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--- title: Send push notifications to specific Android apps using Azure Notification Hubs description: Learn how to send push notifications to specific Android apps by using Azure Notification Hubs. services: notification-hubs author: sethmanheim manager: lizross ms.service: azure-notification-hubs ms.tgt_pltfrm: mobile-android ms.devlang: java ms.topic: tutorial ms.custom: mvc, devx-track-java, devx-track-dotnet ms.date: 02/06/2024 ms.author: sethm ms.reviewer: heathertian ms.lastreviewed: 02/06/2024 --- # Tutorial: Send push notifications to specific Android apps using Azure Notification Hubs [!INCLUDE [notification-hubs-selector-aspnet-backend-notify-users](../../includes/notification-hubs-selector-aspnet-backend-notify-users.md)] > [!NOTE] > For information about Firebase Cloud Messaging deprecation and migration steps, see [Google Firebase Cloud Messaging migration](notification-hubs-gcm-to-fcm.md). This tutorial shows you how to use Azure Notification Hubs to send push notifications to a specific app user on a specific device. An ASP.NET WebAPI backend is used to authenticate clients and to generate notifications, as shown in the guidance article [Registering from your app backend](notification-hubs-push-notification-registration-management.md#registration-management-from-a-backend). This tutorial builds on the notification hub that you created in the [Tutorial: Push notifications to Android devices by using Azure Notification Hubs and Firebase Cloud Messaging](notification-hubs-android-push-notification-google-fcm-get-started.md). In this tutorial, you take the following steps: > [!div class="checklist"] > * Create the backend Web API project that authenticates users. > * Update the Android application. > * Test the app ## Prerequisites Complete the [Tutorial: Push notifications to Android devices by using Azure Notification Hubs and Firebase Cloud Messaging](notification-hubs-android-push-notification-google-fcm-get-started.md) before doing this tutorial. [!INCLUDE [notification-hubs-aspnet-backend-notifyusers](../../includes/notification-hubs-aspnet-backend-notifyusers.md)] ## Create the Android Project The next step is to update the Android application created in the [Tutorial: Push notifications to Android devices by using Azure Notification Hubs and Firebase Cloud Messaging](notification-hubs-android-push-notification-google-fcm-get-started.md). 1. Open your `res/layout/activity_main.xml` file, replace the following content definitions: It adds new EditText controls for logging in as a user. Also a field is added for a username tag that will be part of notifications you send: ```xml <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <EditText android:id="@+id/usernameText" android:layout_width="match_parent" android:layout_height="wrap_content" android:ems="10" android:hint="@string/usernameHint" android:layout_above="@+id/passwordText" android:layout_alignParentEnd="true" /> <EditText android:id="@+id/passwordText" android:layout_width="match_parent" android:layout_height="wrap_content" android:ems="10" android:hint="@string/passwordHint" android:inputType="textPassword" android:layout_above="@+id/buttonLogin" android:layout_alignParentEnd="true" /> <Button android:id="@+id/buttonLogin" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/loginButton" android:onClick="login" android:layout_above="@+id/toggleButtonFCM" android:layout_centerHorizontal="true" android:layout_marginBottom="24dp" /> <ToggleButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:textOn="WNS on" android:textOff="WNS off" android:id="@+id/toggleButtonWNS" android:layout_toLeftOf="@id/toggleButtonFCM" android:layout_centerVertical="true" /> <ToggleButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:textOn="FCM on" android:textOff="FCM off" android:id="@+id/toggleButtonFCM" android:checked="true" android:layout_centerHorizontal="true" android:layout_centerVertical="true" /> <ToggleButton android:layout_width="wrap_content" android:layout_height="wrap_content" android:textOn="APNS on" android:textOff="APNS off" android:id="@+id/toggleButtonAPNS" android:layout_toRightOf="@id/toggleButtonFCM" android:layout_centerVertical="true" /> <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/editTextNotificationMessageTag" android:layout_below="@id/toggleButtonFCM" android:layout_centerHorizontal="true" android:hint="@string/notification_message_tag_hint" /> <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/editTextNotificationMessage" android:layout_below="@+id/editTextNotificationMessageTag" android:layout_centerHorizontal="true" android:hint="@string/notification_message_hint" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/send_button" android:id="@+id/sendbutton" android:onClick="sendNotificationButtonOnClick" android:layout_below="@+id/editTextNotificationMessage" android:layout_centerHorizontal="true" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello