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In this blog, we will learn about Secondary Display Control via Android Presentation Class.
Well, the title line certainly deals with a lot of words that probably most of the developers are not aware of and frankly, even I was not aware of this beauty of Android until last month.
Before we start, let me just tell you a few practical use cases for what you can build after following along.
After reading this blog you will also be able to build something similar.
Before we start talking about code let’s just clear what the words in the title are.
A display is referred to as a screen or area which can show the content.
As a result, an Android device can control any number of displays.
The main point to note is that the application’s code should be able to handle each display separately and these are in sync with the main display.
This display refers to the actual screen provided by the manufacturer of the Android device.
Hence, this screen listens to all the user interactions, gestures and motions events.
As a result, this display is referred to as Main Display.
This display refers to a secondary screen which is somehow (Bluetooth, wired connections, RFC) connected to your Android device.
By Default, this screen is not user interactive and hence it is called as Display and not Screen.
A presentation is a special kind of dialog whose purpose is to present content on a secondary display. A Presentation is associated with the target Display at creation time and configures its context and resource configuration according to the display’s metrics.
— developer.android.com
For Simple understanding, we need to extend this class to build a view to display on our Secondary Display.
With this understanding, now you can do anything you want on Secondary Display.
Now, in this blog, we will just be making a Welcome TextView on the Secondary Display.
File Name –> secondary_display.xml
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<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".SecondaryDisplay"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:layout_margin="8dp" android:padding="4dp" android:text="Hello, Presentation Api, \nThis text will be displayed on the secondary display" android:textAppearance="?android:attr/textAppearanceMedium" /> </RelativeLayout> |
File Name –> SecondaryDisplay.java
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public class SecondaryDisplay extends Presentation { /** * Creates a new presentation that is attached to the specified display * using the default theme. * * @param outerContext The context of the application that is showing the presentation. * The presentation will create its own context (see {@link #getContext()}) based * on this context and information about the associated display. * @param display The display to which the presentation should be attached. */ public SecondaryDisplay(Context outerContext, Display display) { super(outerContext, display); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.secondary_display); } } |
With the help of lines below, you can set the Secondary Display Content.
Last Step:
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public class MainActivity extends AppCompatActivity{ public DisplayManager displayManager = null; public Display[] presentationDisplays = null; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); displayManager = (DisplayManager)getSystemService(Context.DISPLAY_SERVICE); if (displayManager!= null){ presentationDisplays = displayManager.getDisplays(DisplayManager.DISPLAY_CATEGORY_PRESENTATION); if (presentationDisplays.length > 0){ SecondaryDisplay secondaryDisplay = new SecondaryDisplay(MainActivity.this, presentationDisplays[0]); secondaryDisplay.show(); } } } } |
With this last change, you have completed the task.
Now, just run your application on a device with Secondary Display and see the magic.
Keep coding and Keep Sharing 🙂
References –> https://developer.android.com/reference/android/app/Presentation
https://developer.android.com/reference/android/view/Display.html
You can easily try this option in any android device or emulators.
All you need to do is to enable the developer options.
Then in the developer options menu find the option “Simulate secondary displays”.
From the list that opens up , you can easily select the width option as per your need.
Thank you!!!
How to controll secondary display?
I am assuming that by control you want to listen to some of the events on the secondary display.
So, if that is all about majorly click listeners then you can add them as you add it to any of the views in your code in your secondary display class as well.
Though, I have not practically implemented any listeners for the secondary display.
But i guess, this should work fine.
Still, if you are looking for soemthing else, then feel free to type more over here.
Regards,
Anchit
Very well explained.
I have a query, How to send data from main activity to 2nd display, for example if we type some thing on main activity, the same should be get displayed on 2nd display
This seems to be pretty easy.
You can either create some method in your secondary display class and update the ui accordingly.
Or
You can declare the components public and then access the same in the main activity.
Both will work.