Layouts for TV

A TV screen is typically viewed from about 10 feet away, and while it is much larger than most other Android device displays, this type of screen does not provide the same level of precise detail and color as a smaller device. These factors require that you create app layouts with TV devices in mind in order to create a useful and enjoyable user experience.

This guide provides direction and implementation details for building effective layouts inN TV apps.

Themes

Android Themes can provide a basis for layouts in your TV apps. You should use a theme to modify the display of your app activities that are meant to run on a TV device. This section explains which themes you should use.

Leanback Theme

The Leanback library provides a standard theme for TV activities, called Theme.Leanback, which establishes a consistent visual style for TV apps. Use of this theme is recommended for most apps. This theme is recommended for any TV app that uses the Leanback library classes. The following code sample shows how to apply this theme to a given activity within an app:

<activity
  android:name="com.example.android.TvActivity"
  android:label="@string/app_name"
  android:theme="@style/Theme.Leanback">

NoTitleBar Theme

The title bar is a standard user interface element for Android apps on phones and tablets, but it is not appropriate for TV apps. If you are not using the Leanback library classes, you should apply this theme to your TV activities. The following code example from a TV app manifest demonstrates how to apply this theme to remove the display of a title bar: 

<application>
  ...

  <activity
    android:name="com.example.android.TvActivity"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.NoTitleBar">
    ...

  </activity>
</application>

Layout Structure

Layouts for TV devices should follow some basic guidelines to ensure they are usable and effective on large screens. Follow these tips to build landscape layouts optimized for TV screens:

  • Build layouts with a landscape orientation. TV screens always display in landscape.
  • Put on-screen navigation controls on the left or right side of the screen and save the vertical space for content.
  • Create UIs that are divided into sections, using Fragments, and use view groups like GridView instead of ListView to make better use of the horizontal screen space.
  • Use view groups such as RelativeLayout or LinearLayout to arrange views. This approach allows the system to adjust the position of the views to the size, alignment, aspect ratio, and pixel density of a TV screen.
  • Add sufficient margins between layout controls to avoid a cluttered UI.

Overscan

Layouts for TV have some unique requirements due to the evolution of TV standards and the desire to always present a full screen picture to viewers. For this reason, TV devices may clip the outside edge of an app layout in order to ensure that the entire display is filled. This behavior is generally referred to as Overscan.

In order to account for the impact of overscan and make sure that all the user interface elements you place in a layout are actually shown on screen, you should incorporate a 10% margin on all sides of your layout. This translates into a 27dp margin on the left and right edges and a 48dp margin on the top and bottom of your base layouts for activities. The following example layout demonstrates how to set these margins in the root layout for a TV app: 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/base_layout"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  android:layout_marginTop="27dp"
  android:layout_marginLeft="48dp"
  android:layout_marginRight="48dp"
  android:layout_marginBottom="27dp" >
</LinearLayout>

Caution: Do not apply overscan margins to your layout if you are using the Leanback Support Library BrowseFragment or related widgets, as those layouts already incorporate overscan-safe margins.

Text and Controls Visibility

The text and controls in a TV app layout should be easily visible and navigable from a distance. Follow these tips to make them easier to see from a distance :

  • Break text into small chunks that users can quickly scan.
  • Use light text on a dark background. This style is easier to read on a TV.
  • Avoid lightweight fonts or fonts that have both very narrow and very broad strokes. Use simple sans-serif fonts and anti-aliasing to increase readability.
  • Use Android's standard font sizes: 
    <TextView
      android:id="@+id/atext"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:gravity="center_vertical"
      android:singleLine="true"
      android:textAppearance="?android:attr/textAppearanceMedium"/>
  • Ensure that all your view widgets are large enough to be clearly visible to someone sitting 10 feet away from the screen (this distance is greater for very large screens). The best way to do this is to use layout-relative sizing rather than absolute sizing, and density-independent pixel units instead of absolute pixel units. For example, to set the width of a widget, use wrap_content instead of a pixel measurement, and to set the margin for a widget, use dip instead of px values.

