Develop Reference

I'm trying to get а real traffic stats data. But, When i count `TrafficStats.getMobileTxBytes()` for whole day its more than my data pack?

eg. I have a 1.5 GB data pack. It gives the total sum of 2.0 GB or more than that .
any idea about how to get correct speed every second.

TrafficStats.getTotalRxBytes() does not return your data pack value. It refers to the total received bytes (either wifi/mobile) since the last boot (turning ON phone). For mobile data, it will be TrafficStats.getMobileRxBytes(). More importantly, these values get reset in every reboot of device.
I have a 1.5 GB data pack. It gives the total sum of 2.0 GB or more
than that .
The android system does not know anything about your data pack. You are adding it again and again. When you call TrafficStats.getMobileRxBytes() at a moment, it returns total mobile data received upto this moment since last boot. Following is an explanation. Hope this helps.
// Suppose, you have just rebooted your device, then received 400 bytes and transmitted 300 bytes of mobile data
// After reboot, so far 'totalReceiveCount' bytes have been received by your device over mobile data.
// After reboot, so far 'totalTransmitCount' bytes have been sent from your device over mobile data.
// Hence after reboot, so far 'totalDataUsed' bytes used actually.
long totalReceiveCount = TrafficStats.getMobileRxBytes();
long totalTransmitCount = TrafficStats.getMobileTxBytes();
long totalDataUsed = totalReceiveCount + totalTransmitCount;
Log.d("Data Used", "" + totalDataUsed + " bytes"); // This will log 700 bytes
// After sometime passed, another 200 bytes have been transmitted from your device over mobile data.
totalDataUsed = TrafficStats.getMobileRxBytes() + TrafficStats.getMobileTxBytes();
Log.d("Data Used", "" + totalDataUsed + " bytes"); // Now this will log 900 bytes
any idea about how to get correct speed every second.
You cannot get actual speed this way. You can only calculate and show how much bytes have been received/transmitted in a second. All the speed meters in android do the same I think. Something like the following:
class SpeedMeter {
private long uptoNow = 0;
private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
private ScheduledFuture futureHandle;
public void startMeter() {
final Runnable meter = new Runnable() {
public void run() {
long now = TrafficStats.getMobileRxBytes() + TrafficStats.getMobileTxBytes();
System.out.println("Speed=" + (now - uptoNow)); // Prints value for current second
uptoNow = now;
}
};
uptoNow = TrafficStats.getMobileRxBytes() + TrafficStats.getMobileTxBytes();
futureHandle = scheduler.scheduleAtFixedRate(meter, 1, 1, SECONDS);
}
public void stopMeter() {
futureHandle.cancel(true);
}
}
And use like this:
SpeedMeter meter = new SpeedMeter();
meter.startMeter();
Although this code is not perfect, however it will suit your needs.

Custom UUID for multiple Bluetooth connection in Android

I have an android device acting as server which connects to multiple bluetooth android clients.
I understand the concept of UUID and how it is unique.
My question is, can I use the same UUID for all my clients connecting to my server?
If not, how do I generate a UUID for my clients programmatically and let my server know about their UUIDs.
The problem started appearing after Android 8.1 where you no longer had access to bluetooth MAC address which I initially used to generate UUIDs for client android devices.

You can generate one like this.
First, is needed to generate as long the 64 least and most significant bits:
private static long get64LeastSignificantBitsForVersion1() {
Random random = new Random();
long random63BitLong = random.nextLong() & 0x3FFFFFFFFFFFFFFFL;
long variant3BitFlag = 0x8000000000000000L;
return random63BitLong + variant3BitFlag;
}
private static long get64MostSignificantBitsForVersion1() {
LocalDateTime start = LocalDateTime.of(1582, 10, 15, 0, 0, 0);
Duration duration = Duration.between(start, LocalDateTime.now());
long seconds = duration.getSeconds();
long nanos = duration.getNano();
long timeForUuidIn100Nanos = seconds * 10000000 + nanos * 100;
long least12SignificatBitOfTime = (timeForUuidIn100Nanos & 0x000000000000FFFFL) >> 4;
long version = 1 << 12;
return
(timeForUuidIn100Nanos & 0xFFFFFFFFFFFF0000L) + version + least12SignificatBitOfTime;
}
next you can use the above methods to build one UUID:
public static UUID generateType1UUID() {
long most64SigBits = get64MostSignificantBitsForVersion1();
long least64SigBits = get64LeastSignificantBitsForVersion1();
return new UUID(most64SigBits, least64SigBits);
}

Answer:
I finally found out that you can use a custom UUID using a generator and it works with multiple devices.
The UUID must be unique and should not collide with the ones that are common & public.
Hopefully someone finds it useful

