Load the Spatializer API with reflection

This change adds a delegate class that loads and forwards calls
to a Spatializer with reflection, so that we can use the Spatializer
API before we update the compile SDK target to 32.

PiperOrigin-RevId: 416027289

library/core/src/main/java/com/google/android/exoplayer2/audio/SpatializerDelegate.java

+/*
+ * Copyright 2021 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 com.google.android.exoplayer2.audio;
+
+import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.ElementType.TYPE_USE;
+
+import android.content.Context;
+import android.media.AudioAttributes;
+import android.media.AudioFormat;
+import android.media.AudioManager;
+import androidx.annotation.IntDef;
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
+import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.Util;
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Executor;
+
+/**
+ * Exposes the android.media.Spatializer API via reflection. This is so that we can use the
+ * Spatializer while the compile SDK target is set to 31.
+ */
+@RequiresApi(31)
+/* package */ final class SpatializerDelegate {
+  /** Level of support for audio spatialization. */
+  @Documented
+  @Retention(RetentionPolicy.SOURCE)
+  @Target({FIELD, METHOD, PARAMETER, LOCAL_VARIABLE, TYPE_USE})
+  @IntDef({
+    SPATIALIZER_IMMERSIVE_LEVEL_MULTICHANNEL,
+    SPATIALIZER_IMMERSIVE_LEVEL_NONE,
+    SPATIALIZER_IMMERSIVE_LEVEL_OTHER
+  })
+  @interface ImmersiveAudioLevel {}
+
+  /** See Spatializer#SPATIALIZER_IMMERSIVE_LEVEL_MULTICHANNEL */
+  public static final int SPATIALIZER_IMMERSIVE_LEVEL_MULTICHANNEL = 1;
+  /** See Spatializer#SPATIALIZER_IMMERSIVE_LEVEL_NONE */
+  public static final int SPATIALIZER_IMMERSIVE_LEVEL_NONE = 0;
+  /** See Spatializer#SPATIALIZER_IMMERSIVE_LEVEL_OTHER */
+  public static final int SPATIALIZER_IMMERSIVE_LEVEL_OTHER = -1;
+
+  /** Wrapper for Spatializer.OnSpatializerStateChangedListener */
+  public interface Listener {
+    /** See Spatializer.OnSpatializerStateChangedListener.onSpatializerEnabledChanged */
+    void onSpatializerEnabledChanged(SpatializerDelegate spatializer, boolean enabled);
+
+    /** See Spatializer.OnSpatializerStateChangedListener.onSpatializerAvailableChanged */
+    void onSpatializerAvailableChanged(SpatializerDelegate spatializer, boolean available);
+  }
+
+  private final Object spatializer;
+  private final Class<?> spatializerClass;
+  private final Class<?> spatializerListenerClass;
+  private final Method isEnabled;
+  private final Method isAvailable;
+  private final Method getImmersiveAudioLevel;
+  private final Method canBeSpatialized;
+  private final Method addListener;
+  private final Method removeListener;
+  private final Map<Listener, Object> listeners;
+
+  /** Creates an instance. */
+  public SpatializerDelegate(Context context)
+      throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException,
+          IllegalAccessException {
+    Method getSpatializerMethod = AudioManager.class.getMethod("getSpatializer");
+    AudioManager manager =
+        Assertions.checkNotNull(
+            (AudioManager) context.getApplicationContext().getSystemService(Context.AUDIO_SERVICE));
+    spatializer = checkStateNotNull(getSpatializerMethod.invoke(manager));
+    spatializerClass = Class.forName("android.media.Spatializer");
+    spatializerListenerClass =
+        Class.forName("android.media.Spatializer$OnSpatializerStateChangedListener");
+    isEnabled = spatializerClass.getMethod("isEnabled");
+    isAvailable = spatializerClass.getMethod("isAvailable");
+    getImmersiveAudioLevel = spatializerClass.getMethod("getImmersiveAudioLevel");
+    canBeSpatialized =
+        spatializerClass.getMethod(
+            "canBeSpatialized", android.media.AudioAttributes.class, AudioFormat.class);
+    addListener =
+        spatializerClass.getMethod(
