Use Travis to extract testing APKs for PSLab

Travis CI is a popular continuous integration tool built to test software and deployments done at GitHub repositories. They provide free plans to open source projects. PSLab Android is using Travis to ensure that all the pull requests made and the merges are build-bug frees. Travis can do this pretty well, but that is not all it can do. It’s a powerful tool and we can think of it as a virtual machine (with high specs) installed in a server for us to utilize efficiently.

There was a need in PSLab development that, if we want to test the functionalities of code at a branch. To fulfil this need, one has to download the branch to his local machine and use gradle to build a new apk. This is a tedious task, not to mention reviewers, even developers wouldn’t like to do this.

If the apk files were generated and in a branch, we can simply download them using a console command.

$ wget https://raw.github.com/fossasia/<repository>/<branch>/<file with extension>

 

With the help of Travis integration, we can create a simple script to generate these apks for us. This is done as follows;

Once the Travis build is complete for a triggering event such as a pull request, it will run it’s “after_success” block. We are going to execute a script at this point. Simply add the following code snippet.

after_success:
  - 'if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then bash <script-name>.sh; fi'

 

This will run the script you have mentioned using bash. Here we will have the following code snippets in the specified bash script.

First of all we have to define the branch we want to build. This can be done using a variable assignment.

export DEVELOPMENT_BRANCH=${DEVELOPMENT_BRANCH:-development}

 

Once the build is complete, there will be new folders in the virtual machine. One of them is the app folder. Inside this folder contains the build folder where all the apk files are generated. So the next step is to copy these apk files to a place of our preference. I am using a folder named apk to make it much sense.

cd apk
\cp -r ../app/build/outputs/apk/*/**.apk .
\cp -r ../app/build/outputs/apk/debug/output.json debug-output.json
\cp -r ../app/build/outputs/apk/release/output.json release-output.json
\cp -r ../README.md .

 

Usually, the build folder has following apk files

  • app-debug.apk
  • app-release-unsigned.apk
  • app-release.apk

Release apks are usually signed with a key and it would cause issues while installation. So we have to filter out the debug apk that we usually use for debugging and get it as the output apk. This involves simple file handling operations in Linux and a bit of git.

First of all, rename the apk file so that it will be different from other files.

# Rename apks with dev prefixes
mv app-debug.apk app-dev-debug.apk

 

Then add and commit them to a specific branch where we want the output from.

git add -A
git commit -am "Travis build pushed [development]"
git push origin apk --force --quiet> /dev/null

 

Once it is all done, you will have a branch created and updated with the apk files you have defined.

 

Figure 1: UI of pslab-android apk branch

Reference:

  1. https://travis-ci.org/
Continue Reading Use Travis to extract testing APKs for PSLab

I2C communication in PSLab Android

PSLab device is a compact electronic device with a variety of features. One of them is the ability to integrate sensors and get readings from them. One might think that why they should use PSLab device to get sensor readings and they can use some other hardware like Arduino. In those devices, user has to create firmware and need to know how to interface them with correct sampling rates and settings. But with PSLab, they all come in the whole package. User just have to plug the device to his phone and the sensor to device and he’s ready.

The idea of this blog post is to show how this sophisticated process is actually happening. Before that, let me give you a basic introduction on how I2C communication protocol works. I2C protocol is superior to UART and SPI protocols as they are device limited or requires many wires. But with I2C, you can literally connect thousands of sensors with just 4 wires. These wires are labeled as follows;

  • VCC – Power line
  • GND – Ground line
  • SDA – Data line
  • SCL – Signal clock

It is required that the SDA and SCL lines need to be connected to VCC line using two pull up resistors. But that’s just hardware. Let’s move on to learn how I2C communicate.

Here there is this communicating concept called master and slave. To start communication, master issues a global signal like a broadcast to all the devices connected to SCL and SDA lines. This signal contains the address of the slave, master needs to address and get data from. If the slave received this call to him, he will pull down the SDA line to signal the master that he heard him and ready to communicate with him. Here communication means reading or writing data. Then the communication happens and the link between master and slave breaks giving opportunity to other masters and slaves.

One might think this is a slow process. But these signals are transmitted at high frequencies. In PSLab it is at 100 kHz and that is one millisecond.

