Introduces Android API level linting, fixes all current API lint errors.

This CL attempts to annotate accesses on >16 API levels using as
small scopes as possible. The TargetApi notations mean "yes, I know
I'm accessing a higher API and I take responsibility for gating the
call on Android API level". The Encoder/Decoder classes are annotated
on the whole class, but they're only accessed through JNI; we should
annotate on method level otherwise and preferably on private methods.

This patch also fixes some compiler-level deprecation warnings (i.e.
-Xlint:deprecation), but probably not all of them.

BUG=webrtc:5063
R=henrika@webrtc.org, kjellander@webrtc.org, magjed@webrtc.org

Review URL: https://codereview.webrtc.org/1412673008 .

Cr-Commit-Position: refs/heads/master@{#10624}

talk/app/webrtc/java/android/org/webrtc/Camera2Enumerator.java

@@ -27,7 +27,9 @@
 
 package org.webrtc;
 
+import android.annotation.TargetApi;
 import android.content.Context;
+
 import android.graphics.ImageFormat;
 import android.hardware.camera2.CameraCharacteristics;
 import android.hardware.camera2.CameraManager;
@@ -45,6 +47,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+@TargetApi(21)
 public class Camera2Enumerator implements CameraEnumerationAndroid.Enumerator {
   private final static String TAG = "Camera2Enumerator";
   private final static double NANO_SECONDS_PER_SECOND = 1.0e9;

talk/app/webrtc/java/android/org/webrtc/CameraEnumerationAndroid.java

@@ -29,7 +29,6 @@ package org.webrtc;
 
 import static java.lang.Math.abs;
 import static java.lang.Math.ceil;
-import android.hardware.Camera;
 import android.graphics.ImageFormat;
 
 import org.json.JSONArray;
@@ -127,8 +126,8 @@ public class CameraEnumerationAndroid {
 
   // Returns device names that can be used to create a new VideoCapturerAndroid.
   public static String[] getDeviceNames() {
-    String[] names = new String[Camera.getNumberOfCameras()];
+    String[] names = new String[android.hardware.Camera.getNumberOfCameras()];
-    for (int i = 0; i < Camera.getNumberOfCameras(); ++i) {
+    for (int i = 0; i < android.hardware.Camera.getNumberOfCameras(); ++i) {
       names[i] = getDeviceName(i);
     }
     return names;
@@ -136,22 +135,22 @@ public class CameraEnumerationAndroid {
 
   // Returns number of cameras on device.
   public static int getDeviceCount() {
-    return Camera.getNumberOfCameras();
+    return android.hardware.Camera.getNumberOfCameras();
   }
 
   // Returns the name of the camera with camera index. Returns null if the
   // camera can not be used.
   public static String getDeviceName(int index) {
-    Camera.CameraInfo info = new Camera.CameraInfo();
+    android.hardware.Camera.CameraInfo info = new android.hardware.Camera.CameraInfo();
     try {
-      Camera.getCameraInfo(index, info);
+      android.hardware.Camera.getCameraInfo(index, info);
     } catch (Exception e) {
       Logging.e(TAG, "getCameraInfo failed on index " + index,e);
       return null;
     }
 
     String facing =
-        (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) ? "front" : "back";
+        (info.facing == android.hardware.Camera.CameraInfo.CAMERA_FACING_FRONT) ? "front" : "back";
     return "Camera " + index + ", Facing " + facing
         + ", Orientation " + info.orientation;
   }
@@ -159,13 +158,13 @@ public class CameraEnumerationAndroid {
   // Returns the name of the front facing camera. Returns null if the
   // camera can not be used or does not exist.
   public static String getNameOfFrontFacingDevice() {
-    return getNameOfDevice(Camera.CameraInfo.CAMERA_FACING_FRONT);
+    return getNameOfDevice(android.hardware.Camera.CameraInfo.CAMERA_FACING_FRONT);
   }
 
   // Returns the name of the back facing camera. Returns null if the
   // camera can not be used or does not exist.
   public static String getNameOfBackFacingDevice() {
-    return getNameOfDevice(Camera.CameraInfo.CAMERA_FACING_BACK);
+    return getNameOfDevice(android.hardware.Camera.CameraInfo.CAMERA_FACING_BACK);
   }
 
   public static String getSupportedFormatsAsJson(int id) throws JSONException {
@@ -194,7 +193,8 @@ public class CameraEnumerationAndroid {
     }
   }
 
