檢查是否已有指定的攝影機

				
					{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable><variable>cameraControl</variable><variable>selectedCameras</variable><variable>recentlySelectedCameras</variable><variable>recentlyUnselectedCameras</variable><variable>value</variable><variable>value2</variable><variable>deviceId</variable><variable>textBlock</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"Camera_enableCameraFeature\"><value name=\"enable\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">TRUE</field></shadow></value><next><block type=\"variables_set\"><field name=\"VAR\">cameraControl</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Camera_getCameraControl\"/></value><next><block type=\"Control_OptionList_setMultiple\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">cameraControl</field></block></value><value name=\"isMultiple\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">TRUE</field></shadow></value><next><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"variables_get\"><field name=\"VAR\">cameraControl</field></block></value><next><block type=\"Camera_setOnCameraControlChanged\"><value name=\"HANDLER_DRAG_PARAM_selectedCameras\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">selectedCameras</field></shadow></value><value name=\"HANDLER_DRAG_PARAM_recentlySelectedCameras\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">recentlySelectedCameras</field></shadow></value><value name=\"HANDLER_DRAG_PARAM_recentlyUnselectedCameras\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">recentlyUnselectedCameras</field></shadow></value><statement name=\"HANDLER\"><block type=\"pxt_controls_for_of\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">value</field></shadow></value><value name=\"LIST\"><block type=\"variables_get\"><field name=\"VAR\">recentlyUnselectedCameras</field></block></value><statement name=\"DO\"><block type=\"ScreenItem_ScreenItem_remove\"><value name=\"this\"><block type=\"ScreenItem_ScreenItem_getParent\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">value</field></block></value></block></value></block></statement><next><block type=\"pxt_controls_for_of\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">value2</field></shadow></value><value name=\"LIST\"><block type=\"variables_get\"><field name=\"VAR\">recentlySelectedCameras</field></block></value><statement name=\"DO\"><block type=\"variables_set\"><field name=\"VAR\">deviceId</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"0\" _input_init=\"false\"></mutation></block></value><next><block type=\"Control_TextBlock_setContent\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">deviceId</field></block></value><value name=\"content\"><block type=\"Camera_Camera_getDeviceId\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">value2</field></block></value></block></value><next><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"variables_get\"><field name=\"VAR\">deviceId</field></block></value><next><block type=\"variables_set\"><field name=\"VAR\">textBlock</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"0\" _input_init=\"false\"></mutation></block></value><next><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"variables_get\"><field name=\"VAR\">textBlock</field></block></value><next><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"variables_get\"><field name=\"VAR\">value2</field></block></value><next><block type=\"controls_if\"><mutation else=\"1\"/><value name=\"IF0\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">TRUE</field></shadow><block type=\"Camera_hasCamera\"><value name=\"deviceId\"><shadow type=\"text\"><field name=\"TEXT\">0a9c24fb5f5271cbef965ab36f48179f57402ea7aee8a50409c88c1363239e6f</field></shadow></value></block></value><statement name=\"DO0\"><block type=\"Control_TextBlock_setContent\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">textBlock</field></block></value><value name=\"content\"><shadow type=\"text\"><field name=\"TEXT\">It contains USB Camera (0c45:6367)</field></shadow></value></block></statement><statement name=\"ELSE\"><block type=\"Control_TextBlock_setContent\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">textBlock</field></block></value><value name=\"content\"><shadow type=\"text\"><field name=\"TEXT\">It doesn't contain USB Camera (0c45:6367)</field></shadow></value></block></statement></block></next></block></next></block></next></block></next></block></next></block></next></block></statement></block></next></block></statement></block></next></block></next></block></next></block></next></block></next></block></next></block></statement></block></xml>"}