Creating alarm in android

Программирование для Android: уведомления с использованием AlarmManager

Многим обладателям телефонов с Android, владеющим элементарными навыками программирования, хотелось или захочется написать свою «программку для телефона». Учитывая рост популярности этой ОС и факт существования Android Market, эта идея может еще и денег принести.
Особенность Android в том, что ребята из Google дают разработчику разрешение использовать все (вернее, почти все) возможности телефона. Можно перехватывать звонки, рассылать SMS, и многое другое. Одна из полезных вещей — уведомления, появляющиеся в соответствующей области вверху экрана. В этом посте я расскажу, как легко и просто их организовать.

Итак, ставим задачу: в определенное время, ежедневно, уведомлять пользователя о необходимости запустить приложение и что-то в нем сделать. Ну и совсем здорово, если по нажатию на уведомление запустится нужное приложение.

Нам понадобятся следующие классы:
AlarmManager — собственно, эта штука и умеет генерировать системные события по заданым параметрам
BroadcastReceiver — для обработки событий AlarmManager
NotificationManager — а эта штука умеет показывать уведомления

Первым делом, создадим класс — приемник:

public class TimeNotification extends BroadcastReceiver <
@Override
public void onReceive(Context context, Intent intent) <
// Этот метод будет вызываться по событию, сочиним его позже
>
>

Обязательно следует упомянуть об этом в манифесте (в разделе application):

Затем, идем в основной класс нашего приложения (допустим, MainActivity). Здесь нам необходимо обеспечить функционал по запуску и настройке AlarmManager.
Предположим, что задачу установки пользователем настроек мы уже решили, и у нас есть глобальная переменная stamp, в которой хранится время следующего показа уведомления.

private void restartNotify() <
am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(this, TimeNotification.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,
intent, PendingIntent.FLAG_CANCEL_CURRENT );
// На случай, если мы ранее запускали активити, а потом поменяли время,
// откажемся от уведомления
am.cancel(pendingIntent);
// Устанавливаем разовое напоминание
am.set(AlarmManager.RTC_WAKEUP, stamp.getTime(), pendingIntent);
>

Почему разовое, спросите вы? У AlarmManager есть метод setRepeat, где можно задать интервал. Но мне кажется, проще перезапустить процесс при обработке события, на случай смены настроек и т.п. Хотя, это личное дело каждого, оба варианта будут работать.

Ну и, собственно, реализуем обработчик

public void onReceive(Context context, Intent intent) <
nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
Notification notification = new Notification(R.drawable.icon, «Test», System.currentTimeMillis());
//Интент для активити, которую мы хотим запускать при нажатии на уведомление
Intent intentTL = new Intent(context, MainActivity.class);
notification.setLatestEventInfo(context, «Test», «Do something!»,
PendingIntent.getActivity(context, 0, intentTL,
PendingIntent.FLAG_CANCEL_CURRENT));
notification.flags = Notification.DEFAULT_LIGHTS | Notification.FLAG_AUTO_CANCEL;
nm.notify(1, notification);
// Установим следующее напоминание.
AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0,
intent, PendingIntent.FLAG_CANCEL_CURRENT);
am.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + AlarmManager.INTERVAL_DAY, pendingIntent);
>

Вот и все. Надеюсь, в будущем написать и о других простых, но полезных возможностях для разработчика приложений под Android

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How to Build a Simple Alarm Setter App in Android?

In this article, we are going to see how to build a much interesting app named Alarm Setter. Alarm plays a vital role in our day-to-day life. Nowadays alarm has become our wake-up assistant. Every mobile phone is associated with an alarm app. We will create this app using android studio. Android Studio provides a great unified environment to build apps for Android phones, tablets, Android Wear, Android TV, and Android Auto because it provides a very large number of app building features and it is also very easy to use. A sample video is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Java language.

Step by Step Implementation

Step 1: Create a New Project

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To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.

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Kotlin Android Alarm Examples

AlarmManager is a class that allows us create alarms. Alarms allow our apps to schedule specific codes to be executed at certain times in the future.

It’s better and more efficient to use AlarmManager class to create alarms for scheduling than using something like a timer.

