Develop Reference

Is HTML5 browser geolocation feature on mobile available while screen off/ suspend?

To substitute my usage of native apps that allow to keep track of my position, I wanted to generate a PWA using the HTML5 Goelocation API.
The result I have been able to achieve so far seems to point a inferior functionality of the HTML5 Goelocation API compared to native Android API.
Below is the code I have used and the issue is, that the PWA/ website application only receives infrequent updates. Additionally the app only receives position while the screen is not off.
This puts a huge obstacle into having a PWA being to track for instance my bike tour, since I cannot keep the screen and browser in the foreground, while ideed I wished the PWA would simply continues running even when the screen is off.
Now I am aware that in most cases a device user and privacy aware person would benefit from the useragent/browser to cut the waste of resources and limit privacy loss by disabling the very feature I search.
In essence however I have looked over the MDN documentation and besides the PositionOptions I was yet unable to find any clue about the guarantees of the API.
Find below the way I have sought to make it work as a code.
Does + Should HTML5 Goelocation API work when screen of on a mobile?
Is there a concrete information about if and how much geolocation information is returedn? like frequency/delay of update and like geofencing imprecision ?
Could for instance google maps navigation work in the browser itself?
My platform is Gecko on Android. If better results could be achieved in Chromium on Android I would be happy to hear about that too.
On Android I use firefox. In it I wanted to have my website provide a page that keeps track of my movements via the geolocation API, in order to replace my strave.
window.addEventListener("load",function(){
var a= document.createElement("div");
var textarea = document.createElement("textarea");
//textarea.value="aaaa"
textarea.style.display="block"
textarea.style.minHeight="5cm"
textarea.style.width="100%"
document.body.appendChild(a);
document.body.appendChild(textarea);
if(confirm("reset data?")){
localStorage.clear() ;
}
localStorage.setItem("start"+Date.now(),startInfo);
var startInfo = Object.keys(localStorage).length+ " " +Date.now()+ " " + (Date.now() % 864000);
var lastTime=0,lastLat=0,lastLon=0,count=0,lastDistance=0;
var startTime = Date.now();
var distance = 0;
if('geolocation' in navigator) {
a.innerHTML="<h2>super wir haben geolocation!</h2>";
setInterval(()=>{
navigator.geolocation.getCurrentPosition((position) => {
// var a = document.createElement("div");
count++;
a.innerHTML="<h1>"+(((Date.now()-startTime)/1000)|0)+" "+((distance*100|0)/100)+"</h1><h3>"+startInfo+"</h3><h2>date="+(new Date()).toString()+"<br>lang="+position.coords.latitude+" long="+ position.coords.longitude+"</h2>";
var lat = ((position.coords.latitude * 10000000) | 0)
var lon = ((position.coords.longitude * 10000000) | 0)
var time = Date.now();
var deltaTime = time - lastTime;
var deltaLat = lat - lastLat;
var deltaLon = lon - lastLon;
if(Math.abs(deltaLat)>100000 || Math.abs(deltaLon) > 100000)
{
} else{
distance += Math.sqrt(deltaLat*deltaLat+deltaLon*deltaLon);
}
var deltaDistance = distance - lastDistance;
lastLat=lat;
lastLon=lon;
lastTime=time;
lastDistance=distance;
newline = (((Date.now()-startTime)/1000)|0) + " dist=" + distance + "("+deltaDistance+") lat=" + lat + "("+deltaLat+") lon=" + lon + "("+deltaLon+") ";
textarea.value = newline + "\n" + textarea.value;
localStorage.setItem("P"+(Date.now()%864000),deltaLat+" "+deltaLon+" "+deltaTime);
},function(){},{timeout:900});
},1000);
} else {
a.innerHTML="<h2> shit</h2>";
}
});

Android - How to know which USB interface to use?

The goal is to connect a guitar to USB host capable Android device, do some processing on the signal and play it through the device.
Problem is I'm not finding much documentation on it. The device shows up can contains 6 interfaces.
However, in all the examples I see, the first interface is always used..
UsbInterface intf = device.getInterface(0);
My device contains 6 interfaces BUT the first interface, i.e. getInterface(0) has no endpoints. 3/6 have no endpoints but the other 3 all have 1 end point.
I read that you need to find the correct interface and endpoint. In my case, I only want an IN endpoint to receive data.
Any advice on how to that would be very appreciated.
Cheers