PSLab library has a special class to handle I2C communication. That is

public class I2C {/**/}

 

Once this class is initiated, one has to call the start function to start communication. This method requires the address we wish to communicate with and the mode of operation stating if it is a read or write operation

public int start(int address, int rw) throws IOException {
   packetHandler.sendByte(commandsProto.I2C_HEADER);
   packetHandler.sendByte(commandsProto.I2C_START);
   packetHandler.sendByte((address << 1) | rw & 0xff);
   return (packetHandler.getAcknowledgement() >> 4);
}

 

Once the address is sent out, protocol requires us to stop and wait for acknowledgement.

public void wait() throws IOException {
   packetHandler.sendByte(commandsProto.I2C_HEADER);
   packetHandler.sendByte(commandsProto.I2C_WAIT);
   packetHandler.getAcknowledgement();
}

 

If there are no congestion in the lines such as reading from multiple devices, the acknowledgement will be instantaneous. Once that is complete, we can start communication either byte-wise or bulk-wise

public int send(int data) throws IOException {
   packetHandler.sendByte(commandsProto.I2C_HEADER);
   packetHandler.sendByte(commandsProto.I2C_SEND);
   packetHandler.sendByte(data);
   return (packetHandler.getAcknowledgement() >> 4);
}

 

As an example, reading sensor values at a given interval can be done using the following method call.

public ArrayList<Byte> read(int length) throws IOException {
   ArrayList<Byte> data = new ArrayList<>();
   for (int i = 0; i < length - 1; i++) {
       packetHandler.sendByte(commandsProto.I2C_HEADER);
       packetHandler.sendByte(commandsProto.I2C_READ_MORE);
       data.add(packetHandler.getByte());
       packetHandler.getAcknowledgement();
   }
   packetHandler.sendByte(commandsProto.I2C_HEADER);
   packetHandler.sendByte(commandsProto.I2C_READ_END);
   data.add(packetHandler.getByte());
   packetHandler.getAcknowledgement();
   return data;
}

 

Once we get the data bundle, either we can save them or display in a graph whatever the way it’s convenient.

Reference:

  1. https://en.wikipedia.org/wiki/I%C2%B2C
Continue Reading I2C communication in PSLab Android

Adding Data Point Markers to OSM

PSLab Android app supports multiple sensors external and internal. Users can view sensor readings and record them into a csv file for later use. They can also have their location embedded into the data set they are recording. Saving the location related to each sensor reading is important. Say in a school experiment teacher can ask the student to measure dust particle concentration in city and inside his house. If the data set didn’t have any reference to the location where it was recorded, it is just incomplete. To facilitate this feature, we have enabled location in data recordings.

Enabling location is just not enough. User should be able to view the locations. Probably on a map itself would be a good idea. With the use of Open Street Maps, we can add markers to specific locations. These markers can be used as a point to show on map where a specific data set had been recorded by the user. This can be implemented further to add additional features such as standardized labels to view which data set is at which location etc.

Figure 1: Markers on Map

Unlike Google Maps API, in Open Street Maps there is no direct implementation to add a marker. But it is not a hard implementation either. We can simply create a class extending map overlays and use that as a base to add markers.

We can start by creating a new class that extends ItemizedOverlay<OverlayItem> class as follows. In this class, it would be wise to have an array list full of markers we are using in the map to modularize the whole markers related tasks into this one class rather than implementing in every place where map is used.

public class MapOverlay extends ItemizedOverlay<OverlayItem> {

    private ArrayList<OverlayItem> overlayItemList = new   ArrayList<OverlayItem>();

}

 

Once the class is initiated, have the following methods implemented. The following method will add markers to the array list we have created at the beginning.

public void addItem(GeoPoint p, String title, String snippet){
  OverlayItem newItem = new OverlayItem(title, snippet, p);
  overlayItemList.add(newItem);
  populate(); 
}

 

This method will be used to handle focusing events related to map markers.

@Override
public boolean onSnapToItem(int arg0, int arg1, Point arg2, IMapView arg3){
  return false;
}

 

Following method is used by the map itself to generate markers from the marker list.