AlarmManager provides to us the access to system alarm services, so it’s not like we are going to invent our scheduling algorithms.

AlarmManager is mostly used together with BroadcastReceivers. Here’s how it works:

• First Alarm goes off or rings.
• The system broadcasts an intent. This is the intent which had been registered for it.
• This automatically starts the target application in case it’s not already running.
• If the device sleeps, the alarms that are already registered get retained.
• If the alarm goes off while the device is sleeping, then the device is woken up. This is optional.
• If the user turns the device off or reboots it, then the alarms are cleared.

You are guaranteed that the phone will not sleep till you have finished handling your broadcast. Broadcast are handled by the onReceive() method of the android.content.BroadcastReceiver . This is a method you override after deriving this class.

As long as the The onReceive() method is still executing, the AlarmManager will hold a CPU wake lock. So the device won’t sleep.

Then the AlarmManager releases the wake lock when the onReceive() finishes executing and returns.

But sometimes just as the onReceive() method finishes, it’s possible that the phone can sleep immediately. Because the device has slept quickly, if you had requested a service using the Context.startService() it won’t be started. This is because the device has slept before it’s called. However, the initial wake lock is no longer in place. It had been released the moment the onReceive() had returned. So what’s the solution? Well you implement a separate wake lock on your BroadcastReceiver and Service. This wake lock will ensure the device runs until the service becomes available.

So when should you use alarm manager and when should you not? Well use alarm manager for scheduling operations. Don’t use it for timing and ticking operations. And don’t use timers for scheduling operations. Scheduled code using alarmmanager do not require teh application to be running all the time. If you used a timer then it would have to run throughout. This wastes memory and processing time.

The Android Operating System shifts alarms so us minimize wakeups and battery use. This is starting from Android API 19(KitKat). This the alarms may not be strictly exact. If you need to be strictly exact, then you can use the setExact() method.

AlarmManager is not directly instantiated. Instead you use the static getSystemService() of the Context class. You pass the Context.ALARM_SERVICE flag.

Example 1: Kotlin Android Build an Alarm Clock

This is an example to teach you usage of Alarms and Broadcastreceiver. In the process you build a simple alarm clock. This example allows you learn these technologies in a practical manner.

Step 1: Create Kotlin Project

Start by creating an empty Kotlin Project in Android Studio.

Step 2: Dependencies

No special dependencies are needed. However because Coroutines are used, be sure to use Kotlin.

Step 3: Permissions

No permissions are needed for this project. However in your in AndroidManifest.xml , be sure to register the receiver since BroadcastReceiver is used in this alarm clock.

Step 4: Design Layout

You only need one layout, the main activity layout. Simply add TextViews and buttons and constraint them using the ConstraintLayout as follows:

activity_main.xml

Step 5: Create model class

Create a model class, Kotlin data class that receives the two integers and a boolean via the constructor. The integers are the hour and the minute while the boolean is an on-off swicth. These will be used to construct a timer view to be rendered in the alarm clock:

AlarmDisplayModel.kt

Step 5: Create an Alarm Receiver

You do this by extending the broadcast receiver and overriding the onReceive() method. Inside the onReceive() you will create a notification channel as well as build a notification.

Here is the full code:

AlarmReceiver.kt

Step 6: Create main Activity

Finally create your main activity as below:

MainActivity.kt

Step 7: Run

Finally run the project.

Reference

Here are the code reference links:

Number	Link
1.	Download code
2.	Follow code author

Example 2: How to Start an Alarm

One of those mobile-like software applications is the Alarm. Or any app that can schedule something to happen in the future. This is even more important in mobile devices than in desktop applications.

Because we never leave or power off our mobile devices. They are our personal assistants. So we use them in more personal ways than we would ever do with desktop applications.

So Android provides us a rich class called AlarmManager. A class that allows us access system services. The class is obviously public and derives from java.lang.Object .

Here’s its definition:

What do we build?

Well let’s see a simple android alarm manager example. We see how to start and cancel an alarm in android. We have a basic edittext. The user enters the time in miliseconds for the alarm to ring. The alarm rings by displaying a simple toast message.

