Add code snippets for Compose focus documentation suite

compose/snippets/src/androidTest/java/com/example/compose/snippets/touchinput/focus/FocusTesting.kt

@@ -0,0 +1,175 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.snippets.touchinput.focus
+
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.input.key.Key
+import androidx.compose.ui.test.assertIsFocused
+import androidx.compose.ui.test.assertIsNotFocused
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.compose.ui.test.onNodeWithTag
+import androidx.compose.ui.test.performClick
+import androidx.compose.ui.test.performKeyInput
+import androidx.compose.ui.test.pressKey
+import androidx.compose.ui.test.withKeyDown
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+// [START android_compose_touchinput_focus_test_setup]
+@RunWith(AndroidJUnit4::class)
+class FocusNavigationTest {
+    @get:Rule
+    val composeTestRule = createComposeRule()
+// [END android_compose_touchinput_focus_test_setup]
+
+    // [START android_compose_touchinput_focus_test_targets]
+    @Test
+    fun interactiveElement_isFocusTarget() {
+        composeTestRule.setContent {
+            AppTheme {
+                CardListScreen()
+            }
+        }
+
+        val firstCard = composeTestRule.onNodeWithTag("card_1")
+        val secondCard = composeTestRule.onNodeWithTag("card_2")
+
+        // Focus the first element
+        firstCard.performClick()
+        firstCard.assertIsFocused()
+        secondCard.assertIsNotFocused()
+    }
+    // [END android_compose_touchinput_focus_test_targets]
+
+    // [START android_compose_touchinput_focus_test_1d_traversal]
+    @Test
+    fun tabKey_navigatesInAppearanceOrder() {
+        composeTestRule.setContent {
+            AppTheme {
+                CardListScreen()
+            }
+        }
+
+        val firstCard = composeTestRule.onNodeWithTag("card_1")
+        val secondCard = composeTestRule.onNodeWithTag("card_2")
+        val thirdCard = composeTestRule.onNodeWithTag("card_3")
+
+        firstCard.performClick()
+        firstCard.assertIsFocused()
+
+        // Press Tab -> Moves to second card
+        firstCard.performKeyInput {
+            pressKey(Key.Tab)
+        }
+        secondCard.assertIsFocused()
+        firstCard.assertIsNotFocused()
+
+        // Press Tab -> Moves to third card
+        secondCard.performKeyInput {
+            pressKey(Key.Tab)
+        }
+        thirdCard.assertIsFocused()
+
+        // Press Shift + Tab -> Moves backward to second card
+        thirdCard.performKeyInput {
+            withKeyDown(Key.ShiftLeft) {
+                pressKey(Key.Tab)
+            }
+        }
+        secondCard.assertIsFocused()
+    }
+    // [END android_compose_touchinput_focus_test_1d_traversal]
+
+    // [START android_compose_touchinput_focus_test_2d_traversal]
+    @Test
+    fun arrowKeys_moveFocusTwoDimensionallyWithoutWrap() {
+        composeTestRule.setContent {
+            AppTheme {
+                GridLayoutScreen()
+            }
+        }
+
+        val topLeftButton = composeTestRule.onNodeWithTag("btn_top_left")
+        val bottomLeftButton = composeTestRule.onNodeWithTag("btn_bottom_left")
+
+        topLeftButton.performClick()
+        topLeftButton.assertIsFocused()
+
+        // Down arrow moves focus downward to bottom-left button
+        topLeftButton.performKeyInput {
+            pressKey(Key.DirectionDown)
+        }
+        bottomLeftButton.assertIsFocused()
+
+        // Directional keys do not wrap around: pressing Down on bottom element stays focused
+        bottomLeftButton.performKeyInput {
+            pressKey(Key.DirectionDown)
+        }
+        bottomLeftButton.assertIsFocused()
+    }
+    // [END android_compose_touchinput_focus_test_2d_traversal]
+
+    // [START android_compose_touchinput_focus_test_text_fields]
+    @Test
+    fun textField_handlesTabAccordingToLineLimits() {
+        composeTestRule.setContent {
+            AppTheme {
+                FormScreen()
+            }
+        }
+
+        val singleLineNode = composeTestRule.onNodeWithTag("single_line_field")
+        val multiLineNode = composeTestRule.onNodeWithTag("multi_line_field")
+        val submitButtonNode = composeTestRule.onNodeWithTag("submit_button")
+
+        // Single-line field advances focus on Tab
+        singleLineNode.performClick()
+        singleLineNode.assertIsFocused()
+        singleLineNode.performKeyInput { pressKey(Key.Tab) }
+        multiLineNode.assertIsFocused()
+
+        // Multi-line field keeps focus and inserts '\t'
+        multiLineNode.performKeyInput { pressKey(Key.Tab) }
+        multiLineNode.assertIsFocused()
+        submitButtonNode.assertIsNotFocused()
+
+        // Shift + Tab escapes multi-line field to previous target
+        multiLineNode.performKeyInput {
+            withKeyDown(Key.ShiftLeft) { pressKey(Key.Tab) }
+        }
+        singleLineNode.assertIsFocused()
+    }
+    // [END android_compose_touchinput_focus_test_text_fields]
+// [START_EXCLUDE]
+}
+
+@Composable
+private fun AppTheme(content: @Composable () -> Unit) {
+    content()
+}
+
+@Composable
+private fun CardListScreen() {}
+
+@Composable
+private fun GridLayoutScreen() {}
+
+@Composable
+private fun FormScreen() {}
+// [END_EXCLUDE]