-  public static int[] getFramerateRange(Camera.Parameters parameters, final int framerate) {
+  public static int[] getFramerateRange(android.hardware.Camera.Parameters parameters,
+      final int framerate) {
     List<int[]> listFpsRange = parameters.getSupportedPreviewFpsRange();
     if (listFpsRange.isEmpty()) {
       Logging.w(TAG, "No supported preview fps range");
@@ -203,27 +203,28 @@ public class CameraEnumerationAndroid {
     return Collections.min(listFpsRange,
         new ClosestComparator<int[]>() {
           @Override int diff(int[] range) {
-            return abs(framerate - range[Camera.Parameters.PREVIEW_FPS_MIN_INDEX])
+            return abs(framerate - range[android.hardware.Camera.Parameters.PREVIEW_FPS_MIN_INDEX])
-                + abs(framerate - range[Camera.Parameters.PREVIEW_FPS_MAX_INDEX]);
+                + abs(framerate - range[android.hardware.Camera.Parameters.PREVIEW_FPS_MAX_INDEX]);
           }
      });
   }
 
-  public static Camera.Size getClosestSupportedSize(
+  public static android.hardware.Camera.Size getClosestSupportedSize(
-      List<Camera.Size> supportedSizes, final int requestedWidth, final int requestedHeight) {
+      List<android.hardware.Camera.Size> supportedSizes, final int requestedWidth,
+      final int requestedHeight) {
     return Collections.min(supportedSizes,
-        new ClosestComparator<Camera.Size>() {
+        new ClosestComparator<android.hardware.Camera.Size>() {
-          @Override int diff(Camera.Size size) {
+          @Override int diff(android.hardware.Camera.Size size) {
             return abs(requestedWidth - size.width) + abs(requestedHeight - size.height);
           }
      });
   }
 
   private static String getNameOfDevice(int facing) {
-    final Camera.CameraInfo info = new Camera.CameraInfo();
+    final android.hardware.Camera.CameraInfo info = new android.hardware.Camera.CameraInfo();
-    for (int i = 0; i < Camera.getNumberOfCameras(); ++i) {
+    for (int i = 0; i < android.hardware.Camera.getNumberOfCameras(); ++i) {
       try {
-        Camera.getCameraInfo(i, info);
+        android.hardware.Camera.getCameraInfo(i, info);
         if (info.facing == facing) {
           return getDeviceName(i);
         }

talk/app/webrtc/java/android/org/webrtc/CameraEnumerator.java

@@ -27,7 +27,6 @@
 
 package org.webrtc;
 
-import android.hardware.Camera;
 import android.os.SystemClock;
 
 import org.webrtc.CameraEnumerationAndroid.CaptureFormat;
@@ -60,11 +59,11 @@ public class CameraEnumerator implements CameraEnumerationAndroid.Enumerator {
   private List<CaptureFormat> enumerateFormats(int cameraId) {
     Logging.d(TAG, "Get supported formats for camera index " + cameraId + ".");
     final long startTimeMs = SystemClock.elapsedRealtime();
-    final Camera.Parameters parameters;
+    final android.hardware.Camera.Parameters parameters;
-    Camera camera = null;
+    android.hardware.Camera camera = null;
     try {
       Logging.d(TAG, "Opening camera with index " + cameraId);
-      camera = Camera.open(cameraId);
+      camera = android.hardware.Camera.open(cameraId);
       parameters = camera.getParameters();
     } catch (RuntimeException e) {
       Logging.e(TAG, "Open camera failed on camera index " + cameraId, e);
@@ -84,10 +83,10 @@ public class CameraEnumerator implements CameraEnumerationAndroid.Enumerator {
         // getSupportedPreviewFpsRange() returns a sorted list. Take the fps range
         // corresponding to the highest fps.
         final int[] range = listFpsRange.get(listFpsRange.size() - 1);
-        minFps = range[Camera.Parameters.PREVIEW_FPS_MIN_INDEX];
+        minFps = range[android.hardware.Camera.Parameters.PREVIEW_FPS_MIN_INDEX];
-        maxFps = range[Camera.Parameters.PREVIEW_FPS_MAX_INDEX];
+        maxFps = range[android.hardware.Camera.Parameters.PREVIEW_FPS_MAX_INDEX];
       }
-      for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
+      for (android.hardware.Camera.Size size : parameters.getSupportedPreviewSizes()) {
         formatList.add(new CaptureFormat(size.width, size.height, minFps, maxFps));
       }
     } catch (Exception e) {

