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2022-07-24 12:30:00 【Sharp surge】

Fringe screen refers to an area on the display screen of some equipment extending to the display surface , This can provide users with a comprehensive screen experience , It can also leave space for important sensors on the front of the equipment .Android On board Android 9（API Level 28） And later devices officially support Liu Haiping . Please note that , Equipment manufacturers can also choose to carry Android 8.1 Bangs are supported on devices at or below .

This topic describes how to support devices with bangs , Including how to deal with “ Bangs area ”, That is, the borderless rectangle containing bangs on the display surface .

What are the requirements on the equipment with bangs

To ensure consistency and application compatibility , carrying Android 9 The equipment must ensure the following bangs ：

An edge can contain at most one bangs .
A device cannot have more than two bangs .
There shall be no bangs on the two longer edges of the equipment .
In vertical screen mode without special signs , The height of the status bar must be at least equal to the height of the bangs .
By default , In full screen mode or horizontal screen mode , The entire fringe area must show a black edge .

Choose how your app handles bangs

If you don't want your content to overlap with the bangs area , Make sure your content doesn't overlap the status bar and navigation bar , This is generally enough . If you want to present the content in the bangs area , You can use WindowInsets.getDisplayCutout() To search DisplayCutout object , This object contains the security lining area and bounding box for each fringe area . You can use these API To check if your content overlaps the bangs area , To reposition as needed .

Be careful ： In multiple API Level management bangs achieve , You can also use it AndroidX library （ It can be done by SDK Manager gets ） Medium DisplayCutoutCompat.

Android It also allows you to control whether content is displayed in the fringe area . Window layout properties layoutInDisplayCutoutMode Control how your content is rendered in the bangs area . You can use layoutInDisplayCutoutMode Set to one of the following values ：

LAYOUT_IN_DISPLAY_CUTOUT_MODE_DEFAULT - This is the default behavior , As mentioned above . In vertical screen mode , The content will be presented in the fringe area ; But in landscape mode , The content will show a black edge .
LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES - In vertical screen mode and horizontal screen mode , The content will be presented in the fringe area .
LAYOUT_IN_DISPLAY_CUTOUT_MODE_NEVER - The content is never presented in the bangs area .

You can program or in Activity Set style in to set bangs mode . The following example defines a style , You can use it to LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES Property applied to Activity.

    <style name="ActivityTheme">
      <item name="android:windowLayoutInDisplayCutoutMode">
        shortEdges <!-- default, shortEdges, never -->
      </item>
    </style>

The following sections describe the different bangs patterns in more detail .

Default behavior

By default , In vertical screen mode without special signs , On a device with a banged screen , The size of the status bar will be adjusted to be at least as high as the bangs , Your content will be displayed in the lower area . In landscape mode or full screen mode , Your application window will show a black edge , Therefore, nothing of your content will be displayed in the bangs area .

Present the content in the short fringe area

For some content （ Video frequency 、 Photo 、 Maps and games ）, It's a good way to present in the fringe area , This can provide users with a more immersive and comprehensive screen experience . If set LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES, In vertical screen mode and horizontal screen mode , The content will extend to the fringe area on the short side of the display , Regardless of whether the system bar is hidden or visible . Please note that , The window cannot extend to the fringe area on the long side of the screen . When using this mode , Please make sure that no important content overlaps with the fringe area .

Please note that ,Android The content view may not be allowed to overlap the system bar . To replace this behavior and force the content to extend to the fringe area , Please pass View.setSystemUiVisibility(int) Method applies any of the following flags to view visibility ：

SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
SYSTEM_UI_FLAG_LAYOUT_STABLE

Here are some LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES Example ：

Please note that , Bangs at the corners can be equivalent to bangs on the short sides , So the same behavior applies ：

Never present content in bangs

If set LAYOUT_IN_DISPLAY_CUTOUT_MODE_NEVER, The window is not allowed to overlap with the fringe area .

This mode should be used to temporarily set View.SYSTEM_UI_FLAG_FULLSCREEN or View.SYSTEM_UI_FLAG_HIDE_NAVIGATION The window of , To avoid performing another window layout when the flag is set or cleared .

Please check the following LAYOUT_IN_DISPLAY_CUTOUT_MODE_NEVER Example ：

Special mode

Some carry Android 8.1（API Level 27） Or earlier devices support a special mode , Allows the user to extend the full screen or horizontal screen application with black edge to the fringe area . This mode is usually controlled using the toggle switch in the navigation bar , A dialog box appears before extending the screen , Ask the user to confirm .

Support Liu Haiping's best practices

Use Hai Ping Liu when , Please be sure to consider the following points ：

Don't let the fringe area cover any important text 、 Control or other information .
Do not place or extend any interactive elements that require fine touch recognition to the fringe area . The touch sensitivity in the fringe area may be lower than that in other areas .
Avoid hard coding the status bar height , Because doing so may cause the content to overlap or be cut off . If possible , Please use WindowInsetsCompat Retrieve the status bar height , And determine the appropriate margin to apply to your content .

Don't assume that the application will occupy the entire window , And should be used View.getLocationInWindow() To confirm the location of the application . Do not use View.getLocationOnScreen().
Be sure to properly handle entering or exiting full screen mode . Please read This article Android Developer blog .
For default bangs behavior in vertical mode , If the fringe area is at the top edge , And the window is not set FLAG_FULLSCREEN or View.SYSTEM_UI_FLAG_FULLSCREEN, Then the window can extend to the fringe area . Again , If the fringe area is at the bottom edge , And the window is not set View.SYSTEM_UI_FLAG_HIDE_NAVIGATION, Then the window can extend to the fringe area . In full screen mode or horizontal screen mode , The layout of the window shall be such that it does not overlap the fringe area .
If your application needs to enter and exit full screen mode , Please use shortEdges or never Bangs pattern . The default fringe behavior can cause the content in the application to move up and down during the full screen mode conversion , As shown in the figure below ：

In full screen mode , Care should be taken when using window and screen coordinates , Because when the black edge is displayed , Your app won't occupy the entire screen . Because the black edge is displayed , Therefore, the coordinates obtained from the screen origin are no longer the same as those obtained from the window origin . You can use getLocationOnScreen() Convert screen coordinates to view coordinates . The following figure shows how the two coordinates are different when the content is displayed with a black edge ：

Handle MotionEvent when , Please use MotionEvent.getX() and MotionEvent.getY() To avoid similar coordinate problems . Do not use MotionEvent.getRawX() or MotionEvent.getRawY().

Test how your content is rendered

Be sure to test all the screens and experiences of the application . If possible , Test on equipment with different types of bangs . If you don't have a device with bangs , You can carry Android 9 Simulate some common bangs configurations on any device or Simulator , The specific operation steps are as follows ：