compose/snippets/src/main/java/com/example/compose/snippets/touchinput/focus/CaptureFocus.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.snippets.touchinput.focus
+
+import androidx.compose.foundation.focusable
+import androidx.compose.foundation.layout.Box
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Close
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.focus.FocusRequester
+import androidx.compose.ui.focus.focusRequester
+import androidx.compose.ui.focus.onFocusChanged
+
+@Composable
+private fun CaptureFocusSample() {
+    // [START android_compose_touchinput_focus_capture_focus]
+    val focusRequester = remember { FocusRequester() }
+
+    Box(
+        modifier = Modifier
+            .focusRequester(focusRequester)
+            .focusable()
+            .onFocusChanged { focusState ->
+                if (focusState.isFocused) {
+                    focusRequester.captureFocus()
+                }
+            }
+    )
+    // [END android_compose_touchinput_focus_capture_focus]
+}
+
+@Composable
+private fun FreeFocusSample() {
+    val focusRequester = remember { FocusRequester() }
+
+    // [START android_compose_touchinput_focus_free_focus]
+    IconButton(
+        onClick = {
+            focusRequester.freeFocus()
+        }
+    ) {
+        Icon(Icons.Default.Close, contentDescription = "Exit focus lock")
+    }
+    // [END android_compose_touchinput_focus_free_focus]
+}

compose/snippets/src/main/java/com/example/compose/snippets/touchinput/focus/FocusGroup.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.snippets.touchinput.focus
+
+import androidx.compose.foundation.focusGroup
+import androidx.compose.foundation.layout.Row
+import androidx.compose.material3.Button
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.focus.FocusRequester
+import androidx.compose.ui.focus.focusProperties
+import androidx.compose.ui.focus.focusRequester
+
+@Composable
+private fun FocusGroupOnEnterSample() {
+    // [START android_compose_touchinput_focus_group_on_enter]
+    val defaultChildRequester = remember { FocusRequester() }
+
+    Row(
+        modifier = Modifier
+            .focusGroup()
+            .focusProperties {
+                // Intercept entry into this group and redirect focus to the primary action
+                onEnter = {
+                    defaultChildRequester.requestFocus()
+                }
+            }
+    ) {
+        Button(onClick = { /* Cancel action */ }) {
+            Text("Cancel")
+        }
+        Button(
+            onClick = { /* Confirm action */ },
+            modifier = Modifier.focusRequester(defaultChildRequester)
+        ) {
+            Text("Confirm (Default)")
+        }
+    }
+    // [END android_compose_touchinput_focus_group_on_enter]
+}

compose/snippets/src/main/java/com/example/compose/snippets/touchinput/focus/FocusInTextFields.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2026 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
+ *
+ *     https://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 com.example.compose.snippets.touchinput.focus
+
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.text.BasicTextField
+import androidx.compose.foundation.text.input.TextFieldLineLimits
+import androidx.compose.foundation.text.input.rememberTextFieldState
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+
+@Composable
+private fun FocusInTextFieldsLineLimitsSample() {
+    val singleLineState = rememberTextFieldState()
+    val multiLineState = rememberTextFieldState()
+
+    // [START android_compose_touchinput_focus_text_fields_line_limits]
+    // Single-line text field: Tab advances focus to the next focus target
+    BasicTextField(
+        state = singleLineState,
+        lineLimits = TextFieldLineLimits.SingleLine,
+        modifier = Modifier.fillMaxWidth()
+    )
+
+    // Multi-line text field: Tab inserts '\t'; Shift + Tab moves to previous target
+    BasicTextField(
+        state = multiLineState,
+        lineLimits = TextFieldLineLimits.MultiLine(),
+        modifier = Modifier.fillMaxWidth()
+    )
+    // [END android_compose_touchinput_focus_text_fields_line_limits]
+}