talk/app/webrtc/java/android/org/webrtc/VideoCapturerAndroid.java

@@ -29,8 +29,6 @@ package org.webrtc;
 
 import android.content.Context;
 import android.graphics.SurfaceTexture;
-import android.hardware.Camera;
-import android.hardware.Camera.PreviewCallback;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.SystemClock;
@@ -68,20 +66,21 @@ import javax.microedition.khronos.egl.EGL10;
 // camera thread. The internal *OnCameraThread() methods must check |camera| for null to check if
 // the camera has been stopped.
 @SuppressWarnings("deprecation")
-public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallback,
+public class VideoCapturerAndroid extends VideoCapturer implements
+    android.hardware.Camera.PreviewCallback,
     SurfaceTextureHelper.OnTextureFrameAvailableListener {
   private final static String TAG = "VideoCapturerAndroid";
   private final static int CAMERA_OBSERVER_PERIOD_MS = 2000;
   private final static int CAMERA_FREEZE_REPORT_TIMOUT_MS = 6000;
 
-  private Camera camera;  // Only non-null while capturing.
+  private android.hardware.Camera camera;  // Only non-null while capturing.
   private HandlerThread cameraThread;
   private final Handler cameraThreadHandler;
   private Context applicationContext;
   // Synchronization lock for |id|.
   private final Object cameraIdLock = new Object();
   private int id;
-  private Camera.CameraInfo info;
+  private android.hardware.Camera.CameraInfo info;
   private final FramePool videoBuffers;
   private final CameraStatistics cameraStatistics;
   // Remember the requested format in case we want to switch cameras.
@@ -108,10 +107,10 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
   private int openCameraAttempts;
 
   // Camera error callback.
-  private final Camera.ErrorCallback cameraErrorCallback =
+  private final android.hardware.Camera.ErrorCallback cameraErrorCallback =
-      new Camera.ErrorCallback() {
+      new android.hardware.Camera.ErrorCallback() {
     @Override
-    public void onError(int error, Camera camera) {
+    public void onError(int error, android.hardware.Camera camera) {
       String errorMessage;
       if (error == android.hardware.Camera.CAMERA_ERROR_SERVER_DIED) {
         errorMessage = "Camera server died!";
@@ -261,7 +260,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
   // Switch camera to the next valid camera id. This can only be called while
   // the camera is running.
   public void switchCamera(final CameraSwitchHandler handler) {
-    if (Camera.getNumberOfCameras() < 2) {
+    if (android.hardware.Camera.getNumberOfCameras() < 2) {
       if (handler != null) {
         handler.onCameraSwitchError("No camera to switch to.");
       }
@@ -292,7 +291,8 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
           pendingCameraSwitch = false;
         }
         if (handler != null) {
-          handler.onCameraSwitchDone(info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT);
+          handler.onCameraSwitchDone(
+              info.facing == android.hardware.Camera.CameraInfo.CAMERA_FACING_FRONT);
         }
       }
     });
@@ -375,13 +375,13 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
   // found. If |deviceName| is empty, the first available device is used.
   private static int lookupDeviceName(String deviceName) {
     Logging.d(TAG, "lookupDeviceName: " + deviceName);
-    if (deviceName == null || Camera.getNumberOfCameras() == 0) {
+    if (deviceName == null || android.hardware.Camera.getNumberOfCameras() == 0) {
       return -1;
     }
     if (deviceName.isEmpty()) {
       return 0;
     }
-    for (int i = 0; i < Camera.getNumberOfCameras(); ++i) {
+    for (int i = 0; i < android.hardware.Camera.getNumberOfCameras(); ++i) {
       if (deviceName.equals(CameraEnumerationAndroid.getDeviceName(i))) {
         return i;
       }
@@ -461,9 +461,9 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
           if (eventsHandler != null) {
             eventsHandler.onCameraOpening(id);
           }
-          camera = Camera.open(id);
+          camera = android.hardware.Camera.open(id);
-          info = new Camera.CameraInfo();
+          info = new android.hardware.Camera.CameraInfo();
-          Camera.getCameraInfo(id, info);
+          android.hardware.Camera.getCameraInfo(id, info);
         }
       } catch (RuntimeException e) {
         openCameraAttempts++;
@@ -525,14 +525,15 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     requestedFramerate = framerate;
 
