Add playground files for cancellation

Author: LukasLechnerDev

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/playground/flow/cancellation/1_cancellation_basics.kt

@@ -2,6 +2,7 @@ package com.lukaslechner.coroutineusecasesonandroid.playground.flow.cancellation
 
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.onCompletion
 import kotlinx.coroutines.launch
@@ -19,6 +20,10 @@ suspend fun main() {
             }
             .collect {
                 println("Collected $it")
+
+                if (it == 2) {
+                    cancel()
+                }
             }
     }.join()
 }

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/playground/flow/cancellation/2_cooperative_cancellation_in_flows.kt

@@ -0,0 +1,47 @@
+package com.lukaslechner.coroutineusecasesonandroid.playground.flow.cancellation
+
+import kotlinx.coroutines.*
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.onCompletion
+import java.math.BigInteger
+import kotlin.coroutines.EmptyCoroutineContext
+
+suspend fun main() {
+    val scope = CoroutineScope(EmptyCoroutineContext)
+
+    scope.launch {
+        intFlow()
+            .onCompletion { throwable ->
+                if (throwable is CancellationException) {
+                    println("Flow got cancelled.")
+                }
+            }
+            .collect {
+                println("Collected $it")
+
+                if (it == 2) {
+                    cancel()
+                }
+            }
+    }.join()
+}
+
+private fun intFlow() = flow {
+    emit(1)
+    emit(2)
+
+    println("Start calculation")
+    calculateFactorialOf(1_000)
+    println("Calculation finished!")
+
+    emit(3)
+}
+
+private suspend fun calculateFactorialOf(number: Int): BigInteger = coroutineScope {
+    var factorial = BigInteger.ONE
+    for (i in 1..number) {
+        factorial = factorial.multiply(BigInteger.valueOf(i.toLong()))
+        ensureActive()
+    }
+    factorial
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/playground/flow/cancellation/3_cancellable_operator.kt

@@ -0,0 +1,30 @@
+package com.lukaslechner.coroutineusecasesonandroid.playground.flow.cancellation
+
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.flow.cancellable
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.onCompletion
+import kotlinx.coroutines.launch
+import kotlin.coroutines.EmptyCoroutineContext
+
+suspend fun main() {
+    val scope = CoroutineScope(EmptyCoroutineContext)
+
+    scope.launch {
+        flowOf(1, 2, 3)
+            .onCompletion { throwable ->
+                if (throwable is CancellationException) {
+                    println("Flow got cancelled.")
+                }
+            }.cancellable()
+            .collect {
+                println("Collected $it")
+
+                if (it == 2) {
+                    cancel()
+                }
+            }
+    }.join()
+}