Alarm Manager Example

Question

I want to implement a schedule function in my project. So I Googled for an Alarm manager program but I can`t find any examples.

Can anyone help me with a basic alarm manager program?

Answer 1

This is working code. It wakes CPU every 10 minutes until the phone turns off.

Add to Manifest.xml:

...
<uses-permission android:name="android.permission.WAKE_LOCK"></uses-permission>
...
<receiver android:process=":remote" android:name=".Alarm"></receiver>
...

Code in your class:

package yourPackage;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.PowerManager;
import android.widget.Toast;

public class Alarm extends BroadcastReceiver 
{    
    @Override
    public void onReceive(Context context, Intent intent) 
    {   
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "");
        wl.acquire();

        // Put here YOUR code.
        Toast.makeText(context, "Alarm !!!!!!!!!!", Toast.LENGTH_LONG).show(); // For example

        wl.release();
    }

    public void setAlarm(Context context)
    {
        AlarmManager am =( AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
        Intent i = new Intent(context, Alarm.class);
        PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
        am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000 * 60 * 10, pi); // Millisec * Second * Minute
    }

    public void cancelAlarm(Context context)
    {
        Intent intent = new Intent(context, Alarm.class);
        PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        alarmManager.cancel(sender);
    }
}

Set Alarm from Service:

package yourPackage;

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;

public class YourService extends Service
{
    Alarm alarm = new Alarm();
    public void onCreate()
    {
        super.onCreate();       
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) 
    {
        alarm.setAlarm(this);
        return START_STICKY;
    }

   @Override        
   public void onStart(Intent intent, int startId)
    {
        alarm.setAlarm(this);
    }

    @Override
    public IBinder onBind(Intent intent) 
    {
        return null;
    }
}

If you want to set alarm repeating at phone boot time:

Add permission and the service to Manifest.xml:

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"></uses-permission>
...
<receiver android:name=".AutoStart">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"></action>
    </intent-filter>
</receiver>
...
<service
        android:name=".YourService"
        android:enabled="true"
        android:process=":your_service" >
</service>

And create a new class:

package yourPackage;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

public class AutoStart extends BroadcastReceiver
{   
    Alarm alarm = new Alarm();
    @Override
    public void onReceive(Context context, Intent intent)
    {   
        if (intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED))
        {
            alarm.setAlarm(context);
        }
    }
}

Answer 2

I tried the solution from XXX and while it did initially work, at some point it stopped working. The onReceive never got called again. I spent hours trying to figure out what it could be. What I came to realize is that the Intent for whatever mysterious reason was no longer being called. To get around this, I discovered that you really do need to specify an action for the receiver in the manifest. Example:

<receiver android:name=".Alarm" android:exported="true">
    <intent-filter>
        <action android:name="mypackage.START_ALARM" >
        </action>
    </intent-filter>
</receiver> 

Note that the name is ".Alarm" with the period. In XXX's setAlarm method, create the Intent as follows:

Intent i = new Intent("mypackage.START_ALARM");

The START_ALARM message can be whatever you want it to be. I just gave it that name for demonstration purposes.

I have not seen receivers defined in the manifest without an intent filter that specifies the action. Creating them the way XXX has specified it seems kind of bogus. By specifying the action name, Android will be forced to create an instance of the BroadcastReceiver using the class that corresponds to the action. If you rely upon context, be aware that Android has several different objects that are ALL called context and may not result in getting your BroadcastReceiver created. Forcing Android to create an instance of your class using only the action message is far better than relying upon some iffy context that may never work.

