Fix viewer timer and lifecycle review findings

- tick() refreshes lastTick on every tick, so a failed video no longer
  advances at once with its whole playback time.
- Photo timer counts only once the photo is shown (or failed), so a slow
  load cannot advance before display.
- Slides started while the activity is stopped stay paused and stopped;
  onStart re-prepares them.
- toggleLike error UI guard no longer indexes a replaced playlist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 18 insertions, 8 deletions

diff --git a/app/src/main/java/mygram/droid/ViewerActivity.java b/app/src/main/java/mygram/droid/ViewerActivity.java
index 098f817..59e6948 100644
--- a/app/src/main/java/mygram/droid/ViewerActivity.java
+++ b/app/src/main/java/mygram/droid/ViewerActivity.java
@@ -77,7 +77,7 @@ public final class ViewerActivity extends Activity {
 	private int index, slide;
 	/** Bumped on every slide change; late callbacks for older slides are dropped. */
 	private volatile int generation;
-	private boolean paused, failed, loadingMore, parkedAtEnd;
+	private boolean paused, failed, loadingMore, parkedAtEnd, shown, stopped;
 	private long photoElapsed, lastTick;
 
 	@Override
@@ -171,6 +171,7 @@ public final class ViewerActivity extends Activity {
 		int gen = ++generation;
 		paused = false;
 		failed = false;
+		shown = false;
 		photoElapsed = 0;
 		lastTick = SystemClock.uptimeMillis();
 		parkedAtEnd = false;
@@ -199,13 +200,20 @@ public final class ViewerActivity extends Activity {
 				@Override
 				public boolean onResourceReady(Drawable d, Object model, Target<Drawable> target, DataSource source,
 						boolean first) {
-					if (gen == generation)
-						photoElapsed = 0; // count from when the photo is on screen
+					if (gen == generation) { // count from when the photo is on screen
+						shown = true;
+						photoElapsed = 0;
+						lastTick = SystemClock.uptimeMillis();
+					}
 					return false;
 				}
 			}).into(photo);
 		}
 		tick();
+		if (stopped) { // page arrived in the background: stay paused, onStart re-prepares
+			setPaused(true);
+			player.stop();
+		}
 	}
 
 	// ponytail: a grab already blocked in setDataSource is not interrupted, so a slow one delays the next post's frame; upgrade: a timeout or per-post cancellation.
@@ -234,14 +242,14 @@ public final class ViewerActivity extends Activity {
 	/** Drives the progress bar and the photo timer. */
 	private void tick() {
 		handler.removeCallbacks(ticker);
+		long now = SystemClock.uptimeMillis(), dt = now - lastTick;
+		lastTick = now;
 		if (media().video && !failed) {
 			long d = player.getDuration();
 			progress.setProgress(d > 0 ? (int) (1000 * player.getCurrentPosition() / d) : 0);
 		} else {
-			long now = SystemClock.uptimeMillis();
-			if (!paused)
-				photoElapsed += now - lastTick;
-			lastTick = now;
+			if (!paused && (shown || failed))
+				photoElapsed += dt;
 			long total = Prefs.photoSeconds() * 1000L;
 			progress.setProgress((int) (1000 * Math.min(photoElapsed, total) / total));
 			if (photoElapsed >= total) {
@@ -315,7 +323,7 @@ public final class ViewerActivity extends Activity {
 			if (Likes.has(p.id) != on)
 				return; // a newer toggle wins
 			Likes.set(p.id, !on);
-			if (!Playlist.posts.isEmpty() && post() == p)
+			if (!isDestroyed() && post() == p)
 				heart.setVisibility(on ? View.GONE : View.VISIBLE);
 			String msg = e.getMessage();
 			Toast.makeText(this, "Like failed" + (msg != null ? ": " + msg : ""), Toast.LENGTH_SHORT).show();
@@ -397,6 +405,7 @@ public final class ViewerActivity extends Activity {
 	@Override
 	protected void onStart() {
 		super.onStart();
+		stopped = false;
 		// The first show() already prepared (state is not IDLE), so this only revives a stopped decoder.
 		if (!Playlist.posts.isEmpty() && media().video && !failed && player.getPlaybackState() == Player.STATE_IDLE) {
 			player.setPlayWhenReady(!paused);
@@ -407,6 +416,7 @@ public final class ViewerActivity extends Activity {
 	@Override
 	protected void onStop() {
 		super.onStop();
+		stopped = true;
 		player.stop(); // free the video decoder while in the background
 	}