This is how I got down to the bottom of it.
The last interface, I believe is the one I am looking for.
It has a direction value of USB_DIR_IN (3)
It has a endpoint type value USB_ENDPOINT_XFER_ISOC (1) signifying the regular isochronous connection I was looking for
// Cycle through interfaces and print out endpoint info
StringBuilder builder = new StringBuilder();
for (int i=0; i<device.getInterfaceCount(); i++)
{
String epDirString = "No endpoints";
String epTypeString = "No endpoints";
if (device.getInterface(i).getEndpointCount() > 0)
{
epDirString = String.valueOf(device.getInterface(i).getEndpoint(0).getDirection());
epTypeString = String.valueOf(device.getInterface(i).getEndpoint(0).getType());
}
builder.append("Int. " + i + " EP count: " + device.getInterface(i).getEndpointCount() +
" || EP direction: " + epDirString + " || EP type: " + epTypeString + "\n");
}
// Show results in a dialog
Builder dBuilder = new AlertDialog.Builder(USBActivity.this);
dBuilder.setMessage(builder.toString()).show();

Android - How to filter emoji (emoticons) from a string?

I'm working on an Android app, and I do not want people to use emoji in the input.
How can I remove emoji characters from a string?

Emojis can be found in the following ranges (source) :
U+2190 to U+21FF
U+2600 to U+26FF
U+2700 to U+27BF
U+3000 to U+303F
U+1F300 to U+1F64F
U+1F680 to U+1F6FF
You can use this line in your script to filter them all at once:
text.replace("/[\u2190-\u21FF]|[\u2600-\u26FF]|[\u2700-\u27BF]|[\u3000-\u303F]|[\u1F300-\u1F64F]|[\u1F680-\u1F6FF]/g", "");

Latest emoji data can be found here:
http://unicode.org/Public/emoji/
There is a folder named with emoji version.
As app developers a good idea is to use latest version available.
When You look inside a folder, You'll see text files in it.
You should check emoji-data.txt. It contains all standard emoji codes.
There are a lot of small symbol code ranges for emoji.
Best support will be to check all these in Your app.
Some people ask why there are 5 digit codes when we can only specify 4 after \u.
Well these are codes made from surrogate pairs. Usually 2 symbols are used to encode one emoji.
For example, we have a string.
String s = ...;
UTF-16 representation
byte[] utf16 = s.getBytes("UTF-16BE");
Iterate over UTF-16
for(int i = 0; i < utf16.length; i += 2) {
Get one char
char c = (char)((char)(utf16[i] & 0xff) << 8 | (char)(utf16[i + 1] & 0xff));
Now check for surrogate pairs. Emoji are located on the first plane, so check first part of pair in range 0xd800..0xd83f.
if(c >= 0xd800 && c <= 0xd83f) {
high = c;
continue;
}
For second part of surrogate pair range is 0xdc00..0xdfff. And we can now convert a pair to one 5 digit code.
else if(c >= 0xdc00 && c <= 0xdfff) {
low = c;
long unicode = (((long)high - 0xd800) * 0x400) + ((long)low - 0xdc00) + 0x10000;
}
All other symbols are not pairs so process them as is.
else {
long unicode = c;
}
Now use data from emoji-data.txt to check if it's emoji.
If it is, then skip it. If not then copy bytes to output byte array.
Finally byte array is converted to String by
String out = new String(outarray, Charset.forName("UTF-16BE"));

For those using Kotlin, Char.isSurrogate can help as well. Find and remove the indexes that are true from that.

Here is what I use to remove emojis. Note: This only works on API 24 and forwards
public String remove_Emojis_For_Devices_API_24_Onwards(String name)
{
// we will store all the non emoji characters in this array list
ArrayList<Character> nonEmoji = new ArrayList<>();
// this is where we will store the reasembled name
String newName = "";
//Character.UnicodeScript.of () was not added till API 24 so this is a 24 up solution
if (Build.VERSION.SDK_INT > 23) {
/* we are going to cycle through the word checking each character
to find its unicode script to compare it against known alphabets*/
for (int i = 0; i < name.length(); i++) {
// currently emojis don't have a devoted unicode script so they return UNKNOWN
if (!(Character.UnicodeScript.of(name.charAt(i)) + "").equals("UNKNOWN")) {
nonEmoji.add(name.charAt(i));//its not an emoji so we add it
}
}
// we then cycle through rebuilding the string
for (int i = 0; i < nonEmoji.size(); i++) {
newName += nonEmoji.get(i);
}
}
return newName;
}
so if we pass in a string:
remove_Emojis_For_Devices_API_24_Onwards("😊 test 😊 Indic:ढ Japanese:な 😊 Korean:ㅂ");
it returns: test Indic:ढ Japanese:な Korean:ㅂ
Emoji placement or count doesn't matter

Phonegap Contacts API - Android - return only phone contacts and not gmail contacts

