childrenRecursiveSequence: fix NoSuchElementException being thrown wh…

…en hasNext() returned true (#388)

anko/library/robolectricTests/src/test/java/ChildrenSequenceTest.kt

@@ -0,0 +1,70 @@
+package test
+
+import android.app.Activity
+import android.os.Bundle
+import android.widget.LinearLayout
+import android.widget.RelativeLayout
+import android.widget.TextView
+import org.jetbrains.anko.*
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.Robolectric
+import org.robolectric.RobolectricGradleTestRunner
+import org.robolectric.annotation.Config
+
+open class ChildrenSequenceTestActivity: Activity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        verticalLayout {
+            id = 1
+
+            relativeLayout {
+                id = 2
+                textView {
+                    id = 3
+                }
+                textView {
+                    id = 4
+                }
+                relativeLayout {
+                    id = 5
+                    textView {
+                        id = 6
+                    }
+                }
+            }
+            textView {
+                id = 7
+            }
+        }
+    }
+}
+
+@RunWith(RobolectricGradleTestRunner::class)
+@Config(constants = BuildConfig::class) class ChildrenSequenceTest {
+    @Test fun testChildrenSequence() {
+        val activity = Robolectric.buildActivity(ChildrenSequenceTestActivity::class.java).create().get()
+
+        val verticalLayout = activity.findViewById(1) as LinearLayout
+        val relativeLayout = activity.findViewById(2) as RelativeLayout
+        val textView = activity.findViewById(3) as TextView
+
+        assertEquals(listOf(2, 7), verticalLayout.childrenSequence().map { it.id }.toList())
+        assertEquals(listOf(3, 4, 5), relativeLayout.childrenSequence().map { it.id }.toList())
+        assert(textView.childrenSequence().toList().isEmpty())
+    }
+
+    @Test fun testChildrenRecursiveSequence() {
+        val activity = Robolectric.buildActivity(ChildrenSequenceTestActivity::class.java).create().get()
+
+        val verticalLayout = activity.findViewById(1) as LinearLayout
+        val relativeLayout = activity.findViewById(2) as RelativeLayout
+        val textView = activity.findViewById(3) as TextView
+
+        assertEquals(listOf(2, 7, 3, 4, 5, 6), verticalLayout.childrenRecursiveSequence().map { it.id }.toList())
+        assertEquals(listOf(3, 4, 5, 6), relativeLayout.childrenRecursiveSequence().map { it.id }.toList())
+        assert(textView.childrenRecursiveSequence().toList().isEmpty())
+    }
+}

anko/library/static/commons/src/viewChildrenSequences.kt

@@ -118,43 +118,34 @@ private class ViewChildrenSequence(private val view: View) : Sequence<View> {
 }
 
 private class ViewChildrenRecursiveSequence(private val view: View) : Sequence<View> {
-    override fun iterator() = RecursiveViewIterator(view)
+    override fun iterator(): Iterator<View> {
+        if (view !is ViewGroup) return emptyList<View>().iterator()
+        return RecursiveViewIterator(view)
+    }
 
     private class RecursiveViewIterator(view: View) : Iterator<View> {
-        private val sequences = arrayListOf(sequenceOf(view))
-        private var itemIterator: Iterator<View>? = null
+        private val sequences = arrayListOf(view.childrenSequence())
+        private var current = sequences.removeLast().iterator()
 
         override fun next(): View {
-            initItemIterator()
-            val iterator = itemIterator ?: throw NoSuchElementException()
-
-            val view = iterator.next()
+            if (!hasNext()) throw NoSuchElementException()
+            val view = current.next()
             if (view is ViewGroup && view.childCount > 0) {
                 sequences.add(view.childrenSequence())
             }
             return view
         }
 
         override fun hasNext(): Boolean {
-            initItemIterator()
-            val iterator = itemIterator ?: return false
-            return iterator.hasNext()
-        }
-
-        private fun initItemIterator() {
-            val seqs = sequences
-            val iterator = itemIterator
-
-            if (iterator == null || (!iterator.hasNext() && seqs.isNotEmpty())) {
-                itemIterator = seqs.removeLast()?.iterator()
-            } else {
-                itemIterator = null
+            if (!current.hasNext() && sequences.isNotEmpty()) {
+                current = sequences.removeLast().iterator()
             }
+            return current.hasNext()
         }
 
         @Suppress("NOTHING_TO_INLINE")
-        private inline fun <T: Any> MutableList<T>.removeLast(): T? {
-            if (isEmpty()) return null
+        private inline fun <T : Any> MutableList<T>.removeLast(): T {
+            if (isEmpty()) throw NoSuchElementException()
             return removeAt(size - 1)
         }
     }