Develop Reference

How does subscribeOn work

I have some doubts regarding the working on the subscribeOn operator. I read some article regarding this.
The observeOn is quite easy to understand, it changes only the downstram, and change affects to all the downstream.
But as told in the article subscribeOn can be put in any place in the stream because it affects only the time of subscription.:
To understand this , I did a samlpe and tried logging the thread at each point of time.
Observable.just("Hello")
.map(s -> {
Log.d(TAG, s + " in " + Thread.currentThread());
return 1;
})
.subscribeOn(Schedulers.newThread())
.map(integer -> {
Log.d(TAG, integer + " in " + Thread.currentThread());
return true;
})
.map(aBoolean -> {
Log.d(TAG, aBoolean + " in " + Thread.currentThread());
return 11.0;
})
.subscribeOn(Schedulers.computation())
.subscribe(aDouble -> {
Log.d(TAG, "accept in " + Thread.currentThread());
Log.d(TAG, "accept: " + aDouble);
});
The result is
Hello in Thread[RxNewThreadScheduler-1,5,main]
1 in Thread[RxNewThreadScheduler-1,5,main]
true in Thread[RxNewThreadScheduler-1,5,main]
accept in Thread[RxNewThreadScheduler-1,5,main]
accept: 11.0
Here twice I'm applying subscribeOn, but everytime the first added one seem to be applied throughout the stream.
Can anyone please explain in simple words how does it actually work, since I'm a beginner and hard to digest this!
Thanks in advance

subscribeOn: If you have multiple subscribeOn then the first one takes effect. If you want to change the Scheduler on the stream after making a subscribeOn, then take a look at observeOn
observeOn: It changes the Scheduler going downstream.
For example:
just("Some String") // Computation
.subscribeOn(Schedulers.computation()) // it changes scheduler to computation beginning from source to observer.
.map(str -> str.length()) // Computation
.observeOn(Schedulers.io) //change the scheduler from here till the observer
.map(length -> 2 * length) // io
.subscribe(number -> Log.d("", "Number " + number));// io

Qt BLE For Android: Characteristic update does not trigger characteristicChanged signal

Here is the thing a device that we have transmits regular updates of a custom characteristic of a custom service. The service and characteristic in this device is defined via a XML file. This, of course, is referring to the Bluetooth BLE protocol.
What I'm trying to do is create a simple Qt Android App that connects to the device and monitors the update. I've gotten as far as discovering the service and connecting it signal to it. I've done that using this code:
void BLETest::on_stateChanged(QLowEnergyService::ServiceState state){
Q_UNUSED(state);
// Only printing data if all services are in correct state.
for (qint32 i = 0; i < monitoredServices.size(); i++){
if (monitoredServices.at(i)->state() != QLowEnergyService::ServiceDiscovered){
logger->out("There are still services that have not been discoverd",Logger::LC_ORANGE);
return;
}
}
QString msg = "PRINTING SERVICE DATA<br>";
for (qint32 i = 0; i < monitoredServices.size(); i++){
QLowEnergyService *monitoredService = monitoredServices.at(i);
QList<QLowEnergyCharacteristic> clist = monitoredService->characteristics();
msg = msg + "SERVICE: " + monitoredService->serviceName() + ". UUID: " + monitoredService->serviceUuid().toString() + "<br>";
// Checking if this is the service that need connection.
if (monitoredService->serviceUuid() == QBluetoothUuid(QString("0a464eef-af72-43fd-8a8b-1f26f6319dab"))){
QString res;
if (connect(monitoredService,SIGNAL(characteristicChanged(QLowEnergyCharacteristic,QByteArray)),this,SLOT(on_charastericChanged(QLowEnergyCharacteristic,QByteArray)))) res = "true";
else res = "false";
logger->out("CONNECTED TO TARGET SERVICE: " + res,Logger::LC_ORANGE);
}
for (int i = 0; i < clist.size(); i++){
QString name = clist.at(i).name();
if (name.isEmpty()) name = "UNDEFINED NAME";
QByteArray buffer = clist.at(i).value();
//QString value = QString(clist.at(i).value());
QString value = QByteArray(buffer.toHex()) + " (BS = " + QString::number(buffer.size()) + ")";
QString properties = QString::number(clist.at(i).properties());
msg = msg + "CHARACTERISTIC: " + clist.at(i).uuid().toString() + " - " + name + ": " + value + ". PROPERTIES: " + properties + "<br>";
}
if (clist.isEmpty()){
msg = msg + "No characteristics found<br>";
}
}
logger->out(msg);
}
The above functions waits for all services to be discovered then prints the UUID, name and Value for all characteristics of all services. When the service I want to monitored is processed a connection is done to the changedCharacteristic signal.
When I do this the printed value of the characteristic of the service I want to monitor is the original value for that characteristic. However as that value updates I'm not notified (the signal never triggers) and so the value never changes in my app.
Do I need to write some code to actually trigger the signals?
PD: Using the Blue Gecko Demo App I can see the values changing.
EDIT: I decided to use a timer to Poll the value of the characteristic and it never changes. Which might indicate why the signal is never generated either.

