fix resuming video playback after background audio only mode.

src-tauri/src/player/android/mod.rs

@@ -1315,6 +1315,66 @@ pub fn update_lockscreen_metadata(meta: &LockscreenMetadata) -> Result<(), Strin
     Ok(())
 }
 
+/// Set the base position offset (seconds) on the lockscreen MediaSession.
+///
+/// Calls `JellyTauPlaybackService.setPositionOffset(double)`. No-op if the
+/// service isn't running yet, so it's safe to call unconditionally.
+pub fn set_position_offset(offset_seconds: f64) -> Result<(), String> {
+    let vm = JAVA_VM.get().ok_or("JavaVM not initialized")?;
+    let mut env = vm.attach_current_thread().map_err(|e| e.to_string())?;
+
+    let context = APP_CONTEXT.get().ok_or("Context not initialized")?;
+
+    let class_loader = env
+        .call_method(context, "getClassLoader", "()Ljava/lang/ClassLoader;", &[])
+        .map_err(|e| format!("Failed to get ClassLoader: {}", e))?
+        .l()
+        .map_err(|e| format!("Failed to convert ClassLoader: {}", e))?;
+
+    let service_class_name = env
+        .new_string("com.dtourolle.jellytau.player.JellyTauPlaybackService")
+        .map_err(|e| format!("Failed to create class name string: {}", e))?;
+
+    let service_class_obj = env
+        .call_method(
+            &class_loader,
+            "loadClass",
+            "(Ljava/lang/String;)Ljava/lang/Class;",
+            &[JValue::Object(&service_class_name.into())],
+        )
+        .map_err(|e| format!("Failed to load JellyTauPlaybackService class: {}", e))?
+        .l()
+        .map_err(|e| format!("Failed to convert to Class: {}", e))?;
+
+    let service_class = JClass::from(service_class_obj);
+
+    let service_obj = env
+        .call_static_method(
+            &service_class,
+            "getInstance",
+            "()Lcom/dtourolle/jellytau/player/JellyTauPlaybackService;",
+            &[],
+        )
+        .map_err(|e| format!("Failed to get service instance: {}", e))?
+        .l()
+        .map_err(|e| format!("Failed to convert to object: {}", e))?;
+
+    // Service not running yet - nothing to offset.
+    if service_obj.is_null() {
+        return Ok(());
+    }
+
+    env.call_method(
+        &service_obj,
+        "setPositionOffset",
+        "(D)V",
+        &[JValue::Double(offset_seconds)],
+    )
+    .map_err(|e| format!("Failed to set position offset: {}", e))?;
+
+    Ok(())
+}
+
 /// Stub implementations for non-Android platforms
 #[cfg(not(target_os = "android"))]
 pub fn enable_remote_volume(_initial_volume: i32) -> Result<(), String> {

src-tauri/src/player/mod.rs

@@ -80,6 +80,22 @@ pub fn update_lockscreen_metadata(_meta: &LockscreenMetadata) -> Result<(), Stri
     }
 }
 
+/// Set the base offset (seconds) added to positions reported to the Android
+/// lockscreen scrubber. Used by the background-audio handoff: the audio stream
+/// starts at the handoff point (StartTimeTicks), so ExoPlayer's position is
+/// relative and must be shifted back to absolute to match the full duration.
+/// Pass 0.0 to clear on exit. No-op off Android.
+pub fn set_lockscreen_position_offset(_offset_seconds: f64) -> Result<(), String> {
+    #[cfg(target_os = "android")]
+    {
+        return android::set_position_offset(_offset_seconds);
+    }
+    #[cfg(not(target_os = "android"))]
+    {
+        Ok(())
+    }
+}
+
 use crate::utils::lock::MutexSafe;
 use log::{debug, error, warn};
 use std::sync::{Arc, Mutex};