Answer 3

Here's a fairly self-contained example. It turns a button red after 5sec.

    public void SetAlarm()
    {
        final Button button = buttons[2]; // replace with a button from your own UI
        BroadcastReceiver receiver = new BroadcastReceiver() {
            @Override public void onReceive( Context context, Intent _ )
            {
                button.setBackgroundColor( Color.RED );
                context.unregisterReceiver( this ); // this == BroadcastReceiver, not Activity
            }
        };

        this.registerReceiver( receiver, new IntentFilter("com.blah.blah.somemessage") );

        PendingIntent pintent = PendingIntent.getBroadcast( this, 0, new Intent("com.blah.blah.somemessage"), 0 );
        AlarmManager manager = (AlarmManager)(this.getSystemService( Context.ALARM_SERVICE ));

        // set alarm to fire 5 sec (1000*5) from now (SystemClock.elapsedRealtime())
        manager.set( AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + 1000*5, pintent );
    }

Remember though that the AlarmManager fires even when your application is not running. If you call this function and hit the Home button, wait 5 sec, then go back into your app, the button will have turned red.

I don't know what kind of behavior you would get if your app isn't in memory at all, so be careful with what kind of state you try to preserve.

Answer 4

MainActivity.java

package com.example.alarmexample;  

import android.app.Activity;  
import android.app.AlarmManager;  
import android.app.PendingIntent;  
import android.content.Intent;  
import android.os.Bundle;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
import android.widget.EditText;  
import android.widget.Toast;  

public class MainActivity extends Activity {  
Button b1;  

    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main); 

        startAlert();  

}   public void startAlert() { 
        int timeInSec = 2;

        Intent intent = new Intent(this, MyBroadcastReceiver.class);  
        PendingIntent pendingIntent = PendingIntent.getBroadcast(  
                                      this.getApplicationContext(), 234, intent, 0);  
        AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);  
        alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (timeInSec * 1000), pendingIntent);  
        Toast.makeText(this, "Alarm set to after " + i + " seconds",Toast.LENGTH_LONG).show();  
    }  

}

MyBroadcastReceiver.java

package com.example.alarmexample;  

import android.content.BroadcastReceiver;  
import android.content.Context;  
import android.content.Intent;  
import android.media.MediaPlayer;  
import android.widget.Toast;  

public class MyBroadcastReceiver extends BroadcastReceiver {  
    MediaPlayer mp;  
    @Override  
    public void onReceive(Context context, Intent intent) {  
        mp=MediaPlayer.create(context, R.raw.alarm);  
        mp.start();  
        Toast.makeText(context, "Alarm", Toast.LENGTH_LONG).show();  
    }  
}  

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>  
<manifest xmlns:android="http://schemas.android.com/apk/res/android"  
    package="com.example.alarmexample" >  

    <uses-permission android:name="android.permission.VIBRATE" />  


    <application  
        android:allowBackup="true"  
        android:icon="@drawable/ic_launcher"  
        android:label="@string/app_name"  
        android:theme="@style/AppTheme" >  

        <activity  
            android:name="com.example.alarmexample.MainActivity"  
            android:label="@string/app_name" >  
            <intent-filter>  
                <action android:name="android.intent.action.MAIN" />  

                <category android:name="android.intent.category.LAUNCHER" />  
            </intent-filter>  
        </activity>  

        <receiver android:name="MyBroadcastReceiver" >  
        </receiver>  
    </application>  

</manifest>  

Answer 5

• AlarmManager in combination with IntentService

I think the best pattern for using AlarmManager is its collaboration with an IntentService. The IntentService is triggered by the AlarmManager and it handles the required actions through the receiving intent. This structure has not performance impact like using BroadcastReceiver. I have developed a sample code for this idea in kotlin which is available here:

MyAlarmManager.kt

import android.app.AlarmManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent

object MyAlarmManager {

    private var pendingIntent: PendingIntent? = null

    fun setAlarm(context: Context, alarmTime: Long, message: String) {
        val alarmManager: AlarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager

        val intent = Intent(context, MyIntentService::class.java)
        intent.action = MyIntentService.ACTION_SEND_TEST_MESSAGE
        intent.putExtra(MyIntentService.EXTRA_MESSAGE, message)

        pendingIntent = PendingIntent.getService(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)
        alarmManager.set(AlarmManager.RTC_WAKEUP, alarmTime, pendingIntent)
    }

    fun cancelAlarm(context: Context) {
        pendingIntent?.let {
            val alarmManager: AlarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
            alarmManager.cancel(it)
        }
    }

