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 you to create app layouts with TV devices in mind in order to create a useful and enjoyable user experience.
This lesson describes the minimum requirements and implementation details for building effective layouts in TV apps.
Use Layout Themes for TV
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.
A support library for TV user interfaces called the v17 leanback library provides a
standard theme for TV activities, called
Theme.Leanback. This theme establishes a
consistent visual style for TV apps. Use of this theme is recommended for most TV apps. This
theme is strongly recommended for any TV app that uses v17 leanback 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">
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 v17 leanback classes, you should apply this theme to your TV activities to suppress the display of a title bar. 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>
Build Basic TV Layouts
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 mode.
- 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
ListViewto make better use of the horizontal screen space.
- Use view groups such as
LinearLayoutto 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.
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.
Avoid screen elements being clipped due to overscan and by incorporating 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
v17 leanback classes, such as
BrowseFragment or related
widgets, as those layouts already incorporate overscan-safe margins.
Build Useable Text and Controls
The text and controls in a TV app layout should be easily visible and navigable from a distance. Follow these tips to make your user interface elements 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 (dip) units instead of absolute pixel units. For example, to set the
width of a widget, use
wrap_contentinstead of a pixel measurement, and to set the margin for a widget, use dip values instead of px values.
For more information about density-independent pixels and building layouts to handle larger screen sizes, see Supporting Multiple Screens.
Manage Layout Resources for TV
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, which is not a good experience for the user. Use high-quality images instead.
For more information on optimizing layouts and resources for large screens see Designing for multiple screens.
Avoid Layout Anti-Patterns
There are a few approaches to building layouts that you should avoid because they do not work well on TV devices 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.
Handle 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 are displayed on the screen. For example, when displaying multiple
images in a
Gallery, only load an image when
getView()is called on the view's
Bitmapviews that are no longer needed.
WeakReferencefor storing references to
Bitmapobjects in an in-memory
- If you fetch images from the network, use
AsyncTaskto fetch and store them on the device for faster access. Never do network transactions on the application's main user interface 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.
For more information on getting the best performance when working with images, see Displaying Bitmaps Efficiently.