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Adds BackPressedHandlerTest
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+146
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lines changed

4 files changed

+146
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‎workflow-ui/core-android/src/androidTest/AndroidManifest.xml‎

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@@ -7,6 +7,6 @@
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<activity
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android:name="com.squareup.workflow1.ui.container.fixtures.BackStackContainerLifecycleActivity"
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android:theme="@style/Theme.AppCompat.NoActionBar"/>
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<activity android:name="androidx.activity.ComponentActivity"/>
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<activity android:name="androidx.activity.ComponentActivity"/>
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</application>
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</manifest>

‎workflow-ui/core-android/src/androidTest/java/com/squareup/workflow1/ui/BackPressedHandlerTest.kt‎

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package com.squareup.workflow1.ui
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import android.view.View
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import android.view.ViewGroup
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import androidx.activity.ComponentActivity
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import androidx.activity.OnBackPressedCallback
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import androidx.activity.OnBackPressedDispatcherSpy
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import androidx.lifecycle.Lifecycle.State.DESTROYED
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import androidx.lifecycle.Lifecycle.State.RESUMED
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import androidx.lifecycle.LifecycleRegistry
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import androidx.lifecycle.ViewTreeLifecycleOwner
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import androidx.test.ext.junit.rules.ActivityScenarioRule
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import com.google.common.truth.Truth.assertThat
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import com.squareup.workflow1.ui.internal.test.DetectLeaksAfterTestSuccess
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import com.squareup.workflow1.ui.internal.test.IdlingDispatcherRule
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import org.junit.Rule
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import org.junit.Test
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import org.junit.rules.RuleChain
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@OptIn(WorkflowUiExperimentalApi::class)
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internal class BackPressedHandlerTest {
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private val scenarioRule = ActivityScenarioRule(ComponentActivity::class.java)
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private val scenario get() = scenarioRule.scenario
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@get:Rule val rules: RuleChain = RuleChain.outerRule(DetectLeaksAfterTestSuccess())
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.around(scenarioRule)
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.around(IdlingDispatcherRule)
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private var viewHandlerCount = 0
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private val viewBackHandler: BackPressHandler = {
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viewHandlerCount++
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}
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@Test fun itWorksWhenHandlerIsAddedBeforeAttach() {
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scenario.onActivity { activity ->
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val view = View(activity)
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view.backPressedHandler = viewBackHandler
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activity.setContentView(view)
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assertThat(viewHandlerCount).isEqualTo(0)
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activity.onBackPressed()
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assertThat(viewHandlerCount).isEqualTo(1)
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}
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}
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@Test fun itWorksWhenHandlerIsAddedAfterAttach() {
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scenario.onActivity { activity ->
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val view = View(activity)
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view.backPressedHandler = viewBackHandler
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activity.setContentView(view)
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assertThat(viewHandlerCount).isEqualTo(0)
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activity.onBackPressed()
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assertThat(viewHandlerCount).isEqualTo(1)
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}
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}
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@Test fun onlyActiveWhileViewIsAttached() {
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var fallbackCallCount = 0
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val defaultBackHandler = object : OnBackPressedCallback(true) {
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override fun handleOnBackPressed() {
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fallbackCallCount++
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}
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}
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scenario.onActivity { activity ->
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activity.onBackPressedDispatcher.addCallback(defaultBackHandler)
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val view = View(activity)
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view.backPressedHandler = viewBackHandler
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activity.onBackPressed()
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assertThat(fallbackCallCount).isEqualTo(1)
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assertThat(viewHandlerCount).isEqualTo(0)
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activity.setContentView(view)
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activity.onBackPressed()
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assertThat(fallbackCallCount).isEqualTo(1)
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assertThat(viewHandlerCount).isEqualTo(1)
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(view.parent as ViewGroup).removeView(view)
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activity.onBackPressed()
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assertThat(fallbackCallCount).isEqualTo(2)
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assertThat(viewHandlerCount).isEqualTo(1)
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activity.setContentView(view)
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activity.onBackPressed()
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assertThat(fallbackCallCount).isEqualTo(2)
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assertThat(viewHandlerCount).isEqualTo(2)
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}
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}
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@Test fun callbackIsRemoved() {
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scenario.onActivity { activity ->
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val spy = OnBackPressedDispatcherSpy(activity.onBackPressedDispatcher)
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assertThat(spy.callbacks()).isEmpty()
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val lifecycle = LifecycleRegistry(activity)
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lifecycle.currentState = RESUMED
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val view = View(activity)
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view.backPressedHandler = viewBackHandler
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assertThat(spy.callbacks()).hasSize(1)
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ViewTreeLifecycleOwner.set(view) { lifecycle }
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activity.setContentView(view)
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(view.parent as ViewGroup).removeView(view)
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assertThat(spy.callbacks()).hasSize(1)
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lifecycle.currentState = DESTROYED
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assertThat(spy.callbacks()).isEmpty()
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}
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}
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}

‎workflow-ui/core-android/src/androidTest/java/com/squareup/workflow1/ui/OnBackPressedDispatcherSpy.java‎

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package androidx.activity;
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import java.util.ArrayDeque;
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public class OnBackPressedDispatcherSpy {
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private final OnBackPressedDispatcher dispatcher;
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public OnBackPressedDispatcherSpy(OnBackPressedDispatcher dispatcher) {
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this.dispatcher = dispatcher;
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}
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public ArrayDeque<OnBackPressedCallback> callbacks() {
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return dispatcher.mOnBackPressedCallbacks;
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}
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}

‎workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/BackPressHandler.kt‎

Lines changed: 13 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -64,9 +64,19 @@ private var View.observerOrNull: AttachStateAndLifecycleObserver?
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* so that we can know when it's time to remove the [onBackPressedCallback] from
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* the dispatch stack
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* ([no memory leaks please](https://github.com/square/workflow-kotlin/issues/889)).
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* As a belt-and-suspenders guard against leaking, we also take care to null out the
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* pointer from the [onBackPressedCallback] to the actual [handler] while the [view]
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* is detached.
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*
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* Why is it okay to wait for the [ViewTreeLifecycleOwner] to be destroyed before we
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* remove [onBackPressedCallback] from the dispatcher? In normal apps that's
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* the `Activity` or a `Fragment`, which will live a very long time, but Workflow UI
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* is more controlling than that. `WorkflowViewStub` and the rest of the stock container
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* classes use `WorkflowLifecycleOwner` to provide a short lived [ViewTreeLifecycleOwner]
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* for each [View] they create, and tear it down before moving to the next one.
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*
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* None the less, as a belt-and-suspenders guard against leaking,
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* we also take care to null out the pointer from the [onBackPressedCallback] to the
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* actual [handler] while the [view] is detached. We can't be confident that the
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* [ViewTreeLifecycleOwner] we find will be a well behaved one that was put in place
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* by `WorkflowLifecycleOwner`. Who knows what adventures our clients will get up to.
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*/
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@WorkflowUiExperimentalApi
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private class AttachStateAndLifecycleObserver(

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