HwAudioSource: wrong native handle check

Playing status of audio source is checked using the native handler
not 0.
However, if AudioSystem#startAudioSource fails, the native handler
returned is not 0, but an error code.
In fact AudioPolicyManager sets the PORT to NONE (0) and sets an error
status.
JNI layer transforms the failure status into a native handler returned
to the caller.

Signed-off-by: Francois Gaffie <francois.gaffie@renault.com>
Change-Id: Iaa920c073885c2556a93a1b5ae23467fa6ffad4f
Merged-In: Iaa920c073885c2556a93a1b5ae23467fa6ffad4f
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

Author: Francois Gaffie

media/java/android/media/HwAudioSource.java

@@ -35,7 +35,13 @@ public class HwAudioSource extends PlayerBase {
     private final AudioDeviceInfo mAudioDeviceInfo;
     private final AudioAttributes mAudioAttributes;
 
-    private int mNativeHandle;
+    /**
+     * The value of the native handle encodes the HwAudioSource state.
+     * The native handle returned by {@link AudioSystem#startAudioSource} is either valid
+     * (aka > 0, so successfully started) or hosting an error code (negative).
+     * 0 corresponds to an untialized or stopped HwAudioSource.
+     */
+    private int mNativeHandle = 0;
 
     /**
      * Class constructor for a hardware audio source based player.
@@ -127,29 +133,38 @@ void playerStop() {
 
     /**
      * Starts the playback from {@link AudioDeviceInfo}.
+     * Starts does not return any error code, caller must check {@link HwAudioSource#isPlaying} to
+     * ensure the state of the HwAudioSource encoded in {@link mNativeHandle}.
      */
     public void start() {
         Preconditions.checkState(!isPlaying(), "HwAudioSource is currently playing");
-        baseStart();
         mNativeHandle = AudioSystem.startAudioSource(
                 mAudioDeviceInfo.getPort().activeConfig(),
                 mAudioAttributes);
+        if (isPlaying()) {
+            baseStart();
+        }
     }
 
     /**
      * Checks whether the HwAudioSource player is playing.
+     * It checks the state of the HwAudioSource encoded in {@link HwAudioSource#isPlaying}.
+     * 0 corresponds to a stopped or uninitialized HwAudioSource.
+     * Negative value corresponds to a status reported by {@link AudioSystem#startAudioSource} to
+     * indicate a failure when trying to start the HwAudioSource.
+     *
      * @return true if currently playing, false otherwise
      */
     public boolean isPlaying() {
-        return mNativeHandle != 0;
+        return mNativeHandle > 0;
     }
 
     /**
      * Stops the playback from {@link AudioDeviceInfo}.
      */
     public void stop() {
-        baseStop();
         if (mNativeHandle > 0) {
+            baseStop();
             AudioSystem.stopAudioSource(mNativeHandle);
             mNativeHandle = 0;
         }