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I'm trying to listen sensors of a Nokia 5800 but this code does not compile. I've downloaded the add-on for the Nokia 5800 and the emulator prototype but nothing. Could be say that it is not possible to access sensors from a J2ME application??

18 Sep
2009

Article Review by Larry101 (20090918)

This article discusses the use of the JSR-256 mobile sensor API. The sensor API has been around for a while now, but has only relatively recently been supported by Nokia devices with the release of the Nokia 5800 Express Music (as an add-on) and by the Nokia N97 (no add-on necessary). This article gives a nice clear code example of how to use the Sensor API to access information about the various sensors available on a mobile device.

The code example shows how to discover which sensors are available on the device in question through the SensorManager.findSensors method. The programmer can then use the returned SensorInfo objects to view various descriptive details about the available sensors, including a textual description, the sensor's model and the quantity the sensor in question measures. For each SensorInfo object, the available ChannelInfo objects can then be retrieved in order to view what kinds of information that sensor provides.

Usefully, the output of the code on the Nokia N97 is provided, showing what is returned for the acceleration sensor on this device. Three channels are reported for this sensor, one for each axis of acceleration. Information regarding the unit of measurement and accuracy of these sensor channels are also reported. It is interesting to note that the API does not provide direct access to some of the N97's sensors such as the ambient light sensor and the magnetometer.

ERROR

On page

How to get information about sensors in Java ME

the link to "SensorInfoMIDlet.zip" does not download but instead uploading.

Jad and jar files The SensorInfoMIDlet.jad and SensorInfoMIDlet.jar files can be downloaded from SensorInfoMIDlet.zip

Mtilli -

I uploaded the real example project because somebody had uploaded trash as SensorInfoMIDlet.zip.

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Article Metadata

Code Example

Source file: Media:SensorInfoMIDlet.zip

Tested with

SDK: Nokia SDK 2.0 for Java, Nokia Belle SDK 1.0

Compatibility

Platform(s): Nokia SDK 2.0 for Java (beta) with Mobile Sensors API 1.0 enabled, Nokia Belle 1.0 SDK

Article

Created: jarmlaht (07 Apr 2009)

Last edited: hamishwillee (03 May 2013)

Overview

The Mobile Sensor API (JSR-256) is now supported in S60 5th Edition devices. The Nokia N97 mobile computer is the first device to have the API as a built-in feature. In addition, the API can be added to the Nokia 5800 XpressMusic using a add-on, which can be downloaded from Nokia Developer here.

Working with the Mobile Sensor API

Determining the available sensors

Various mobile devices are equipped with different types of sensors. The first step for any application is therefore to find out which sensors are available for use with the Mobile Sensor API. The SensorManager.findSensors() method enables applications to do this. This method returns an array of SensorInfo objects, which contain information about the sensors.

The SensorInfo array can be created like this:

// if quantity and contextType are null, information about every sensor in the device is returned
SensorInfo[] infos = SensorManager.findSensors(String quantity, String contextType);

Now, for example, a readable description of the sensors can be listed using the following code:

    for (int i = 0; i < length; i ++) {
        System.out.println("Sensor #" + (i+1) + ": Description: " + infos[i].getDescription());
    }

Working example

Here is a simple SensorInfoMIDlet for listing all the sensors and detailed information about them.

Source code: SensorInfoMIDlet.java

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.midlet.MIDlet;
import javax.microedition.sensor.SensorInfo;
import javax.microedition.sensor.SensorManager;
import javax.microedition.sensor.MeasurementRange;
import javax.microedition.sensor.ChannelInfo;
 
public class SensorInfoMIDlet extends MIDlet implements CommandListener {
    private SensorInfo[] infos;
    private MeasurementRange[] ranges;
    private Form form;
    private Command exitCommand;
 
	public SensorInfoMIDlet() {
            form = new Form("Sensor Info");
            exitCommand = new Command("Exit", Command.EXIT, 1);
            form.addCommand(exitCommand);
            form.setCommandListener(this);
            Display.getDisplay(this).setCurrent(form);
	}
 