@Override
protected OverlayItem createItem(int arg0) {
  return overlayItemList.get(arg0);
}

 

This method is an overriden method we will have to include in the class body.

@Override
public int size() {
  return overlayItemList.size();
}

 

Once the overlay class is completed, we can move on to actual implementation of a map on Openstreetmap view.

From the main activity where the map is viewed, initiate the marker overlay class and pass the drawable that needs to be shown as the marker to the class constructor as follows:

MapOverlay mapoverlay = null;
Drawable marker=getResources().getDrawable(android.R.drawable.map_hand);
int markerWidth = marker.getIntrinsicWidth();
int markerHeight = marker.getIntrinsicHeight();
marker.setBounds(0, markerHeight, markerWidth, 0);

ResourceProxy resourceProxy = new DefaultResourceProxyImpl(getApplicationContext());
mapoverlay = new MapOverlay(marker, resourceProxy);
mapView.getOverlays().add(mapoverlay);
         
GeoPoint point = new GeoPoint(55.75, 37.616667);
mapoverlay.addItem(point, "Russia", "Russia");

 

We can add as many GeoPoints as we want to markers list and they all will be displayed on the map like this;

Figure 2: Final Output of Markers

Reference:

http://android-coding.blogspot.com/2012/06/example-of-implementing-openstreetmap.html

Continue Reading Adding Data Point Markers to OSM

Adding Open Street Maps to PSLab Android

PSLab Android app is an open source app that uses fully open libraries and tools so that the community can use all it’s features without any compromises related to pricing or feature constraints. This will brings us to the topic how to implement a map feature in PSLab Android app without using proprietary tools and libraries. This is really important as now the app is available on Fdroid and they don’t allow apps to have proprietary tools in them if they are published there. In other words, it simply says we cannot use Google Maps APIs no matter how powerful they are in usage.

There is a workaround and that is using Open Street Maps (OSM). OSM is an open source project which is supported by a number of developers all around the globe to develop an open source alternative to Google Maps. It supports plenty of features we need in PSLab Android app as well. Starting from displaying a high resolution map along with caching the places user has viewed, we can add markers to show data points and locations in sensor data logging implementations.

All these features can be made available once we add the following dependencies in gradle build file. Make sure to use the latest version as there will be improvements and bug fixes in each newer version

implementation "org.osmdroid:osmdroid-android:$rootProject.osmVersion"
implementation "org.osmdroid:osmdroid-mapsforge:$rootProject.mapsforgeVersion"
implementation "org.osmdroid:osmdroid-geopackage:$rootProject.geoPackageVersion"

 

OSM will be functional only after the following permission states were granted.

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"  />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

 

In a view xml file, add the layout org.osmdroid.views.MapView to initiate the map view. There is a known issue in OSM library. That is during the initiation, if the zoom factor is set to a small value, there will be multiple instances of maps as shown in Fig 1. The solution is to have a higher zoom value when the map is loaded.

Figure 1: Multiple map tiles in OSM

Once we initialize the map view inside an activity, a zoom level can be easily set using a map controller as follows;

map = findViewById(R.id.osmmap);
map.setTileSource(TileSourceFactory.MAPNIK);
map.setBuiltInZoomControls(true);
map.setMultiTouchControls(true);

IMapController mapController = map.getController();
mapController.setZoom((double) 9);
GeoPoint startPoint = new GeoPoint(0.00, 0.00);
mapController.setCenter(startPoint);

 

After successfully implementing the map view, we can develop the business logic to add markers and descriptions to improve the usability of OS Maps. They will be available in the upcoming blog posts.

Reference:

  1. https://github.com/osmdroid/osmdroid/wiki/How-to-add-the-osmdroid-library-via-Gradle
  2. https://www.openstreetmap.org/
Continue Reading Adding Open Street Maps to PSLab Android

Capturing Position Data with PSLab Android App

PSLab Android app by FOSSASIA can be used to visualize different waveforms, signal levels and patterns. Many of them involve logging data from different instruments. These data sets can be unique and the user might want them to be specific to a location or a time. To facilitate this feature, PSLab Android app offers a feature to save user’s current location along with the data points.

