I am implementing an android application and i can't figure out how to solve this problem : When user clicks to the update button , i want to connect to the my server and check if there is any update on the data , if there is , i want to get data from server and update the database.Should i use xml structure to check and get updates from server or is there any smarter ways to achieve this ?
Yes, there's a smarter way to do so, it will require some work on both server and client side though. This is how it works: all data should be available to download in JSON or XML format (I'd rather prefer JSON). So, you will have something like this in the server: http://example.com/resource.json. In order to know if there's a new version of the data, what you can do is adding a header version to the HTTP response (that way you don't have to download and parse the whole resource in order to know if there's a new version).
In order for you to check those headers, you will have something like this:
URLConnection urlConnection = null;
try {
urlConnection = url.openConnection();
urlConnection.connect();
String currentVersionHeader = urlConnection.getHeaderField("your-version-header");
if( currentVersionHeader == null ) {
currentVersionHeader = "-1";
}
int version = Long.parseLong(currentVersionHeader);
// then you compare with the old version
if( oldVersion < version ){
// download the data
}
} catch (Exception e) {}
Downloading and parsing a JSON resource is something that has been already treated and you will find a bunch of tutorials and references on Google and here.
You are not providing details of the server side (is PHP? Java? .NET?), so I also won't give you details of how to implement/add a version header. I'm just explained you what's one the best way to do this kind of things based on my own experience.
Related
I am making an app that blocks inappropriate websites for parental control, I have the blocked websites in a text file which 50MB in size. I want to add them all to room database so that I can check if a url is blocked or not.
But reading and looping through each line in the text file taking forever, is there any better way I can read the file and add each line to room database?
FileInputStream inputStream = null;
Scanner sc = null;
try {
inputStream = new FileInputStream(path);
sc = new Scanner(inputStream, "UTF-8");
while (sc.hasNextLine()) {
String line = sc.nextLine();
// insert to room database
}
// note that Scanner suppresses exceptions
if (sc.ioException() != null) {
throw sc.ioException();
}
} finally {
if (inputStream != null) {
inputStream.close();
}
if (sc != null) {
sc.close();
}
}
Make it as json and place it your project..
And when starting the application show a syncing state and load data to db ..
Do this only once.
You have a few options. As previously stated you could load the websites into json. This website should help automate that a bit. https://pdfmall.com/txt-to-json. This approach would still lead to an O(n) time complexity for searching.
While it will take a bit of memory, the method I'd recommend would be to build a custom object that holds all of those lines as Strings. Every time you start the app you would need to rebuild this object, but that's better than scanning constantly. You could implement an Async thread to do this in the background.
If you take this approach I would recommend storing them in a Olog(n) data structure like a binary tree. You don't want to just throw them into an Arraylist of strings, because then you'd be doing the same thing and having to scan through the entire array. If you store them in a tree, ordered by alphabetical order or perhaps length - whatever you want to do- then you reduce your search complexity from O(n) to Olog(n). Keep in mind when using custom objects, if you intend to pass them between Activities, you will need to implement Parcelable or another method.
Third you could use an Sql database, but in your case I don't believe this would speed anything up, so I wouldn't recommend it.
Keep the urls in the text file sorted alphabetically.
Load the file in a string array list.
Do a simple binary search in the sorted list to check for an specific url.
I am new t ajax, but quite familiar with android. I am converting a ajax program to android app. As a part of it, i need to post data to the server. Below is the given post command in ajax.
var postTo = 'xyz.php';
$.post(postTo,{employee_name: $('[name=employee_name]').val() , phone: $('[name=phone]').val(), employee_type: 'guest' } ,
function(data) {
if(data.success){
window.localStorage["sa_id"] = data.mid;
window.location="getempdb.html";
}
if(data.message) {
$('#output').html(data.message);
} else {
$('#output').html('Could not connect');
}
},'json');
I want to implement this in android but under very little from the above statements. Could anyone who is good at ajax help me out with this thing. As of now, i get the user name and telephone number as a edit text input. I need to send this to php using http client. I know how to send data using php, but do not know what format to send and whether its a string to send or as a json object to send. Please help in interpreting the above code and oblige.
Apparently, this uses UrlEncodedFormEntity if you are using HttpClient in android.
This is created by using a List of NameValuePair.
from the parameters to the $.post:
{employee_name: $('[name=employee_name]').val() , phone: $('[name=phone]').val(), employee_type: 'guest' }
You have to create a NameValuePair for employee_name, one for phone ... each of which is fetched from a HTML element name employee_name, phone ... This is where you put the values from your EditTexts.
It returns a JSON formatted String, which you have to parse (typically using JSONObject obj = new JSONObject(result); once you have fetched the result from the server)
In this JSON object, you have a key named success, which format is not specified, except you can assume things went well if it is present ; a key mid, and a key message.
I need some text data (street names of a 2 million town) to get into my android application. I think the best way to do this is to store it into a sqlite database read-only when it starts the first time. As I read, doing this with a pre-defined database is pretty tedious and not clean but you have to copy it from external storage or something and have the data twice then. So I thought about using a CSV file from raw resources and delete it after import, but this is not possible too because this data will be built into the sdk file and can't be deleted any more.
