        DirectionsResponse response = DirectionsResponse.fromJson(loadJsonFromAsset());
        // modify the backend response following normal api call process
        DirectionsResponse modifiedResponse = new RequestParamsWrapper().wrapRequestParams(response, RouteRequestParams.builder().build());
        NavViewConfig.Builder config =
                NavViewConfig.builder().route(modifiedResponse.routes().get(0))
                        // The visibility of speedometer can be set here before starting navigation
                        .showSpeedometer(true)
                        // add this so the exit button in Navigation view would work
                        .navigationListener(this)
                        .shouldSimulateRoute(true);
        navigationView.startNavigation(config.build());
    }

    private static String convertStreamToString(InputStream is) {
        Scanner s = new Scanner(is).useDelimiter("\\A");
        return s.hasNext() ? s.next() : "";
    }

    private String loadJsonFromAsset() {
        // Using this method to load GeoJSON files from the assets folder.
        try {
            return convertStreamToString(getApplicationContext().getAssets().open("directions-route.json"));
        } catch (IOException ex) {
            ex.printStackTrace();
            return null;
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        navigationView.onStart();
    }

    @Override
    public void onResume() {
        super.onResume();
        navigationView.onResume();
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
        navigationView.onLowMemory();
    }

    @Override
    public void onBackPressed() {
        // If the navigation view didn't need to do anything, call super
        if (!navigationView.onBackPressed()) {
            super.onBackPressed();
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        navigationView.onSaveInstanceState(outState);
        super.onSaveInstanceState(outState);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        navigationView.onRestoreInstanceState(savedInstanceState);
    }

    @Override
    public void onPause() {
        super.onPause();
        navigationView.onPause();
    }

    @Override
    public void onStop() {
        super.onStop();
        navigationView.onStop();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        navigationView.onDestroy();
    }

    @Override
    public void onCancelNavigation() {
        finish();
    }

    @Override
    public void onNavigationFinished() {

    }

    @Override
    public void onNavigationRunning() {

    }
}
```

### Code Highlights

The main logic of the code example is to use a switch button to control the visibility of the Recenter button and the Sound button in the navigation view.

The **controlDisPlayOfElement()** function shows how to display or hide the corresponding view during navigation.

### Code summary

The code snippet is for an Android activity that allows users to control the visibility of elements in a navigation view. The activity extends the AppCompatActivity class and implements the OnNavigationReadyCallback and NavigationListener interfaces.

The activity's **onCreate()** method first inflates the activity_custom_element_visibility layout. It then finds the navigationView view in the layout and calls its **onCreate()** method. Finally, it calls the **initialize()** method on the navigationView to initialize it.

The activity's **onCreateOptionsMenu()** method inflates the **mainmenu** menu. It then finds the **myswitch** menu item and gets its **SwitchCompat** view. The activity then calls the **controlDisplayOfElements()** method to set the initial visibility of the elements in the navigation view. The activity also sets a listener on the **myswitch** view so that it can be updated when the user changes the switch's state.

The **controlDisplayOfElements()** method takes a boolean value as input. If the value is true, the method shows the Recenter button and the Sound button in the navigation view. If the value is false, the method hides the buttons.

The **onNavigationReady()** method is called when the navigation view is ready. The method reads the original backend response from a file. It then modifies the response and creates a NavViewConfig object. The NavViewConfig object specifies the route that will be navigated, whether the speedometer will be shown and whether the navigation listener will be used. The method then calls the **startNavigation()** method on the navigation view to start navigation.

The **convertStreamToString()** method converts an input stream to a string. The method uses a Scanner object to read the stream and a delimiter to determine where the stream ends.

The **loadJsonFromAsset()** method loads a GeoJSON file from the assets folder. The method tries to open the file and read its contents. If the file cannot be opened, the method returns null.

The activity uses the **NavigationView** class to display a navigation view in the user interface. The activity also uses the **OnNavigationReadyCallback** and **NavigationListener** interfaces to interact with the navigation view.