     // Find closest supported format for |width| x |height| @ |framerate|.
-    final Camera.Parameters parameters = camera.getParameters();
+    final android.hardware.Camera.Parameters parameters = camera.getParameters();
     final int[] range = CameraEnumerationAndroid.getFramerateRange(parameters, framerate * 1000);
-    final Camera.Size previewSize = CameraEnumerationAndroid.getClosestSupportedSize(
+    final android.hardware.Camera.Size previewSize =
-        parameters.getSupportedPreviewSizes(), width, height);
+        CameraEnumerationAndroid.getClosestSupportedSize(
+            parameters.getSupportedPreviewSizes(), width, height);
     final CaptureFormat captureFormat = new CaptureFormat(
         previewSize.width, previewSize.height,
-        range[Camera.Parameters.PREVIEW_FPS_MIN_INDEX],
+        range[android.hardware.Camera.Parameters.PREVIEW_FPS_MIN_INDEX],
-        range[Camera.Parameters.PREVIEW_FPS_MAX_INDEX]);
+        range[android.hardware.Camera.Parameters.PREVIEW_FPS_MAX_INDEX]);
 
     // Check if we are already using this capture format, then we don't need to do anything.
     if (captureFormat.equals(this.captureFormat)) {
@@ -554,8 +555,9 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     parameters.setPreviewFormat(captureFormat.imageFormat);
     // Picture size is for taking pictures and not for preview/video, but we need to set it anyway
     // as a workaround for an aspect ratio problem on Nexus 7.
-    final Camera.Size pictureSize = CameraEnumerationAndroid.getClosestSupportedSize(
+    final android.hardware.Camera.Size pictureSize =
-        parameters.getSupportedPictureSizes(), width, height);
+        CameraEnumerationAndroid.getClosestSupportedSize(
+            parameters.getSupportedPictureSizes(), width, height);
     parameters.setPictureSize(pictureSize.width, pictureSize.height);
 
     // Temporarily stop preview if it's already running.
@@ -572,8 +574,8 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     this.captureFormat = captureFormat;
 
     List<String> focusModes = parameters.getSupportedFocusModes();
-    if (focusModes.contains(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO)) {
+    if (focusModes.contains(android.hardware.Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO)) {
-      parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
+      parameters.setFocusMode(android.hardware.Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
     }
 
     camera.setParameters(parameters);
@@ -637,7 +639,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     Logging.d(TAG, "switchCameraOnCameraThread");
     stopCaptureOnCameraThread();
     synchronized (cameraIdLock) {
-      id = (id + 1) % Camera.getNumberOfCameras();
+      id = (id + 1) % android.hardware.Camera.getNumberOfCameras();
     }
     dropNextFrame = true;
     startCaptureOnCameraThread(requestedWidth, requestedHeight, requestedFramerate, frameObserver,
@@ -699,7 +701,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
 
   private int getFrameOrientation() {
     int rotation = getDeviceOrientation();
-    if (info.facing == Camera.CameraInfo.CAMERA_FACING_BACK) {
+    if (info.facing == android.hardware.Camera.CameraInfo.CAMERA_FACING_BACK) {
       rotation = 360 - rotation;
     }
     return (info.orientation + rotation) % 360;
@@ -707,7 +709,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
 
   // Called on cameraThread so must not "synchronized".
   @Override
-  public void onPreviewFrame(byte[] data, Camera callbackCamera) {
+  public void onPreviewFrame(byte[] data, android.hardware.Camera callbackCamera) {
     checkIsOnCameraThread();
     if (camera == null) {
       return;
@@ -752,7 +754,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     }
 
     int rotation = getFrameOrientation();
-    if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
+    if (info.facing == android.hardware.Camera.CameraInfo.CAMERA_FACING_FRONT) {
       // Undo the mirror that the OS "helps" us with.
       // http://developer.android.com/reference/android/hardware/Camera.html#setDisplayOrientation(int)
       transformMatrix =
@@ -784,7 +786,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     // keeping the buffers alive and for finding the corresponding ByteBuffer given a timestamp.
     private final Map<Long, ByteBuffer> pendingBuffers = new HashMap<Long, ByteBuffer>();
     private int frameSize = 0;
-    private Camera camera;
+    private android.hardware.Camera camera;
 
     public FramePool(Thread thread) {
       this.thread = thread;
@@ -797,7 +799,7 @@ public class VideoCapturerAndroid extends VideoCapturer implements PreviewCallba
     }
 
