Add LazyColumn shortform demo with single-player preloading (addresses #1853)

demos/shortform/build.gradle

@@ -14,6 +14,7 @@
 apply from: '../../constants.gradle'
 apply plugin: 'com.android.application'
 apply plugin: 'kotlin-android'
+apply plugin: 'org.jetbrains.kotlin.plugin.compose'
 
 android {
     namespace 'androidx.media3.demo.shortform'
@@ -57,6 +58,7 @@ android {
     }
     buildFeatures {
         viewBinding true
+        compose true
     }
     sourceSets {
         main {
@@ -80,4 +82,14 @@ dependencies {
     implementation project(modulePrefix + 'lib-exoplayer-dash')
     implementation project(modulePrefix + 'lib-exoplayer-hls')
     implementation project(modulePrefix + 'lib-ui')
+
+    // Compose dependencies
+    def composeBom = platform('androidx.compose:compose-bom:2024.12.01')
+    implementation composeBom
+    implementation 'androidx.activity:activity-compose:1.9.0'
+    implementation 'androidx.compose.foundation:foundation'
+    implementation 'androidx.compose.material3:material3'
+    implementation 'androidx.compose.ui:ui-tooling-preview'
+    implementation 'androidx.compose.runtime:runtime'
+    debugImplementation 'androidx.compose.ui:ui-tooling'
 }

demos/shortform/src/main/AndroidManifest.xml

@@ -34,6 +34,10 @@
       android:exported="false"
       android:label="@string/title_activity_view_pager"
       android:name=".viewpager.ViewPagerActivity"/>
+    <activity
+      android:exported="false"
+      android:label="@string/title_activity_lazy_column"
+      android:name=".lazycolumn.LazyColumnActivity"/>
   </application>
 
   <uses-permission android:name="android.permission.INTERNET" />

demos/shortform/src/main/java/androidx/media3/demo/shortform/MainActivity.kt

@@ -23,6 +23,7 @@ import android.view.View
 import android.widget.EditText
 import androidx.appcompat.app.AppCompatActivity
 import androidx.media3.common.util.UnstableApi
+import androidx.media3.demo.shortform.lazycolumn.LazyColumnActivity
 import androidx.media3.demo.shortform.viewpager.ViewPagerActivity
 import java.lang.Integer.max
 import java.lang.Integer.min
@@ -56,6 +57,12 @@ class MainActivity : AppCompatActivity() {
         Intent(this, ViewPagerActivity::class.java).putExtra(NUM_PLAYERS_EXTRA, numberOfPlayers)
       )
     }
+
+    findViewById<View>(R.id.lazy_column_button).setOnClickListener {
+      startActivity(
+        Intent(this, LazyColumnActivity::class.java).putExtra(NUM_PLAYERS_EXTRA, numberOfPlayers)
+      )
+    }
   }
 
   companion object {

demos/shortform/src/main/java/androidx/media3/demo/shortform/MediaItemDatabase.kt

@@ -32,4 +32,6 @@ class MediaItemDatabase {
     val uri = mediaUris[index.mod(mediaUris.size)]
     return MediaItem.Builder().setUri(uri).setMediaId(index.toString()).build()
   }
+
+    fun size(): Int = mediaUris.size
 }

demos/shortform/src/main/java/androidx/media3/demo/shortform/lazycolumn/BitmapProvider.kt

@@ -0,0 +1,29 @@
+package androidx.media3.demo.shortform.lazycolumn
+
+import android.graphics.Bitmap
+import android.media.MediaMetadataRetriever
+import android.os.Build
+
+class BitmapProvider {
+    companion object {
+        private const val THUMB_EXTRACT_TIME = 1 * 1000L * 1000L
+    }
+
+    fun getBitmap(
+        ids: List<String?>?,
+        metadataRetriever: MediaMetadataRetriever,
+    ): Bitmap? {
+        if (ids.isNullOrEmpty()) return null
+        if (ids.size > 1) {
+            val customDataSource = ConcatMediaDataSource(ids)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+                metadataRetriever.setDataSource(customDataSource)
+            }
+        } else {
+            metadataRetriever.setDataSource(ids.getOrNull(0))
+        }
+        return metadataRetriever.getFrameAtTime(0) ?: metadataRetriever.getFrameAtTime(
+            THUMB_EXTRACT_TIME
+        )
+    }
+}

demos/shortform/src/main/java/androidx/media3/demo/shortform/lazycolumn/ConcatMediaDataSource.kt