}

MyIntentService.kt

import android.app.IntentService
import android.content.Intent

class MyIntentService : IntentService("MyIntentService") {

    override fun onHandleIntent(intent: Intent?) {
        intent?.apply {
            when (intent.action) {
                ACTION_SEND_TEST_MESSAGE -> {
                    val message = getStringExtra(EXTRA_MESSAGE)
                    println(message)
                }
            }
        }
    }

    companion object {
        const val ACTION_SEND_TEST_MESSAGE = "ACTION_SEND_TEST_MESSAGE"
        const val EXTRA_MESSAGE = "EXTRA_MESSAGE"
    }

}

manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.aminography.alarm">

    <application
        ... >

    <service
        android:name="path.to.MyIntentService"
        android:enabled="true"
        android:stopWithTask="false" />

    </application>

</manifest>

Usage:

val calendar = Calendar.getInstance()
calendar.add(Calendar.SECOND, 10)
MyAlarmManager.setAlarm(applicationContext, calendar.timeInMillis, "Test Message!")

If you want to to cancel the scheduled alarm, try this:

MyAlarmManager.cancelAlarm(applicationContext)

Answer 6

This code will help you to make a repeating alarm. The repeating time can set by you.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
     <LinearLayout 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"
     android:orientation="vertical" 
     android:background="#000000"
     android:paddingTop="100dp">

    <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center" >

    <EditText
        android:id="@+id/ethr"
    android:layout_width="50dp"
    android:layout_height="wrap_content"
    android:ems="10"
    android:hint="Hr"
    android:singleLine="true" >


        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/etmin"
    android:layout_width="55dp"
    android:layout_height="wrap_content"

    android:ems="10"
    android:hint="Min"
    android:singleLine="true" />

    <EditText
        android:id="@+id/etsec"
    android:layout_width="50dp"
    android:layout_height="wrap_content"

    android:ems="10"
    android:hint="Sec"
    android:singleLine="true" />

    </LinearLayout>

   <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content" 
    android:gravity="center"
    android:paddingTop="10dp">


    <Button
        android:id="@+id/setAlarm"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onClickSetAlarm"
        android:text="Set Alarm" />

</LinearLayout>

</LinearLayout>

MainActivity.java

public class MainActivity extends Activity {
    int hr = 0;
    int min = 0;
    int sec = 0;
    int result = 1;

    AlarmManager alarmManager;
    PendingIntent pendingIntent;
    BroadcastReceiver mReceiver;

    EditText ethr;
    EditText etmin;
    EditText etsec;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ethr = (EditText) findViewById(R.id.ethr);
        etmin = (EditText) findViewById(R.id.etmin);
        etsec = (EditText) findViewById(R.id.etsec);
        RegisterAlarmBroadcast();
    } 

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

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

    public void onClickSetAlarm(View v) {
        String shr = ethr.getText().toString();
        String smin = etmin.getText().toString();
        String ssec = etsec.getText().toString();

        if(shr.equals("")) 
            hr = 0;
        else {
            hr = Integer.parseInt(ethr.getText().toString());
            hr=hr*60*60*1000;
        }

        if(smin.equals(""))
            min = 0;
        else {
            min = Integer.parseInt(etmin.getText().toString());
            min = min*60*1000;
        }

        if(ssec.equals(""))
            sec = 0;
        else {
             sec = Integer.parseInt(etsec.getText().toString());
             sec = sec * 1000;
        }
        result = hr+min+sec;
        alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), result , pendingIntent); 
    }

    private void RegisterAlarmBroadcast() {
        mReceiver = new BroadcastReceiver() {
            // private static final String TAG = "Alarm Example Receiver";
            @Override
            public void onReceive(Context context, Intent intent) {
                Toast.makeText(context, "Alarm time has been reached", Toast.LENGTH_LONG).show();
            }
        };

        registerReceiver(mReceiver, new IntentFilter("sample"));
        pendingIntent = PendingIntent.getBroadcast(this, 0, new Intent("sample"), 0);
        alarmManager = (AlarmManager)(this.getSystemService(Context.ALARM_SERVICE));
    }

    private void UnregisterAlarmBroadcast() {
        alarmManager.cancel(pendingIntent); 
        getBaseContext().unregisterReceiver(mReceiver);
    }
}