World!" android:id="@+id/text_hello" /> </RelativeLayout> ``` 2. Open your `res/values/strings.xml` file and replace the `send_button` definition with the following lines that redefine the string for the `send_button` and add strings for the other controls: ```xml <string name="usernameHint">Username</string> <string name="passwordHint">Password</string> <string name="loginButton">1. Sign in</string> <string name="send_button">2. Send Notification</string> <string name="notification_message_hint">Notification message</string> <string name="notification_message_tag_hint">Recipient username</string> ``` Your `main_activity.xml` graphical layout should now look like the following image: ![Screenshot of an emulator displaying what the main activity X M L graphical layout will look like.][A1] 3. Create a new class named `RegisterClient` in the same package as your `MainActivity` class. Use the code below for the new class file. ```java import java.io.IOException; import java.io.UnsupportedEncodingException; import java.util.Set; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpPost; import org.apache.http.client.methods.HttpPut; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.util.EntityUtils; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import android.content.Context; import android.content.SharedPreferences; import android.util.Log; public class RegisterClient { private static final String PREFS_NAME = "ANHSettings"; private static final String REGID_SETTING_NAME = "ANHRegistrationId"; private String Backend_Endpoint; SharedPreferences settings; protected HttpClient httpClient; private String authorizationHeader; public RegisterClient(Context context, String backendEndpoint) { super(); this.settings = context.getSharedPreferences(PREFS_NAME, 0); httpClient = new DefaultHttpClient(); Backend_Endpoint = backendEndpoint + "/api/register"; } public String getAuthorizationHeader() { return authorizationHeader; } public void setAuthorizationHeader(String authorizationHeader) { this.authorizationHeader = authorizationHeader; } public void register(String handle, Set<String> tags) throws ClientProtocolException, IOException, JSONException { String registrationId = retrieveRegistrationIdOrRequestNewOne(handle); JSONObject deviceInfo = new JSONObject(); deviceInfo.put("Platform", "fcm"); deviceInfo.put("Handle", handle); deviceInfo.put("Tags", new JSONArray(tags)); int statusCode = upsertRegistration(registrationId, deviceInfo); if (statusCode == HttpStatus.SC_OK) { return; } else if (statusCode == HttpStatus.SC_GONE){ settings.edit().remove(REGID_SETTING_NAME).commit(); registrationId = retrieveRegistrationIdOrRequestNewOne(handle); statusCode = upsertRegistration(registrationId, deviceInfo); if (statusCode != HttpStatus.SC_OK) { Log.e("RegisterClient", "Error upserting registration: " + statusCode); throw new RuntimeException("Error upserting registration"); } } else { Log.e("RegisterClient", "Error upserting registration: " + statusCode); throw new RuntimeException("Error upserting registration"); } } private int upsertRegistration(String registrationId, JSONObject deviceInfo) throws UnsupportedEncodingException, IOException, ClientProtocolException { HttpPut request = new HttpPut(Backend_Endpoint+"/"+registrationId); request.setEntity(new StringEntity(deviceInfo.toString())); request.addHeader("Authorization", "Basic "+authorizationHeader); request.addHeader("Content-Type", "application/json"); HttpResponse response = httpClient.execute(request); int statusCode = response.getStatusLine().getStatusCode(); return statusCode; } private String retrieveRegistrationIdOrRequestNewOne(String handle) throws ClientProtocolException, IOException { if (settings.contains(REGID_SETTING_NAME)) return settings.getString(REGID_SETTING_NAME, null); HttpUriRequest request = new HttpPost(Backend_Endpoint+"?handle="+handle); request.addHeader("Authorization", "Basic "+authorizationHeader); HttpResponse response = httpClient.execute(request); if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) { Log.e("RegisterClient", "Error creating registrationId: " + response.getStatusLine().getStatusCode()); throw new RuntimeException("Error creating Notification Hubs registrationId"); } String registrationId = EntityUtils.toString(response.getEntity()); registrationId = registrationId.substring(1, registrationId.length()-1); settings.edit().putString(REGID_SETTING_NAME, registrationId).commit(); return registrationId; } } ``` This component implements the REST calls required to contact the app backend to register for push notifications. It also locally stores the *registrationIds* created by the Notification Hub as detailed in [Registering from your app backend](notification-hubs-push-notification-registration-management.md#registration-management-from-a-backend). It uses an authorization token stored in local storage when you click the **Sign in** button. 