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A Kotlin demo app for multi-window and large-screen behavior on Android: it shows the window size, multi-window and picture-in-picture state live, launches a page in the adjacent window, drags text across windows, and keeps its log across configuration changes. It is a demo app, not a library (no Maven coordinate).

• Version 2.0.0, minSdk 24, targetSdk 36, Kotlin, AppCompat DayNight (no Material Components).

Download the sample APK

Screenshot

Home	Dark mode	Status & callbacks	Adjacent launch

Split-screen drag	Freeform drag	Picture-in-picture	ViewModel

Captured on a real device running Android 17. Split screen comes from the adjacent-launch button, freeform windows from adb shell am start --windowingMode 5.

What the demo covers

Feature	Where
Live window size (Configuration.screenWidthDp/HeightDp), multi-window and PiP state	BaseActivity, StatusActivity
Callbacks: onMultiWindowModeChanged(Boolean, Configuration), onPictureInPictureModeChanged(Boolean, Configuration)	BaseActivity.onWindowEvent()
Launch in the adjacent window: FLAG_ACTIVITY_LAUNCH_ADJACENT or FLAG_ACTIVITY_NEW_TASK	AdjacentActivity
Cross-window text drag and drop (startDragAndDrop + DRAG_FLAG_GLOBAL, OnDragListener)	DragActivity, DropParser
Keep state across recreation with ViewModel	ConfigActivity, ConfigViewModel, WindowViewModel
Handle configuration changes yourself (configChanges) + PiP	PipActivity (and configChanges in the manifest)

// Query and callback (the single-argument overload is deprecated since API 26)
val inMultiWindow = isInMultiWindowMode
override fun onMultiWindowModeChanged(isInMultiWindowMode: Boolean, newConfig: Configuration) { ... }

// Open another activity in the adjacent window (best effort, not guaranteed)
startActivity(
    Intent(this, PeerActivity::class.java)
        .addFlags(Intent.FLAG_ACTIVITY_LAUNCH_ADJACENT or Intent.FLAG_ACTIVITY_NEW_TASK)
)

What changed in Android (checked against the official docs)

All statements below were checked against the page quoted in the link.

1. Android 12 (API 31) makes multi-window standard. On large screens (medium / expanded window size class) all apps support multi-window regardless of configuration; resizeableActivity="false" puts the app in compatibility mode when needed. On small screens the system checks minWidth / minHeight, and resizeableActivity="false" still blocks multi-window. Support multi-window mode
2. Android 12L (API 32): the Recents screen gets a Split action, and FLAG_ACTIVITY_LAUNCH_ADJACENT can make a full-screen app enter split-screen and open the target in the adjacent window (same page, "Programmatic split-screen"). OEMs can enable this behavior on older versions.
3. Multi-resume (Android 10+): all visible activities stay RESUMED in multi-window; use onTopResumedActivityChanged() for exclusive resources such as camera / microphone. Before Android 10 only the most recently used one is resumed. Same page.
4. Android 16 (API 36), apps with targetSdk 36: on displays with smallest width >= 600dp, screenOrientation, resizeableActivity, minAspectRatio, maxAspectRatio, setRequestedOrientation() and getRequestedOrientation() are ignored (the app is resizable and fills the window, no pillarboxing). Exceptions: games (android:appCategory), users who opt in to the app's default behavior in the aspect-ratio settings, and displays smaller than sw600dp. A temporary opt-out is PROPERTY_COMPAT_ALLOW_RESTRICTED_RESIZABILITY, and it will not work for apps targeting API 37. Behavior changes: Android 16, App orientation, aspect ratio, and resizability
   • Consequence for this demo: the resizeableActivity="true" in AndroidManifest.xml only matters below sw600dp or below targetSdk 36; on large screens it is ignored. Rotation and window resizing recreate activities more often, so state must be preserved (Save UI states).
5. How to enable freeform (desktop) windows today: the official docs only say desktop windowing "can be enabled by manufacturers of large screen devices" (Support multi-window mode). The official developer-preview post says to use a Pixel Tablet on Android 15 QPR1 Beta 2 or the Pixel Tablet emulator, then select Enable freeform windows in Developer options; it does not mention root (Android Developers Blog, Sep 2024). So the old recipe of rooting and running settings put global enable_freeform_support 1 is no longer the documented path. Tested on a real device running Android 17: pm has-feature android.software.freeform_window_management returns true, the enable_freeform_support global setting is unset, and adb shell am start --windowingMode 5 -n <activity> opens the activity as a freeform window (two such windows can be resized with am task resize and dragged between).

Migration from 1.x (Android N demo)

• Rewritten in Kotlin; compileSdk / targetSdk 36, minSdk 24 (unchanged).
• Dropped the com.wx.android.common dependency and the old support library; the old log buffer (a static StringBuilder) is replaced by a ViewModel.
• Drag and drop now carries plain text only (the old image drag is removed).
• Not applicable: Android N-only instructions in the old README (rooting for freeform mode); see item 5 above.

Alternatives

For apps with multiple panes use Activity embedding (Jetpack WindowManager); for adaptive layouts use window size classes. Google's old MultiWindowPlayground sample is the official reference for Android N.

Maintenance

Maintained as a small demo. Adjacent launch (it produces a real top/bottom split screen), cross-window drag, PiP and freeform windows have been checked by hand on a real device running Android 17.

Credits

The sample app bundles these fonts, both licensed under the SIL Open Font License 1.1 (license texts in app/licenses/):

• Space Grotesk: Copyright 2020 The Space Grotesk Project Authors
• JetBrains Mono: Copyright 2020 The JetBrains Mono Project Authors

License

Apache License 2.0, see LICENSE.