Fix video qt shutdown

Author: tiagocoutinho

examples/video/qt/grid.py

@@ -31,9 +31,6 @@ def close():
         logging.info("Stopping all cameras...")
         for qcamera in qcameras:
             qcamera.stop()
-        logging.info("waiting for cameras to stop...")
-        for qcamera in qcameras:
-            qcamera.wait()
         logging.info("Done!")
 
     app = QtWidgets.QApplication([])

linuxpy/video/qt.py

@@ -27,6 +27,7 @@ def __init__(self, device: Device):
         self.capture = VideoCapture(device)
         self._stop = False
         self._stream = None
+        self._notifier = None
         self._state = "stopped"
 
     def on_frame(self):
@@ -63,8 +64,12 @@ def resume(self):
         self.setState("running")
 
     def stop(self):
-        self._notifier.setEnabled(False)
-        self._stream.close()
+        if self._notifier is not None:
+            self._notifier.setEnabled(False)
+            self._notifier = None
+        if self._stream is not None:
+            self._stream.close()
+            self._stream = None
         self.capture.close()
         self.device.close()
         self._notifier = None