Add adapterview listener setters

api/current.txt

@@ -663,6 +663,14 @@ package androidx.core.view {
 
 package androidx.core.widget {
 
+  public final class AdapterViewKt {
+    ctor public AdapterViewKt();
+    method public static <T> void onItemClick(android.widget.AdapterView<?>, kotlin.jvm.functions.Function1<? super T,kotlin.Unit> onItemClick);
+    method public static <T> void onItemLongClick(android.widget.AdapterView<?>, kotlin.jvm.functions.Function1<? super T,java.lang.Boolean> onItemLongClick);
+    method public static void onItemSelected(android.widget.AdapterView<?>, kotlin.jvm.functions.Function1<? super android.widget.AdapterView<?>,kotlin.Unit> onNothingSelected = "{}", kotlin.jvm.functions.Function4<? super android.widget.AdapterView<?>,? super android.view.View,? super java.lang.Integer,? super java.lang.Long,kotlin.Unit> onItemSelected);
+    method public static <T> void onItemSelected(android.widget.AdapterView<?>, kotlin.jvm.functions.Function0<kotlin.Unit> onNothingSelected = "{}", kotlin.jvm.functions.Function1<? super T,kotlin.Unit> onItemSelected);
+  }
+
   public final class ToastKt {
     ctor public ToastKt();
     method public static android.widget.Toast toast(android.content.Context, CharSequence text, int duration = "Toast.LENGTH_SHORT");

