Develop Reference

using Android HttpGet/HttpPost to communicate with odbc database: is there a faster way?

I'm writing an app to use an Android device to get and set data from an Access database on a local area network. I'm using HttpPost and/or HttpGet to communicate with php pages on the server which in turn communicate with the db via odbc.
It works well, but takes almost a second for each query to complete. Is there a faster way?
I'm debugging via usb on the actual device. When I access the php pages from the browser on the device, it's much faster. There is no other traffic on this network.
Thanks!
Edit: Here's the code to retrieve a dataset:
private JSONArray getData(String phpFile,ArrayList<NameValuePair> nameValuePairs){
String result = "";
InputStream is = null;
JSONArray jArray=null;
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://" + mServerIP + "/dressageNet/"+ phpFile);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");}
is.close();
result=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
try{
jArray = new JSONArray(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
nameValuePairs.clear();
return jArray;
}

Create custom server application in whatever you language want and stop using http server and PHP. PHP is slow and this creates overhead. of course you will need to implement your own protocol but it will be a lot faster. I did something like this in java me, and performance was way better than doing POST/GET.

How to fix "Error parsing data org.json.JSONException: Value <?xml of type java.lang.String cannot be converted to JSONArray" in my program

I am very new to android and I'm trying to make a program that shows you results from a database that I have. So when I type in a first name and the database sends the information of that person to me. However, when I look at the LogCat it says
"09-09 22:05:39.544: ERROR/log_tag(8813): Error parsing data org.json.JSONException: Value
This is my code:
public class PS extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//get the two controls we created earlier, also with the resource reference and the id
final EditText et_Text = (EditText)findViewById(R.id.et_Text);
//add new KeyListener Callback (to record key input)
et_Text.setOnKeyListener(new OnKeyListener()
{
//function to invoke when a key is pressed
public boolean onKey(View v, int keyCode, KeyEvent event)
{
//check if there is
if (event.getAction() == KeyEvent.ACTION_DOWN)
{
//check if the right key was pressed
if (keyCode == KeyEvent.KEYCODE_ENTER)
{
InputStream is = null;
String result = "";
//the name data to send
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("name",et_Text.getText().toString()));
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://myIPaddress/sampleDB/testSend.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
// At this point is should be set, if it isn't, tell user what went wrong
if (is != null) {
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
//parse json data
try{
JSONArray jArray = new JSONArray(result);
for(int i=0;i<jArray.length();i++){
JSONObject json_data = jArray.getJSONObject(i);
Log.i("log_tag","PersonID: "+json_data.getInt("personID")+
", FirstName: "+json_data.getString("FirstName")+
", LastName: "+json_data.getString("LastName")+
", Age: "+json_data.getInt("Age")
);
}
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}} else {Log.i("log_tag", "Something went wrong!"//I don't know what to put here);} ;
et_Text.setText("");
//and clear the EditText control
return true;
}
}
return false;
}
});
}
}
This is my php code:
<?php
$con = mysql_connect("localhost","username","password");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("_usersDB", $con);
$q=mysql_query("SELECT * FROM Persons WHERE FirstName='".$_REQUEST['name']."'");
while($e=mysql_fetch_assoc($q))
$output[]=$e;
print(json_encode($output));
mysql_close($con);
?>
The output it's parsing on is when I input "Eric" then It'll give me personID of 1, FirstName of Eric, LastName of (my last name), and age of 15. I'm not sure if you were asking for that...

First of all, it may not be wise to share your database connection details with the rest of the world. Second of all, it's not a great idea to do networking operations on the UI Thread.
Lastly (which is what you want to know), it looks likes the output on the server may be different than what the client is expecting. Can you post the output it is parsing on? I'll revise this answer once you do so.

It looks as if the server is prepending an XML declaration to the JSON (). You might want to examine the HTTP traffic output by the web server (via logging or wireshark) as a first step to see if the problem lies with the client or the server.

Android connectivity with MySQL

I am developing a final year project where I need to connect Android emulator with MySQL database in order to retrieve values. Java file:
public class connectivity extends Activity {
/** Called when the activity is first created. */
TextView txt;
public static final String KEY_121 = "http://10.0.2.2/mysqlcon.php";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LinearLayout rootLayout = new LinearLayout(getApplicationContext());
txt = new TextView(getApplicationContext());
rootLayout.addView(txt);
setContentView(rootLayout);
// Set the text and call the connect function.
txt.setText("Connecting...");
// call the method to run the data retreival
txt.setText(getServerData(KEY_121));
}
private String getServerData(String returnString) {
InputStream is = null;
String result = null;
// the year data to send
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("year", "1970"));
// http post
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_121);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
// convert response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = "0";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
// parse json data
try {
JSONArray jArray = new JSONArray(result);
JSONObject json_data = null;
for (int i = 0; i < jArray.length(); i++) {
json_data = jArray.getJSONObject(i);
Log.i("log_tag", "id: " + json_data.getInt("id") + ", name: " + json_data.getString("name") + ", sex: " + json_data.getInt("sex") + ", birthyear: " + json_data.getInt("birthyear"));
// Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
return returnString;
}
}
I have also given an internet permission in my Android manifest file. But after running the application I get the following error in logcat:
ERROR PARSING DATA org.json.JSONException:A JSONArraytext must start with '[' at character 0
I think this goes to show that a null value is being returned. Please help me out as this is my final year project. I have spent hours trying to find the solutions but it has been of no use.
I am currently using Android 2.2. The wamp server is on the localhost so I am using the address 10.0.2.2 which is a special alias to localhost (127.0.0.1). Any help will be really appreciated.
Here is the PHP code:
<?php
mysql_connect("127.0.0.1","root","chetan");
mysql_select_db("db1");
$q=mysql_query("SELECT * FROM people WHERE birthyear>'".$_REQUEST['year']."'");
while($e=mysql_fetch_assoc($q))
$output[]=$e;
print(json_encode($output,JSON_FORCE_OBJECT));
mysql_close();

