Develop Reference

Integration of android app with backend

i am developing an android app which i have to integrate with backend(developed in java and spring). Which will be the best way to integrate either WebServices or through http(JSON)..?
Thanks in advance.

To get a JSON Response in Android/Java you need to do this:
Create a custom API Connector class
Declare a method that will return a JSON Array
Create a AsyncTask class (optional)
Decode JSONArray
1.
public class CustomAPIConnector {
public final String URL = "http://10.0.2.2/your-project-url/"; // 10.0.2.2 goes to computer localhost if you put localhost, it will go to the devices localhost which should not exist
2.
public JSONArray getUserInfo(String username, String password) {
HttpEntity httpEntity = null;
// Add your POST variables to receive on your backend
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("username",username));
nameValuePairs.add(new BasicNameValuePair("password",password));
try {
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(URL + "login.php"); // have split up URL and page so you can redirect to different links easier if the URL changes
httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse httpResponse = httpClient.execute(httpPost);
httpEntity = httpResponse.getEntity();
} catch (IOException e) {
e.printStackTrace();
}
JSONArray jsonArray = null;
if(httpEntity != null) {
try {
String entityResponse = EntityUtils.toString(httpEntity);
jsonArray = new JSONArray(entityResponse);
} catch (JSONException e) {
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
}
}
return jsonArray;
}
}
3.
private class AvailableUser extends AsyncTask<ApiConnector,Boolean,JSONArray> {
#Override
protected JSONArray doInBackground(ApiConnector... params) {
return params[0].availableUsername(etusername.getText().toString());
}
#Override
protected void onPostExecute(JSONArray jsonArray) {
checkAvailableUsername(jsonArray);
}
}
private class AvailableEmail extends AsyncTask<ApiConnector,Boolean,JSONArray> {
#Override
protected JSONArray doInBackground(ApiConnector... params) {
return params[0].availableEmail(etemail.getText().toString());
}
#Override
protected void onPostExecute(JSONArray jsonArray) {
checkAvailableEmail(jsonArray);
}
}
4.
private void checkAvailableEmail(JSONArray jsonArray) {
String s = "";
if(jsonArray != null) {
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject json = null;
try {
json = new JSONObject();
json = jsonArray.getJSONObject(i);
if(!json.getString("count").isEmpty()) {
if(json.getString("count").equalsIgnoreCase("0")) {
status.setText("");
passedemail = true;
return;
} else {
status.setText("Email Taken");
passedemail = false;
return;
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
} else {
status.setText("Failed - checkAvailableEmail");
}
}
Please note that this is actual code I have in one of my apps that registersa user, the getUserInfo gets all information from the user, and the Available email asynctask class is separate from the getUserInfo, it is the registering part, that checks if the email is available.
From here on, you can copy the code and change what you need to.

JSON as name says java script object notation would help you to exploit OOPS , POST/GET and js at backend .
I use JSON , its easy to code , parse and handle