Project Structure

Here’s the project structure:

Step 1 – Create Android Project

• In your android studio go to File — New — New Project.
• Type Project Name.
• Choose minimum sdk.
• From templates choose empty activity or bla.

Step 2. – Let’s modify our build.gradle.

This is our second step. Android projets created in android studio have two buil.gradle files. We are interested in the app level build.gradle.

Add the followng code under the dependencies section:

We’ve added two dependencies from support library: AppCompat and design .

Step 3. Let’s prepare our resources.

The only resource we need to prepare in this case is the layouts. I chose the basic activity as my template. So I have two layouts:

• _activitymain.xm : template layout
• _contentmain.xml : this what we modify.

All I need is add one edittext and one button. The edittext where the user will enter the time in seconds and the start button to start the alarm.

Step 4. Let’s create our BroadcastReceiver class.

A BroadcastReceiver is one of the android components. Others include Activity, Service and ContentProvider.
A BroadcastReceiver listens to System events.

It’s actually an abstract class that’s obviously public. It derives form java.lang.Object :

Intents sent by the sendBroadcast() will be received by this base class.

It’s an abstract class so we will override the onReceive() method.

First create a java class :

Add the folowing imports:

Make it derive from android.content.BroadcastReceiver:

This will force us to ovveride the onReceive() method:

Step 5. Let’s come to our MainActivity class.

Activities are android components that represent a user interface. We create activities by deriving from an activity. To support more devices we use AppCompatActivity .

So let’s create an activity:

Add the following imports on top of the activity:

Our activity will have three methods and two fields:

First we define our two fields: basically a button an edittext. Add them inside the MainActivity class:

Then we create a method go() . This method will be responsible for initializing our alarmmanager and starting the alarm:

Then we come create another method to initialize our button and edittext and handle the onclick listener of the button:

Step 6. Let’s check on the Androidmanifest

Go over the androidmanifest.xml. We want to ensure our BroadcastReceiver class is registered inside our manifest.

You can see that our broadcastreceiver class is registered:

Here’s what I have:

Example: Android AlarmManager – Schedule Showing of Toast

Android Engineers added AlarmManager class in API level 1, so it’s been around since the beginning of android. This class allows for scheduling of operations to be done sometime in the future. With AlarmManager, you can set some code that will be executed in the future.

This is cool given that it’s not necessary for your app to be running for that code to be run. Of course your app will be started, but only at the registered time. Alarm Maanager belongs to android.app package and inherits from java.lang.Object.

Even while the device is asleep, alarms are retained as long as they were registered. You can find more details about AlarmManager here.

Screenshot

• Here’s the screenshot of the project.

Common Questions this example explores

• How to use android alarmmanager.
• What is AlarmManager?
• How do I schedule work to be done in future in android?
• Easy alarm manager example with a toast.

Tools Used

This example was written with the following tools:

• Windows 8
• AndroidStudio IDE
• Genymotion Emulator

Source Code

Lets jump directly to the source code.

Build.Gradle

• Normally in android projects, there are two build.gradle files. One is the app level build.gradle, the other is project level build.gradle. The app level belongs inside the app folder and its where we normally add our dependencies and specify the compile and target sdks.
• Also Add dependencies for AppCompat and Design support libraries.
• Our MainActivity shall derive from AppCompatActivity while we shall also use Floating action button from design support libraries.

MyReceiver.java»

• Our Broadcast Receiver class.
• Make it extend android.app.content.BroadCastReceiver.
• We then override the OnReceive() method. This is where we write the code to be executed when alarm rings.
• In this case we simply display a toast message.

MainActivity.java

• Launcher activity.
• ActivityMain.xml inflated as the contentview for this activity.
• We initialize views and widgets inside this activity.
• We also initialize and start our alarm inside here using the alarmmanager object.

ActivityMain.xml

• Template layout.
• Contains our ContentMain.xml.
• Also defines the appbarlayout, toolbar as well as floatingaction buttton.

ContentMain.xml

• Content Layout.
• Defines the views and widgets to be displayed inside the MainActivity.

