Develop Reference

What is the correct way to write a response body in Android?

I am using the following function to make a POST request in kotlin.
fun makeRequest(url: String, body: String): String{
var builder = StringBuilder()
val connection = URL(url).openConnection() as HttpURLConnection
connection.setDoOutput(true)
connection.setChunkedStreamingMode(0)
connection.requestMethod = "POST"
connection.setRequestProperty("Content-Type", "application/json; charset=utf-8")
val jsonbody = Gson().toJson(body)
val wr = OutputStreamWriter(connection.outputStream, "utf-8")
wr.write(jsonbody)
wr.flush()
try{
var data: Int = connection.inputStream.read()
while (data != -1) {
builder.append(data.toChar())
data = connection.inputStream.read()
}
}catch(e: Exception){
builder = StringBuilder()
builder.append(connection.responseMessage)
}finally {
wr.close()
connection.disconnect()
}
return builder.toString()
}
and inside my fragment, I have a button onClickListener as follows:
signInButton.setOnClickListener {
val acc = userAccountTextField.text.toString()
val pw = userPasswordTextField.text.toString()
val body = """{"username":$acc,"password":$pw}"""
CoroutineScope(Dispatchers.IO).launch{
val output = makeRequest( getString(R.string.url)+"user/login" , body)
Snackbar.make( view , output, Snackbar.LENGTH_SHORT).show()
}
}
I am able to make request to my localhost, however, it does not detect request body and returns 400 error. What is the proper way to write a response body? Is the issue with the string i pass to the method, or the outputstreamwriter?
I also found this error on my sailsjs project, so I am assuming that theres something wrong with the way I am writing the json?
error: Unable to parse HTTP body- error occurred :: 'SyntaxError: Unexpected token # in JSON at position 0\n' +
' at JSON.parse (<anonymous>)\n' +
' at createStrictSyntaxError
ngrok

How to store the return value of suspended function to a variable?

I'm trying to understand Kotlin couroutine. So here's my code (based on this tutorial). To keep the code relatively simple, I deliberately avoid MVVM, LiveData, etc. Just Kotlin couroutine and Retrofit.
Consider this login process.
ApiInterface.kt
interface ApiInterface {
// Login
#POST("/user/validate")
suspend fun login(#Body requestBody: RequestBody): Response<ResponseBody>
}
ApiUtil.kt
class ApiUtil {
companion object {
var API_BASE_URL = "https://localhost:8100/testApi"
fun getInterceptor() : OkHttpClient {
val logging = HttpLoggingInterceptor()
logging.level = HttpLoggingInterceptor.Level.BODY
val okHttpClient = OkHttpClient.Builder()
.addInterceptor(logging)
.build()
return okHttpClient
}
fun createService() : ApiInterface {
val retrofit = Retrofit.Builder()
.client(getInterceptor())
.addConverterFactory(GsonConverterFactory.create())
.baseUrl(OJIRE_BASE_URL)
.build()
return retrofit.create(ApiInterface::class.java)
}
}
fun login(userParam: UserParam): String {
val gson = Gson()
val json = gson.toJson(userParam)
var resp = ""
val requestBody = json.toString().toRequestBody("application/json".toMediaTypeOrNull())
CoroutineScope(Dispatchers.IO).launch {
val response = createService().login(requestBody)
withContext(Dispatchers.Main){
if (response.isSuccessful){
val gson = GsonBuilder().setPrettyPrinting().create()
val prettyJson = gson.toJson(
JsonParser.parseString(
response.body()
?.string()
)
)
resp = prettyJson
Log.d("Pretty Printed JSON :", prettyJson)
}
else {
Log.e("RETROFIT_ERROR", response.code().toString())
}
}
}
return resp
}
}
LoginActivity.kt
class LoginActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
edtUsername = findViewById(R.id.edtUsername)
edtPassword = findViewById(R.id.edtPassword)
btnLogin = findViewById(R.id.btnLogin)
btnLogin.setOnClickListener {
val api = ApiUtil()
val userParam = UserParam(edtMobileNo.text.toString(), edtPassword.text.toString())
val response = JSONObject(api.login(userParam))
var msg = ""
if (response.getString("message").equals("OK")){
msg = "Login OK"
}
else {
msg = "Login failed"
}
Toast.makeText(applicationContext, msg, Toast.LENGTH_SHORT).show()
}
}
}
When debugging the login activity, the API response is captured properly on prettyJson
The problem is resp is still empty. Guess that's how async process work. What I want is to wait until the API call is completed, then the result can be nicely passed to resp as the return value of login(). How to do that?