How to parse or read json file from external storage on Android app

I currently implemented parsing json from a server (url). But I couldn't find a way to parse json from sdcard (/Download/example.json). Can someone help me to solve this issue/change this code?
I used asyncTask for this. sample tutorial or sample code is more appreciated. (sorry for my English.)
public class Main extends Activity {
private TextView shopsDisplay;
private static String searchURL = "http://example.com/sample.json";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.baby);
//reference throughout class
shopsDisplay = (TextView)findViewById(R.id.tweet_txt);
new GetShops().execute(searchURL);
}
private class GetShops extends AsyncTask<String, Void, String> {
/*
* Carry out fetching task in background
* - receives search URL via execute method
*/
#Override
protected String doInBackground(String... shopsURL) {
//start building result which will be json string
StringBuilder shopsFeedBuilder = new StringBuilder();
//should only be one URL, receives array
for (String searchURL : shopsURL) {
HttpClient shopsClient = new DefaultHttpClient();
try {
//pass search URL string to fetch
HttpGet shopsGet = new HttpGet(searchURL);
//execute request
HttpResponse shopsResponse = shopsClient.execute(shopsGet);
//check status, only proceed if ok
StatusLine searchStatus = shopsResponse.getStatusLine();
if (searchStatus.getStatusCode() == 200) {
//get the response
HttpEntity shopsEntity = shopsResponse.getEntity();
InputStream shopsContent = shopsEntity.getContent();
//process the results
InputStreamReader shopsInput = new InputStreamReader(shopsContent);
BufferedReader shopsReader = new BufferedReader(shopsInput);
String lineIn;
while ((lineIn = shopsReader.readLine()) != null) {
shopsFeedBuilder.append(lineIn);
}
}
else
shopsDisplay.setText("Whoops - something went wrong!");
}
catch(Exception e){
shopsDisplay.setText("Whoops - something went wrong!");
e.printStackTrace();
}
}
//return result string
return shopsFeedBuilder.toString();
}
/*
* Process result of search query
* - this receives JSON string representing shops with search term included
*/
protected void onPostExecute(String result) {
//start preparing result string for display
StringBuilder shopsResultBuilder = new StringBuilder();
try {
//get JSONObject from result
JSONObject resultObject = new JSONObject(result);
//get JSONArray contained within the JSONObject retrieved - "results"
JSONArray shopsArray = resultObject.getJSONArray("shops");
//loop through each item in the shops array
for (int t=0; t<shopsArray.length(); t++) {
//each item is a JSONObject
JSONObject shopsObject = shopsArray.getJSONObject(t);
//for if condition
String id = (String) shopsObject.get("id");
//get the name and description for each shops
if (id.equals("550")){
shopsResultBuilder.append(shopsObject.getString("name")+": ");
shopsResultBuilder.append(shopsObject.get("description")+"\n\n");
}
}
}
catch (Exception e) {
shopsDisplay.setText("Whoops - something went wrong!");
e.printStackTrace();
}
//check result exists
if(shopsResultBuilder.length()>0)
shopsDisplay.setText(shopsResultBuilder.toString());
else
shopsDisplay.setText("Sorry - no shops found for your search!");
}
}
}

For JSONObject, use standard Java file I/O to read the file into a String, then pass it to the JSONObject constructor.
If you have a large JSON file, though, you may wish to switch to some other JSON parser (e.g., JsonReader), which may give you different options (e.g., use a FileReader with JsonReader).

Multiple Async Tasks for post in same activity

i wrote those threads:
How to manage multiple Async Tasks efficiently in Android
Running multiple AsyncTasks at the same time -- not possible?
but didnt find answer for my question, maybe someone can help..
I have android app which makes Login POST and getting json response,
if the Json is OK i need to POST another data to get another response.
i have extends Async Class which doing the post to the URL:
public class AsyncHttpPost extends AsyncTask<String, String, String> {
private HashMap<String, String> mData = null;
public AsyncHttpPost(HashMap<String, String> data) {
mData = data;
}
#Override
protected String doInBackground(String... params) {
byte[] result = null;
String str = "";
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(params[0]);// in this case, params[0] is URL
try {
ArrayList<NameValuePair> nameValuePair = new ArrayList<NameValuePair>();
Iterator<String> it = mData.keySet().iterator();
while (it.hasNext()) {
String key = it.next();
nameValuePair.add(new BasicNameValuePair(key, mData.get(key)));
}
post.setEntity(new UrlEncodedFormEntity(nameValuePair, "UTF-8"));
HttpResponse response = client.execute(post);
StatusLine statusLine = response.getStatusLine();
if(statusLine.getStatusCode() == HttpURLConnection.HTTP_OK){
result = EntityUtils.toByteArray(response.getEntity());
str = new String(result, "UTF-8");
}
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
catch (Exception e) {
return null;
}
return str;
}
#Override
protected void onPostExecute(String result) {
try {
JSONArray Loginjson = new JSONArray(result);
strStt = Loginjson.getJSONObject(0).getJSONObject("fields").getString("status");
if (strStt.equals("ERR")) {
ErrorMsg("Authentication failed");
} else if (strStt.equals("OK")) {
ErrorMsg("Login OK!!!");
ClientPage();
} else {
ErrorMsg("Connection Error");
}
} catch (JSONException e) {
ErrorMsg("Connection Error");
}
}
}
Now - i need to get another POST if the status is Error. do i need to make another Async class? with the same all procedures ? the issue is only the onPostExecute part is different.. actually the "doInBackground" will be always the same..
any idea how can i easily do multiple posts in the same activity?

