| # SystemUI | |
| “Everything you see in Android that's not an app” | |
| SystemUI is a persistent process that provides UI for the system but outside | |
| of the system_server process. | |
| The starting point for most of sysui code is a list of services that extend | |
| SystemUI that are started up by SystemUIApplication. These services then depend | |
| on some custom dependency injection provided by Dependency. | |
| Inputs directed at sysui (as opposed to general listeners) generally come in | |
| through IStatusBar. Outputs from sysui are through a variety of private APIs to | |
| the android platform all over. | |
| ## SystemUIApplication | |
| When SystemUIApplication starts up, it will start up the services listed in | |
| config_systemUIServiceComponents or config_systemUIServiceComponentsPerUser. | |
| Each of these services extend SystemUI. SystemUI provides them with a Context | |
| and gives them callbacks for onConfigurationChanged (this historically was | |
| the main path for onConfigurationChanged, now also happens through | |
| ConfigurationController). They also receive a callback for onBootCompleted | |
| since these objects may be started before the device has finished booting. | |
| Each SystemUI service is expected to be a major part of system ui and the | |
| goal is to minimize communication between them. So in general they should be | |
| relatively silo'd. | |
| ## Dependencies | |
| The first SystemUI service that is started should always be Dependency. | |
| Dependency provides a static method for getting a hold of dependencies that | |
| have a lifecycle that spans sysui. Dependency has code for how to create all | |
| dependencies manually added. SystemUIFactory is also capable of | |
| adding/replacing these dependencies. | |
| Dependencies are lazily initialized, so if a Dependency is never referenced at | |
| runtime, it will never be created. | |
| If an instantiated dependency implements Dumpable it will be included in dumps | |
| of sysui (and bug reports), allowing it to include current state information. | |
| This is how \*Controllers dump state to bug reports. | |
| If an instantiated dependency implements ConfigurationChangeReceiver it will | |
| receive onConfigurationChange callbacks when the configuration changes. | |
| ## IStatusBar | |
| CommandQueue is the object that receives all of the incoming events from the | |
| system_server. It extends IStatusBar and dispatches those callbacks back any | |
| number of listeners. The system_server gets a hold of the IStatusBar when | |
| StatusBar calls IStatusBarService#registerStatusBar, so if StatusBar is not | |
| included in the XML service list, it will not be registered with the OS. | |
| CommandQueue posts all incoming callbacks to a handler and then dispatches | |
| those messages to each callback that is currently registered. CommandQueue | |
| also tracks the current value of disable flags and will call #disable | |
| immediately for any callbacks added. | |
| There are a few places where CommandQueue is used as a bus to communicate | |
| across sysui. Such as when StatusBar calls CommandQueue#recomputeDisableFlags. | |
| This is generally used a shortcut to directly trigger CommandQueue rather than | |
| calling StatusManager and waiting for the call to come back to IStatusBar. | |
| ## Default SystemUI services list | |
| ### [com.android.systemui.Dependency](/packages/SystemUI/src/com/android/systemui/Dependency.java) | |
| Provides custom dependency injection. | |
| ### [com.android.systemui.util.NotificationChannels](/packages/SystemUI/src/com/android/systemui/util/NotificationChannels.java) | |
| Creates/initializes the channels sysui uses when posting notifications. | |
| ### [com.android.systemui.keyguard.KeyguardViewMediator](/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardViewMediator.java) | |
| Manages keyguard view state. | |
| ### [com.android.systemui.recents.Recents](/packages/SystemUI/src/com/android/systemui/recents/Recents.java) | |
| Recents tracks all the data needed for recents and starts/stops the recents | |
| activity. It provides this cached data to RecentsActivity when it is started. | |
| ### [com.android.systemui.volume.VolumeUI](/packages/SystemUI/src/com/android/systemui/volume/VolumeUI.java) | |
| Registers all the callbacks/listeners required to show the Volume dialog when | |
| it should be shown. | |
| ### [com.android.systemui.stackdivider.Divider](/packages/SystemUI/src/com/android/systemui/stackdivider/Divider.java) | |
| Shows the drag handle for the divider between two apps when in split screen | |
| mode. | |
| ### [com.android.systemui.status.phone.StatusBar](/packages/SystemUI/src/com/android/systemui/status/phone/StatusBar.java) | |
| This shows the UI for the status bar and the notification shade it contains. | |
| It also contains a significant amount of other UI that interacts with these | |
| surfaces (keyguard, AOD, etc.). StatusBar also contains a notification listener | |
| to receive notification callbacks. | |
| ### [com.android.systemui.usb.StorageNotification](/packages/SystemUI/src/com/android/systemui/usb/StorageNotification.java) | |
| Tracks USB status and sends notifications for it. | |
| ### [com.android.systemui.power.PowerUI](/packages/SystemUI/src/com/android/systemui/power/PowerUI.java) | |
| Tracks power status and sends notifications for low battery/power saver. | |
| ### [com.android.systemui.media.RingtonePlayer](/packages/SystemUI/src/com/android/systemui/media/RingtonePlayer.java) | |
| Plays ringtones. | |
| ### [com.android.systemui.keyboard.KeyboardUI](/packages/SystemUI/src/com/android/systemui/keyboard/KeyboardUI.java) | |
| Shows UI for keyboard shortcuts (triggered by keyboard shortcut). | |
| ### [com.android.systemui.pip.PipUI](/packages/SystemUI/src/com/android/systemui/pip/PipUI.java) | |
| Shows the overlay controls when Pip is showing. | |
| ### [com.android.systemui.shortcut.ShortcutKeyDispatcher](/packages/SystemUI/src/com/android/systemui/shortcut/ShortcutKeyDispatcher.java) | |
| Dispatches shortcut to System UI components. | |
| ### @string/config_systemUIVendorServiceComponent | |
| Component allowing the vendor/OEM to inject a custom component. | |
| ### [com.android.systemui.util.leak.GarbageMonitor$Service](/packages/SystemUI/src/com/android/systemui/util/leak/GarbageMonitor.java) | |
| Tracks large objects in sysui to see if there are leaks. | |
| ### [com.android.systemui.LatencyTester](/packages/SystemUI/src/com/android/systemui/LatencyTester.java) | |
| Class that only runs on debuggable builds that listens to broadcasts that | |
| simulate actions in the system that are used for testing the latency. | |
| ### [com.android.systemui.globalactions.GlobalActionsComponent](/packages/SystemUI/src/com/android/systemui/globalactions/GlobalActionsComponent.java) | |
| Shows the global actions dialog (long-press power). | |
| ### [com.android.systemui.ScreenDecorations](/packages/SystemUI/src/com/android/systemui/ScreenDecorations.java) | |
| Draws decorations about the screen in software (e.g. rounded corners, cutouts). | |
| ### [com.android.systemui.biometrics.BiometricDialogImpl](/packages/SystemUI/src/com/android/systemui/biometrics/BiometricDialogImpl.java) | |
| Biometric UI. | |
| --- | |
| * [Plugins](/packages/SystemUI/docs/plugins.md) | |
| * [Demo Mode](/packages/SystemUI/docs/demo_mode.md) |