Well, you got several things wrong here. We'll try to fix them all.
First, the main problem you described is that you need to acquire resp in login() synchronously. You got this problem only because you first launched an asynchronous operation there. Solution? Don't do that, get the response synchronously by removing launch(). I guess withContext() is also not required as we don't do anything that requires the main thread. After removing them the code becomes much simpler and fully synchronous.
Last thing that we need to do with login() is to make it suspendable. It needs to wait for the request to finish, so it is a suspend function. The resulting login() should be similar to:
suspend fun login(userParam: UserParam): String {
val gson = Gson()
val json = gson.toJson(userParam)
val requestBody = json.toString().toRequestBody("application/json".toMediaTypeOrNull())
val response = createService().login(requestBody)
return if (response.isSuccessful){
val gson = GsonBuilder().setPrettyPrinting().create()
gson.toJson(
JsonParser.parseString(
response.body()
?.string()
)
)
}
else {
Log.e("RETROFIT_ERROR", response.code().toString())
// We need to do something here
}
}
Now, as we converted login() to suspendable, we can't invoke it from the listener directly. Here we really need to launch asynchronous operation, but we won't use CoroutineScope() as you did in your example, because it leaked background tasks and memory. We will use lifecycleScope like this:
btnLogin.setOnClickListener {
val api = ApiUtil()
val userParam = UserParam(edtMobileNo.text.toString(), edtPassword.text.toString())
lifecycleScope.launch {
val response = JSONObject(api.login(userParam))
var msg = ""
if (response.getString("message").equals("OK")){
msg = "Login OK"
}
else {
msg = "Login failed"
}
withContext(Dispatchers.Main) {
Toast.makeText(applicationContext, msg, Toast.LENGTH_SHORT).show()
}
}
}
Above code may not be fully functional. It is hard to provide working examples without all required data structures, etc. But I hope you get the point.
Also, there are several other things in your code that could be improved, but I didn't touch them to not confuse you.

How to call filtered twitter STREAM API in android?

I want to stream twitter tweets continuously with twitter stream api with retrofit and without any 3rd party libraries. When i try to call the api " https://api.twitter.com/2/tweets/search/stream " I'm only getting the result first time. How to stream it?

I have finally achieved it using this snippet
override suspend fun streamTweets(): Flow<Resource<TweetResponseModel>> {
return flow {
val client: OkHttpClient = OkHttpClient().newBuilder().addInterceptor(
BasicAuthInterceptor(getAPIKey(), getAPISecretKey())
).build()
val request: Request = Request.Builder()
.url(TWITTER_STREAM_URL)
.method("GET", null)
.build()
val response: okhttp3.Response = client.newCall(request).execute()
val source = response.body?.source()
val buffer = Buffer()
while (!source!!.exhausted()) {
response.body?.source()?.read(buffer, 8192)
val data = buffer.readString(Charset.defaultCharset())
try {
val tweetResponseModel: TweetResponseModel =
Gson().fromJson(data, TweetResponseModel::class.java)
emit(Resource.Success(tweetResponseModel))
} catch (e: Exception) {
Log.e("jsonException", data)
}
}
}.flowOn(ioDispatcher)
}

Change DNS on all requests

I need to change DNS on all Android requests. How to get it done?
I found this:
class HTTPDNSInterceptor : Interceptor {
override fun intercept(chain: Interceptor.Chain): Response {
val originRequest = chain.request()
val httpUrl = originRequest.url()
val url = httpUrl.toString()
val host = httpUrl.host()
val hostIP = HttpDNS.getIpByHost(host)
val builder = originRequest.newBuilder()
if (hostIP != null) {
builder.url(HttpDNS.getIpUrl(url, host, hostIP))
builder.header("host", hostIP)
}
val newRequest = builder.build()
val newResponse = chain.proceed(newRequest)
return newResponse
}
}
But, I don't have all the helper classes and I have not found any library where I can explicitly set certain DNS. Even if there is a way to dynamically check valid DNS and setting any working, would be great too.