+            "addOnSpatializerStateChangedListener", Executor.class, spatializerListenerClass);
+    removeListener =
+        spatializerClass.getMethod(
+            "removeOnSpatializerStateChangedListener", spatializerListenerClass);
+    listeners = new HashMap<>();
+  }
+
+  /** Delegates to Spatializer.isEnabled() */
+  public boolean isEnabled() {
+    try {
+      return (boolean) Util.castNonNull(isEnabled.invoke(spatializer));
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  /** Delegates to Spatializer.isAvailable() */
+  public boolean isAvailable() {
+    try {
+      return (boolean) Util.castNonNull(isAvailable.invoke(spatializer));
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  /** Delegates to Spatializer.getImmersiveAudioLevel() */
+  @ImmersiveAudioLevel
+  public int getImmersiveAudioLevel() {
+    try {
+      return (int) Util.castNonNull(getImmersiveAudioLevel.invoke(spatializer));
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  /** Delegates to Spatializer.canBeSpatialized() */
+  public boolean canBeSpatialized(AudioAttributes attributes, AudioFormat format) {
+    try {
+      return (boolean) Util.castNonNull(canBeSpatialized.invoke(spatializer, attributes, format));
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  /** Delegates to Spatializer.addOnSpatializerStateChangedListener() */
+  public void addOnSpatializerStateChangedListener(Executor executor, Listener listener) {
+    if (listeners.containsKey(listener)) {
+      return;
+    }
+    Object listenerProxy = createSpatializerListenerProxy(listener);
+    try {
+      addListener.invoke(spatializer, executor, listenerProxy);
+      listeners.put(listener, listenerProxy);
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  /** Delegates to Spatializer.removeOnSpatializerStateChangedListener() */
+  public void removeOnSpatializerStateChangedListener(Listener listener) {
+    @Nullable Object proxy = listeners.get(listener);
+    if (proxy == null) {
+      return;
+    }
+    try {
+      removeListener.invoke(spatializer, proxy);
+      listeners.remove(listener);
+    } catch (IllegalAccessException | InvocationTargetException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+
+  private Object createSpatializerListenerProxy(Listener listener) {
+    return Proxy.newProxyInstance(
+        spatializerListenerClass.getClassLoader(),
+        new Class<?>[] {spatializerListenerClass},
+        new ProxySpatializerListener(this, listener));
+  }
+
+  /** Proxy-based implementation of Spatializer.OnSpatializerStateChangedListener. */
+  private static final class ProxySpatializerListener implements InvocationHandler {
+    private final SpatializerDelegate spatializerDelegate;
+    private final Listener listener;
+
+    private ProxySpatializerListener(SpatializerDelegate spatializerDelegate, Listener listener) {
+      this.spatializerDelegate = spatializerDelegate;
+      this.listener = listener;
+    }
+
+    @Override
+    public Object invoke(Object o, Method method, Object[] objects) {
+      String methodName = method.getName();
+      Class<?>[] parameterTypes = method.getParameterTypes();
+      if (methodName.equals("onSpatializerAvailableChanged")
+          && parameterTypes.length == 2
+          && spatializerDelegate.spatializerClass.isAssignableFrom(parameterTypes[0])
+          && parameterTypes[1].equals(Boolean.TYPE)) {
+        listener.onSpatializerAvailableChanged(spatializerDelegate, (boolean) objects[1]);
+      } else if (methodName.equals("onSpatializerEnabledChanged")
+          && parameterTypes.length == 2
+          && spatializerDelegate.spatializerClass.isAssignableFrom(parameterTypes[0])
+          && parameterTypes[1].equals(Boolean.TYPE)) {
+        listener.onSpatializerEnabledChanged(spatializerDelegate, (boolean) objects[1]);
+      }
+      return this;
+    }
+  }
+}