Firstly, since your doInBackground() code will always stay the same, I recommend you move it into a general utility class.
Beyond that, you can go one of two ways:
Create a new AsyncTask for each type of request that can call your utility class, and have its own onPostExecute()
Create one AsyncTask that has a flag in it, which can be checked in the onPostExecute() method to see what code needs to be executed there. You will have to pass the flag in in the constructor or as a parameter in execute.

You can use a parameter at AsyncHttpPost constructor/execute or global variable to indicate if it is first or second POST (by other words - a flag). Then just create and execute another instance of AsyncHttpPost in onPostExecute (only if parameter/variable is set as "first POST").

Code in FOR loop not executed

I have a ProgressDialog that retrieves in background data from database by executing php script.
I'm using gson Google library. php script is working well when executed from browser:
{"surveys":[{"id_survey":"1","question_survey":"Are you happy with the actual government?","answer_yes":"50","answer_no":"20"}],"success":1}
However, ProgressDialog background treatment is not working well:
#Override
protected Void doInBackground(Void... params) {
String url = "http://192.168.1.4/tn_surveys/get_all_surveys.php";
HttpGet getRequest = new HttpGet(url);
Log.d("GETREQUEST",getRequest.toString());
try {
DefaultHttpClient httpClient = new DefaultHttpClient();
Log.d("URL1",url);
HttpResponse getResponse = httpClient.execute(getRequest);
Log.d("GETRESPONSE",getResponse.toString());
final int statusCode = getResponse.getStatusLine().getStatusCode();
Log.d("STATUSCODE",Integer.toString(statusCode));
Log.d("HTTPSTATUSOK",Integer.toString(HttpStatus.SC_OK));
if (statusCode != HttpStatus.SC_OK) {
Log.w(getClass().getSimpleName(), "Error " + statusCode + " for URL " + url);
return null;
}
HttpEntity getResponseEntity = getResponse.getEntity();
Log.d("RESPONSEENTITY",getResponseEntity.toString());
InputStream httpResponseStream = getResponseEntity.getContent();
Log.d("HTTPRESPONSESTREAM",httpResponseStream.toString());
Reader inputStreamReader = new InputStreamReader(httpResponseStream);
Gson gson = new Gson();
this.response = gson.fromJson(inputStreamReader, Response.class);
}
catch (IOException e) {
getRequest.abort();
Log.w(getClass().getSimpleName(), "Error for URL " + url, e);
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
Log.d("HELLO","HELLO");
StringBuilder builder = new StringBuilder();
Log.d("STRINGBUILDER","STRINGBUILDER");
for (Survey survey : this.response.data) {
String x= survey.getQuestion_survey();
Log.d("QUESTION",x);
builder.append(String.format("<br>ID Survey: <b>%s</b><br> <br>Question: <b>%s</b><br> <br>Answer YES: <b>%s</b><br> <br>Answer NO: <b>%s</b><br><br><br>", survey.getId_survey(), survey.getQuestion_survey(),survey.getAnswer_yes(),survey.getAnswer_no()));
}
Log.d("OUT FOR","OUT");
capitalTextView.setText(Html.fromHtml(builder.toString()));
progressDialog.cancel();
}
HELLO Log is displayed.
STRINGBUILDER Log is displayed.
QUESTION Log is NOT displayed.
OUT FOR Log is displayed.
Survey Class:
public class Survey {
int id_survey;
String question_survey;
int answer_yes;
int answer_no;
public Survey() {
this.id_survey = 0;
this.question_survey = "";
this.answer_yes=0;
this.answer_no=0;
}
public int getId_survey() {
return id_survey;
}
public String getQuestion_survey() {
return question_survey;
}
public int getAnswer_yes() {
return answer_yes;
}
public int getAnswer_no() {
return answer_no;
}
}
Response Class:
public class Response {
ArrayList<Survey> data;
public Response() {
data = new ArrayList<Survey>();
}
}
Any help please concerning WHY the FOR loop is not executed.
Thank you for helping.