This implementation can be done in two ways. One is to use Google Maps APIs and the other one is to use LocationManager classes provided by Android itself. The first one is more on to proprietary libraries and it will give errors when used in an open source publishing platform like Fdroid as they require all the libraries used in an app to be open. So we have to go with the latter, using LocationManager classes.

As first step, we will have to request permission from the user to allow the app access his current location. This can be easily done by adding a permission tag in the Manifest.xml file.

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

 

Since we are not using Google Maps APIs, capturing the current location will take a little while and that can be considered as the only downfall of using this method. We have to constantly check for a location change to capture the data related to current location. This can be easily done by attaching a LocationListener as it will do the very thing for us.

private LocationListener locationListener = new LocationListener() {
   @Override
   public void onLocationChanged(Location location) {
       locationAvailable = true;
   }

   @Override
   public void onStatusChanged(String s, int i, Bundle bundle) {/**/}

   @Override
   public void onProviderEnabled(String s) {/**/}

   @Override
   public void onProviderDisabled(String s) {
       // TODO: Handle GPS turned on/off situations
   }
};

 

In case if the user has turned off GPS in his device, this method wouldn’t work. We will have to request him to turn the feature on using a simple dialog box or a bottom sheet dialog.

We can also customize how frequent the locationlistener should check for a location using another class named LocationManager. This class can be instantiated as follows:

locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

 

Then we can easily set the time interval using requestLocationUpdates method. Here I have requested location updates in every one second. That is a quite reasonable rate.

locationManager.requestLocationUpdates(provider, 1000, 1, locationListener);

 

Once we have set all this up, we can capture the current location assuming that the user has turned on the GPS option from his device settings and the LocationManager class has a new location as we checked earlier.

if (locationAvailable) {
   Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
}

 

Each location will contain details related to its position such as latitudes and longitudes. We can log these data using the CSVLogger class implementation in PSLab Android app and let user have this option while doing his experiments.

Reference:

  1. An open source implementation : https://github.com/borneq/HereGPSLocation/blob/master/app/src/main/java/com/borneq/heregpslocation/MainActivity.java

Google Maps: https://developers.google.com/maps/documentation/android-sdk/intro

Continue Reading Capturing Position Data with PSLab Android App

Setting up environment to build PSLab Android app using Fdroid Build

Fdroid is a place for open source enthusiasts and developers to host their Free and Open Source Software (FOSS) for free and get more people onboard into their community. In order to host an app in their repository, one has to go through a several steps of builds and tests. This is to ensure that the software provided by them are as quality and safe as they can ever be. They are not allowing proprietary libraries or tools to integrate into any app or they will  be published outside the Fdroid main repository (fdroid-data) so that the users will know what they are downloading.

In a normal Linux computer where we are developing Android apps and have setup Android Studio will not be able to run the build command using:

$ fdroid build -v -l org.fossasia.pslab

The reason behind this is that we have not installed gradle and build tools required by the “fdroid build” because they are not useful in our day today activities for standalone activities. First thing we need to do is, install gradle separately. This will include adding gradle to $PATH as well.

Download the latest gradle version zip file or the version your project is using with the following command. In PSLab Android app, we are using 4.5.1 version and the snippet below include that version.

$ wget https://services.gradle.org/distributions/gradle-4.5.1-bin.zip

Next step is to install this in a local folder. We can select any path we want, but /opt/ folder is generally used in such scenarios.

sudo mkdir /opt/gradle
sudo unzip -d /opt/gradle gradle-4.5.1-bin.zip

Then we can add gradle to our $PATH variable using the following command:

$ export PATH=$PATH:/opt/gradle/gradle-4.5.1/bin

Now we are all set with gradle settings. Next step is to verify that the fdroid server is properly configured and up to date. When you run the build command after setting up the gradle in PC, it will throw an error similar to “failed to find any output apks”. This causes if the installed fdroid server version is old.

Fdroid server is running on python 3 and it will require some additional libraries pre-installed to properly function.

$ sudo apt-get install vagrant virtualbox git python3-certifi python3-libvirt python3-requestbuilder python3-yaml python3-clint python3-vagrant python3-paramiko python3-pyasn1 python3-pyasn1-modules

Once these libraries are installed, remove the previous instance of fdroidserver by using the following command:

$ sudo apt-get remove fdroidserver

Then we can reinstall the latest version of fdroid server from git using the following command:

$ git clone https://gitlab.com/fdroid/fdroidserver.git
export PATH="$PATH:$PWD/fdroidserver"

Now we are all set to do a brand new lint build on our PC to make our app ready to be published in Fdroid repository!