	public void startApp() {
            listSensors();
	}
 
	public void destroyApp(boolean unconditional) {}
 
	public void pauseApp() {}
 
    /**
     * Lists all the sensors in the device and the following details:<BR>
     * - sensor quantity<BR>
     * - readable description of the sensor<BR>
     * - the context type of the sensor<BR>
     * - the model of the sensor<BR>
     * - the URL needed to open a SensorConnection<BR>
     * - the datatype of the sensor<BR>
     * - the measurement range: smallest and largest values and the resolution<BR>
     * - channel info: the datatypes of the channels, their names, scales and units<BR>
     */
    private void listSensors() {
	infos = SensorManager.findSensors(null, null);
	if (infos.length==0) return;
        int length = infos.length;
        int datatypes[] = new int[length];
        for (int i = 0; i < length; i ++) {
            datatypes[i] = infos[i].getChannelInfos()[0].getDataType();
            ranges = infos[i].getChannelInfos()[0].getMeasurementRanges();
            addText("Sensor #" + (i+1) + ": Quantity: " + infos[i].getQuantity());
            addText("Sensor #" + (i+1) + ": Description: " + infos[i].getDescription());
            addText("Sensor #" + (i+1) + ": ContextType: " + infos[i].getContextType());
            addText("Sensor #" + (i+1) + ": Model: " + infos[i].getModel());
            addText("Sensor #" + (i+1) + ": Url: " + infos[i].getUrl());
            String datatype = "";
            if (datatypes[i] == 1) datatype = "TYPE_DOUBLE";        //ChannelInfo.TYPE_DOUBLE = 1
            else if (datatypes[i] == 2) datatype = "TYPE_INT";      //ChannelInfo.TYPE_INT = 2
            else if (datatypes[i] == 4) datatype = "TYPE_OBJECT";   //ChannelInfo.TYPE_OBJECT = 4
            addText("Sensor #" + (i+1) + ": DataType: " + datatype);
            addText("Sensor #" + (i+1) + ": MeasurementRange, smallest value: " + ranges[0].getSmallestValue());
            addText("Sensor #" + (i+1) + ": MeasurementRange, largest value: " + ranges[0].getLargestValue());
            addText("Sensor #" + (i+1) + ": MeasurementRange, resolution: " + ranges[0].getResolution());
            SensorInfo sensorinfo = infos[i];
            ChannelInfo channelInfo[] = sensorinfo.getChannelInfos();
            for(int j = 0; j < channelInfo.length; j++) {
                ChannelInfo channelinfo = channelInfo[j];
                addText("Sensor #" + (i+1) + ": " + (j+1) + ". channel, accuracy:" + channelinfo.getAccuracy());
                int d_type = channelinfo.getDataType();
                if (d_type == 1) datatype = "TYPE_DOUBLE";        //ChannelInfo.TYPE_DOUBLE = 1
                else if (d_type == 2) datatype = "TYPE_INT";      //ChannelInfo.TYPE_INT = 2
                else if (d_type == 4) datatype = "TYPE_OBJECT";   //ChannelInfo.TYPE_OBJECT = 4
                addText("Sensor #" + (i+1) + ": " + (j+1) + ". channel, data type: " + datatype);
                addText("Sensor #" + (i+1) + ": " + (j+1) + ". channel, name: " + channelinfo.getName());
                int scale = channelinfo.getScale();
                String scaleString = "";
                if (scale == 0) scaleString = "scaling not needed";
                else scaleString = "" + scale;
                addText("Sensor #" + (i+1) + ": " + (j+1) + ". channel, scale: " + scaleString);
                addText("Sensor #" + (i+1) + ": " + (j+1) + ". channel, unit: " + channelinfo.getUnit());
            }
        }
    }
 
    private void addText(String text) {
        form.append(text + "\n");
        System.out.println(text);
    }
 
    public void commandAction(Command c, Displayable d) {
        if (c == exitCommand) notifyDestroyed();
    }
}

Jad and jar files

The SensorInfoMIDlet.jad and SensorInfoMIDlet.jar files can be downloaded from SensorInfoMIDlet.zip.

Reviewing the output

The SensorInfoMIDlet prints the information generated to standard output. The MIDPLogger application can be used to view the output and saving it to a file.

If run on a Nokia N97 device - which supports accelerometer (actually two of them), battery charge sensor, charger state sensor, and network field intensity sensor - the output for an accelerometer sensor looks like this:

Sensor #1: Quantity: acceleration
Sensor #1: Description: acceleration sensor has channels axis_x, axis_y, and axis_z that measure x, y, and z axis accelerations; used, for example, to get the orientation of the device. Always on
Sensor #1: ContextType: user
Sensor #1: Model: Nokia
Sensor #1: Url: sensor:acceleration;contextType=user;model=Nokia;location=NoLoc
Sensor #1: DataType: TYPE_DOUBLE
Sensor #1: MeasurementRange, smallest value: -19.62
Sensor #1: MeasurementRange, largest value: 19.62
Sensor #1: MeasurementRange, resolution: 0.15328125
Sensor #1:, 1. channel, accuracy:0.1
Sensor #1:, 1. channel, data type: TYPE_DOUBLE
Sensor #1:, 1. channel, name: axis_x
Sensor #1:, 1. channel, scale: 0
Sensor #1:, 1. channel, unit: m/s^2
Sensor #1:, 2. channel, accuracy:0.1
Sensor #1:, 2. channel, data type: TYPE_DOUBLE
Sensor #1:, 2. channel, name: axis_y
Sensor #1:, 2. channel, scale: 0
Sensor #1:, 2. channel, unit: m/s^2
Sensor #1:, 3. channel, accuracy:0.1
Sensor #1:, 3. channel, data type: TYPE_DOUBLE
Sensor #1:, 3. channel, name: axis_z
Sensor #1:, 3. channel, scale: 0
Sensor #1:, 3. channel, unit: m/s^2

Development tools

S60 SDKs

The Nokia N97 SDK provides support for developing with the Mobile Sensor API. The latest version of the SDK can be downloaded from Nokia Developer here.

Adding support to NetBeans

Here are the instructions on how to add the RI to NetBeans as a platform:

download "RI Binary for JSR-256 Mobile Sensor API 1.0" from the Nokia Developer website here.
unzip the package to a suitable folder.
In NetBeans, from the menu bar select Tools > Java Platforms > Add platforms > Java ME MIDP Platform Emulator > Next. After the search click Find More Java ME Platform Folders and choose the folder where the unzipped RI package was saved.
Select a platform, such as C:\Users\JSR_256_RI_1_0\Nokia_Prototype_SDK_2_0\devices\Prototype_2_0_S60_MIDP_Emulator, and click Next.
In the Detected Platforms give more descriptive name to the platform, if required, then click Finish.

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