Android with Kotlin - How to use HttpUrlConnection

I´m trying to get data from a url inside an AsyncTask but I get an error when creating a new instance of HttpUrlConnection.
Something like this on Java
URL url = new URL("http://www.android.com/");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
try {
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
readStream(in);
finally {
urlConnection.disconnect();
}
But I keep getting the error shown below.
class GetWeatherTask : AsyncTast<Void, Void, Void>() {
override fun doInBackground(vararg params: Void?): Void? {
val httpClient = HttpURLConnection();
return null
}
override fun onPreExecute() {
super.onPreExecute()
}
override fun onPostExecute(result: Void?) {
super.onPostExecute(result)
}
}
Cannot access '': it is 'protected/protected and package/' in 'HttpURLConnection' Cannot create an instance of an abstract class
Am I missing something? I tryied to create a class object extending HttpUrlConnection and try to implement the init method but I couldn't
Thanks in advance.

Here is a simplification of the question and answer.
Why does this fail?
val connection = HttpURLConnection()
val data = connection.inputStream.bufferedReader().readText()
// ... do something with "data"
with error:
Kotlin: Cannot access '': it is 'protected/protected and package/' in 'HttpURLConnection'
This fails because you are constructing a class that is not intended to directly be constructed. It is meant to be created by a factory, which is in the URL class openConnection() method. This is also not a direct port of the sample Java code in the original question.
The most idiomatic way in Kotlin to open this connection and read the contents as a string would be:
val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
val data = connection.inputStream.bufferedReader().readText()
This form will auto close everything when done reading the text or on an exception. If you want to do custom reading:
val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
connection.inputStream.bufferedReader().use { reader ->
// ... do something with the reader
}
NOTE: the use() extension function will open and close the reader and handle closing on errors automatically.
About the disconnect() method
The docs for disconnect say:
Each HttpURLConnection instance is used to make a single request
but the underlying network connection to the HTTP server may be
transparently shared by other instances. Calling the close() methods
on the InputStream or OutputStream of an HttpURLConnection
after a request may free network resources associated with this
instance but has no effect on any shared persistent connection.
Calling the disconnect() method may close the underlying socket
if a persistent connection is otherwise idle at that time.
So you decide if you want to call it or not. Here is a version of the code that calls disconnect:
val connection = URL("http://www.android.com/").openConnection() as HttpURLConnection
try {
val data = connection.inputStream.bufferedReader().use { it.readText() }
// ... do something with "data"
} finally {
connection.disconnect()
}