Reference:

  1. Install gradle : https://www.vultr.com/docs/how-to-install-gradle-on-ubuntu-16-10
  2. Gradle versions : https://gradle.org/releases
  3. Setting up Fdroid-server : https://f-droid.org/en/docs/Build_Server_Setup/

Installing fdroidserver : https://gitlab.com/fdroid/fdroiddata/blob/master/README.md#quickstart

Continue Reading Setting up environment to build PSLab Android app using Fdroid Build

Using external UART modules to debug PSLab operations

Pocket Science Lab by FOSSASIA is a compact tool that can be used for circuit analytics and debugging. To make things more interesting, this device can be accessed via the user interface using an Android app or also a desktop app. Both these apps use the UART protocol (Universal Asynchronous Receiver-Transmitter) to transmit commands to the PSLab device from mobile phone or PC and receive commands vice versa. The peculiar thing about hardware is that the developer cannot simply log data just like developing and debugging a software program. He needs some kind of an external mechanism or a tool to visualize those data packets travelling through the wires.

Figure 1: UART Interface in PSLab

PSLab has a UART interface extracted out simply for this reason and also to connect external sensors that use the UART protocol. With this, a developer who is debugging any of the Android app or the desktop app can view the command and data packets transmitted between the device and the user end application.

This  requires some additional components. UART interface has two communication related pins: Rx(Receiver) and Tx(Transmitter). We will need to monitor both these pin signals for input and output data packets. It should be kept in mind that PSLab is using 3.3V signals. This voltage level is important to mention here because if someone uses 5V signals on these pins, it will damage the main IC. There are FTDI modules available in market. FTDI stands for Future Technology Devices International which is a company name and their main product is this USB transceiver chip. These chips play a major role in electronic industry due to product reliability and multiple voltage support. PSLab uses 3.3V USB Tx Rx pins and modules other than FTDI wouldn’t support it.

Figure 2: FTDI Module from SparkFun

The module shown in Fig.2 is a FTDI module which you can simply plug in to computer and have a serial monitor interface. There are cheaper versions in shopping websites like eBay or Alibaba and they will also work fine. Both Tx and Rx pins will require two of these modules and connectivity is as follows;

PSLab [Rx Pin] → FTDI Module 1 [Rx Pin]
PSLab [Tx Pin] → FTDI Module 2 [Rx Pin]

This might look strange because everywhere we see a UART module is connected Rx → Tx and Tx → Rx. Notice that our idea is to monitor data packets. Not communicate with PSLab device directly. We want to see if our mobile phone Android app is sending correct commands to PSLab device or not and if PSLab device is transmitting back the expected result or not. This method helped a lot when debugging resistance measurement application in PSLab Android app.

Monitoring these UART data packets can be done simply using a serial monitor. You can either download and install some already built serial monitors or you can simply write a python script as follows which does the trick.

import serial

ser = serial.Serial(
    port='/dev/ttyUSB1',
    baudrate=1000000000
)

ser.isOpen()
while 1 :
    data = ''
    while ser.inWaiting() > 0:
        data += ser.read(1)

    if data != '':
        print ">>" + data

Once you are getting commands and responses, it will look like debugging a software using console.

References:

  1. PySerial Library : http://pyserial.readthedocs.io/en/latest/shortintro.html
  2. UART Protocol : https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter
  3. FTDI : https://en.wikipedia.org/wiki/FTDI
Continue Reading Using external UART modules to debug PSLab operations

Implementing Multimeter in PSLab Android App

The Pocket Science Lab Android app being on the verge of development have various new features adding up per day. One of the new things added up recently is the splitting of the control section in three different instruments and implementing the control read section into a multimeter. This blog will be discussing about how the multimeter is implemented.

The different instruments are power section, multimeter and wave generator. While in the previous implementation of control section it was divided into three parts namely control main, control read and control advanced as shown in figure (1). The control is the power source, read is the multimeter and advanced section is the wave generator.

