Load preset input from JSON file in EffectActivity

The JSON file contains a list of playlists, each with a name and a list of media items. The EffectActivity loads the JSON file and creates a list of PlaylistHolder objects, which contain the playlist name and the list of media items.

PiperOrigin-RevId: 703069411

demos/effect/src/main/assets/media.playlist.json

@@ -0,0 +1,27 @@
+[
+  {
+    "name": "Cats -> Dogs",
+    "playlist": [
+      {
+        "uri": "https://html5demos.com/assets/dizzy.mp4"
+      },
+      {
+        "uri": "https://storage.googleapis.com/exoplayer-test-media-1/mkv/android-screens-lavf-56.36.100-aac-avc-main-1280x720.mkv"
+      }
+    ]
+  },
+  {
+    "name": "Android Block -> Dogs -> BigBuckBunny",
+    "playlist": [
+      {
+        "uri": "https://storage.googleapis.com/exoplayer-test-media-0/android-block-1080-hevc.mp4"
+      },
+      {
+        "uri": "https://storage.googleapis.com/exoplayer-test-media-1/mkv/android-screens-lavf-56.36.100-aac-avc-main-1280x720.mkv"
+      },
+      {
+        "uri": "https://storage.googleapis.com/exoplayer-test-media-0/BigBuckBunny_320x180.mp4"
+      }
+    ]
+  }
+]

demos/effect/src/main/java/androidx/media3/demo/effect/EffectActivity.kt

@@ -49,6 +49,7 @@ import androidx.compose.ui.res.dimensionResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.viewinterop.AndroidView
 import androidx.core.content.ContextCompat
+import androidx.lifecycle.lifecycleScope
 import androidx.media3.common.MediaItem
 import androidx.media3.common.util.UnstableApi
 import androidx.media3.common.util.Util.SDK_INT
@@ -60,11 +61,16 @@ class EffectActivity : ComponentActivity() {
 
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
-    setContent { EffectDemo() }
+    val playlistHolderList = mutableStateOf<List<PlaylistHolder>>(emptyList())
+    lifecycleScope.launch {
+      playlistHolderList.value =
+        loadPlaylistsFromJson(JSON_FILENAME, this@EffectActivity, "EffectActivity")
+    }
+    setContent { EffectDemo(playlistHolderList.value) }
   }
 
   @Composable
-  fun EffectDemo() {
+  private fun EffectDemo(playlistHolderList: List<PlaylistHolder>) {
     val snackbarHostState = remember { SnackbarHostState() }
     val coroutineScope = rememberCoroutineScope()
     val context = LocalContext.current
@@ -100,7 +106,7 @@ class EffectActivity : ComponentActivity() {
   }
 
   @Composable
-  fun InputChooser(onException: (String) -> Unit, onNewUri: (Uri) -> Unit) {
+  private fun InputChooser(onException: (String) -> Unit, onNewUri: (Uri) -> Unit) {
     var showLocalFilePicker by remember { mutableStateOf(false) }
     Row(
       modifier = Modifier.padding(vertical = dimensionResource(id = R.dimen.small_padding)),
@@ -128,7 +134,7 @@ class EffectActivity : ComponentActivity() {
 
   @OptIn(UnstableApi::class)
   @Composable
-  fun LocalFilePicker(onException: (String) -> Unit, onFileSelected: (Uri) -> Unit) {
+  private fun LocalFilePicker(onException: (String) -> Unit, onFileSelected: (Uri) -> Unit) {
     val context = LocalContext.current
     val localFilePickerLauncher =
       rememberLauncherForActivityResult(
@@ -166,7 +172,7 @@ class EffectActivity : ComponentActivity() {
   }
 
   @Composable
-  fun PlayerScreen(exoPlayer: ExoPlayer) {
+  private fun PlayerScreen(exoPlayer: ExoPlayer) {
     val context = LocalContext.current
     AndroidView(
       factory = { PlayerView(context).apply { player = exoPlayer } },
@@ -177,9 +183,13 @@ class EffectActivity : ComponentActivity() {
   }
 
   @Composable
-  fun Effects(onException: (String) -> Unit) {
+  private fun Effects(onException: (String) -> Unit) {
     Button(onClick = { onException("Button is not yet implemented.") }) {
       Text(text = stringResource(id = R.string.apply_effects))
     }
   }
+
+  companion object {
+    const val JSON_FILENAME = "media.playlist.json"
+  }
 }

demos/effect/src/main/java/androidx/media3/demo/effect/EffectDemoUtil.kt

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2024 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 androidx.media3.demo.effect
+
+import android.content.Context
+import android.net.Uri
+import android.util.JsonReader
+import android.util.Log
+import androidx.media3.common.MediaItem
+import java.io.IOException
+import java.io.InputStreamReader
+import java.nio.charset.StandardCharsets
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+
+internal suspend fun loadPlaylistsFromJson(
+  jsonFilename: String,
+  context: Context,
+  tag: String,
+): List<PlaylistHolder> =
+  withContext(Dispatchers.IO) {
+    try {
+      context.assets.open(jsonFilename).use { inputStream ->
+        val reader = JsonReader(InputStreamReader(inputStream, StandardCharsets.UTF_8))
+        val playlistHolders = buildList {
+          reader.beginArray()
+          while (reader.hasNext()) {
+            readPlaylist(reader)?.let { add(it) }
+          }
+          reader.endArray()
+        }
+        playlistHolders
+      }
+    } catch (e: IOException) {
+      Log.e(tag, context.getString(R.string.playlist_loading_error, jsonFilename, e))
+      emptyList()
+    }
+  }
+
+private fun readPlaylist(reader: JsonReader): PlaylistHolder? {
+  val playlistHolder = PlaylistHolder("", emptyList())
+  reader.beginObject()
+  while (reader.hasNext()) {
+    val name = reader.nextName()
+    if (name.equals("name")) {
+      playlistHolder.title = reader.nextString()
+    } else if (name.equals("playlist")) {
+      playlistHolder.mediaItems = buildList {
+        reader.beginArray()
+        while (reader.hasNext()) {
+          reader.beginObject()
+          reader.nextName()
+          add(MediaItem.fromUri(Uri.parse(reader.nextString())))
+          reader.endObject()
+        }
+        reader.endArray()
+      }
+    }
+  }
+  reader.endObject()
+  // Only return the playlistHolder object if it has media items
+  return if (playlistHolder.mediaItems.isNotEmpty()) playlistHolder else null
+}
+
+internal data class PlaylistHolder(var title: String, var mediaItems: List<MediaItem>)

demos/effect/src/main/res/values/strings.xml

@@ -19,4 +19,5 @@
   <string name="choose_local_file">Choose local file</string>
   <string name="apply_effects">Apply effects</string>
   <string name="ok">OK</string>
+  <string name="playlist_loading_error">Error loading playlist from %1$s: %2$s</string>
 </resources>