@@ -0,0 +1,74 @@
+package androidx.media3.demo.shortform.lazycolumn
+
+import android.annotation.SuppressLint
+import android.media.MediaDataSource
+import java.io.ByteArrayOutputStream
+import java.io.FileInputStream
+import java.io.SequenceInputStream
+import java.util.Enumeration
+import kotlin.math.min
+
+@SuppressLint("NewApi")
+class ConcatMediaDataSource(ids: List<String?>) : MediaDataSource() {
+
+    private var data: ByteArray? = null
+    private val mergedInputStream: SequenceInputStream by lazy { getInputStream(ids) }
+
+    private fun ensureDataBuffered() {
+        synchronized(this) {
+            if (data != null) return
+            ByteArrayOutputStream().use { buffer ->
+                mergedInputStream.use { input ->
+                    input.copyTo(buffer)
+                }
+                data = buffer.toByteArray()
+            }
+        }
+    }
+
+    override fun readAt(
+        position: Long,
+        buffer: ByteArray,
+        offset: Int,
+        size: Int,
+    ): Int {
+        synchronized(this) {
+            ensureDataBuffered()
+            data?.let {
+                if (position > it.size) return -1
+                val actualSize = min(size, it.size - position.toInt())
+                System.arraycopy(it, position.toInt(), buffer, offset, actualSize)
+                return actualSize
+            } ?: run {
+                return -1
+            }
+        }
+    }
+
+    override fun getSize(): Long {
+        synchronized(this) {
+            return (data?.size?.toLong() ?: -1)
+        }
+    }
+
+    override fun close() {
+        synchronized(this) {
+            mergedInputStream.close()
+            data = null
+        }
+    }
+
+    private fun getInputStream(files: List<String?>): SequenceInputStream {
+        val inputStreams = files.map { FileInputStream(it) }
+        val allInputStreams = listOf(*inputStreams.toTypedArray())
+        return SequenceInputStream(allInputStreams.iterator().asEnumeration())
+    }
+}
+
+fun <T> Iterator<T>.asEnumeration(): Enumeration<T> {
+    return object : Enumeration<T> {
+        override fun hasMoreElements(): Boolean = this@asEnumeration.hasNext()
+
+        override fun nextElement(): T = this@asEnumeration.next()
+    }
+}

demos/shortform/src/main/java/androidx/media3/demo/shortform/lazycolumn/LazyColumnActivity.kt

@@ -0,0 +1,73 @@
+/*
+ * 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
+ *
+ *      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.media3.demo.shortform.lazycolumn
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.media3.common.util.UnstableApi
+import androidx.media3.demo.shortform.lazycolumn.composable.ShortFormLazyColumn
+
+@UnstableApi
+class LazyColumnActivity : ComponentActivity() {
+    companion object {
+        const val LOAD_CONTROL_MIN_BUFFER_MS = 3_000
+        const val LOAD_CONTROL_MAX_BUFFER_MS = 20_000
+        const val LOAD_CONTROL_BUFFER_FOR_PLAYBACK_MS = 500
+        const val PLAYER_CACHE_DIRECTORY = "exo_player"
+    }
+
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContent {
+            MaterialTheme {
+                Surface(
+                    modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background
+                ) {
+                    ShortFormContent()
+                }
+            }
+        }
+    }
+}
+
+@UnstableApi
+@Composable
+fun ShortFormContent() {
+    val context = LocalContext.current
+    val playerManager = remember {
+        LazyColumnPlayerManager(context)
+    }
+
+    DisposableEffect(Unit) {
+        onDispose {
+            playerManager.release()
+        }
+    }
+
+    ShortFormLazyColumn(
+        playerManager = playerManager
+    )
+}