Develop Reference

With Android you can transfer data to any site's form and trigger the send button

hello any site you want to log in form with an Android app in the background. How I can do this process, but I did not find a result if you can help me, thank you in advance.
more examples
Any educational institution has a student add form. I want to send my student information from my own database to this form

You can create AsyncTask class to submit the form data to the URL either using POST or GET.
for example:
`
class NetworkActivity extends AsyncTask<String,Void,String>{
#Override
protected String doInBackground(String.. params)
{
try{
Url url = new URL("Your URL Here");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.requestMethod("POST");
connection.setInstanceFollowRedirects(false);
connection.setDoOutput(true);
OutputStream os = connection.getOutputStream();
os.write("Form data here"+params[0]); // write form data here e.g. studentname=XYZ&rollno=123
InputStream is = connection.getInputStream();
BuffredReader br = new BufferedReader(new InputStreamReader(is));
//Fetch the output into a String
StringBuilder output = new StringBuilder();
while((line=br.readLine())!=null)
{
output.append(line);
}
return output.toString();
}
catch(Exception e)
{
e.printStackTrace();
return null;
}
}
protected OnPostExecute(String result)
{
//Process the output here.
}
}
`
Now create a new object of this class and call the execute function the initiate the Network activity.
new NetworkActivity().execute("form data");

asynctask setRequestMethod to post not working

I am trying to make a POST request in an AsyncTask, but the request method stays as GET all the time.
I have this issue since I moved the HTTP request to AsyncTask, the same code worked before, when it was in the UI thread.
The doInBackground code is below:
protected String doInBackground(String... string) {
httpPostToArduino (string[0]);
return null;
}
#Override
protected void onPreExecute() {
super.onPreExecute ();
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute (s);
}
public void httpPostToArduino(String message){
curArd1UrlString="http://myprivateurl.com";
URL url = null;
try {
url = new URL (curArd1UrlString);
} catch (MalformedURLException e) {
e.printStackTrace ();
}
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
StringBuilder result = new StringBuilder (); //test
try {
urlConnection = (HttpURLConnection) url.openConnection ();
//Set header content
urlConnection.setRequestMethod("POST");
urlConnection.setRequestProperty("Authorization","password");
urlConnection.setDoOutput(true);
//Set body content
OutputStreamWriter os = new OutputStreamWriter (urlConnection.getOutputStream());
os.write(message.toString ());
os.flush();
InputStream in = new BufferedInputStream (urlConnection.getInputStream ());
reader = new BufferedReader (new InputStreamReader (in));
//Read the first line of the response - just the JSON
result.append (reader.readLine ());
//The below WHILE reads all the content of the response message, but we only need the first line
String ReceivedJSON = result.toString ();
JSONObject parentObject = new JSONObject (ReceivedJSON);
In the debugger, under urlConnection, for method field, it is always GET. Below a snip from debugger mode, to be clearer.
I get a response after each request, but the response depends on the body content of the POST request.
What should I change in the code in order to change the request method to POST?

I had the same Problem, for me it happened, because I did not specify the full URL path.
There are two ways to fix this. The first way is to specify the full url (with file.php at the end) and the second way is to rewrite the url in the web server config.
I fixed it by rewriting the url in my web server. This is for nginx.
This adds .php to the end of the requested URL.
location /api {
rewrite ^(/api/.*)/(\w+) $1/$2.php last;
}
For example you have the Url http://example.com/api/v1/file . After specifying the rewrite this url will be rewritten to http://www.example.com/api/v1/file.php

