Add relative volume support

app/src/main/java/io/habets/jellyfish/AudioService.kt

@@ -53,14 +53,29 @@ class AudioService : Service() {
         audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC)
     }
     private var previousVolume = -1
+    private var previousValue = -1
 
     private fun changeVolume(value: Int): Int {
         if (value == -1) return -1
-        val newVolume = map(value, 0, 15, 0, maxVolume)
+
+        val newVolume = if (Settings.isRelative(this)) {
+            val currentVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC)
+            when {
+                value > previousValue -> currentVolume + 2
+                value < previousValue -> currentVolume - 2
+                else -> currentVolume
+            }
+        } else {
+            map(value, 0, 15, 0, maxVolume)
+        }
+
+
         if (previousVolume != newVolume) {
-            previousVolume = newVolume
             audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, newVolume, if (BuildConfig.DEBUG) AudioManager.FLAG_SHOW_UI else 0)
         }
+
+        previousValue = value
+        previousVolume = newVolume
         return previousVolume
     }
 
@@ -70,10 +85,6 @@ class AudioService : Service() {
 
     override fun onBind(intent: Intent): IBinder? = null
 
-    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
-        return super.onStartCommand(intent, flags, startId)
-    }
-
     override fun onCreate() {
         super.onCreate()
         createNotificationChannel(this)

app/src/main/java/io/habets/jellyfish/MainActivity.kt

@@ -7,8 +7,6 @@ import android.os.Bundle
 import android.support.v7.app.AppCompatActivity
 import android.view.Menu
 import android.view.MenuItem
-import kotlinx.android.synthetic.main.activity_main.*
-import kotlinx.android.synthetic.main.content_main.*
 import org.greenrobot.eventbus.EventBus
 import org.greenrobot.eventbus.Subscribe
 import org.greenrobot.eventbus.ThreadMode
@@ -26,6 +24,9 @@ class MainActivity : AppCompatActivity() {
             startService(Intent(this, AudioService::class.java))
         }
         buttonDisable.setOnClickListener { stopService(Intent(this, AudioService::class.java)) }
+        checkBox.setOnClickListener {
+            checkBox.isChecked = Settings.toggleRelative(this)
+        }
         volumeControlStream = AudioManager.STREAM_MUSIC
     }
 

app/src/main/java/io/habets/jellyfish/Settings.kt

@@ -0,0 +1,28 @@
+package io.habets.jellyfish
+
+import android.content.Context
+
+object Settings {
+
+    private const val KEY = "settings"
+    private const val KEY_RELATIVE = "relative"
+
+    fun isRelative(context: Context): Boolean {
+        return context.getSharedPreferences(KEY, Context.MODE_PRIVATE)
+                .getBoolean(KEY_RELATIVE, false)
+    }
+
+    fun setRelative(context: Context, isRelative: Boolean) {
+        context.getSharedPreferences(KEY, Context.MODE_PRIVATE)
+                .edit()
+                .putBoolean(KEY_RELATIVE, isRelative)
+                .apply()
+    }
+
+    fun toggleRelative(context: Context): Boolean {
+        val prefs = context.getSharedPreferences(KEY, Context.MODE_PRIVATE)
+        val new = !prefs.getBoolean(KEY_RELATIVE, false)
+        prefs.edit().putBoolean(KEY_RELATIVE, new).apply()
+        return new
+    }
+}

app/src/main/res/layout/content_main.xml

@@ -6,35 +6,35 @@
     android:layout_height="match_parent"
     app:layout_behavior="@string/appbar_scrolling_view_behavior"
     tools:context="io.habets.jellyfish.MainActivity"
-    tools:showIn="@layout/activity_main"
+    tools:layout_editor_absoluteX="0dp"
     tools:layout_editor_absoluteY="81dp"
-    tools:layout_editor_absoluteX="0dp">
+    tools:showIn="@layout/activity_main">
 
     <Button
         android:id="@+id/buttonEnable"
         android:layout_width="wrap_content"
         android:layout_height="45dp"
+        android:layout_marginTop="16dp"
         android:text="Enable"
-        tools:layout_editor_absoluteX="16dp"
-        tools:layout_editor_absoluteY="19dp"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintHorizontal_bias="0.5"
         app:layout_constraintEnd_toStartOf="@+id/buttonDisable"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent"
-        android:layout_marginTop="16dp" />
+        tools:layout_editor_absoluteX="16dp"
+        tools:layout_editor_absoluteY="19dp" />
 
     <Button
         android:id="@+id/buttonDisable"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
+        android:layout_marginTop="16dp"
         android:text="Disable"
-        tools:layout_editor_absoluteX="280dp"
-        tools:layout_editor_absoluteY="16dp"
-        app:layout_constraintStart_toEndOf="@+id/buttonEnable"
-        app:layout_constraintHorizontal_bias="0.5"
         app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toEndOf="@+id/buttonEnable"
         app:layout_constraintTop_toTopOf="parent"
-        android:layout_marginTop="16dp" />
+        tools:layout_editor_absoluteX="280dp"
+        tools:layout_editor_absoluteY="16dp" />
 
     <TextView
         android:id="@+id/textView"
@@ -49,4 +49,15 @@
         app:layout_constraintTop_toTopOf="parent"
         tools:layout_editor_absoluteX="162dp"
         tools:layout_editor_absoluteY="245dp" />
+
+    <CheckBox
+        android:id="@+id/checkBox"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:text="Relative mode"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toStartOf="parent" />
 </android.support.constraint.ConstraintLayout>