Fix for bug 2001, verify that the AudioTrack is properly initialized

...and fail to initialize the audio backend if it's not!

android-project/src/org/libsdl/app/SDLActivity.java

@@ -452,7 +452,7 @@ public static void flipEGL() {
     }
 
     // Audio
-    public static void audioInit(int sampleRate, boolean is16Bit, boolean isStereo, int desiredFrames) {
+    public static int audioInit(int sampleRate, boolean is16Bit, boolean isStereo, int desiredFrames) {
         int channelConfig = isStereo ? AudioFormat.CHANNEL_CONFIGURATION_STEREO : AudioFormat.CHANNEL_CONFIGURATION_MONO;
         int audioFormat = is16Bit ? AudioFormat.ENCODING_PCM_16BIT : AudioFormat.ENCODING_PCM_8BIT;
         int frameSize = (isStereo ? 2 : 1) * (is16Bit ? 2 : 1);
@@ -467,9 +467,20 @@ public static void audioInit(int sampleRate, boolean is16Bit, boolean isStereo,
         mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, sampleRate,
                 channelConfig, audioFormat, desiredFrames * frameSize, AudioTrack.MODE_STREAM);
 
+        // Instantiating AudioTrack can "succeed" without an exception and the track may still be invalid
+        // Ref: https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/media/java/android/media/AudioTrack.java
+        // Ref: http://developer.android.com/reference/android/media/AudioTrack.html#getState()
+
+        if (mAudioTrack.getState() != AudioTrack.STATE_INITIALIZED) {
+            Log.e("SDL", "Failed during initialization of Audio Track");
+            return -1;
+        }
+
         audioStartThread();
 
         Log.v("SDL", "SDL audio: got " + ((mAudioTrack.getChannelCount() >= 2) ? "stereo" : "mono") + " " + ((mAudioTrack.getAudioFormat() == AudioFormat.ENCODING_PCM_16BIT) ? "16-bit" : "8-bit") + " " + (mAudioTrack.getSampleRate() / 1000f) + "kHz, " + desiredFrames + " frames buffer");
+
+        return 0;
     }
 
     public static void audioStartThread() {

src/core/android/SDL_android.c

@@ -123,7 +123,7 @@ void SDL_Android_Init(JNIEnv* mEnv, jclass cls)
     midFlipBuffers = (*mEnv)->GetStaticMethodID(mEnv, mActivityClass,
                                 "flipBuffers","()V");
     midAudioInit = (*mEnv)->GetStaticMethodID(mEnv, mActivityClass,
-                                "audioInit", "(IZZI)V");
+                                "audioInit", "(IZZI)I");
     midAudioWriteShortBuffer = (*mEnv)->GetStaticMethodID(mEnv, mActivityClass,
                                 "audioWriteShortBuffer", "([S)V");
     midAudioWriteByteBuffer = (*mEnv)->GetStaticMethodID(mEnv, mActivityClass,
@@ -456,7 +456,11 @@ int Android_JNI_OpenAudioDevice(int sampleRate, int is16Bit, int channelCount, i
     audioBuffer16Bit = is16Bit;
     audioBufferStereo = channelCount > 1;
 
-    (*env)->CallStaticVoidMethod(env, mActivityClass, midAudioInit, sampleRate, audioBuffer16Bit, audioBufferStereo, desiredBufferFrames);
+    if ((*env)->CallStaticIntMethod(env, mActivityClass, midAudioInit, sampleRate, audioBuffer16Bit, audioBufferStereo, desiredBufferFrames) != 0) {
+        /* Error during audio initialization */
+        __android_log_print(ANDROID_LOG_WARN, "SDL", "SDL audio: error on AudioTrack initialization!");
+        return 0;
+    }
 
     /* Allocating the audio buffer from the Java side and passing it as the return value for audioInit no longer works on
      * Android >= 4.2 due to a "stale global reference" error. So now we allocate this buffer directly from this side. */