Best way to request data from server

I need to fetch some data from my server in order to make my app work. In order to do that, I will be using POST. As far as I know, I have to request that data in a thread which can not be the main thread. I am finding it a little bit difficult to put the data I am receiving in a variable defined in the UI thread. So, my question is, which is the best way to do it?
Is it correct to set the value of a variable defined, for example, in my main activity, with a setter called inside an AsyncTask? Or is there a better option than this?
Thread nt = new Thread(){
#Override
public void run(){
try{
//get data with POST and then something like main.setValue(data);
}catch(Exception e){
e.printStackTrace();
}
}
};
nt.start();
I have read that I may use Interfaces in order to archive that, but it is a concept that I do not understand very well yet. I would like to directly use a method which returns the data, but as far as I know, it is not possible.
EDIT: new code according to NoChinDeluxe answer:
public class LoginHandler {
public static class Login extends AsyncTask<String, String, Integer> {
LoginCallback listener;
#Override
protected Integer doInBackground(String... params) {
URL url;
postDataParams.put("name", params[0]);
HashMap<String, String> postDataParams = new HashMap<String, String>();
postDataParams.put("password", params[1]);
try {
url = new URL("http://mashiron.xyz/_03z/gmpia/proc.php");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(15000);
conn.setConnectTimeout(15000);
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
writer.write(HttpHandler.getPostDataString(postDataParams));
writer.flush();
writer.close();
os.close();
System.out.println("Respuesta: "+conn.getResponseCode());
return conn.getResponseCode();
} catch (Exception e) {
e.printStackTrace();
return 404;
}
}
protected void onPostExecute(int result){
System.out.println("Respuesta 2: "+result);
listener.onResultReceived(result);
}
}
public interface LoginCallback {
void onResultReceived(int result);
}
}
EDIT: added exception for NoChinDeluxe:
03-24 17:38:09.072 13312-13312/com.pitazzo.geomoments E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.pitazzo.geomoments, PID: 13312
java.lang.NullPointerException: Attempt to invoke interface method 'void com.pitazzo.geomoments.Handlers.LoginHandler$LoginCallback.onResultReceived(int)' on a null object reference
at com.pitazzo.geomoments.Handlers.LoginHandler$Login.onPostExecute(LoginHandler.java:65)
at com.pitazzo.geomoments.Handlers.LoginHandler$Login.onPostExecute(LoginHandler.java:17)
at android.os.AsyncTask.finish(AsyncTask.java:636)
at android.os.AsyncTask.access$500(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5300)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
EDIT: more code for NoChainDeluxe
public class LoginActivity extends AppCompatActivity implements LoginHandler.LoginCallback{
EditText name;
EditText password;
Button login;
int code;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login_activity);
/*
if(logueado){
}
*/
name = (EditText) findViewById(R.id.loginuser);
password = (EditText) findViewById(R.id.loginpassword);
login = (Button) findViewById(R.id.loginlogin);
login.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String params[] = {name.getText().toString(), password.getText().toString()};
System.out.println("Params: "+params.toString());
new LoginHandler.Login().execute(params);
System.out.println("Respuesta 4: "+code);
if(code == 200){
Toast toast1 =
Toast.makeText(getApplicationContext(),
"Iniciado sesión", Toast.LENGTH_SHORT);
toast1.show();
}else{
Toast toast1 =
Toast.makeText(getApplicationContext(),
"Nombre de usuario y/o contraseña incorrectos: "+code, Toast.LENGTH_SHORT);
toast1.show();
}
}
});
}
public void onResultReceived(int resultado) {
code = resultado;
System.out.println("Respuesta 3: "+code);
}
}

The best way to achieve this is to use an HttpURLConnection to make your web calls inside an AsyncTask and then pass the result back to your calling Activity through a callback. Here's some code to help you get started:
The first thing you should understand is how to properly use a callback with an AsyncTask. Here is an example AsyncTask that defines a callback interface:
import android.os.AsyncTask;
public class TestTask extends AsyncTask<String, Void, String> {
TestTaskCallback listener;
public TestTask(TestTaskCallback listener) {
this.listener = listener;
}
protected String doInBackground(String... args) {
String input = args[0];
String output = "simulated return value";
return output;
}
protected void onPostExecute(String result) {
listener.onResultReceived(result);
}
public interface TestTaskCallback {
void onResultReceived(String result);
}
}
The way this works is, you define a public interface that you then implement in your Activity. This acts as a "listener" that is waiting for any data that is sent through to it. We define the interface TestTaskCallback because we are going to be sending our data from our AsyncTask to our calling Activity.
Then in the Activity, we need to implement this interface, and pass in a reference to our implementation to the task when we create it. That way, when the task fires, it knows where to send the result, which is back to our Activity. An example implementation might look like this:
public class TestActivity extends AppCompatActivity implements TestTask.TestTaskCallback {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);
new TestTask(this).execute("Some input");
}
public void onResultReceived(String result) {
Log.d("TEST TASK RESULT", result);
}
}
So our Activity implements the interface that we defined inside our AsyncTask, and notice that our AsyncTask takes the reference to this implementation (passed in through the constructor) and sends data to it in the onPostExecute() method. This will allow your result to be sent to the main UI thread so that you can update your Activity appropriately.
The only thing left is to actually make the web calls. I would recommend using an HttpURLConnection for this. You would put this code inside the doInBackground() method of your AsyncTask.
I'll show you an example web service call I have set up. This shows how to make a web service call to retrieve a JSON response. It looks something like this:
//The JSON we will get back as a response from the server
JSONObject jsonResponse = null;
//Http connections and data streams
URL url;
HttpURLConnection httpURLConnection = null;
OutputStreamWriter outputStreamWriter = null;
try {
//open connection to the server
url = new URL("your_url_to_web_service");
httpURLConnection = (HttpURLConnection) url.openConnection();
//set request properties
httpURLConnection.setDoOutput(true); //defaults request method to POST
httpURLConnection.setDoInput(true); //allow input to this HttpURLConnection
httpURLConnection.setRequestProperty("Content-Type", "application/json"); //header params
httpURLConnection.setRequestProperty("Accept", "application/json"); //header params
httpURLConnection.setFixedLengthStreamingMode(jsonToSend.toString().getBytes().length); //header param "content-length"
//open output stream and POST our JSON data to server
outputStreamWriter = new OutputStreamWriter(httpURLConnection.getOutputStream());
outputStreamWriter.write(jsonToSend.toString());
outputStreamWriter.flush(); //flush the stream when we're finished writing to make sure all bytes get to their destination
//prepare input buffer and get the http response from server
StringBuilder stringBuilder = new StringBuilder();
int responseCode = httpURLConnection.getResponseCode();
//Check to make sure we got a valid status response from the server,
//then get the server JSON response if we did.
if(responseCode == HttpURLConnection.HTTP_OK) {
//read in each line of the response to the input buffer
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream(),"utf-8"));
String line;
while ((line = bufferedReader.readLine()) != null) {
stringBuilder.append(line).append("\n");
}
bufferedReader.close(); //close out the input stream
try {
//Copy the JSON response to a local JSONObject
jsonResponse = new JSONObject(stringBuilder.toString());
} catch (JSONException je) {
je.printStackTrace();
}
}
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
if(httpURLConnection != null) {
httpURLConnection.disconnect(); //close out our http connection
}
if(outputStreamWriter != null) {
try {
outputStreamWriter.close(); //close our output stream
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
//Return the JSON response from the server.
return jsonResponse;
This is pretty much all you need to know to do exactly what it is you are trying to do. I realize this is a ton of info to throw at you all at once, but if you take your time and work through it piece by piece, you'll find it's not too difficult after all and is actually a VERY powerful tool that you'll use all the time programming Android apps!
Hope this helps. Feel free to ask questions for any parts you don't fully understand yet!

