Android InboxStyle Notification As Deep As Possible

InboxStyle notification is one of the notification styles provided by Android officially. In expand state, there are several more lines for displaying more information to user than that in its collapsed state. Unlike BigTextStyle notification, each line is fixed to be a single line and content is truncated at the end when it is too long. Sample use case is adding snippets from incoming emails.

Anatomy of an InboxStyle notification

In InboxSytle notification, there are 3 properties that can be configured. They are BigContentTitle, SummaryText and line. They can all be styled by either limited HTML tags or Spannables.

During my study about InboxStyle, I unexpectedly find an Android documentation issue, which I have submitted to Google Issue Tracker, and will include it at the later part of this article. Let’s start!

All-in-one codes

1. BigContentTitle (CharSequence)

Position of BigContentTitle

This BigContentTitle is only shown when the BigText notification is expanded. It is a replacement of the contentTitle which is set at the Notification builder (See the line 27 of the above sample code).

2. SummaryText (CharSequence)

Position of SummaryText

This is a supplementary text shown in between the app name and the time (when) property of notification.

Bear in mind that this summaryText is overridden by the subText of the NotificationBuilder. See the line 31 of the sample code shown above.

3. Line

Position of Line

Each line is represented by an individual TextView and is fixed to be in single line. Text is truncated at the end when it is too long.

There is a discrepancy on the limit of line stated at different official documentation pages. This official page states the limit is 6 while the another one states it is 5. So which one is correct?

Notification creation official documentation

Notification.InboxStyle official documentation

I was confused with these documentations when I was studying about InboxStyle. Therefore, I decided to read through the InboxStyle open source code and finally find out a mysterious answer — Max number of line is actually 7!

Starting from the line 7879, it is the makeBigContentView function which is called to construct a view for the notification expanded state. In line 7884, the rowIds array is constructed by a set of 7 view ids and each id points to a TextView. At this moment, I am curious whether the maximum number of line is 7. After running the following codes, the 8th line is not shown and it verifies my suspicion.

So, can we say that the maximum number of line is “always” 7? No! Let’s take a look at the line 7898. The maximum number of line has to be reduced by 1 in order to release spaces for displaying a row of action button.

See below codes:

Screenshot with action button

Is there any even more undocumented situation the maximum number of line is not either 6 or 7? Yes and it is the number of remote input history added. See the codes from line 7901 to 7922.:

Source code showing the value of NUMBER_OR_HISTORY_ALLOWED_UNTIL_REDUCTION

Source code showing the value of MAX_REMOTE_INPUT_HISTOYR_LINES

These codes mean the maximum number of row would be reduced when there are more than 2 remote input histories. Moreover, there can only be at most 3 remote input histories to be shown at the same time.

Below are the codes for verification and screenshots of results:

Screenshot when there is only 1 remote input history

Screenshot when there is only 2 remote input histories

Screenshot when there is only 3 remote input histories

To conclude, the max number of line to be shown depends on both the existence of action button and the number of remote histories shown. This documentation issue has been submitted to Google Issue Tracker since I wrote this article in 2020. See below table for a short summary:

Text styling

All texts in Notification can be styled manually by HTML tag, which is suggested officially at the official documentation. Here is an example:

However, beyond the suggested method, the texts can also be styled with Spanned since all the functions for setting texts accept CharSequence as a parameter. Here is an example:

To understand more about styling notification, please refer to the following article:

Android Notification Styling

Want to know more about Android Notification:

1. Custom Notification

Android Custom Notification in 6 Mins

2. Android Notification All-In-One

Android Notification All-in-One

3. BigTextSytle Notification

Android Notification BigTextStyle As Deep As Possible

4. BigPictureStyle Notification

Android Notification BigPictureStyle As Deep As Possible

Summary

1. InboxStyle notification is used for adding multiple short summary lines. Sample use case is the email notification.
2. BigContentTitle, summaryText and line are customisable properties in InboxStyle notification. They are all simple TextView for displaying single line information.
3. The maximum number of line shown in InboxStyle notification is wrongly documented in the official websites and actually depends on the existence of action button and the number of remote histories shown. It ranges from 3 to 7.
4. All text in notification can be styled by either HTML tag and Spanned.

Reference

1. Android Notification open source code

core/java/android/app/Notification.java - platform/frameworks/base - Git at Google

2. Official documentation of how to create expandable notification

Create an Expandable Notification | Android Developers

3. Inbox style official documentation

Notification.InboxStyle | Android Developers

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