If you need alarm only for a single time then replace

alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), result , pendingIntent);

with

 alarmManager.set( AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + result , pendingIntent );

Answer 7

Alarm Manager:

Add To XML Layout (*init these view on create in main activity)

  <TimePicker
    android:id="@+id/timepicker"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="2"></TimePicker>

  <Button
    android:id="@+id/btn_start"
    android:text="start Alarm"
    android:onClick="start_alarm_event"
    android:layout_width="match_parent"
    android:layout_height="52dp" />

Add To Manifest (Inside application tag && outside activity)

 <receiver android:name=".AlarmBroadcastManager"
        android:enabled="true"
        android:exported="true"/>

Create AlarmBroadcastManager Class(inherit it from BroadcastReceiver)

 public class AlarmBroadcastManager extends BroadcastReceiver{
    @Override
    public void onReceive(Context context, Intent intent) {
      MediaPlayer mediaPlayer=MediaPlayer.create(context,Settings.System.DEFAULT_RINGTONE_URI);
      mediaPlayer.start();
    }
 }

In Main Activity (Add these Functions):

 @RequiresApi(api = Build.VERSION_CODES.M)
 public  void start_alarm_event(View view){
    Calendar calendar=Calendar.getInstance();
    calendar.set(
    calendar.get(Calendar.YEAR),
    calendar.get(Calendar.MONTH),
    calendar.get(Calendar.DAY_OF_MONTH),
    timePicker.getHour(),
    timePicker.getMinute(),
    0
    );
    setAlarm(calendar.getTimeInMillis());
 }

 public void setAlarm(long timeInMillis){
    AlarmManager alarmManager=(AlarmManager) getSystemService(Context.ALARM_SERVICE);
    Intent intent=new Intent(this,AlarmBroadcastManager.class);
    PendingIntent pendingIntent=PendingIntent.getBroadcast(this,0,intent,0);
     alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,timeInMillis,AlarmManager.INTERVAL_DAY,pendingIntent);
    Toast.makeText(getApplicationContext(),"Alarm is Set",Toast.LENGTH_SHORT).show();


 }

Answer 8

I have made my own implementation to do this on the simplest way as possible.

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;

import junit.framework.Assert;

/**
 * Created by Daniel on 28/08/2016.
 */
public abstract class AbstractSystemServiceTask {

    private final Context context;
    private final AlarmManager alarmManager;
    private final BroadcastReceiver broadcastReceiver;
    private final PendingIntent pendingIntent;

    public AbstractSystemServiceTask(final Context context, final String id, final long time, final AlarmType alarmType, final BackgroundTaskListener backgroundTaskListener) {

        Assert.assertNotNull("ApplicationContext can't be null", context);
        Assert.assertNotNull("ID can't be null", id);

        this.context = context;

        this.alarmManager = (AlarmManager) this.context.getSystemService(Context.ALARM_SERVICE);

        this.context.registerReceiver(
                this.broadcastReceiver = this.getBroadcastReceiver(backgroundTaskListener),
                new IntentFilter(id));

        this.configAlarmManager(
                this.pendingIntent = PendingIntent.getBroadcast(this.context, 0, new Intent(id), 0),
                time,
                alarmType);
    }

    public void stop() {

        this.alarmManager.cancel(this.pendingIntent);
        this.context.unregisterReceiver(this.broadcastReceiver);
    }

    private BroadcastReceiver getBroadcastReceiver(final BackgroundTaskListener backgroundTaskListener) {