Better use an AsyncTask to propagate the data to your UI thread, just use onPostExecute() to set the result on your activity's class.

The error you are getting is because of accessing UI elements from background thread.
AsyncTask is a Thread pool based api that runs your task in a seperate thread
,but your UI part runs in a thread usually called UI thread,
to update any changes to ui put the logic onPostExecute()
NOTE: Use okhttp to get consistent http api, it also supports http2.Their github wiki is very helpful, check here for examples.

How to Connect Android Device with web serve using AsyncTask

I have this asynctask.I need to connect device with web server.Need to send a JSON Arry and receive JSON array. Can i use httpUrlConnection ? or httpClient. Does httpClient support latest versions of Android?
class background_thread extends AsyncTask<JSONArray, Void, Boolean> {
protected Boolean doInBackground(JSONArray... params) {
//connect with server side php script
String UR = "127.0.0.1/abc/index.php";
try {
URL url = new URL(UR);
try {
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
json_array=json_encode();
conn.setDoOutput(true);
conn.setChunkedStreamingMode(0);
OutputStream out = new BufferedOutputStream(conn.getOutputStream());
writeStream(out);
} catch (IOException e) {
e.printStackTrace();
}
} catch (MalformedURLException e) {
e.printStackTrace();
}
return true;
}

You should use google's own volley library to make network calls and handle the response data in model classes. This is the most modular approach. Refer this link for official documentation.

Android HttpUrlConnection response object

Hey i'm using HttpUrlConnection in my app. And it's seems to me that every time when I'm making call as .getInputStream() or urlConnection.getResponseCode() etc it makes another request, so it is not good for me, when i'm making POST request. Is there a way to get some kind of response object which encapsulates response data and can be accessible from UI thread, something like this:
private class RegisterAsync extends AsyncTask<String, Void, HttpResponse> {
protected String doInBackground(String... strings) {
HttpURLConnection urlConnection = null;
String message = null;
try {
URL url = new URL(REGISTER_URL);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setChunkedStreamingMode(0);
OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
out.write(strings[0].getBytes("UTF-8"));
out.flush();
out.close();
HttpResponse response = urlConnection.getResponse();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
urlConnection.disconnect();
}
return Response;
}
protected void onPostExecute(HttpResponse response) {
//Do some with response object: get status, headers, content etc?
}
}

you can do the following steps:
Create the webservice call in a singleton class
Parse the response and encapsulate it in a custom object(made by you) and save the parsed object into the singleton as instance object.
After this, you can simply send a broadcast message to your activity to let it know that the parsed data is available in the singleton
the onReceive() method of BroadcastReceiver runs on UI thread so you can quickly update your UI there..
After you implement that you can simply call the singleton webservice call method from your activity right after you register to the intent that will be sent from the singleton...