My target is it to make some kind of initial data transfer from local and delete this data source. Any ideas how to achieve that properly? I'd like to go without downloading the data from a server because this would mean that the only reason my application needs an internet connection is because of downloading the initial data. Otherwise it wouldn't need an internet connection.
What about putting the .csv file in you asset folder and read it.
String next[] = {};
List<String[]> list = new ArrayList<String[]>();
try {
CSVReader reader = new CSVReader(new InputStreamReader(getAssets().open("test.csv")));
for(;;) {
next = reader.readNext();
if(next != null) {
list.add(next);
} else {
break;
}
}
} catch (IOException e) {
e.printStackTrace();
}
I'm thinking I'd compress the data in the initial installation resource and expand it on install. This answer sees to reference a 7zip open source java api.
Data compression on Android (other than java.util.zip ?)
Meanwhile I know that the data I will use in my app is too complex to populate the data by hand. Moreover the app needs internet access at any rate, so I will use a Json string to get the data.
If you check my previous questions, you will see that they are all in some way related to "\" or "/" for Android and why my implementations of code wasn't working when other people's versions were.
I now know why mine wasn't working.
I am developing for a live client who has access to a content management system, from which I am getting the data. Other than the general checks, they can post anything they want to the site.
They are posting sizes in inches; e.g. 5-1/2
It is this, and this alone, which is screwing up my Restful json.
For example, 1 eigth has become
1\\\/8
Currently, I am doing a string rewrite at the WCF point to catch these 'fractions' and turn them into decimal just so I can continue development. But I can't code for every eventuality and Android/Eclipse fails at JSONArray json=new JSONArray(result);
Would appreciate any input on this.
Dave
On reflection, and further investigation, it isn't the escaped fractions causing the problem.
It is something more fundamental.
Will close the question.
I have searched high and wide for an answer to this, and have finally found it.
I will share for anyone else experiencing the same issue:
It is the WCF Rest service.
Learning WCF and Android at the same time led me to believe that the response from WCF should be a String serialized in the Json format.
To do this, a .Net object, array or whatever would go through DataContractJsonSerializer before being returned as a String to Android for further parsing.
Something like this:
Dim stream1 As MemoryStream = New MemoryStream
Dim ser As DataContractJsonSerializer = New DataContractJsonSerializer(GetType(myType))
ser.WriteObject(stream1, myThing)
Dim _json As String = Encoding.UTF8.GetString(stream1.ToArray())
stream1.Close()
return _json
Wrong.
Keep your object, array or whatever and return that instead; WCF will take care of the proper escaping for you.
For example (this is VB);
IService:
<OperationContract()> _
<WebGet(BodyStyle:=WebMessageBodyStyle.WrappedRequest, RequestFormat:=WebMessageFormat.Json, ResponseFormat:=WebMessageFormat.Json, UriTemplate:="/MyKit/{AccountID}")> _
Function GetKit(ByVal AccountID As String) As MyKit
Service:
Public Function GetKit(ByVal AccountID As String) As MyKit Implements IService1.GetKit
Dim allKit As New MyKit() //Your object
objDal.CommandText = 'run some sql here - or whatever
Using dr As SqlDataReader = "blah"
//populate your object
End Using
Return allKit //return the object, not the string representation of it
End Function
Using DataContractJsonSerializer for sending as Json to Android from WCF effectively 'pre-escapes' the data. When it gets to Android, the Json parser is unable to handle it, because it also escapes the data.
I want to know a good way to create a list in my android app. I have all info in my DB and want to load data from it each time I start the app and make a list from it (id and title).
What is the best approach?
Should I make a PHP-script that responds with a JSON encoded array with all list items or should I make an XML-file that generates each time the data in the DB changes that I import to the app each time it starts? or any other good way to do it?
Since all stuff are made by XML-files in android it feels like importing a XML would be a good thing, is it? And how do I import an XML-file from a web server into the app?
// Daniel
You can use either JSON or XML.
You can use the web service approach or you can include your db with your application.
In fact, I most often choose to create a sqlite3 database of my data and include it in the assets folder, which can be copied to the app's data folder on startup.
As for copying your sqlite3 database from assets/ to the db data directory, I found these instructions helpful.
In your situation I would pick JSON over XML for all the reason's stated in the following post: http://ajaxian.com/archives/json-vs-xml-the-debate
Plus, in android, there are JSON Array's built in by default so you don't have to do any extra passing of the code.
return new JSONArray("my json string goes here...");
Since we are talking about a mobile device, I would always generate changes in your php script rather than have a full sync as this will be a lot smaller in size that a full sync. However, you will need to give your user a option to do a full re-sync if this is applicable to your app. I would use a SQLite database to store the data and only update the changes in that.
To also make the stream smaller, you can gzip compress your output from php as this can be natively read by the android device. In my app, I compress 500kb down to ~110kb before transmitting, a huge saving on performance. Here a partial example of how to read the stream:
InputStream in = null;
HttpURLConnection httpConn = null; // you will have to write your on code for this bit.
if (httpConn.getContentEncoding() != null)
{
String contentEncoding = httpConn.getContentEncoding().toString();
if (contentEncoding.contains("gzip"))
{
in = new GZIPInputStream(httpConn.getInputStream());
}
}
else
{
in = httpConn.getInputStream();
}
I hope that this all makes sense, it's been a long day programming :)
Stu