🐛 Android Crash on Second Connection After App Relaunch (monitorCharacteristicForDevice)

[rrubankumar-ctrl]

Prerequisites

• I checked the documentation and FAQ without finding a solution
• I checked to make sure that this issue has not already been filed

Expected Behavior

The application crashes on Android when connecting to a BLE device for the second time after closing and reopening the app. The crash occurs when navigating to the reading screen where monitorCharacteristicForDevice() is used.

Current Behavior

This seems related to a known issue where the app crashes instead of handling disconnection properly.

Library version

3.5.0

Device

all devices

Environment info

The application crashes on Android when connecting to a BLE device for the second time after closing and reopening the app. The crash occurs when navigating to the reading screen where monitorCharacteristicForDevice() is used.

Steps to reproduce

1. …
2. …Install and open the application on an Android device.

Scan and connect to a BLE peripheral device.

Navigate to the reading/data screen where monitorCharacteristicForDevice() is started.

Verify that data is being received correctly.

Close or kill the application from recent apps (without manually disconnecting the BLE device).

Reopen the application.

Connect to the same BLE device again.

Navigate to the reading/data screen again.

Formatted code sample or link to a repository

nil

Relevant log output

nil

Additional information

No response

[rrubankumar-ctrl]

useFocusEffect(
useCallback(() => {
isMountedRef.current = true;

  const timer = setTimeout(() => {
    void onClickNewTestRef.current(); // latest devices, not stale closure from old useCallback
  }, 5000); // 🔥 small delay is critical

  return () => {
    isMountedRef.current = false;

    clearTimeout(timer);

    cancelListenersRef.current.forEach((cancel) => {
      try {
        cancel?.();
      } catch (e) {
        console.warn("Cleanup error:", e);
      }
    });

    cancelListenersRef.current = [];

    shownErrors.current.clear();
    modalQueue.current = [];
    isModalOpen.current = false;

    coldFingerStatusRef.current.left = { count: 0, isCold: false };
    coldFingerStatusRef.current.right = { count: 0, isCold: false };
  };
}, [leftSensor?.device?.id, rightSensor?.device?.id])

);
const onClickNewTest = async () => {
cancelListenersRef.current.forEach((stopFn) => {
try {
stopFn?.();
} catch (e) {
console.warn("Error stopping listener:", e);
}
});
cancelListenersRef.current = [];

try {
  if (leftSensor?.device) {
    const connected = await isPeripheralConnected(leftSensor.device);
    if (!connected) {
      if (__DEV__) {
        console.warn("[FuncTestPreparation] Left sensor not connected; skip monitor");
      }
    } else {
      const { stop } = monitorDeviceSensorData(
        leftSensor.device as any,
        throttleSample("left")
      );
      cancelListenersRef.current.push(stop);
    }
  }

  if (rightSensor?.device) {
    const connected = await isPeripheralConnected(rightSensor.device);
    if (!connected) {
      if (__DEV__) {
        console.warn("[FuncTestPreparation] Right sensor not connected; skip monitor");
      }
    } else {
      const { stop } = monitorDeviceSensorData(
        rightSensor.device as any,
        throttleSample("right")
      );
      cancelListenersRef.current.push(stop);
    }
  }
} catch (error) {
  console.error("❌ Error during monitoring:", error);
}

};