Figure  (1): Screenshot of control section

Figure (1) shows the previous implementation of a multimeter i.e the read section but as we know this is way different than the actual implementation of a multimeter and thus from here comes the task of implementing a new multimeter.

What is a Multimeter, how does it looks?

A multimeter basically is an instrument designed to measure electric current, voltage, and usually resistance, typically over several ranges of value.

          Figure (2): Showing a real multimeter instrument and its different sections [2]

Figure(2) clearly shows how an actual multimeter looks. It basically has three important components i.e the display the buttons and the rotary knob or the dial and thus the task was to implement the same in PSLab android.

Implementation in PSLab

Figure (3) :  Screenshot of new implementation of multimeter

The implementation of multimeter is thus inspired from its original look i.e it has got basic buttons, a rotary knob and a display. Figure (3) shows the implementation of multimeter in the android-app

Back-end of Multimeter

A separate multimeter activity was implemented for the multimeter. The main back-end part of getting the resistance, capacitance, frequency and count pulse were taken from the communication related classes such as the ScienceLab class and PacketHandler class. For example to get the voltage calculation we use the getRawableVoltage function

private double getRawAverageVoltage(String channelName) {
  try {
      int chosa = this.calcCHOSA(channelName);
      mPacketHandler.sendByte(mCommandsProto.ADC);
      mPacketHandler.sendByte(mCommandsProto.GET_VOLTAGE_SUMMED);
      mPacketHandler.sendByte(chosa);
      int vSum = mPacketHandler.getVoltageSummation();
      mPacketHandler.getAcknowledgement();
      return vSum / 16.0;
  } catch (IOException | NullPointerException e) {
      e.printStackTrace();
      Log.e(TAG, "Error in getRawAverageVoltage");
  }
  return 0;
}

The above function shows the pure backend of PSLab and how data is taken from the hardware using the packet handler class, after which the data is processed in various other functions after we getting the final result. Similarly the function to get count pulse is

public int readPulseCount() {
 try {
  mPacketHandler.sendByte(mCommandsProto.COMMON);
  mPacketHandler.sendByte(mCommandsProto.FETCH_COUNT);
  int count = mPacketHandler.getVoltageSummation();
  mPacketHandler.getAcknowledgement();
  return 10 * count;
 } catch (IOException e) {
  e.printStackTrace();
 }
 return -1;
}

As we see that the data is being taken through a similar manner in the above function i.e using the packetHandler class(by sending and receiving bytes). Thus in all the other functions for capacitance, frequency similar communication model can be found.

Similarly all the functions are implemented in the ScienceLab class and thus all the functions are directly called from the ScienceLab class in the Multimeter activity. For more knowledge on these one can directly have a look at the PSLab android app codes available in Github.

Implementation of the Rotary Knob

The rotary knob is implemented using the BeppiMenozzi Knob library. More information regarding the same can be found in my previous blog on implementing the rotary knob.

Resources:

Continue Reading Implementing Multimeter in PSLab Android App

Implementing Settings for Lux Meter Instrument in PSLab Android App

In PSLab android app, we have included sensor instruments which use either inbuilt sensor of smartphone or external sensor to record sensor data. For example, Lux Meter uses the light sensor to record lux data but the problem is that these instruments doesn’t contain settings option to configure the sensor record-setting like which sensor to use, change the update period etc.

Therefore, we need to create a settings page for the Lux Meter instrument which allows the user to modify the properties of the sensor instrument. For that I will use Android Preference APIs to build a settings interface that is similar to setting activity in any other android app.

The main building block of the settings activity is the Preference object. Each preference appears as a single setting item in an activity and it corresponds to key-value pair which stores the settings in default Shared Preferences file. Every time any setting is changed by the user the Android will store the updated value of the setting in the default shared preferences which we can read in any other activity across the app.

In the following steps I will describe instruction on how to create the setting interface in Android app: 

Step1 Include the dependency

First, we need to include the dependency for v7 Preference Support Library by including the following code:

dependencies { 
compile fileTree(dir: 'libs', include: ['*.jar']) 
compile 'com.android.support:appcompat-v7:23.1.1' 
compile 'com.android.support:design:23.1.1' 
compile 'com.android.support:preference-v7:23.1.1' 
}

 Step 2 Creating the preferences screen in XML

For this step, I have created a preference screen which will be inflated when the settings fragment is being created.

