Tarea de programación android para ejecutarse en horas específicas diarias

Estoy deseando cambiar el volumen de mi tono de timbre a una hora específica cada día. Utilicé un calendario para especificar la hora, y estoy intentando utilizar alarmManager para ejecutarlo. Esto es lo que tengo. (Soy un noobie ir fácil en mí)

package com.example.ringervolume.app; import android.app.Activity; import android.app.AlarmManager; import android.app.PendingIntent; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.media.AudioManager; import android.os.Bundle; import android.support.v7.app.ActionBarActivity; import android.view.Menu; import android.view.MenuItem; import android.widget.TextView; import java.util.Calendar; public class MainActivity extends ActionBarActivity { private AudioManager audio; private PendingIntent pendingIntentam; private PendingIntent pentdingIntentpm; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); TextView textViewTime = (TextView) findViewById (R.id.textTime); audio = (AudioManager)getSystemService(Context.AUDIO_SERVICE); //ringer volume for the am. Calendar calendaram = Calendar.getInstance(); calendaram.set(Calendar.HOUR_OF_DAY, 21); calendaram.set(Calendar.MINUTE, 32); calendaram.set(Calendar.SECOND, 0); calendaram.set(Calendar.AM_PM,Calendar.PM); Intent myIntent = new Intent(MainActivity.this, MyReceiver.class); pendingIntentam = PendingIntent.getBroadcast(MainActivity.this, 0,myIntent,0); AlarmManager alarmManageram = (AlarmManager)getSystemService(ALARM_SERVICE); alarmManageram.set(AlarmManager.RTC, calendaram.getTimeInMillis(), pendingIntentam); } public class MyReceiver extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { Intent scheduledIntent = new Intent(context, myscheduleactivity.class); scheduledIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); context.startActivity(scheduledIntent); } } public class myscheduleactivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); audio.setRingerMode(AudioManager.RINGER_MODE_VIBRATE); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } } 

 private AlarmManager alarmMgr; private PendingIntent alarmIntent; ... alarmMgr = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE); Intent intent = new Intent(context, AlarmReceiver.class); alarmIntent = PendingIntent.getBroadcast(context, 0, intent, 0); // Set the alarm to start at 21:32 PM Calendar calendar = Calendar.getInstance(); calendar.setTimeInMillis(System.currentTimeMillis()); calendar.set(Calendar.HOUR_OF_DAY, 21); calendar.set(Calendar.MINUTE, 32); // setRepeating() lets you specify a precise custom interval--in this case, // 1 day alarmMgr.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), AlarmManager.INTERVAL_DAY, alarmIntent); 

 @Override public void onReceive(Context context, Intent intent) { AudioManager am = (AudioManager)getSystemService(Context.AUDIO_SERVICE); am.setRingerMode(AudioManager.RINGER_MODE_SILENT); } 

 <uses-permission android:name="android.permission.WRITE_SETTINGS" ></uses-permission> <uses-permission android:name="android.permission.CHANGE_CONFIGURATION" ></uses-permission> <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" ></uses-permission> 

 <receiver android:name=".receivers.MyReceiver" />