Smartphones, Tablets, and Mobile Devices Documents
Introduction
This example shows you how to build a native Android application for simple data monitoring.
Application Architecture
- Measurement Application - Performs your measurement and publishes the latest data value to a variable.
- LabVIEW Web Service - Retrieves the latest data value in the variable and returns it.
- Android Application - Periodically calls the web service and plots the latest data value. (Note: the Android application may miss data points if the Measurement Application is sampling faster than the Android Application calls the web service.)
Download Example Code
Simple Data Monitor (LabVIEW Project).zip
Simple Data Monitor (Android Application).zip
Tutorial
Part 1: Measurement Application
LabVIEW VI's can share data between other VI's using shared variables. In this example, we perform a single point acquisition, plot the point to a chart, and publish it to the shared variable.
Part 2: LabVIEW Web Services
LabVIEW Web Services allow any web capable device to access data from your application through any web interface. Your measurement application continually runs in parallel with your web service VI. When the web service VI is called by a web client, it reads the value from the shared variable, generates an XML string, and writes a HTTP response with the data back to the web client.
After you create your web service VI, you must deploy it within the LabVIEW project.
It can then be invoked via URL web request.
Additional Resources:
Part 3: Android Application
Getting Started with Android
This code snippet contains the core functionality. It first sets up a connection to the URL, configures the XML parser, reads and parses the XML from the input stream, adds the data value to an array of all data values received, and plots the array of values on the chart.
while (!mStop)
{// First, open a connection to the machine where LabVIEW is running
URL url = new URL(mURLText.getText().toString());URLConnection connection = url.openConnection();// Set resonable timeoutsconnection.setConnectTimeout(5000);connection.setReadTimeout(5000);// Create an XML document builder with the default settingsDocumentBuilder docbuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();// Parse XML from the web service into a DOM treeDocument doc = docbuilder.parse(connection.getInputStream());// Now, pull out the value attribute of the first channel elementString value = doc.getElementsByTagName("channel").item(0).getAttributes().getNamedItem("value").getNodeValue();// Create an array of data to add to the chart. There is only one// channel of data right now, so just add one point.ArrayList<Double> data = new ArrayList<Double>();data.add(Double.parseDouble(value));// Add the data to the chart.mChart.addDataPoint(data);}
