Initial commit retro music app

app/src/main/java/code/name/monkey/retromusic/volume/AudioVolumeContentObserver.java

@@ -0,0 +1,46 @@
+package code.name.monkey.retromusic.volume;
+
+import android.database.ContentObserver;
+import android.media.AudioManager;
+import android.net.Uri;
+import android.os.Handler;
+import android.support.annotation.NonNull;
+
+public class AudioVolumeContentObserver extends ContentObserver {
+
+    private final OnAudioVolumeChangedListener mListener;
+    private final AudioManager mAudioManager;
+    private final int mAudioStreamType;
+    private int mLastVolume;
+
+    AudioVolumeContentObserver(@NonNull Handler handler, @NonNull AudioManager audioManager,
+                               int audioStreamType,
+                               @NonNull OnAudioVolumeChangedListener listener) {
+
+        super(handler);
+        mAudioManager = audioManager;
+        mAudioStreamType = audioStreamType;
+        mListener = listener;
+        mLastVolume = audioManager.getStreamVolume(mAudioStreamType);
+    }
+
+    /**
+     * Depending on the handler this method may be executed on the UI thread
+     */
+    @Override
+    public void onChange(boolean selfChange, Uri uri) {
+        if (mAudioManager != null && mListener != null) {
+            int maxVolume = mAudioManager.getStreamMaxVolume(mAudioStreamType);
+            int currentVolume = mAudioManager.getStreamVolume(mAudioStreamType);
+            if (currentVolume != mLastVolume) {
+                mLastVolume = currentVolume;
+                mListener.onAudioVolumeChanged(currentVolume, maxVolume);
+            }
+        }
+    }
+
+    @Override
+    public boolean deliverSelfNotifications() {
+        return super.deliverSelfNotifications();
+    }
+}

app/src/main/java/code/name/monkey/retromusic/volume/AudioVolumeObserver.java

@@ -0,0 +1,45 @@
+package code.name.monkey.retromusic.volume;
+
+import android.content.Context;
+import android.media.AudioManager;
+import android.os.Handler;
+import android.support.annotation.NonNull;
+
+public class AudioVolumeObserver {
+
+    private final Context mContext;
+    private final AudioManager mAudioManager;
+    private AudioVolumeContentObserver mAudioVolumeContentObserver;
+
+    public AudioVolumeObserver(@NonNull Context context) {
+        mContext = context;
+        mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
+    }
+
+    public void register(int audioStreamType, @NonNull OnAudioVolumeChangedListener listener) {
+
+        Handler handler = new Handler();
+        // with this handler AudioVolumeContentObserver#onChange() 
+        //   will be executed in the main thread
+        // To execute in another thread you can use a Looper
+        // +info: https://stackoverflow.com/a/35261443/904907
+
+        mAudioVolumeContentObserver = new AudioVolumeContentObserver(
+                handler,
+                mAudioManager,
+                audioStreamType,
+                listener);
+
+        mContext.getContentResolver().registerContentObserver(
+                android.provider.Settings.System.CONTENT_URI,
+                true,
+                mAudioVolumeContentObserver);
+    }
+
+    public void unregister() {
+        if (mAudioVolumeContentObserver != null) {
+            mContext.getContentResolver().unregisterContentObserver(mAudioVolumeContentObserver);
+            mAudioVolumeContentObserver = null;
+        }
+    }
+}

app/src/main/java/code/name/monkey/retromusic/volume/OnAudioVolumeChangedListener.java

@@ -0,0 +1,6 @@
+package code.name.monkey.retromusic.volume;
+
+public interface OnAudioVolumeChangedListener {
+
+    void onAudioVolumeChanged(int currentVolume, int maxVolume);
+}