Navigation (#130)

* Adding landing screen with navigation destinations.

* Apply Spotless

* Updating the navigation to use an enum class that enumerated all possible destinations. They go on to populate a LazyColumn in NavigationButtons.

* Apply Spotless

* Updating the navigation to use an enum class that enumerated all possible destinations. They go on to populate a LazyColumn in NavigationButtons.

* Removing when block from NavigationItems.

* Apply Spotless

---------

Co-authored-by: jakeroseman <jakeroseman@users.noreply.github.com>

compose/snippets/src/main/java/com/example/compose/snippets/LandingScreen/LandingScreen.kt

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2023 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.LandingScreen
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.Button
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.example.compose.snippets.navigation.Destination
+
+@Composable
+fun LandingScreen(
+    navigate: (Destination) -> Unit
+) {
+    Column(
+        modifier = Modifier
+            .padding(16.dp)
+            .fillMaxSize(),
+        verticalArrangement = Arrangement.spacedBy(24.dp),
+    ) {
+        Text(
+            modifier = Modifier.fillMaxWidth(),
+            style = TextStyle(
+                fontSize = 24.sp,
+                fontWeight = FontWeight.Bold,
+                textAlign = TextAlign.Center,
+            ),
+            text = "Android snippets",
+        )
+        Text(
+            text = "Use the following buttons to view a selection of the snippets used in the Android documentation."
+        )
+        NavigationItems { navigate(it) }
+    }
+}
+
+@Composable
+fun NavigationItems(navigate: (Destination) -> Unit) {
+    LazyColumn(
+        modifier = Modifier
+            .padding(16.dp)
+            .fillMaxSize(),
+        verticalArrangement = Arrangement.spacedBy(8.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        items(Destination.values().toList()) { destination ->
+            NavigationItem(destination) {
+                navigate(
+                    destination
+                )
+            }
+        }
+    }
+}
+
+@Composable
+fun NavigationItem(destination: Destination, onClick: () -> Unit) {
+    Button(
+        onClick = { onClick() }
+    ) {
+        Text(destination.title)
+    }
+}

compose/snippets/src/main/java/com/example/compose/snippets/SnippetsActivity.kt

@@ -19,31 +19,42 @@ package com.example.compose.snippets
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
-import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
 import androidx.compose.ui.Modifier
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.rememberNavController
+import com.example.compose.snippets.LandingScreen.LandingScreen
+import com.example.compose.snippets.graphics.BrushExamplesScreen
 import com.example.compose.snippets.images.ImageExamplesScreen
+import com.example.compose.snippets.navigation.Destination
 import com.example.compose.snippets.ui.theme.SnippetsTheme
 
 class SnippetsActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContent {
             SnippetsTheme {
+                val navController = rememberNavController()
                 // A surface container using the 'background' color from the theme
                 Surface(
                     modifier = Modifier.fillMaxSize(),
                     color = MaterialTheme.colorScheme.background
                 ) {
-                    // TODO - We should put these in different navigation destinations
-                    Column(
-                        modifier = Modifier
-                            .fillMaxSize()
-                    ) {
-                        // BrushExamplesScreen()
-                        ImageExamplesScreen()
+                    NavHost(navController, startDestination = "LandingScreen") {
+                        composable("LandingScreen") {
+                            LandingScreen { navController.navigate(it.route) }
+                        }
+                        Destination.values().forEach { destination ->
+                            composable(destination.route) {
+                                when (destination) {
+                                    Destination.BrushExamples -> BrushExamplesScreen()
+                                    Destination.ImageExamples -> ImageExamplesScreen()
+                                }
+                            }
+                        }
                     }
                 }
             }

compose/snippets/src/main/java/com/example/compose/snippets/navigation/Destination.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2023 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.navigation
+
+enum class Destination(val route: String, val title: String) {
+    BrushExamples("brushExamples", "Brush Examples"),
+    ImageExamples("imageExamples", "Image Examples"),
+}