4. In your `MainActivity` class, and add a field for the `RegisterClient` class and a string for your ASP.NET backend's endpoint. Be sure to replace `<Enter Your Backend Endpoint>` with your actual backend endpoint obtained previously. For example, `http://mybackend.azurewebsites.net`. ```java private RegisterClient registerClient; private static final String BACKEND_ENDPOINT = "<Enter Your Backend Endpoint>"; FirebaseInstanceId fcm; String FCM_token = null; ``` 5. In your `MainActivity` class, in the `onCreate` method, remove, or comment out the initialization of the `hub` field and the call to the `registerWithNotificationHubs` method. Then add code to initialize an instance of the `RegisterClient` class. The method should contain the following lines: ```java @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mainActivity = this; FirebaseService.createChannelAndHandleNotifications(getApplicationContext()); fcm = FirebaseInstanceId.getInstance(); registerClient = new RegisterClient(this, BACKEND_ENDPOINT); setContentView(R.layout.activity_main); } ``` 7. Add the following `import` statements to your `MainActivity.java` file. ```java import android.util.Base64; import android.view.View; import android.widget.EditText; import android.widget.Button; import android.widget.ToggleButton; import java.io.UnsupportedEncodingException; import android.content.Context; import java.util.HashSet; import android.widget.Toast; import org.apache.http.client.ClientProtocolException; import java.io.IOException; import org.apache.http.HttpStatus; import android.os.AsyncTask; import org.apache.http.HttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.DefaultHttpClient; import android.app.AlertDialog; import android.content.DialogInterface; import com.google.firebase.iid.FirebaseInstanceId; import com.google.firebase.iid.InstanceIdResult; import com.google.android.gms.tasks.OnSuccessListener; import java.util.concurrent.TimeUnit; ``` 8. Replace code on the onStart method with the following code: ```java super.onStart(); Button sendPush = (Button) findViewById(R.id.sendbutton); sendPush.setEnabled(false); ``` 9. Then, add the following methods to handle the **Sign in** button click event and sending push notifications. ```java public void login(View view) throws UnsupportedEncodingException { this.registerClient.setAuthorizationHeader(getAuthorizationHeader()); final Context context = this; new AsyncTask<Object, Object, Object>() { @Override protected Object doInBackground(Object... params) { try { FirebaseInstanceId.getInstance().getInstanceId().addOnSuccessListener(new OnSuccessListener<InstanceIdResult>() { @Override public void onSuccess(InstanceIdResult instanceIdResult) { FCM_token = instanceIdResult.getToken(); Log.d(TAG, "FCM Registration Token: " + FCM_token); } }); TimeUnit.SECONDS.sleep(1); registerClient.register(FCM_token, new HashSet<String>()); } catch (Exception e) { DialogNotify("MainActivity - Failed to register", e.getMessage()); return e; } return null; } protected void onPostExecute(Object result) { Button sendPush = (Button) findViewById(R.id.sendbutton); sendPush.setEnabled(true); Toast.makeText(context, "Signed in and registered.", Toast.LENGTH_LONG).show(); } }.execute(null, null, null); } private String getAuthorizationHeader() throws UnsupportedEncodingException { EditText username = (EditText) findViewById(R.id.usernameText); EditText password = (EditText) findViewById(R.id.passwordText); String basicAuthHeader = username.getText().toString()+":"+password.getText().toString(); basicAuthHeader = Base64.encodeToString(basicAuthHeader.getBytes("UTF-8"), Base64.NO_WRAP); return basicAuthHeader; } /** * This method calls the ASP.NET WebAPI backend to send the notification message * to the platform notification service based on the pns parameter. * * @param pns The platform notification service to send the notification message to. Must * be one of the following ("wns", "fcm", "apns"). * @param userTag The tag for the user who will receive the notification message. This string * must not contain spaces or special characters. * @param message The notification message string. This string must include the double quotes * to be used as JSON content. */ public void sendPush(final String pns, final String userTag, final String