        Assert.assertNotNull("BackgroundTaskListener can't be null.", backgroundTaskListener);

        return new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {

                backgroundTaskListener.perform(context, intent);
            }
        };
    }

    private void configAlarmManager(final PendingIntent pendingIntent, final long time, final AlarmType alarmType) {

        long ensurePositiveTime = Math.max(time, 0L);

        switch (alarmType) {
            case REPEAT:
                this.alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), ensurePositiveTime, pendingIntent);
                break;
            case ONE_TIME:
            default:
                this.alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + ensurePositiveTime, pendingIntent);
        }
    }

    public interface BackgroundTaskListener {

        void perform(Context context, Intent intent);

    }

    public enum AlarmType {

        REPEAT, ONE_TIME;

    }

}

The only next step, implement it.

import android.content.Context;
import android.content.Intent;
import android.util.Log;

import ...AbstractSystemServiceTask;

import java.util.concurrent.TimeUnit;

/**
 * Created by Daniel on 28/08/2016.
 */
public class UpdateInfoSystemServiceTask extends AbstractSystemServiceTask {

    private final static String ID = "UPDATE_INFO_SYSTEM_SERVICE";
    private final static long REPEAT_TIME = TimeUnit.SECONDS.toMillis(10);
    private final static AlarmType ALARM_TYPE = AlarmType.REPEAT;

    public UpdateInfoSystemServiceTask(Context context) {

        super(context, ID, REPEAT_TIME, ALARM_TYPE, new BackgroundTaskListener() {

            @Override
            public void perform(Context context, Intent intent) {

                Log.i("MyAppLog", "-----> UpdateInfoSystemServiceTask");

                //DO HERE WHATEVER YOU WANT...
            }
        });

        Log.i("MyAppLog", "UpdateInfoSystemServiceTask started.");
    }

}

I like to work with this implementation, but another possible good way, it's don't make the AbstractSystemServiceTask class abstract, and build it through a Builder.

I hope it help you.

UPDATED Improved to allow several BackgroundTaskListener on the same BroadCastReceiver.

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;

import junit.framework.Assert;

import java.util.HashSet;
import java.util.Set;

/**
 * Created by Daniel on 28/08/2016.
 */
public abstract class AbstractSystemServiceTask {

    private final Context context;
    private final AlarmManager alarmManager;
    private final BroadcastReceiver broadcastReceiver;
    private final PendingIntent pendingIntent;

    private final Set<BackgroundTaskListener> backgroundTaskListenerSet;

    public AbstractSystemServiceTask(final Context context, final String id, final long time, final AlarmType alarmType) {

        Assert.assertNotNull("ApplicationContext can't be null", context);
        Assert.assertNotNull("ID can't be null", id);

        this.backgroundTaskListenerSet = new HashSet<>();

        this.context = context;

        this.alarmManager = (AlarmManager) this.context.getSystemService(Context.ALARM_SERVICE);

        this.context.registerReceiver(
                this.broadcastReceiver = this.getBroadcastReceiver(),
                new IntentFilter(id));

        this.configAlarmManager(
                this.pendingIntent = PendingIntent.getBroadcast(this.context, 0, new Intent(id), 0),
                time,
                alarmType);
    }

    public synchronized void registerTask(final BackgroundTaskListener backgroundTaskListener) {

        Assert.assertNotNull("BackgroundTaskListener can't be null", backgroundTaskListener);

        this.backgroundTaskListenerSet.add(backgroundTaskListener);
    }

    public synchronized void removeTask(final BackgroundTaskListener backgroundTaskListener) {