This is actually an issue I've run into before. The problem is your server isn't outputting valid JSON. It's missing some of the markup. I suggest you print the raw text of the response to Logcat and examine it. Perhaps even pass it into a JSON validator. That will also help you figure out if it is returning an empty value. If it's returning an empty value, then you'll need to debug your server...not your client...
Additionally, try visiting the php page from your browser and letting it simply display the JSON response. This will allow you to see what's being written by the server and help you determine where the problem really is. Just be aware, because the server is expecting a POST the easiest way to test this would probably to be to create a simple html form to POST the test data to that page. Without doing that, getting a browser to do a POST on it's own can be a pain.

do u need to use connection to php??? if not you can directly connect to mysql db to retrieve the result:
// Assume function to be :
public String customerData() {
String customerInfo = ""; //To store result
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con =
DriverManager.getConnection(
"jdbc:mysql://10.0.2.2:3306/retailer","root","pswrd");
PreparedStatement statement = con.prepareStatement("SELECT * FROM customers");
ResultSet result = statement.executeQuery();
while(result.next()) {
customerInfo = customerInfo + result.getString("name") + "&" +
result.getString("C_ID") + "&" + result.getString("address") +
"&" + result.getString("email");
// Here "&"s are added to the return string. This is help to split the
// string in Android application
}
} catch(Exception exc) {
System.out.println(exc.getMessage());
}
return customerInfo;
}
But to your project library include Connector jar file for Mysql.

Android app using data from webservice

I want to write an Android application that can display some data received(polled) from an internet resource.
I guess that I need to write some logic that will periodically call and get data from some endpoint, parse the response and display it. Is there a good tutorial for all this steps?
I know very little about Android programming at the momment and maybe it is better to start with something simpler. I just want to know what to look for while learning an gather some resources on this.

What you want to do is developing a rest api that provides data for your android app. E.g. you website has some content that you want use in your app, then you could write a php script that just returns that data in a specific format.
E.g. mysite.net/rest/fetchAllLocations.php?maybe_some_parameters
This would return locations in e.g. json format, here is an example how that looks like:
[{"id":1,"shop_lng":8.5317153930664,"shop_lat":52.024803161621,"shop_zipcode":33602,"shop_city":"Bielefeld","shop_street":"Arndtstra\u00dfe","shop_snumber":3,"shop_name":"M\u00fcller","shop_desc":"Kaufhaus"}]
Here is an example for a rest api request:
http://shoqproject.supervisionbielefeld.de/public/gateway/gateway/get-shops-by-city/city/Bielefeld
So when you have your rest api set up you can deal with receiving that data with your android phone. I use a static method to get this data:
public class JsonGrabber{
public static JSONArray receiveData(){
String url = "your url";
String result = "";
DefaultHttpClient client = new DefaultHttpClient();
HttpGet method = new HttpGet(url);
HttpResponse res = null;
try {
res = client.execute(method);
} catch (ClientProtocolException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
try{
InputStream is = res.getEntity().getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
JSONArray jArray = null;
try{
jArray = new JSONArray(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
}
Well thats all, once you have your data in json format you just have to parse it:
JSONArray test = (JSONArray) JsonGrabber.receiveData()
try {
for(int i=0;i<test.length();i++){
JSONObject json_data = test.getJSONObject(i);
int id = json_data.getInt("id");
}
}
The web request should run in another thread, because it can be a time consuming process. So you need to deal with AsyncTask. Here are some resources:
Painless Threading
Multithreading for performance
Hello Android Tutorial

Updateing Android application content via internet?

i want to develop an Android application that will take the content from internet (server) and present it in the application.
(ex. i take the todays weather forecast, put the numbers in SQLite database or .txt file , put the database/txt file on internet server so when i open the application, the app connects&downloads the database via the net and presents me with todays forecast)
If you can references me to some example/video tutorial/book that deals with this issue i will be very thankful!

What you want to do is developing a rest api that provides data for your android app. E.g. you website has some content that you want use in your app, then you could write a php script that just returns that data in a specific format.
E.g. mysite.net/rest/fetchAllLocations.php?maybe_some_parameters
This would return locations in e.g. json format, here is an example how that looks like:
[{"id":1,"shop_lng":8.5317153930664,"shop_lat":52.024803161621,"shop_zipcode":33602,"shop_city":"Bielefeld","shop_street":"Arndtstra\u00dfe","shop_snumber":3,"shop_name":"M\u00fcller","shop_desc":"Kaufhaus"}]
Here is an example for a rest api request:
http://shoqproject.supervisionbielefeld.de/public/gateway/gateway/get-shops-by-city/city/Bielefeld
So when you have your rest api set up you can deal with receiving that data with your android phone. I use a static method to get this data:
public class JsonGrabber{
public static JSONArray receiveData(){
String url = "your url";
String result = "";
DefaultHttpClient client = new DefaultHttpClient();
HttpGet method = new HttpGet(url);
HttpResponse res = null;
try {
res = client.execute(method);
} catch (ClientProtocolException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
try{
InputStream is = res.getEntity().getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
JSONArray jArray = null;
try{
jArray = new JSONArray(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
}
Well thats all, once you have your data in json format you just have to parse it:
JSONArray test = (JSONArray) JsonGrabber.receiveData()
try {
for(int i=0;i<test.length();i++){
JSONObject json_data = test.getJSONObject(i);
int id = json_data.getInt("id");
}
}
The web request should run in another thread, because it can be a time consuming process. So you need to deal with AsyncTask. Here are some resources:
Painless Threading
Multithreading for performance
Hello Android Tutorial