I created a file named  “lux_meter_settings.xml” and place it in the res/xml/ directory.

The root node for the XML file must be a <PreferenceScreen> element. We have to add each Preference within this element. Each child I added within the <PreferenceScreen> element appears as a single item in the list of settings.

The preference which I have used are:

<EdittextPreference> This preference opens up a dialog box with edit text and stores whatever value is written by the user in the edit text. I have used this preference for inputting update period and high limit of data during recording.

<CheckboxPreference> shows an item with a checkbox for a setting that is either enabled or disabled. The saved value is a boolean (true if it’s checked). I have used this preference for enabling or disabling location data with the recorded data.

<ListPreference> opens a dialog with a list of radio buttons. The saved value can be any one of the supported value types. I have used this preference to allow the user to choose between multiple sensor types.

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
       <EditTextPreference
           android:key="setting_lux_update_period"
           android:title="@string/update_period"
           android:dialogTitle="@string/update_period"
           android:defaultValue="1000"
           android:dialogMessage="Please provide time interval(in ms) at which data will be updated"
           android:summary="Update period is 900ms"/>

       <EditTextPreference
           android:key="setting_lux_high_limit"
           android:title="High Limit"
           android:dialogTitle="High Limit"
           android:defaultValue="2000"
           android:dialogMessage="Please provide maximum limit of LUX value to be recorded"
           android:summary="High Limit is 2000 Lux"/>

       <CheckBoxPreference
           android:defaultValue="false"
           android:key="include_location_sensor_data"
           android:summary="Include the location data in the logged file"
           android:title="Include Location Data" />
</PreferenceScreen>

The above XML file will produce a layout as shown in Figure 1 below:

Figure 1 shows a preview of settings layout in Android Studio

 

Step 3 Implementing the backend of setting interface

As android Documentation clearly states:

As your app’s settings UI is built using Preference objects instead of View objects, you need to use a specialized Activity or Fragment subclass to display the list settings:

  • If your app supports versions of Android older than 3.0 (API level 10 and lower), you must build the activity as an extension of the PreferenceActivity class.
  • On Android 3.0 and later, you should instead use a traditional Activity that hosts a PreferenceFragment that displays your app settings.

Therefore, I first created an Activity named “SettingsActivity” which will act as a host for a Fragment. This gist contains code for SettingsActivity which I defined in the PSLab android app which will show the Setting Fragment.

Now, for setting fragment I have created a new fragment and name it “LuxMeterSettingsFragment” and make that fragment class extends the PreferenceFragmentCompat class and for which I needed to add this import statement.

import android.support.v7.preference.PreferenceFragmentCompat;

And then inside the SettingsFragment, I overridden the following method like this:

@Override
public void onCreatePreferences(Bundle savedInstanceState,
                                String rootKey) {
    setPreferencesFromResource(R.xml.lux_meter_settings, rootKey);
}

This method is called when the Android is creating the Preferences that is when we need to call the method ‘setPreferencesFromResource()’ and pass the resource file in which we have defined our preferences along with the root key which comes as a parameter. Here, the Android will create preferences referred by the key which we have provided and initialize it to the default value in the default SharedPreferences file.

Step 4 Providing setting option to navigate to setting activity

First I included a setting option in the menu file which is getting inflated in the Lux Meter Activity toolbar as shown in below code.

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto">
  
   ...

   <item
       android:id="@+id/settings"
       android:title="@string/lux_meter_settings"
       app:showAsAction="never" />
</menu>

Then, heading over to  Lux Meter Activity in the onOptionItemSelected() method I added below code in which I created intent to open Setting Activity when the setting option is selected.

@Override
public boolean onOptionsItemSelected(MenuItem item) {
case R.id.settings:
   Intent settingIntent = new Intent(this, SettingsActivity.class);
   settingIntent.putExtra("title", "Lux Meter Settings");
   startActivity(settingIntent);
   break;
}

After this step, we can see the settings option in Lux Meter Activity as shown in Figure 2

Figure 2 shows the setting option in the overflow menu

 

To see if its working opens the app -> open Lux Meter Instrument-> Open Overflow Menu -> click on Lux Meter Setting Option to open settings.