        Assert.assertNotNull("BackgroundTaskListener can't be null", backgroundTaskListener);

        this.backgroundTaskListenerSet.remove(backgroundTaskListener);
    }

    public void stop() {

        this.backgroundTaskListenerSet.clear();

        this.alarmManager.cancel(this.pendingIntent);
        this.context.unregisterReceiver(this.broadcastReceiver);
    }

    private BroadcastReceiver getBroadcastReceiver() {

        return new BroadcastReceiver() {

            @Override
            public void onReceive(final Context context, final Intent intent) {

                for (BackgroundTaskListener backgroundTaskListener : AbstractSystemServiceTask.this.backgroundTaskListenerSet) {

                    backgroundTaskListener.perform(context, intent);
                }
            }
        };
    }

    private void configAlarmManager(final PendingIntent pendingIntent, final long time, final AlarmType alarmType) {

        long ensurePositiveTime = Math.max(time, 0L);

        switch (alarmType) {
            case REPEAT:
                this.alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), ensurePositiveTime, pendingIntent);
                break;
            case ONE_TIME:
            default:
                this.alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + ensurePositiveTime, pendingIntent);
        }
    }

    public interface BackgroundTaskListener {

        void perform(Context context, Intent intent);

    }

    public enum AlarmType {

        REPEAT, ONE_TIME;

    }

}

Answer 9

Here's an example with Alarm Manager using Kotlin:

class MainActivity : AppCompatActivity() {

    val editText: EditText by bindView(R.id.edit_text)
    val timePicker: TimePicker by bindView(R.id.time_picker)
    val buttonSet: Button by bindView(R.id.button_set)
    val buttonCancel: Button by bindView(R.id.button_cancel)
    val relativeLayout: RelativeLayout by bindView(R.id.activity_main)
    var notificationId = 0

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        timePicker.setIs24HourView(true)

        val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager

        buttonSet.setOnClickListener {
            if (editText.text.isBlank()) {
                Toast.makeText(applicationContext, "Title is Required!!", Toast.LENGTH_SHORT).show()
                return@setOnClickListener
            }
            alarmManager.set(
                AlarmManager.RTC_WAKEUP,
                Calendar.getInstance().apply {
                    set(Calendar.HOUR_OF_DAY, timePicker.hour)
                    set(Calendar.MINUTE, timePicker.minute)
                    set(Calendar.SECOND, 0)
                }.timeInMillis,
                PendingIntent.getBroadcast(
                    applicationContext,
                    0,
                    Intent(applicationContext, AlarmBroadcastReceiver::class.java).apply {
                        putExtra("notificationId", ++notificationId)
                        putExtra("reminder", editText.text)
                    },
                    PendingIntent.FLAG_CANCEL_CURRENT
                )
            )
            Toast.makeText(applicationContext, "SET!! ${editText.text}", Toast.LENGTH_SHORT).show()
            reset()
        }

        buttonCancel.setOnClickListener {
            alarmManager.cancel(
                PendingIntent.getBroadcast(
                    applicationContext, 0, Intent(applicationContext, AlarmBroadcastReceiver::class.java), 0))
            Toast.makeText(applicationContext, "CANCEL!!", Toast.LENGTH_SHORT).show()
        }
    }

    override fun onTouchEvent(event: MotionEvent?): Boolean {
        (getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager)
            .hideSoftInputFromWindow(relativeLayout.windowToken, InputMethodManager.HIDE_NOT_ALWAYS)
        relativeLayout.requestFocus()
        return super.onTouchEvent(event)
    }

    override fun onResume() {
        super.onResume()
        reset()
    }

    private fun reset() {
        timePicker.apply {
            val now = Calendar.getInstance()
            hour = now.get(Calendar.HOUR_OF_DAY)
            minute = now.get(Calendar.MINUTE)
        }
        editText.setText("")
    }
}

Answer 10

After ten years, you can read this training explanation on the official documentation.

Answer 11

I was having a problem with alarms in Android too. The problem was about the doze mode (https://developer.android.com/training/monitoring-device-state/doze-standby). For example, the alarm worked fine when I set it to one hour further, but it didn't work if it was set to 4am. I just discovered it is very simple, I just should use AlarmManager.setAlarmClock() instead of AlarmManager.set().

So I decided to create an example application on github. https://github.com/carlosabreu/androidalarm