     // Discards previous queued buffers and adds new callback buffers to camera.
-    public void queueCameraBuffers(int frameSize, Camera camera) {
+    public void queueCameraBuffers(int frameSize, android.hardware.Camera camera) {
       checkIsOnValidThread();
       this.camera = camera;
       this.frameSize = frameSize;

talk/app/webrtc/java/src/org/webrtc/MediaCodecVideoDecoder.java

@@ -27,6 +27,7 @@
 
 package org.webrtc;
 
+import android.graphics.SurfaceTexture;
 import android.media.MediaCodec;
 import android.media.MediaCodecInfo;
 import android.media.MediaCodecInfo.CodecCapabilities;
@@ -48,6 +49,7 @@ import java.util.concurrent.TimeUnit;
 
 // Java-side of peerconnection_jni.cc:MediaCodecVideoDecoder.
 // This class is an implementation detail of the Java PeerConnection API.
+@SuppressWarnings("deprecation")
 public class MediaCodecVideoDecoder {
   // This class is constructed, operated, and destroyed by its C++ incarnation,
   // so the class and its methods have non-public visibility.  The API this

talk/app/webrtc/java/src/org/webrtc/MediaCodecVideoEncoder.java

@@ -27,6 +27,7 @@
 
 package org.webrtc;
 
+import android.annotation.TargetApi;
 import android.media.MediaCodec;
 import android.media.MediaCodecInfo.CodecCapabilities;
 import android.media.MediaCodecInfo;
@@ -44,6 +45,8 @@ import java.util.concurrent.CountDownLatch;
 
 // Java-side of peerconnection_jni.cc:MediaCodecVideoEncoder.
 // This class is an implementation detail of the Java PeerConnection API.
+@TargetApi(19)
+@SuppressWarnings("deprecation")
 public class MediaCodecVideoEncoder {
   // This class is constructed, operated, and destroyed by its C++ incarnation,
   // so the class and its methods have non-public visibility.  The API this

talk/libjingle.gyp

@@ -227,6 +227,12 @@
             'libjingle_peerconnection_so',
           ],
           'variables': {
+            # Designate as Chromium code and point to our lint settings to
+            # enable linting of the WebRTC code (this is the only way to make
+            # lint_action invoke the Android linter).
+            'android_manifest_path': '<(webrtc_root)/build/android/AndroidManifest.xml',
+            'suppressions_file': '<(webrtc_root)/build/android/suppressions.xml',
+            'chromium_code': 1,
             'java_in_dir': 'app/webrtc/java',
             'webrtc_base_dir': '<(webrtc_root)/base',
             'webrtc_modules_dir': '<(webrtc_root)/modules',

webrtc/build/android/AndroidManifest.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  This is a dummy manifest which is required by:
+  1. aapt when generating R.java in java.gypi:
+     Nothing in the manifest is used, but it is still required by aapt.
+  2. lint: [min|target]SdkVersion are required by lint and should
+     be kept up-to-date.
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="dummy.package">
+
+      <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="23" />
+
+</manifest>

webrtc/build/android/suppressions.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<lint>
+  <!-- These lint settings is for the Android linter that gets run by
+       lint_action.gypi on compile of WebRTC java code. All WebRTC java code
+       should lint cleanly for the issues below. -->
+  <!-- TODO(phoglund): make work with suppress.py or remove printout referring
+       to suppress.py. -->
+  <issue id="NewApi"></issue>
+
+  <issue id="Locale" severity="ignore"/>
+  <issue id="SdCardPath" severity="ignore"/>
+  <issue id="UseValueOf" severity="ignore"/>
+  <issue id="InlinedApi" severity="ignore"/>
+  <issue id="DefaultLocale" severity="ignore"/>
+  <issue id="Assert" severity="ignore"/>
+  <issue id="UseSparseArrays" severity="ignore"/>
+
+  <!-- These are just from the dummy AndroidManifest.xml we use for linting.
+       It's in the same directory as this file. -->
+  <issue id="MissingApplicationIcon" severity="ignore"/>
+  <issue id="AllowBackup" severity="ignore"/>
+  <issue id="MissingVersion" severity="ignore"/>
+</lint>