You should connect a chracteristic changed handler to the service:
connect(service, SIGNAL(characteristicChanged(QLowEnergyCharacteristic, QByteArray)), this, SLOT(on_characteristicChanged(QLowEnergyCharacteristic, QByteArray)));
In the slot you can explore the data array.
However, the signal (characteristicChanged()) will only emitted by the service if the for this chracteristic notification is enabled. This works only, if the characteritic has a notify property, that should the case in your application.

Not cheatable Google fit step counter

i have a question to Google Fit.
I am creating a step counter (oh wonder g). This i have already done so far and it not really hard.
But now we come to my problem. I am only reading the steps with the Sensor API. The issue is, i can add new data via for example the Google Fit app and it will be counted in my app too. This introduces cheating and i do not want this.
So i need to have a way to only read "device created" data and not manually added data. Is there a nice way to to this?
From the SDK documentation it is not really clear how to proceed here.

So i need to have a way to only read "device created" data and not
manually added data. Is there a nice way to to this?
You will want to use Private Custom Data Types to achieve that. Read about the different types of Fitness data you can upload to Google Fit here.
1. Public data types
Standard data types provided by the platform, like com.google.step_count.delta. Any app can read and write data of
these types. For more information, see Public Data Types.
2. Private custom data types
Custom data types defined by an specific app. Only the app that defines the data type can read and write data
of this type. For more information, see Custom Data Types.
3. Shareable data types
Custom data types submitted to the platform by an app developer. Once approved, any app can read data of a
shareable type, but only whitelisted apps as specified by the
developer can write data of that shareable type. For more information,
see Shareable Data Types.

I was able to do this with the help of this alogrithm. But remember due to Android fragmentation this code still removes some of the user's data and count it as penalty
private String dumpDataSet(DataSet dataSet, int x) {
List<String> days = new ArrayList<>();
days.add("Monday");
days.add("Tuesday");
days.add("Wednesday");
days.add("Thursday");
days.add("Friday");
days.add("Saturday");
days.add("Sunday");
String day = days.get(Math.round(x / 24));
Log.d(TAG, "\tDay: " + day);
Log.i(TAG, "Data returned for Data type: " + dataSet.getDataType().getName());
DateFormat dateFormat = getTimeInstance();
String text = "";
try {
for (DataPoint dp : dataSet.getDataPoints()) {
Log.i(TAG, "\tStepCount getStreamName: " + dp.getOriginalDataSource().getStreamName());
Log.i(TAG, "\tStepCount getStreamIdentifier: " + dp.getOriginalDataSource().getStreamIdentifier());
Log.i(TAG, "\tStepCount App Type: " + dp.getDataType().getName());
Log.i(TAG, "\tStepCount Type: " + dp.getOriginalDataSource().getType());
for (Field field : dp.getDataType().getFields()) {
Log.i(TAG, "\tField: " + field.getName() + " Value: " + dp.getValue(field));
text += dp.getValue(field);
String si[] = dp.getOriginalDataSource().getStreamIdentifier().toLowerCase().split(":");
if ((((si[si.length - 1].contains("soft")) || (si[si.length - 1].contains("step"))) && si[si.length - 1].contains("counter"))) {
totalSteps += Integer.parseInt(dp.getValue(field).toString());
Log.d(TAG, "\tStepCount" + " Added Steps -> " + dp.getValue(field) + " steps");
text += "\n\n";
} else {
Log.e(TAG, "\tStepCount PENALTY ---------------------------------------------------------------");
Log.e(TAG, "\tDay = " + day + " | Hour Number = " + x + " | StepCount" + " PENALTY DEDUCTED -> " + dp.getValue(field) + " steps");
Log.e(TAG, "\tStepCount PENALTY getStreamIdentifier: " + dp.getOriginalDataSource().getStreamIdentifier());
Log.e(TAG, "\tStepCount PENALTY getStreamName: " + dp.getOriginalDataSource().getStreamName());
Log.e(TAG, "\tStepCount PENALTY App Type: " + dp.getDataType().getName());
Log.e(TAG, "\tStepCount PENALTY Type: " + dp.getOriginalDataSource().getType());
Log.e(TAG, "\tStepCount PENALTY ---------------------------------------------------------------");
}
}
}
} catch (Exception ex) {
ex.getStackTrace();
}
return text;
}
----- UPDATE -----
You can also call
DataPoint.getOriginalDataSource().getAppPackageName()
to filter out smartwatches and other apps.