src/androidTest/java/androidx/core/widget/AdapterViewTest.kt

@@ -0,0 +1,217 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.core.widget
+
+import android.support.test.InstrumentationRegistry
+import android.widget.AbsListView.CHOICE_MODE_SINGLE
+import android.widget.AdapterView
+import android.widget.AdapterView.INVALID_POSITION
+import android.widget.AdapterView.INVALID_ROW_ID
+import android.widget.ArrayAdapter
+import android.widget.ListView
+import android.widget.Spinner
+import androidx.core.view.get
+import androidx.testutils.assertThrows
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import java.lang.ClassCastException
+import java.lang.reflect.InvocationTargetException
+
+class AdapterViewTest {
+
+    private val context = InstrumentationRegistry.getContext()
+
+    private val data = listOf("KitKat", "Lollipop", "Marshmallow", "Nougat", "Oreo")
+    private val arrayAdapter: ArrayAdapter<String>
+        get() = ArrayAdapter<String>(context, android.R.layout.simple_list_item_1, data)
+            .apply { setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item) }
+
+    private val listView: ListView
+        get() = ListView(context).apply { adapter = arrayAdapter; choiceMode = CHOICE_MODE_SINGLE }
+    private val spinner: Spinner
+        get() = Spinner(context).apply { adapter = arrayAdapter }
+
+    private var testItem: Any? = null
+    private var testOnNothingSelectedTriggered = false
+
+    @Before
+    fun setup() {
+        testItem = null
+        testOnNothingSelectedTriggered = false
+    }
+
+    @Test
+    fun onItemClick() {
+        val adapterView = listView
+        adapterView.onItemClick { item: String -> testItem = item }
+        for (position in data.indices) {
+            assertTrue(
+                "listener not set",
+                adapterView.performItemClick(null, position, INVALID_ROW_ID)
+            )
+            assertEquals(data[position], testItem)
+        }
+    }
+
+    @Test(expected = ClassCastException::class)
+    fun onItemClickCastExceptionOnWrongClass() {
+        val adapterView = listView
+        adapterView.onItemClick { item: WrongClass -> testItem = item }
+        adapterView.performItemClick(null, 1, INVALID_ROW_ID)
+    }
+
+    @Test(expected = RuntimeException::class)
+    fun onItemClickRuntimeExceptionWithSpinner() {
+        spinner.onItemClick { _: Any? -> }
+    }
+
+    /**
+     * borrowed from [AdapterViewTest line:279](https://android.googlesource.com/platform/cts/+/42fbcbb2518ea10cc729c44614a93b182bf58696/tests/tests/widget/src/android/widget/cts/AdapterViewTest.java#279)
+     */
+    @Test
+    fun onItemLongClick() {
+        val adapterView = listView
+        adapterView.onItemLongClick { item: String -> testItem = item; true }
+        adapterView.layout(0, 0, LAYOUT_WIDTH, LAYOUT_HEIGHT)
+        val position = 1
+        adapterView.showContextMenuForChild(adapterView[position])
+        assertEquals(data[position], testItem)
+    }
+
+    @Test(expected = ClassCastException::class)
+    fun onItemLongClickCastExceptionOnWrongClass() {
+        val adapterView = listView
+        adapterView.onItemLongClick { item: WrongClass -> testItem = item; true }
+        adapterView.layout(0, 0, LAYOUT_WIDTH, LAYOUT_HEIGHT)
+        adapterView.showContextMenuForChild(adapterView[1])
+    }
+
+    @Test
+    fun onItemSelected() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected { parent, _, position, _ ->
+                testItem = parent.getItemAtPosition(position)
+            }
+            for (i in data.indices) checkSelectionForPosition(adapterView, i)
+        }
+    }
+
+    @Test
+    fun onItemSelectedWithCast() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected { item: String -> testItem = item }
+            for (i in data.indices) checkSelectionForPosition(adapterView, i)
+        }
+    }
+
+    @Test
+    fun onItemSelectedWithCastIgnoresOnNothingSelectedActions() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected { item: String -> testItem = item }
+            assertFalse(testOnNothingSelectedTriggered)
+            assertNull(testItem)
+            selectAndFireOnSelected(adapterView, INVALID_POSITION)
+            assertFalse(testOnNothingSelectedTriggered)
+            assertNull(testItem)
+        }
+    }
+
+    @Test
+    fun onItemSelectedWithCastExceptionOnWrongClass() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected<WrongClass> { item -> testItem = item }
+            assertThrows<ClassCastException> {
+                for (i in data.indices) checkSelectionForPosition(adapterView, i)
+            }
+        }
+    }
+
+    @Test
+    fun onItemSelectedWithHandledOnNothingSelected() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected(
+                onNothingSelected = { _: AdapterView<*> -> testOnNothingSelectedTriggered = true },
+                onItemSelected = { parent, _, position, _ ->
+                    testItem = parent.getItemAtPosition(position)
+                })
+            checkSelectionForPosition(adapterView, INVALID_POSITION)
+            for (i in data.indices) checkSelectionForPosition(adapterView, i)
+            checkSelectionForPosition(adapterView, INVALID_POSITION)
+        }
+    }
+
+    @Test
+    fun onItemSelectedWithCastWithHandledOnNothingSelected() {
+        listOf(listView, spinner).forEach { adapterView ->
+            adapterView.onItemSelected(
+                onNothingSelected = { testOnNothingSelectedTriggered = true },
+                onItemSelected = { item: String -> testItem = item }
+            )
+            checkSelectionForPosition(adapterView, INVALID_POSITION)
+            for (i in data.indices) checkSelectionForPosition(adapterView, i)
+            checkSelectionForPosition(adapterView, INVALID_POSITION)
+        }
+    }
+
+    private fun checkSelectionForPosition(adapterView: AdapterView<*>, position: Int) {
+        assertFalse(testOnNothingSelectedTriggered)
+        assertNull(testItem)
+        selectAndFireOnSelected(adapterView, position)
+        if (position < 0) {
+            assertTrue(testOnNothingSelectedTriggered)
+            assertNull(testItem)
+        } else {
+            assertFalse(testOnNothingSelectedTriggered)
+            assertEquals(data[position], testItem)
+        }
+        testOnNothingSelectedTriggered = false
+        testItem = null
+    }
+
+    companion object {
+        private const val LAYOUT_WIDTH = 200
+        private const val LAYOUT_HEIGHT = 200
+
+        class WrongClass
+
+        /**
+         * Reflection used to shortcut trigger selection via AdapterView#fireOnSelected()
+         *
+         * More comprehensive test would involve ActivityRule like in [AdapterViewTest line:286](https://android.googlesource.com/platform/cts/+/42fbcbb2518ea10cc729c44614a93b182bf58696/tests/tests/widget/src/android/widget/cts/AdapterViewTest.java#286)
+         *
+         * @see android.widget.AdapterView
+         */
+        private fun selectAndFireOnSelected(adapterView: AdapterView<*>, position: Int) {
+            try {
+                AdapterView::class.java
+                    .getDeclaredMethod("setNextSelectedPositionInt", Int::class.java)
+                    .apply { isAccessible = true }
+                    .invoke(adapterView, position)
+                AdapterView::class.java
+                    .getDeclaredMethod("fireOnSelected")
+                    .apply { isAccessible = true }
+                    .invoke(adapterView)
+            } catch (e: InvocationTargetException) {
+                throw e.targetException
+            }
+        }
+    }
+}