Screen Density and Image Resources

The common high-definition TV display resolutions are 720p, 1080i, and 1080p. Your TV layout should target a screen size of 1920 x 1080 pixels, and then allow the Android system to downscale your layout elements to 720p if necessary. In general, downscaling (removing pixels) does not degrade your layout presentation quality. However, upscaling can cause display artifacts that degrade the quality of your layout and have a negative impact on the user experience of your app.

To get the best scaling results for images, provide them as 9-patch image elements if possible. If you provide low quality or small images in your layouts, they will appear pixelated, fuzzy, or grainy. This is not a good experience for the user. Instead, use high-quality images.

For more information on optimizing layouts and resources for large screens see Designing for multiple screens.

Layout Anti-Patterns

There are a few approaches to building layouts for TV that you should avoid because they do not work well and lead to bad user experiences. Here are some user interface approaches you should specifically not use when developing a layout for TV.

  • Re-using phone or tablet layouts - Do not reuse layouts from a phone or tablet app without modification. Layouts built for other Android device form factors are not well suited for TV devices and should be simplified for operation on a TV.
  • ActionBar - While this user interface convention is recommended for use on phones and tablets, it is not appropriate for a TV interface. In particular, using an action bar options menu (or any pull-down menu for that matter) is strongly discouraged, due to the difficulty in navigating such a menu with a remote control.
  • ViewPager - Sliding between screens can work great on a phone or tablet, but don't try this on a TV!

For more information on designing layouts that are appropriate to TV, see the TV Design guide.

Handling Large Bitmaps

TV devices, like any other Android device, have a limited amount of memory. If you build your app layout with very high-resolution images or use many high-resolution images in the operation of your app, it can quickly run into memory limits and cause out of memory errors. To avoid these types of problems, follow these tips:

  • Load images only when they're displayed on the screen. For example, when displaying multiple images in a GridView or Gallery, only load an image when getView() is called on the View's Adapter.
  • Call recycle() on Bitmap views that are no longer needed.
  • Use WeakReference for storing references to Bitmap objects in an in-memory Collection.
  • If you fetch images from the network, use AsyncTask to fetch and store them on the device for faster access. Never do network transactions on the application's UI thread.
  • Scale down large images to a more appropriate size as you download them; otherwise, downloading the image itself may cause an out of memory exception. The following sample code demonstrates how to scale down images while downloading: 
      // Get the source image's dimensions
  BitmapFactory.Options options = new BitmapFactory.Options();
  // This does not download the actual image, just downloads headers.
  options.inJustDecodeBounds = true;
  BitmapFactory.decodeFile(IMAGE_FILE_URL, options);
  // The actual width of the image.
  int srcWidth = options.outWidth;
  // The actual height of the image.
  int srcHeight = options.outHeight;

  // Only scale if the source is bigger than the width of the destination view.
  if(desiredWidth > srcWidth)
    desiredWidth = srcWidth;

  // Calculate the correct inSampleSize/scale value. This approach helps reduce
  // memory use. This value should be a power of 2.
  int inSampleSize = 1;
  while(srcWidth / 2 > desiredWidth){
    srcWidth /= 2;
    srcHeight /= 2;
    inSampleSize *= 2;
  }

  float desiredScale = (float) desiredWidth / srcWidth;

  // Decode with inSampleSize
  options.inJustDecodeBounds = false;
  options.inDither = false;
  options.inSampleSize = inSampleSize;
  options.inScaled = false;
  // Ensures the image stays as a 32-bit ARGB_8888 image.
  // This preserves image quality.
  options.inPreferredConfig = Bitmap.Config.ARGB_8888;

  Bitmap sampledSrcBitmap = BitmapFactory.decodeFile(IMAGE_FILE_URL, options);

  // Resize
  Matrix matrix = new Matrix();
  matrix.postScale(desiredScale, desiredScale);
  Bitmap scaledBitmap = Bitmap.createBitmap(sampledSrcBitmap, 0, 0,
      sampledSrcBitmap.getWidth(), sampledSrcBitmap.getHeight(), matrix, true);
  sampledSrcBitmap = null;

  // Save
  FileOutputStream out = new FileOutputStream(LOCAL_PATH_TO_STORE_IMAGE);
  scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out);
  scaledBitmap = null;