webrtc/examples/androidapp/AndroidManifest.xml

@@ -7,7 +7,7 @@
     <uses-feature android:name="android.hardware.camera" />
     <uses-feature android:name="android.hardware.camera.autofocus" />
     <uses-feature android:glEsVersion="0x00020000" android:required="true" />
-    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
+    <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="21" />
 
     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioEffects.java

@@ -10,6 +10,7 @@
 
 package org.webrtc.voiceengine;
 
+import android.annotation.TargetApi;
 import android.media.audiofx.AcousticEchoCanceler;
 import android.media.audiofx.AudioEffect;
 import android.media.audiofx.AudioEffect.Descriptor;
@@ -119,6 +120,7 @@ class WebRtcAudioEffects {
 
   // Returns true if the platform AEC should be excluded based on its UUID.
   // AudioEffect.queryEffects() can throw IllegalStateException.
+  @TargetApi(18)
   private static boolean isAcousticEchoCancelerExcludedByUUID() {
     for (Descriptor d : AudioEffect.queryEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_AEC) &&
@@ -131,6 +133,7 @@ class WebRtcAudioEffects {
 
   // Returns true if the platform AGC should be excluded based on its UUID.
   // AudioEffect.queryEffects() can throw IllegalStateException.
+  @TargetApi(18)
   private static boolean isAutomaticGainControlExcludedByUUID() {
     for (Descriptor d : AudioEffect.queryEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_AGC) &&
@@ -143,6 +146,7 @@ class WebRtcAudioEffects {
 
   // Returns true if the platform NS should be excluded based on its UUID.
   // AudioEffect.queryEffects() can throw IllegalStateException.
+  @TargetApi(18)
   private static boolean isNoiseSuppressorExcludedByUUID() {
     for (Descriptor d : AudioEffect.queryEffects()) {
       if (d.type.equals(AudioEffect.EFFECT_TYPE_NS) &&
@@ -368,7 +372,11 @@ class WebRtcAudioEffects {
   // AudioEffect.Descriptor array that are actually not available on the device.
   // As an example: Samsung Galaxy S6 includes an AGC in the descriptor but
   // AutomaticGainControl.isAvailable() returns false.
+  @TargetApi(18)
   private boolean effectTypeIsVoIP(UUID type) {
+    if (!WebRtcAudioUtils.runningOnJellyBeanMR2OrHigher())
+      return false;
+
     return (AudioEffect.EFFECT_TYPE_AEC.equals(type)
         && isAcousticEchoCancelerSupported())
         || (AudioEffect.EFFECT_TYPE_AGC.equals(type)

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioManager.java

@@ -10,6 +10,7 @@
 
 package org.webrtc.voiceengine;
 
+import android.annotation.TargetApi;
 import android.content.Context;
 import android.content.pm.PackageManager;
 import android.media.AudioFormat;
@@ -189,20 +190,26 @@ public class WebRtcAudioManager {
     // No overrides available. Deliver best possible estimate based on default
     // Android AudioManager APIs.
     final int sampleRateHz;
-    if (!WebRtcAudioUtils.runningOnJellyBeanMR1OrHigher()) {
+    if (WebRtcAudioUtils.runningOnJellyBeanMR1OrHigher()) {
-      sampleRateHz = WebRtcAudioUtils.getDefaultSampleRateHz();
+      sampleRateHz = getSampleRateOnJellyBeanMR10OrHigher();
     } else {
-      String sampleRateString = audioManager.getProperty(
+      sampleRateHz = WebRtcAudioUtils.getDefaultSampleRateHz();
-          AudioManager.PROPERTY_OUTPUT_SAMPLE_RATE);
-      sampleRateHz = (sampleRateString == null)
-          ? WebRtcAudioUtils.getDefaultSampleRateHz()
-          : Integer.parseInt(sampleRateString);
     }
     Logging.d(TAG, "Sample rate is set to " + sampleRateHz + " Hz");
     return sampleRateHz;
   }
 
