设定在装置没有任何摄影机时显示的信息

				
					{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable><variable>cameraControl</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=\"Camera_setNoCameraDetectedMessage\"><value name=\"msg\"><shadow type=\"text\"><field name=\"TEXT\">There is no camera.</field></shadow></value></block></next></block></next></block></next></block></next></block></statement></block></xml>"}