**Note:** Some features have subfeatures like *android.hardware.camera.front*, as described in the [Feature reference](https://developer.android.google.cn/guide/topics/manifest/uses-feature-element.html#features-reference). Be sure to mark as *required="false"* any subfeatures also used in your app.
Caution: Declaring a hardware feature as required by setting its value to true prevents your app from being installed on TV devices or appearing in the Android TV home screen launcher.

Pausing playback during low-power mode

Some TV devices support a low-power mode when the user switches the device off. Instead of shutting down, the device disables the display and keeps Android TV running in the background. Audio output is still enabled in this mode, so your app should stop any currently playing content when the device is in low-power mode.

To avoid playback during low-power mode, override [onStop()](https://developer.android.google.cn/reference/android/app/Activity.html#onStop()) and stop any currently playing content:

@Overridepublic void onStop() {  // App-specific method to stop playback  stopPlayback();  super.onStop();}

Ⅲ.Handle controller disconnects

Controllers for TV are frequently Bluetooth devices which may attempt to save power by periodically going into sleep mode and disconnecting from the TV device. This means that an app might be interrupted or restarted if it is not configured to handle these reconnect events. These events can happen in any of the following circumstances:

While watching a video which is several minutes long, a D-Pad or game controller goes into sleep mode, disconnects from the TV device and then reconnects later on.
During gameplay, a new player joins the game using a game controller that is not currently connected.
During gameplay, a player leaves the game and disconnects a game controller.
Any TV app activity that is subject to disconnect and reconnect events must be configured to handle reconnection events in the app manifest. The following code sample demonstrates how to enable an activity to handle configuration changes, including a keyboard or navigation device connecting, disconnecting, or reconnecting:

              ...

This configuration change allows the app to continue running through a reconnection event, rather than being restarted by the Android framework, which is not a good user experience.

Handle button events

When the user clicks a button on a controller, your app receives an event with a KeyEvent. The intended behavior for the button might be a media event (like play, pause, or stop) or it could be a TV-type event (like selection or navigation). In order to provide a good user experience, your app should assign consistent behavior to controller buttons.

TV UI events

Buttons that generate these KeyEvents should be handled by the app according to table below.

Media events

When the user is watching media, buttons that generate these KeyEvents should be handled by app according to table below. If your app is controlling a MediaSession, it should call one of the TransportControls methods as shown below. Note that the selection buttons act as Play/Pause buttons in this context.

Ⅳ.Build 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 you to create app layouts with TV devices in mind in order to create a useful and enjoyable user experience.

Use layout themes for TV

Leanback theme

The v17 leanback support library includes Theme.Leanback, a theme for TV activities that provides a consistent visual style. We strongly recommend using this theme for any TV app built with the v17 leanback classes. The following code sample shows how to apply this theme to an activity:

**Caution:**The leanback theme does not include an action bar, since there none in an Android TV app. If your app uses support fragments, like BrowseSupportFragment, your activity must extend FragmentActivity. Do not use AppCompatActivitywhich tries to theme the action bar and produces the error

java.lang.RuntimeException: Unable to start activity ComponentInfo{...} :java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with thisactivity.

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 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:

  ...      ...  

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 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

Screen elements that must be visible to the user at all times should be positioned within the overscan safe area. Adding a 5% margin of 48dp on the left and right edges and 27dp on the top and bottom edges to a layout ensures that screen elements in that layout will be within the overscan safe area.Example:

<?xml version="1.0" encoding="utf-8"?>                  

**Caution:** Do not apply overscan margins to your layout if you are using the v17 leanback classes, such asBrowseFragmentor 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:

• 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_content instead 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.

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 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 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 Display bitmaps efficiently.

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.

Provide effective advertising

For the living room environment, we recommend you use video ads solutions that are full-screen and dismissable within 30 seconds. Functionality for advertising on Android TV, such as dismiss buttons and clickthroughs, must be accessible using the D-pad rather than touch.

Android TV does not provide a web browser. Your ads must not attempt to launch a web browser or redirect to Google Play Store content that is not approved for Android TV devices.
**Note:** You can use theWebViewclass for logins to services like Google+ and Facebook.

Ⅴ.Create TV navigation

Note: You should only use these attributes to modify the navigation order if the default order that the system applies does not work well.
he following code sample shows how to define the next control to receive focus for a TextView layout object:

@Overridepublic void onPause() {  super.onPause();  if (mVideoView.isPlaying()) {    // Argument equals true to notify the system that the activity    // wishes to be visible behind other translucent activities    if (! requestVisibleBehind(true)) {      // App-specific method to stop playback and release resources      // because call to requestVisibleBehind(true) failed      stopPlayback();    }  } else {    // Argument equals false because the activity is not playing    requestVisibleBehind(false);  }}@Overridepublic void onVisibleBehindCanceled() {  // App-specific method to stop playback and release resources  stopPlayback();  super.onVisibleBehindCanceled();}