I am using phonegap 2.9.0 to retrieve the contacts list on android and iOS.
As you can see on the screenshot below, I got 67 contacts on the phone + 952 gmail contacts
The following code returns 1019 contacts. How is it possible to retrieve only the real contacts with the phonegap API?
Is there a group notion in phonegap? I read the documentation but the filter is pretty basic.
var options = new ContactFindOptions();
options.multiple = true;
var fields = ["name", "phoneNumbers"];
navigator.contacts.find(fields, function(contacts) {
for (var i = 0; i < contacts.length; i++) {
console.log("Display Name = " + contacts[i].name.formatted);
if(contacts[i].phoneNumbers)
console.log("phone = " + contacts[i].phoneNumbers[0].value);
}
}, function(contact_error) {
$scope.contact_has_error = true;
}, options);
thanks for your help

FYI, I wrote a plugin to return only the contacts with at least one phone numbers. The performances are way better.
https://github.com/dbaq/cordova-plugin-contacts-phone-numbers

SpannableStringBuffer limited to 9,999 characters?

My app reads in large amounts of data from text files assets and displays them on-screen in a TextView. (The largest is ~450k.) I read the file in, line-by-line into a SpannableStringBuffer (since there is some metadata I remove, such as section names). This approach has worked without complaints in the two years that I've had the app on the market (over 7k active device installs), so I know that the code is reasonably correct.
However, I got a recent report from a user on a LG Lucid (LGE VS840 4G, Android 2.3.6) that the text is truncated. From log entries, my app only got 9,999 characters in the buffer. Is this a known issue with a SpannableStringBuffer? Are there other recommended ways to build a large Spannable buffer? Any suggested workarounds?
Other than keeping a separate expected length that I update each time I append to the SpannableStringBuilder, I don't even have a good way to detect the error, since the append interface returns the object, not an error!
My code that reads in the data is:
currentOffset = 0;
try {
InputStream is = getAssets().open(filename);
BufferedReader br = new BufferedReader(new InputStreamReader(is));
ssb.clear();
jumpOffsets.clear();
ArrayList<String> sectionNamesList = new ArrayList<String>();
sectionOffsets.clear();
int offset = 0;
while (br.ready()) {
String s = br.readLine();
if (s.length() == 0) {
ssb.append("\n");
++offset;
} else if (s.charAt(0) == '\013') {
jumpOffsets.add(offset);
String name = s.substring(1);
if (name.length() > 0) {
sectionNamesList.add(name);
sectionOffsets.add(offset);
if (showSectionNames) {
ssb.append(name);
ssb.append("\n");
offset += name.length() + 1;
}
}
} else {
if (!showNikud) {
// Remove nikud based on Unicode character ranges
// Does not replace combined characters (\ufb20-\ufb4f)
// See
// http://en.wikipedia.org/wiki/Unicode_and_HTML_for_the_Hebrew_alphabet
s = s. replaceAll("[\u05b0-\u05c7]", "");
}
if (!showMeteg) {
// Remove meteg based on Unicode character ranges
// Does not replace combined characters (\ufb20-\ufb4f)
// See
// http://en.wikipedia.org/wiki/Unicode_and_HTML_for_the_Hebrew_alphabet
s = s.replaceAll("\u05bd", "");
}
ssb.append(s);
ssb.append("\n");
offset += s.length() + 1;
}
}
sectionNames = sectionNamesList.toArray(new String[0]);
currentFilename = filename;
Log.v(TAG, "ssb.length()=" + ssb.length() +
", daavenText.getText().length()=" +
daavenText.getText().length() +
", showNikud=" + showNikud +
", showMeteg=" + showMeteg +
", showSectionNames=" + showSectionNames +
", currentFilename=" + currentFilename
);
After looking over the interface, I plan to replace the showNikud and showMeteg cases with InputFilters.

Is this a known issue with a SpannableStringBuffer?
I see nothing in the source code to suggest a hard limit on the size of a SpannableStringBuffer. Given your experiences, my guess is that this is a problem particular to that device, due to a stupid decision by an engineer at the device manufacturer.
Any suggested workarounds?
If you are distributing through the Google Play Store, block this device in your console.
Or, don't use one massive TextView, but instead use several smaller TextView widgets in a ListView (so they can be recycled), perhaps one per paragraph. This should have the added benefit of reducing your memory footprint.
Or, generate HTML and display the content in a WebView.

After writing (and having the user run) a test app, it appears that his device has this arbitrary limit for SpannableStringBuilder, but not StringBuilder or StringBuffer. I tested a quick change to read into a StringBuilder and then create a SpannableString from the result. Unfortunately, that means that I can't create the spans until it is fully read in.
I have to consider using multiple TextView objects in a ListView, as well as using Html.FromHtml to see if that works better for my app's long term plans.