I tried as suggested by Ali Shah lakhani but
DataPoint.getOriginalDataSource().getAppPackageName();
/*I also tried but could not achieve what I wanted*/
DataPoint.getOriginalDataSource().getStreamName();
DataPoint.getOriginalDataSource().getStreamIdentifier();
did not work at least for me while retrieving data. I ended up using readDailyTotalFromLocalDevice() as shown below in order to capture steps captured by device only.
Fitness.HistoryApi.readDailyTotalFromLocalDevice(mApiClient, DataType.TYPE_STEP_COUNT_DELTA).await(1, TimeUnit.MINUTES)
I cross checked the same with some of the apps that avoids manual entries in their app and the count provided by the function above is exactly the same.
Note: If a user is having multiple devices and is using the app on all of them, readDailyTotalFromLocalDevice() will have different value for each and every device since the function is responsible for returning device specific data only.

Managing data in android cache?

I'm trying to finish the 'backbone' of my app in the next 3 weeks, however, one of the few obstacles I stutter at is saving data. I've had a look at saving data internally, but there is limited tutorials from what I can find of reading and writing multiple lines to files in the apps cache directory.
Basically what I'm trying to do is save the values stored inside a fragment. This fragment resets all its values when the user clicks a button and changes text to match a page number. (A number of duplicates that contain various values.) I would do multiple fragments, however, thought it would be beneficial to use just one fragment to minimize storage space needed.
I've only got round to writing to the files, and created two methods to manage this which are then called on the click of a button. One creates these files and the other writes to them. Unfortunately I'm inexperienced using adb and could only find that the files are created, but don't know if they are being correctly written to. Is there any chance someone could review this and possibly assist with re-reading the files? Help is much appreciated.
The two methods (Warning: A great number of lines ahead):
public void createEmptyFiles() {
try {
outputTempExerciseFileE1 = File.createTempFile("temp_exercise_1",
".txt", outputTempExerciseDir);
outputTempExerciseFileE2 = File.createTempFile("temp_exercise_2",
".txt", outputTempExerciseDir);
outputTempExerciseFileE3 = File.createTempFile("temp_exercise_3",
".txt", outputTempExerciseDir);
} catch (IOException e) {
e.printStackTrace();
Log.w("rscReporter", "Encountered an error when creating empty files!");
}
}
public void writeTemporaryFiles() {
try {
if (counterAnotherExercise == 1) {
writerTemp = new FileWriter(outputTempExerciseFileE1);
writerTemp
.write(editTextExerciseName.getText().toString() + "\n"
+ counterNoSets + "\n" + counterRepsPerSet
+ "\n" + counterMeanRepTime + "\n"
+ counterMeanRepTimeRefined + "\n"
+ counterSetInterval);
writerTemp.close();
} else if (counterAnotherExercise == 2) {
writerTemp = new FileWriter(outputTempExerciseFileE2);
writerTemp
.write(editTextExerciseName.getText().toString() + "\n"
+ counterNoSets + "\n" + counterRepsPerSet
+ "\n" + counterMeanRepTime + "\n"
+ counterMeanRepTimeRefined + "\n"
+ counterSetInterval);
writerTemp.close();
} else if (counterAnotherExercise == 3) {
writerTemp = new FileWriter(outputTempExerciseFileE3);
writerTemp
.write(editTextExerciseName.getText().toString() + "\n"
+ counterNoSets + "\n" + counterRepsPerSet
+ "\n" + counterMeanRepTime + "\n"
+ counterMeanRepTimeRefined + "\n"
+ counterSetInterval);
writerTemp.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
Any of the text files should look like:
editTextExerciseName
counterNoSets
counterRepsPerSet
counterMeanRepTime
counterMeanRepTimeRefined
counterSetInterval
Where the two methods are called:
// In a switch statement as there are around 15 buttons
case R.id.button_another_exercise_foreground:
// Increases page number in fragment
counterAnotherExercise++;
// This then checks the page number and changes text
checkPageNo();
// Writing to files is called, files were created in onCreateView()
writeTemporaryFiles();
// Resets all the counters, giving the imitation it is a completely new fragment
counterReset();
// default array exercise is then set to the page number which is then displayed as title
// For example: Exercise 1, Exercise 2, Exercise 3...
textViewExerciseTitle.setText(defaultArrayExercise);
break;
I only know the basics of Java and Android, for myself this is ambitious, however, you gotta learn somewhere! Additional suggestion for saving values are welcomed.