+  @TargetApi(17)
+  private int getSampleRateOnJellyBeanMR10OrHigher() {
+    String sampleRateString = audioManager.getProperty(
+        AudioManager.PROPERTY_OUTPUT_SAMPLE_RATE);
+    return (sampleRateString == null)
+        ? WebRtcAudioUtils.getDefaultSampleRateHz()
+        : Integer.parseInt(sampleRateString);
+  }
+
   // Returns the native output buffer size for low-latency output streams.
+  @TargetApi(17)
   private int getLowLatencyOutputFramesPerBuffer() {
     assertTrue(isLowLatencyOutputSupported());
     if (!WebRtcAudioUtils.runningOnJellyBeanMR1OrHigher()) {

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioTrack.java

@@ -13,6 +13,7 @@ package org.webrtc.voiceengine;
 import java.lang.Thread;
 import java.nio.ByteBuffer;
 
+import android.annotation.TargetApi;
 import android.content.Context;
 import android.media.AudioFormat;
 import android.media.AudioManager;
@@ -90,13 +91,9 @@ class WebRtcAudioTrack {
         assertTrue(sizeInBytes <= byteBuffer.remaining());
         int bytesWritten = 0;
         if (WebRtcAudioUtils.runningOnLollipopOrHigher()) {
-          bytesWritten = audioTrack.write(byteBuffer,
+          bytesWritten = writeOnLollipop(audioTrack, byteBuffer, sizeInBytes);
-                                          sizeInBytes,
-                                          AudioTrack.WRITE_BLOCKING);
         } else {
-          bytesWritten = audioTrack.write(byteBuffer.array(),
+          bytesWritten = writePreLollipop(audioTrack, byteBuffer, sizeInBytes);
-                                          byteBuffer.arrayOffset(),
-                                          sizeInBytes);
         }
         if (bytesWritten != sizeInBytes) {
           Logging.e(TAG, "AudioTrack.write failed: " + bytesWritten);
@@ -123,6 +120,15 @@ class WebRtcAudioTrack {
       audioTrack.flush();
     }
 
+    @TargetApi(21)
+    private int writeOnLollipop(AudioTrack audioTrack, ByteBuffer byteBuffer, int sizeInBytes) {
+      return audioTrack.write(byteBuffer, sizeInBytes, AudioTrack.WRITE_BLOCKING);
+    }
+
+    private int writePreLollipop(AudioTrack audioTrack, ByteBuffer byteBuffer, int sizeInBytes) {
+      return audioTrack.write(byteBuffer.array(), byteBuffer.arrayOffset(), sizeInBytes);
+    }
+
     public void joinThread() {
       keepAlive = false;
       while (isAlive()) {
@@ -224,16 +230,21 @@ class WebRtcAudioTrack {
   private boolean setStreamVolume(int volume) {
     Logging.d(TAG, "setStreamVolume(" + volume + ")");
     assertTrue(audioManager != null);
-    if (WebRtcAudioUtils.runningOnLollipopOrHigher()) {
+    if (isVolumeFixed()) {
-      if (audioManager.isVolumeFixed()) {
+      Logging.e(TAG, "The device implements a fixed volume policy.");
-        Logging.e(TAG, "The device implements a fixed volume policy.");
+      return false;
-        return false;
-      }
     }
     audioManager.setStreamVolume(AudioManager.STREAM_VOICE_CALL, volume, 0);
     return true;
   }
 
+  @TargetApi(21)
+  private boolean isVolumeFixed() {
+    if (!WebRtcAudioUtils.runningOnLollipopOrHigher())
+      return false;
+    return audioManager.isVolumeFixed();
+  }
+
   /** Get current volume level for a phone call audio stream. */
   private int getStreamVolume() {
     Logging.d(TAG, "getStreamVolume");

webrtc/modules/audio_device/android/java/src/org/webrtc/voiceengine/WebRtcAudioUtils.java

@@ -144,6 +144,11 @@ public final class WebRtcAudioUtils {
     return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1;
   }
 
+  public static boolean runningOnJellyBeanMR2OrHigher() {
+    // July 24, 2013: Android 4.3. API Level 18.
+    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2;
+  }
+
   public static boolean runningOnLollipopOrHigher() {
     // API Level 21.
     return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP;