Lift the curtain on Android Windows!
The Android Framework is missing critical Window related APIs. This library fills the gaps.
Developers are not in control of the entirety of their code and therefore need APIs for managing components in a centralized way. App developers constantly leverage 3rd party libraries, work in codebases which high complexity and a large number of collaborators. Library developers write code that gets integrated within code they do not control.
In practice, this manifests as a lack of central API for tracking the lifecycle of Android windows (e.g. you can't know if a library shows a dialog), Android manifest components (services, providers, broadcast receiver) or accessing view state without subclassing.
The Curtains library provides centralized APIs for managing Window related concerns. Its internals are a happy mix of hacks, workarounds for known Android bugs and glue code for simplifying APIs.
Here are a few use cases that Curtains enables:
- TODO Add link to touch event bug
- TODO frozen touch
- TODO Detecting first draw
- TODO intercept / cancel touch events / layers
- LeakCanary needs to know when root views are detached to detect if they might be leaking.
- The Espresso UI test library needs
access to the list of attached root views to state view expectations, interactions, and assertions.
Espresso does not use Curtains but internally relies on the exact same hacks (see RootsOracle).
class ExampleApplication : Application() {
override fun onCreate() {
super.onCreate()
Curtains.windowAttachStateListeners += WindowAttachedListener { window ->
if (window.decorView.windowAttachCount == 0) {
window.touchEventInterceptors += TouchEventListener { motionEvent ->
Log.d("ExampleApplication", "$window received $motionEvent")
}
}
}
}
}class MainActivity : Activity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
window.onContentChangedListeners += OnContentChangedListener {
val newContentView = findViewById<View>(android.R.id.content)
Log.d("MainActivity", "Content changed to $newContentView")
}
setContentView(R.layout.main)
}
}activity.window.onDecorViewReady { decorView ->
// Avoid the side effects of calling Window.getDecorView() too early
}class ExampleApplication : Application() {
override fun onCreate() {
super.onCreate()
val handler = Handler(Looper.getMainLooper())
Curtains.windowAttachStateListeners += WindowAttachedListener { window ->
val windowAddedAt = SystemClock.uptimeMillis()
window.onNextDraw {
// Post at front to fully account for drawing time.
handler.postAtFrontOfQueue {
val duration = SystemClock.uptimeMillis() - windowAddedAt
Log.d("ExampleApplication", "$window fully drawn in $duration ms")
}
}
}
}
}Add the curtains dependency to your app's build.gradle file:
dependencies {
implementation 'com.squareup.curtains:curtains:1.0'
}TODO
TODO
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