You don't really need files as you are only writing and then reading a handful of fixed data. Use SharedPreferences like this:
to write:
PreferenceManager.getDefaultSharedPreferences(YourActivity.this).edit().putString("editTextExerciseName", "my exercise").commit();
to read:|
PreferenceManager.getDefaultSharedPreferences(YourActivity.this).getString("editTextExerciseName");

Android - Remove the last incomplete line in .txt file

The app records the sensor data and write the data into a .txt file into the phone SD card.
During the data collection process, one may press the stop button anytime to stop writing.
The relevant writing part is as follows:
myFile = new File("/sdcard/ResearchData/"
+ txtData.getText() + ".txt");
myFile.createNewFile();
fOut = new FileOutputStream(myFile);
myOutWriter = new OutputStreamWriter(fOut);
myBufferedWriter = new BufferedWriter(myOutWriter);
myPrintWriter = new PrintWriter(myBufferedWriter);
myPrintWriter.write(currentTime - startTime + " " + acceleration[0]
+ " " + acceleration[1] + " " + acceleration[2] + "\n");
Once the STOP button is pressed, the following codes are executed.
myOutWriter.close();
fOut.close();
The codes are functioning okay, but the only problem is that because one may press STOP anytime, so the last line of the .txt file is always INCOMPLETE. Due to the need for data analysis, I need the data to be a nice rectangular matrix. Thus, I need to remove the last incomplete line. How may I do it?
Or solve this question from another angle. Can I make the STOP button synchronous to the writing process? i.e., after one line has been completely written in, then the STOP is checked.

You need a variable of bool type which is initially false and let's call it isStopPressed.
In button's down event, you should assign it to true.
I assume you create your file inside a top function, and modify this file inside onSensorChanged() function.
Then, after this line
myPrintWriter.write(currentTime - startTime + " " + acceleration[0]
+ " " + acceleration[1] + " " + acceleration[2] + "\n");
you need a conditional like,
if(isStopPressed) {
mSensorManager.unregisterListener([Your Sensor Listener]);
myOutWriter.close();
fOut.close();
}
This will provide you the most comprehensive, valid interval for your needs.

You may try setting up a boolean flag, like isStopped to indicate the STOP button is pressed.
When the STOP button is pressed, set the isStopped flag to true.
In your file writing part, check the isStopped flag. if it's true, exit the loop and close the file. Otherwise, the code can continue writing lines to the file.