The simplest way to do a get post request using HTTPUrlConnection is to create a common helper class that can be called from anywhere in the app to call the GET and POST request methods, without writing the same code again and again.
Below is the helper object (Singleton) class that you can use for the network call for GET and POST requests.
package com.dewari.ajay.androidnetworkcommunication.network
import org.json.JSONObject
import java.io.BufferedReader
import java.io.BufferedWriter
import java.io.IOException
import java.io.InputStreamReader
import java.io.OutputStream
import java.io.OutputStreamWriter
import java.net.HttpURLConnection
import java.net.URL
import java.net.URLEncoder
import javax.net.ssl.HttpsURLConnection
object RequestHandler {
const val GET : String = "GET"
const val POST : String = "POST"
#Throws(IOException::class)
fun requestPOST(r_url: String?, postDataParams: JSONObject): String? {
val url = URL(r_url)
val conn: HttpURLConnection = url.openConnection() as HttpURLConnection
conn.readTimeout = 3000
conn.connectTimeout = 3000
conn.requestMethod = POST
conn.doInput = true
conn.doOutput = true
val os: OutputStream = conn.outputStream
val writer = BufferedWriter(OutputStreamWriter(os, "UTF-8"))
writer.write(encodeParams(postDataParams))
writer.flush()
writer.close()
os.close()
val responseCode: Int = conn.responseCode // To Check for 200
if (responseCode == HttpsURLConnection.HTTP_OK) {
val `in` = BufferedReader(InputStreamReader(conn.inputStream))
val sb = StringBuffer("")
var line: String? = ""
while (`in`.readLine().also { line = it } != null) {
sb.append(line)
break
}
`in`.close()
return sb.toString()
}
return null
}
#Throws(IOException::class)
fun requestGET(url: String?): String? {
val obj = URL(url)
val con = obj.openConnection() as HttpURLConnection
con.requestMethod = GET
val responseCode = con.responseCode
println("Response Code :: $responseCode")
return if (responseCode == HttpURLConnection.HTTP_OK) { // connection ok
val `in` =
BufferedReader(InputStreamReader(con.inputStream))
var inputLine: String?
val response = StringBuffer()
while (`in`.readLine().also { inputLine = it } != null) {
response.append(inputLine)
}
`in`.close()
response.toString()
} else {
""
}
}
#Throws(IOException::class)
private fun encodeParams(params: JSONObject): String? {
val result = StringBuilder()
var first = true
val itr = params.keys()
while (itr.hasNext()) {
val key = itr.next()
val value = params[key]
if (first) first = false else result.append("&")
result.append(URLEncoder.encode(key, "UTF-8"))
result.append("=")
result.append(URLEncoder.encode(value.toString(), "UTF-8"))
}
return result.toString()
}
}
Using the above object class you can do your GET and POST requests as shown below:
//As this is network call it should be done in a separate thread
Thread(Runnable {
RequestHandler.requestGET(url)
RequestHandler.requestPOST(url, postJSONObject)
}).start()
Instead of using thread you can also use AsyncTask as followed:
class NetworkAsyncCall(private val context: Context, private val url: String, private val requestType:
String, private val postJSONObject: JSONObject = JSONObject()
) : AsyncTask<String?, String?, String?>() {
override fun doInBackground(vararg p0: String?): String? {
return when (requestType) {
RequestHandler.GET -> RequestHandler.requestGET(url)
RequestHandler.GET -> RequestHandler.requestPOST(url, postJSONObject)
else -> ""
}
}
override fun onPostExecute(s: String?) {
if (s != null) {
Toast.makeText(context, s, Toast.LENGTH_LONG).show()
}
}
}
You can create the asyncTask as a inner class of Activity or a seperate indipendent class.
Now to call the newtwork call via the AsyncTask NetworkAsyncCall in your onCreate() or any function from which you want call the api you can write:
NOTE: The mentioned url will not work so, you have to replace it with your own.
override fun onCreate(savedInstanceState: Bundle?) {
setContentView(R.layout.activity_main)
// Change the url with your own GET URL request
val urlGET = "http://my-json-feed"
//GET Request
NetworkAsyncCall(this#MainActivity, urlGET, RequestHandler.GET).execute();
// POST Request
// doPost()
}
For POST request you can call:
private fun doPost() {
// Change the url with your own POST URL request
val urlPOST = "http://my-json-feed"
val postDataParams = JSONObject()
postDataParams.put("name", "Ajay")
postDataParams.put("email", "aj****ri#gmail.com")
postDataParams.put("phone", "+91 78******25")
NetworkAsyncCall(this#MainActivity, urlPOST, RequestHandler.POST, postDataParams).execute()
}
you can check the complete code in github here.
For a good explanation you can check this link.
the advantage of using the NetworkAsyncCall as seperate indipendent class is you don't have to write the AsyncTask code again, just call the same AsyncTask NetworkAsyncCall with a new object from different activitys/functions, however with this you have to implement a listener interface that you will require for the callback on onPostExecute() after getting the response from the api and to return back the response to the activity you have to perform the callback using that interface.

You can adaptaion your code; Don't forget user Runnable thread.
Thread(Runnable {
try {
val url = URL("www.android.com")
val con = url.openConnection() as HttpURLConnection
val datas = con.inputStream.bufferedReader().readText()
val json = JSONObject(datas)
val blockList = json.getJSONObject("blockList")
val warning = json.get("warnMessage").toString()
val keys = blockList.keys()
var permission = HashMap<String, Array<String?>>()
while (keys.hasNext()) {
val key = keys.next()
val kods = blockList.getJSONArray(key)
val permissonArray = arrayOfNulls<String>(kods.length())
for (i in permissonArray.indices) {
permissonArray[i] = kods.getString(i)
}
permission[key] = permissonArray;
}
} catch (ex: Exception) {
Log.d("Exception", ex.toString())
}
}).start()