src/main/java/androidx/core/widget/AdapterView.kt

@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.core.widget
+
+import android.view.View
+import android.widget.AdapterView
+
+/**
+ * Sets click listener with automatic item casting
+ * (ClassCastException will be thrown if adapter's item type does not match)
+ */
+inline fun <T> AdapterView<*>.onItemClick(crossinline onItemClick: (item: T) -> Unit) {
+    setOnItemClickListener { parent, _, position, _ ->
+        @Suppress("UNCHECKED_CAST")
+        onItemClick(parent.getItemAtPosition(position) as T)
+    }
+}
+
+/**
+ * Sets long click listener with automatic item casting
+ * (ClassCastException will be thrown if adapter's item type does not match)
+ */
+inline fun <T> AdapterView<*>.onItemLongClick(crossinline onItemLongClick: (item: T) -> Boolean) {
+    setOnItemLongClickListener { parent, _, position, _ ->
+        @Suppress("UNCHECKED_CAST")
+        onItemLongClick(parent.getItemAtPosition(position) as T)
+    }
+}
+
+/**
+ * Simple use case (empty `onNothingSelected` default provided):
+ * ```kotlin
+ *     spinner.onItemSelected { parent, _, position, _ ->
+ *         val item = parent.getItemAtPosition(position)
+ *         ???
+ *     }
+ * ```
+ * Use case with `onNothingSelected` handling:
+ * ```kotlin
+ *     spinner.onItemSelected(
+ *         onNothingSelected = { _: AdapterView<*> -> ??? },
+ *         onItemSelected = { parent, _, position, _ ->
+ *             val item = parent.getItemAtPosition(position)
+ *             ???
+ *     })
+ * ```
+ * @see android.widget.AdapterView.OnItemSelectedListener
+ */
+inline fun AdapterView<*>.onItemSelected(
+    crossinline onNothingSelected: (parent: AdapterView<*>) -> Unit = {},
+    crossinline onItemSelected: (
+        parent: AdapterView<*>,
+        view: View?,
+        position: Int,
+        id: Long
+    ) -> Unit
+) {
+    onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
+        override fun onNothingSelected(parent: AdapterView<*>) = onNothingSelected(parent)
+
+        override fun onItemSelected(parent: AdapterView<*>, view: View?, position: Int, id: Long) {
+            onItemSelected(parent, view, position, id)
+        }
+    }
+}
+
+/**
+ * Sets selection listener with automatic item casting
+ * (ClassCastException will be thrown if adapter's item type does not match)
+ *
+ * Simple use case (empty `onNothingSelected` default provided):
+ * ```kotlin
+ *     spinner.onItemSelected { item: T -> ??? }
+ * ```
+ * Use case with `onNothingSelected` handling:
+ * ```kotlin
+ *
+ *     spinner.onItemSelected(
+ *         onNothingSelected = { ??? },
+ *         onItemSelected = { item: String -> ??? }
+ *     )
+ * ```
+ * @param onNothingSelected optional action, default `{}`
+ * @param onItemSelected action with casted item passed
+ * @see android.widget.AdapterView.OnItemSelectedListener
+ */
+inline fun <T> AdapterView<*>.onItemSelected(
+    crossinline onNothingSelected: () -> Unit = {},
+    crossinline onItemSelected: (item: T) -> Unit
+) {
+    onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
+        override fun onNothingSelected(parent: AdapterView<*>) = onNothingSelected()
+
+        override fun onItemSelected(parent: AdapterView<*>, view: View?, position: Int, id: Long) {
+            @Suppress("UNCHECKED_CAST")
+            onItemSelected(parent.getItemAtPosition(position) as T)
+        }
+    }
+}