How to use Alarm Manager - alarmmanager

Question

I am trying to create an alarm but it is not working.I followed many tutorials I found on the internet and downloaded projects from GitHub but still not working. Can you check the code please.
public class MainActivity extends AppCompatActivity {
AlarmManager alarmManager;
private PendingIntent pendingIntent;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent myIntent = new Intent(MainActivity.this, hi.class);
pendingIntent = PendingIntent.getService(MainActivity.this, 0, myIntent, 0);
AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 10*1000, pendingIntent);
}
}
public class hi extends BroadcastReceiver {
public void onReceive(final Context context, Intent intent) {
//perform your task
Toast.makeText(context, "Alarm Received after 10 seconds.", Toast.LENGTH_SHORT).show();
}
}
xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.suad.cakchild">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver android:name=".hi" android:process=":remote"/>
</application>
</manifest>