Estimate remaining battery time in android

I am trying to estimate the approx. remaining battery time in Android using below method, but it is not accurate in all the times. Please provide any suggestion to improve the accuracy,
Below method will save current time stamp in preference when battery reach 20%, 15%
It will calculate approx estimation from above 2 saved times
Thanks
public static String getBatteryEstimation(Context context){
String contentText = "";
try{
//timestamp recorded when battery reach 20%
long time1 = PreferencesUtil.getInstance().getLong(PreferencesUtil.KEY_BATTERY_THERESHOLD_TIME_1);
//timestamp recorded when battery reach 15%
long time2 = PreferencesUtil.getInstance().getLong(PreferencesUtil.KEY_BATTERY_THERESHOLD_TIME_2);
long timeDiffInMillis = time2 - time1;
long timeTakenFor1Percentage = Math.round(timeDiffInMillis/5);
long timeLastForNext15Percentage = timeTakenFor1Percentage * 15;
long hoursLast = Math.abs(TimeUnit.MILLISECONDS.toHours(timeLastForNext15Percentage));
long minutesLast = Math.abs(TimeUnit.MILLISECONDS.toMinutes(timeLastForNext15Percentage)- TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(timeLastForNext15Percentage)));
String timeLastMessage = "";
if(hoursLast > 0){
timeLastMessage = String.valueOf(minutesLast)+" hour(s) "+String.valueOf(minutesLast) + " min(s)";
} else {
timeLastMessage = String.valueOf(minutesLast) + " min(s)";
}
DateFormat dateFormat = new SimpleDateFormat("HH:mm dd MMM");
Date date = new Date();
contentText = String.format(context.getString(R.string.battery_low_content_1), timeLastMessage, dateFormat.format(date));
} catch (Exception e){
e.printStackTrace();
}
return contentText;
}

Estimating the remaining battery life is based on analytics. As the other people said you have to listen for battery level changes and in addition you have to keep track of them. After some time you will have enough data to calculate what is the average time the battery lasts. In addition you know when the battery drains fast and when drains slow so you can improve your estimation based on this. Also you will know in what time the user charges the devices. There are a lot of events that can be tracked and using the battery level. In addition you can also track when the screen is on or off. The algorithm of calculating the remaining battery life depends on you :)
You can try this :
Collect all information from the battery statistics, and count the usage in total. Then calculate the usage per second, how much the battery was drained per second.
Get the battery capacity in mAh, and calculate the remaining live with this formula: total capacity per speed of the usage
I hope this explains (at least a bit).

Using UsageStatsManager to get the foreground app

I'm trying to use UsageStatsManager to get the foreground app on a Nexus 5 with Marshmallow. I remember it used to work, but for some reason I'm getting null strings for package/class names now.
Here's my implementation
public String[] getForegroundPackageNameClassNameByUsageStats() {
String packageNameByUsageStats = null;
String classByUsageStats = null;
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
UsageStatsManager mUsageStatsManager = (UsageStatsManager)getSystemService("usagestats");
final long INTERVAL = 1000;
final long end = System.currentTimeMillis();
final long begin = end - INTERVAL;
final UsageEvents usageEvents = mUsageStatsManager.queryEvents(begin, end);
while (usageEvents.hasNextEvent()) {
UsageEvents.Event event = new UsageEvents.Event();
usageEvents.getNextEvent(event);
if (event.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND) {
packageNameByUsageStats = event.getPackageName();
classByUsageStats = event.getClassName();
Log.d(TAG, "packageNameByUsageStats is" + packageNameByUsageStats + ", classByUsageStats is " + classByUsageStats);
}
}
}
return new String[]{packageNameByUsageStats,classByUsageStats};
}
For some reason, it doesn't go into the while loop, i.e. usageEvents.hasNextEvent() is false. Because of this, it returns null package/class names.
Any idea what I'm doing wrong?
Thanks.

OK, so I found that once I set the interval to 10000 instead of 1000, it works. Apparently a 1s interval is too small.

I am using this myself. I think the usage stats will only be updated when an app comes to foreground. So if the foreground app got to the foreground (and stayed) before your 'begin' timestamp then you will not get it. :(
On the other hand when you use a long time ago you will get a giant list where you only need the highest time to determine the foreground app.
So what I do is I create 3 different times: 1min ago, 1 hour ago and 12 hours ago.
When I get an empty list on 1min I repeat request with 1h and so on. That way I get foreground most of the time. But I never get it to work ALL of the time.
I really miss the old way of just asking the package manager which app is foreground (prior to android 5), the new way is a bit messy.

Android BLE: Convert ScanResult timestampNanos to System nanoTime

When scanning for Bluetooth Low Energy packets I receive ScanCallback with ScanResult being set. I can get "Device timestamp when the scan result was observed" with result.getTimestampNanos() but this time is not aligned with the Systems.nanoTime(). Is there a way to convert from one to the other?

Use the following code to convert the getTimestampNanos() to system millis by using SystemClock.elapsedRealtime():
long rxTimestampMillis = System.currentTimeMillis() -
SystemClock.elapsedRealtime() +
scanResult.getTimestampNanos() / 1000000;
This can be converted easily to a Date object:
Date rxDate = new Date(rxTimestampMillis);
Then you then get the time as a string:
String sDate = new SimpleDateFormat("HH:mm:ss.SSS").format(rxDate);

More elegant way to do that
long actualTime = System.currentTimeMillis() - TimeUnit.MILLISECONDS.convert(SystemClock.elapsedRealtimeNanos() - scanResult.getTimestampNanos(), TimeUnit.NANOSECONDS)```