message) throws ClientProtocolException, IOException { new AsyncTask<Object, Object, Object>() { @Override protected Object doInBackground(Object... params) { try { String uri = BACKEND_ENDPOINT + "/api/notifications"; uri += "?pns=" + pns; uri += "&to_tag=" + userTag; HttpPost request = new HttpPost(uri); request.addHeader("Authorization", "Basic "+ getAuthorizationHeader()); request.setEntity(new StringEntity(message)); request.addHeader("Content-Type", "application/json"); HttpResponse response = new DefaultHttpClient().execute(request); if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) { DialogNotify("MainActivity - Error sending " + pns + " notification", response.getStatusLine().toString()); throw new RuntimeException("Error sending notification"); } } catch (Exception e) { DialogNotify("MainActivity - Failed to send " + pns + " notification ", e.getMessage()); return e; } return null; } }.execute(null, null, null); } ``` The `login` handler for the **Sign in** button generates a basic authentication token using on the input username and password (it represents any token your authentication scheme uses), then it uses `RegisterClient` to call the backend for registration. The `sendPush` method calls the backend to trigger a secure notification to the user based on the user tag. The platform notification service that `sendPush` targets depends on the `pns` string passed in. 10. Add the following `DialogNotify` method to the `MainActivity` class. ```java protected void DialogNotify(String title, String message) { AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create(); alertDialog.setTitle(title); alertDialog.setMessage(message); alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); alertDialog.show(); } ``` 11. In your `MainActivity` class, update the `sendNotificationButtonOnClick` method to call the `sendPush` method with the user's selected platform notification services as follows. ```java /** * Send Notification button click handler. This method sends the push notification * message to each platform selected. * * @param v The view */ public void sendNotificationButtonOnClick(View v) throws ClientProtocolException, IOException { String nhMessageTag = ((EditText) findViewById(R.id.editTextNotificationMessageTag)) .getText().toString(); String nhMessage = ((EditText) findViewById(R.id.editTextNotificationMessage)) .getText().toString(); // JSON String nhMessage = "\"" + nhMessage + "\""; if (((ToggleButton)findViewById(R.id.toggleButtonWNS)).isChecked()) { sendPush("wns", nhMessageTag, nhMessage); } if (((ToggleButton)findViewById(R.id.toggleButtonFCM)).isChecked()) { sendPush("fcm", nhMessageTag, nhMessage); } if (((ToggleButton)findViewById(R.id.toggleButtonAPNS)).isChecked()) { sendPush("apns", nhMessageTag, nhMessage); } } ``` 12. In the `build.gradle` file, add the following line to the `android` section after the `buildTypes` section. ```java useLibrary 'org.apache.http.legacy' ``` 13. If your app is targeting API level 28 (Android 9.0) or above, include the following declaration within the `<application>` element of `AndroidManifest.xml`. ```xml <uses-library android:name="org.apache.http.legacy" android:required="false" /> ``` 14. Build the project. ## Test the app 1. Run the application on a device or an emulator using Android Studio. 2. In the Android app, enter a username and password. They must both be the same string value and they must not contain spaces or special characters. 3. In the Android app, click **Sign in**. Wait for a toast message that states **Signed in and registered**. It enables the **Send Notification** button. ![Screenshot of an emulator showing what the Notification Hubs Notify Users app looks like after logging in.][A2] 4. Click the toggle buttons to enable all platforms where you ran the app and registered a user. 5. Enter the user's name that receives the notification message. That user must be registered for notifications on the target devices. 6. Enter a message for the user to receive as a push notification message. 7. Click **Send Notification**. Each device that has a registration with the matching username tag receives the push notification. ## Next steps In this tutorial, you learned how to push notifications to specific users that have tags associated with their registrations. To learn how to push location-based notifications, advance to the following tutorial: > [!div class="nextstepaction"] >[Push location-based notifications](notification-hubs-push-bing-spatial-data-geofencing-notification.md) [A1]: ./media/notification-hubs-aspnet-backend-android-notify-users/android-notify-users.png [A2]: ./media/notification-hubs-aspnet-backend-android-notify-users/android-notify-users-enter-password.png