More Resources:

How To Run

1. Download the project above.
2. You’ll get a zipped file,extract it.
3. Open the Android Studio.
4. Now close, already open project.
5. From the Menu bar click on File >New> Import Project.
6. Now Choose a Destination Folder, from where you want to import project.
7. Choose an Android Project.
8. Now Click on “OK“.
9. Done, your done importing the project,now edit it.

Conclusion.

We saw a simple android alarm manager example.

Example: Android Schedule Repeating/Recurring Alarms

AlarmManager has existed since the beginning of Android. It enables us schedule tasks to be done sometime in the future.

With AlarmManager, you can set some code that will be executed in the future.

Alarm Maanager belongs to android.app package and inherits from java.lang.Object. Even while the device is asleep, alarms are retained as long as they were registered. In this example we will see how to work with a Recurring/repeating alarms.

We will schedule showing of toast messages after a given number of seconds. For example, the user enters 5 in the edittexts and clicks start button, after every 5 seconds the toast message gets shown until the user clicks the cancel button to cancell the alarms. So we see how to start repeating alarms and cancel them. You can find more details about AlarmManager here.

Screenshot

• Here’s the screenshot of the project.

Android Recurring Alarms Example

Common Questions this example explores

• How to use android alarmmanager.
• How to set repeating/recurring alarms in android and cancel them.
• Starting and canceling alarms in android.
• How do I schedule work to be done in future in android?
• Easy recurring alarm manager example with a toast.

Tools Used

This example was written with the following tools:

• Windows 8
• AndroidStudio IDE
• Genymotion Emulator
• Language : Java
• Topic : Android Recurring Alarms, AlarmManager, Start Cancel Repeating alarms

Libaries Used

• We don’t use any third part library.

Source Code

Lets jump directly to the source code.

Build.Gradle

• Normally in android projects, there are two build.gradle files. One is the app level build.gradle, the other is project level build.gradle. The app level belongs inside the app folder and its where we normally add our dependencies and specify the compile and target sdks.
• Also Add dependencies for AppCompat and Design support libraries.
• Our MainActivity shall derive from AppCompatActivity while we shall also use Floating action button from design support libraries.

MyReceiver.java

• Our MyReceiver class.
• Derives from android.content.BroadcastReceiver.
• We override onReceive() method and perform task to be done when alarm rings here.

MainActivity.java

• Our MainActivity class.
• Derives from AppCompatActivity which is a Base class for activities that use the support library action bar features.
• Methods: onCreate(),initializeViews(),initializeAlarmManager(),go().
• Inflated From activity_main.xml using the setContentView() method.
• The views we use are EditTexts and buttons.
• Reference them from our layout specification using findViewById().
• Initialize alarm manager.
• Start alarm using the setInExactRepeating().

ActivityMain.xml

• ActivityMain.xml.
• This is a template layout for our MainActivity.
• Root layout tag is CoordinatorLayout from design support library.
• CordinatorLayout is viewgroup that is a superpowered on framelayout.
• CoordinatorLayout is intended for two primary use cases: As a top-level application decor or chrome layout As a container for a specific interaction with one or more child views
• Inside our CordinatorLayout we add : AppBarLayout,FloatingActionButton and include content_main.xml.
• AppBarLayout is vertical LinearLayout that implements scrolling features of material design concept.
• It should be a direct child of CordinatorLayout, otherwise alot of features won’t work.
• Inside the AppBarLayout we add our toolbar,which we give a blue color.
• We will add our widgets in our content_main.xml, not here as this is a template layout.
• Finally we have a FloatingActionButton, a class that derives from android.support.design.widget.VisibilityAwareImageButton. Its the round button you see in our user interface.

ContentMain.xml

• Our ContentMain.xml file.
• Shall get inflated to MainActivity.
• Root tag is ConstraintLayout.
• Contains EditTexts and two buttons.
• User will enter the number of seconds after which alarm rings in edittext.
• Then click start button to start alarm.
• And Cancel button to cancel alarm.

Video/Preview

• We have a YouTube channel with almost a thousand tutorials, this one below being one of them.

Download

• You can Download the full Project below. Source code is well commented.

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