Any help please concerning WHY the FOR loop is not executed.
Simply put: data is empty. (So there is nothing for the loop to iterate over...)
Try something like this, from GSON's documentation:
Type listType = new TypeToken<List<String>>() {}.getType();
List<String> target = new LinkedList<String>();
target.add("blah");
Gson gson = new Gson();
String json = gson.toJson(target, listType);
List<String> target2 = gson.fromJson(json, listType);
I haven't used GSON myself, but there are other examples of how to read lists:
Android gson deserialization into list
GSON : custom object deserialization

Your onPostExecute takes in a parameter called result. Your for loop iterates over the elements in an instance variable called response. Are they supposed to be the same?

android http post asynctask

Please can anyone tell me how to make an http post to work in the background with AsyncTask and how to pass the parameters to the AsyncTask? All the examples that I found were not clear enough for me and they were about downloading a file.
I'm running this code in my main activity and my problem is when the code sends the info to the server the app slows down as if it is frozen for 2 to 3 sec's then it continues to work fine until the next send. This http post sends four variables to the server (book, libadd, and time) the fourth is fixed (name)
Thanks in advance
public void SticketFunction(double book, double libadd, long time){
Log.v("log_tag", "%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% SticketFunction()");
//HttpClient
HttpClient nnSticket = new DefaultHttpClient();
//Response handler
ResponseHandler<String> res = new BasicResponseHandler();
HttpPost postMethod = new HttpPost("http://www.books-something.com");
try {
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(5);
nameValuePairs.add(new BasicNameValuePair("book", book+""));
nameValuePairs.add(new BasicNameValuePair("libAss", libass+""));
nameValuePairs.add(new BasicNameValuePair("Time", time+""));
nameValuePairs.add(new BasicNameValuePair("name", "jack"));
//Encode and set entity
postMethod.setEntity(new UrlEncodedFormEntity(nameValuePairs, HTTP.UTF_8));
//Execute
//manSticket.execute(postMethod);
String response =Sticket.execute(postMethod, res).replaceAll("<(.|\n)*?>","");
if (response.equals("Done")){
//Log.v("log_tag", "!!!!!!!!!!!!!!!!!! SticketFunction got a DONE!");
}
else Log.v("log_tag", "!!!!!!!?????????? SticketFunction Bad or no response: " + response);
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
//Log.v("log_tag", "???????????????????? SticketFunction Client Exception");
} catch (IOException e) {
// TODO Auto-generated catch block
//Log.v("log_tag", "???????????????????? IO Exception");
}
}
}

At first,
You put a class like following:
public class AsyncHttpPost extends AsyncTask<String, String, String> {
interface Listener {
void onResult(String result);
}
private Listener mListener;
private HashMap<String, String> mData = null;// post data
/**
* constructor
*/
public AsyncHttpPost(HashMap<String, String> data) {
mData = data;
}
public void setListener(Listener listener) {
mListener = listener;
}
/**
* background
*/
#Override
protected String doInBackground(String... params) {
byte[] result = null;
String str = "";
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(params[0]);// in this case, params[0] is URL
try {
// set up post data
ArrayList<NameValuePair> nameValuePair = new ArrayList<NameValuePair>();
Iterator<String> it = mData.keySet().iterator();
while (it.hasNext()) {
String key = it.next();
nameValuePair.add(new BasicNameValuePair(key, mData.get(key)));
}
post.setEntity(new UrlEncodedFormEntity(nameValuePair, "UTF-8"));
HttpResponse response = client.execute(post);
StatusLine statusLine = response.getStatusLine();
if(statusLine.getStatusCode() == HttpURLConnection.HTTP_OK){
result = EntityUtils.toByteArray(response.getEntity());
str = new String(result, "UTF-8");
}
}
catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
catch (Exception e) {
}
return str;
}
/**
* on getting result
*/
#Override
protected void onPostExecute(String result) {
// something...
if (mListener != null) {
mListener.onResult(result)
}
}
}
Now.
You just write some lines like following:
HashMap<String, String> data = new HashMap<String, String>();
data.put("key1", "value1");
data.put("key2", "value2");
AsyncHttpPost asyncHttpPost = new AsyncHttpPost(data);
asyncHttpPost.setListener(new AsyncHttpPost.Listener(){
#Override
public void onResult(String result) {
// do something, using return value from network
}
});
asyncHttpPost.execute("http://example.com");

First i would not recommend do a Http request in a AsyncTask, you better try a Service instead. Going back to the issue on how to pass parameter into an AsyncTask when you declared it you can defined each Object class of the AsyncTask like this.
public AsyncTask <Params,Progress,Result> {
}
so in your task you should go like this
public MyTask extends<String,Void,Void>{
public Void doInBackground(String... params){//those Params are String because it's declared like that
}
}
To use it, it's quite simple
new MyTask().execute("param1","param2","param3")