Pro Android with Kotlin

144
CHAPTER 8: APIs
Figure 8-1. Smartphone notification
Figure 8-2. Notification content

---

145
CHAPTER 8: APIs
Notifications also allow for actions, such as calling custom activities when tapped, or they 
can contain special action buttons or even edit fields a user can fill out. Likewise, although 
notifications were primarily built to show only short text snippets, with current Android 
versions, it is possible to present longer text there as well.
The online API documentation suggests to use the NotificationCompat API from the 
support library. Using this compatibility layer allows older versions to present similar or no-
op variants on features that were made available only later, simplifying the development. 
Although using this compatibility layer removes the burden from the developer of presenting 
many branches inside the code to take care of different Android API levels, caution must be 
taken to not make an app unusable by depending too much on the latest notification API 
features.
To make sure the compatibility API is available for your project inside Android Studio, check 
the build.gradle setting of your module in the dependencies section (only one line; remove 
the newline after implementation).
implementation
"com.android.support:support-compat:27.0.2"
The following sections present an outline of the notification API. With this API having grown 
considerably during the last years, please consult the online documentation for a more 
detailed description of all notification features.
Creating and Showing Notifications
To create and show a notification, you prepare action intents for a tap and additional action 
buttons, use a notification builder to construct the notification, register a notification channel, 
and finally make the framework show the notification. An example looks like this:
val NOTIFICATION_CHANNEL_ID = "1"
val NOTIFICATION_ID = 1
// Make sure this Activity exists
val intent = Intent(this, AlertDetails::class.java)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
//or Intent.FLAG_ACTIVITY_CLEAR_TASK
val tapIntent = PendingIntent.getActivity(this, 0,
intent, 0)
// Make sure this broadcast receiver exists and can
// be called by explicit Intent like this
val actionIntent = Intent(this, MyReceiver::class.java)
actionIntent.action = "com.xyz.MAIN"
actionIntent.putExtra(EXTRA_NOTIFICATION_ID, 0)
val actionPendingIntent =
PendingIntent.getBroadcast(this, 0, actionIntent, 0)
val builder = NotificationCompat.Builder(this,
NOTIFICATION_CHANNEL_ID)
.setSmallIcon( ... an icon resource id... )

---