Here we can the Lux Meter Setting as shown by the Figure 3.

Figure 3 shows the screenshot of the Lux Meter Setting activity on the actual device

 

Step 5 Implementing listener for change in Preferences item

Now we can also implement a listener by making SettingsFragment class implement SharedPreference.OnSharedPreferenceChangeListener interface and then overriding the onSharedPreferenceChanged() method.

Now, to register this listener with the Preference Screen which we will do it in the onResume() method of the fragment and deregister the listener in the onPause() method to correspond with the lifecycle of the fragment.

@Override
public void onResume() {
   super.onResume();
      
getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}
@Override
public void onPause() {
   super.onPause();
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}

Thus we have successfully implemented settings for the Lux Meter Instrument.

Resources

  1. Adding Settings to an App – Google Developer Fundamental Course Article on how to add settings.
  2. Gist – Setting Activity implementation – The gist used for setting activity in the app
Continue Reading Implementing Settings for Lux Meter Instrument in PSLab Android App

Implementing Rotary Knob in PSLab Android App

PSLab android application as we all know has got various instrument such as oscilloscope, logic analyzer, wave generator, etc.. . Although many of  these instrument require redesigning of it’s UI. One such instrument is the  Multimeter. The Multimeter UI required the implementation of the rotary knob as it is also present in an actual Multimeter.Thus this blog is solely on how to implement a Rotary Knob in an Android App.

Figure 1: Showing a basic knob

What is Rotary Knob ?

A Rotary knob is  a customizable selector that replicates the behaviour of a knob with discrete values.The knob is a powerful tool it has a lot of advantages over other radio-buttons, seek bars or other selectors.[1][2]

      • It has an immediate graphical indication of the current value, the number of choices and where the value is in the overall range.
      • Works fine also with few choices, as a multi-state toggle.
      • Swipe gestures allow to change values very quickly, using the entire screen for the gesture, but only a tiny zone of it for the graphics.

Implementation of Rotary Knob in your app[1]

In this blog the rotary knob is implemented using the BeppiMenozzi Knob library[1] as by doing this we don’t have to manually create the extra class for the knob and we don’t have to write the code from scratch.

This blog will give you step by step guide on how to implement this on your app.

        1. In your project level build.gradle file add the following lines of code.
          allprojects {
            repositories {
                   ….
                maven { url "https://jitpack.io" }
                ….
            }
          }
        2. In you app level build.gradle file add the following lines of codes in your dependencies.
          compile 'com.github.BeppiMenozzi:Knob:1.9.
        3. Minimal code :-
          This contains the minimum number of lines of code for knob

          xmlns:app="http://schemas.android.com/apk/res-auto"
          ...
          <it.beppi.knoblibrary.Knob
                  android:layout_width="64dp"
                  android:layout_height="64dp"
                  android:id="@+id/knob"
                  app:kNumberOfStates="6"
           />

          Java listener-

          xmlns:app="http://schemas.android.com/apk/res-auto"
          Knob knob = (Knob) findViewById(R.id.knob);
          knob.setState(firstState);
          knob.setOnStateChanged(new Knob.OnStateChanged() {
                  @Override
                  public void onState(int state) {
                  // do something
                  }
              });

          This java method gives the user the position of the tip of theknob.
          Also there are various other advantages of using this library.

              • The Knob is completely customizable. The many customizable attributes can all be set both via xml file, and programmatically.
              • This  page gives the list of all the methods for customizing a knob.

           

        4.  Implementing a simple knob app
          tv= (TextView)findViewById(R.id.tv);
          Knob knob = (Knob) findViewById(R.id.knob);
          knob.setState(0);
          knob.setOnStateChanged(new Knob.OnStateChanged() {
             @Override
             public void onState(int state) {
                 // do something
                 tv.setText(String.valueOf(state));
             }
          });

Now let us see the implementation of this simple app

Figure 2: showing basic knob implementation in android

So this is how we can implement a rotary knob in any Android Application.

Resources:

 

 

 

Continue Reading Implementing Rotary Knob in PSLab Android App