Update progress without binder calls

The implementation is pretty much a copy of
MediaSessionRecord#getStateWithUpdatedPosition.

Bug: 154352658
Test: manual - played music and checked that seek bar updated
Change-Id: Id494f01dd18095f5df6c0806f34a7a5c92ddaf35

packages/SystemUI/src/com/android/systemui/media/SeekBarViewModel.kt

@@ -19,6 +19,7 @@ package com.android.systemui.media
 import android.media.MediaMetadata
 import android.media.session.MediaController
 import android.media.session.PlaybackState
+import android.os.SystemClock
 import android.view.MotionEvent
 import android.view.View
 import android.widget.SeekBar
@@ -31,6 +32,38 @@ import com.android.systemui.util.concurrency.DelayableExecutor
 
 private const val POSITION_UPDATE_INTERVAL_MILLIS = 100L
 
+private fun PlaybackState.isInMotion(): Boolean {
+    return this.state == PlaybackState.STATE_PLAYING ||
+            this.state == PlaybackState.STATE_FAST_FORWARDING ||
+            this.state == PlaybackState.STATE_REWINDING
+}
+
+/**
+ * Gets the playback position while accounting for the time since the [PlaybackState] was last
+ * retrieved.
+ *
+ * This method closely follows the implementation of
+ * [MediaSessionRecord#getStateWithUpdatedPosition].
+ */
+private fun PlaybackState.computePosition(duration: Long): Long {
+    var currentPosition = this.position
+    if (this.isInMotion()) {
+        val updateTime = this.getLastPositionUpdateTime()
+        val currentTime = SystemClock.elapsedRealtime()
+        if (updateTime > 0) {
+            var position = (this.playbackSpeed * (currentTime - updateTime)).toLong() +
+                    this.getPosition()
+            if (duration >= 0 && position > duration) {
+                position = duration.toLong()
+            } else if (position < 0) {
+                position = 0
+            }
+            currentPosition = position
+        }
+    }
+    return currentPosition
+}
+
 /** ViewModel for seek bar in QS media player. */
 class SeekBarViewModel(val bgExecutor: DelayableExecutor) {
 
@@ -98,7 +131,8 @@ class SeekBarViewModel(val bgExecutor: DelayableExecutor) {
 
     @AnyThread
     private fun checkPlaybackPosition(): Runnable = bgExecutor.executeDelayed({
-        val currentPosition = controller?.playbackState?.position?.toInt()
+        val duration = _data?.duration ?: -1
+        val currentPosition = playbackState?.computePosition(duration.toLong())?.toInt()
         if (currentPosition != null && _data.elapsedTime != currentPosition) {
             _data = _data.copy(elapsedTime = currentPosition)
         }
@@ -109,13 +143,7 @@ class SeekBarViewModel(val bgExecutor: DelayableExecutor) {
 
     @WorkerThread
     private fun shouldPollPlaybackPosition(): Boolean {
-        val state = playbackState?.state
-        val moving = if (state == null) false else
-                state == PlaybackState.STATE_PLAYING ||
-                state == PlaybackState.STATE_BUFFERING ||
-                state == PlaybackState.STATE_FAST_FORWARDING ||
-                state == PlaybackState.STATE_REWINDING
-        return moving && listening
+        return listening && playbackState?.isInMotion() ?: false
     }
 
     /** Gets a listener to attach to the seek bar to handle seeking. */

packages/SystemUI/tests/src/com/android/systemui/media/SeekBarViewModelTest.kt

@@ -362,28 +362,21 @@ public class SeekBarViewModelTest : SysuiTestCase() {
 
     @Test
     fun taskUpdatesProgress() {
-        // GIVEN that the PlaybackState contins the current position
-        val position = 200L
+        // GIVEN that the PlaybackState contins the initial position
+        val initialPosition = 0L
         val state = PlaybackState.Builder().run {
-            setState(PlaybackState.STATE_PLAYING, position, 1f)
+            setState(PlaybackState.STATE_PLAYING, initialPosition, 1f)
             build()
         }
         whenever(mockController.getPlaybackState()).thenReturn(state)
         viewModel.updateController(mockController, Color.RED)
-        // AND the playback state advances
-        val nextPosition = 300L
-        val nextState = PlaybackState.Builder().run {
-            setState(PlaybackState.STATE_PLAYING, nextPosition, 1f)
-            build()
-        }
-        whenever(mockController.getPlaybackState()).thenReturn(nextState)
         // WHEN the task runs
         with(fakeExecutor) {
             advanceClockToNext()
             runAllReady()
         }
-        // THEN elapsed time is captured
-        assertThat(viewModel.progress.value!!.elapsedTime).isEqualTo(nextPosition.toInt())
+        // THEN elapsed time has increased
+        assertThat(viewModel.progress.value!!.elapsedTime).isGreaterThan(initialPosition.toInt())
     }
 
     @Test