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Tag Archive: php

Why flush ?

Interesting stuff i came to know about which i was unaware of. This post is more of a discussion on the problem. I haven’t understood the solution and so would request you to have a say.

I have done json parsing numerous times. I can tell if json is valid or not by looking it. I was using google-gson for android application and its awesome. Application was supported by php web service. The solution that fixed the problem is related to php and i am not a php developer and don’t have that much inner understanding of it. It was regular json parsing routine. Application just crashed when gson was parsing the json response from php service.

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 2

From error I understood the reason but that was not it. I was very confident that something else was the problem because json response was perfect. I wrote quick objective-c routine(SBJSON) to parse same json response and it worked there. I even did validation on jsonlint.com
After doing bit of research I came across a working solution. In php before sending response I had to put this:

ob_clean();
echo header('Content-Type: application/json');

I checked the php manual to understand what those lines means, header function was quite obvious. According to manual, ob_clean:

This function discards the contents of the output buffer.

Now I have no idea why discarding the contents of output buffer was working. This was the case for android, I mean in iphone I didn’t need ob_clean. I am still looking for the explanation on this.

Well i have been playing around a lot with android client connectivity with remote MySQL database. Lately i wanted a UI/View, something input textfield, i wanted to show completion suggestions automatically in a drop down menu while the user is typing, suggestions would be coming from MySQL database. Basically whenever i type, i am calling php sending the input and php will query database and return the values(in my case just names) that have “input” as substring (like if i type ‘pa’ then it would return names that have ‘pa’ as substring). I am sending results to android client via encoded json. In android side i am decoding json and filling my ArrayAdapter. Lets see the points that are being done:

1) PHP

I somehow looking at google i wrote this code. This php gets the input text from my android and it runs query at database for records whose company names has “input text” as a substring. You can see the query statement above. In the end it encodes the result in json.

2) Main.xml (my layout)
Here is the xml layout file for my ui.





3) Main Activity class
Here is the main class that extends Activity. Here is the code of calling php module and parsing json. I have explained this all in my previous post so you could go through it. i’l explain just AutoCompleteTextView part here.

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.widget.ArrayAdapter;
public class AutoComptest extends Activity {
    
	private CustomAutoCompleteView autoComplete;	 	
	 
	private ArrayAdapter autoCompleteAdapter;
	
	/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        autoCompleteAdapter = new ArrayAdapter(this, android.R.layout.simple_dropdown_item_1line); 
        autoCompleteAdapter.setNotifyOnChange(true); // This is so I don't have to manually sync whenever changed  
        autoComplete = (CustomAutoCompleteView)  findViewById(R.id.autoCompleteCountry);
        autoComplete.setHint("Country");
        autoComplete.setThreshold(3);
        autoComplete.setAdapter(autoCompleteAdapter);
        
        autoComplete.addTextChangedListener(textChecker);
        
    }
    
    final TextWatcher textChecker = new TextWatcher() {
        public void afterTextChanged(Editable s) {}
 
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
 
        public void onTextChanged(CharSequence s, int start, int before, int count)
        {
                   
                autoCompleteAdapter.clear();
                
                callPHP();
                               
        }     
    };
   
    private void callPHP(){
    	String result = "";   	
    	InputStream is=null;    	
    	try{
    			ArrayList nameValuePairs = new ArrayList();
    			nameValuePairs.add(new BasicNameValuePair("st",autoComplete.getText().toString()));
    	        HttpClient httpclient = new DefaultHttpClient();
    	        HttpPost httppost = new HttpPost("http://10.0.2.2/gaanza_android/android_database.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());
    	}
    	
    	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;icatch(JSONException e){ Log.e(“log_tag”, “Error parsing data “+e.toString()); } } }

Note: remember “http://10.0.2.2/” in my last post. I had to use 10.0.2.2 instead of localhost because emulator consider itself as localhost and my xammp local server is not in emulator localhost.

Ok so i want to detect an event when a text is typed/deleted from my autocompletetextview, basically i want a listener which detects a change in text of my view. So what should we do ? Well in my case i searched the android developer documentation 😀 , there i found something called TextWatcher. What i am doing is attach a TextWatcher object to editable like my AutoCompleteTextView so whenever any text changes in my editable the functions/methods of TextWatcher will be called and in these methods i had to write my logic codes which is what i want to achieve if text changes in autocompletetextview ?. There are three abstract methods in TextWatcher class so you have to override them, well anyway thats what we wanted. Methods are:

afterTextChanged(Editable s)
	beforeTextChanged(CharSequence c, int start, int count, int after)
	onTextChanged(CharSequence c, int start, int before, int count)

Best way to understand them is going through the document here. Anyway i had to write my logic code on beforeTextChanged() method so that it performs action whenever there is a change in text of autocompletetextview.

In above code sample i am calling PHP whenever i am typing something. So i am calling callPHP function at onTextChanged() method. So whenever i type something it will call PHP giving text to the function in PHP and PHP will query MySql database for results and PHP will send results to me in json. This is it. So i decode json and fill the results in ArrayAdapter after clearing it, whenever ArrayAdapter changes it notify the changes being made and AutoCompleteView will show the new drop down suggestions.

There was still one very minor problem and i solved it with my another very stupid solution 😛 So problem was that whenever the results from database gets filled in ArrayAdapter and AutoCompleteTextView shows drop down suggestions, it showed me filtered suggestions like suppose i type “can” and i get results(which has “can” as substring) from database, so for “can” ArrayAdapter contents get filtered and i get suggestion starting with text “can” which i didn’t wanted because i already has got filtered results from database and i wanted to show all results that i am receiving from database. So for this i had to write my custom AutoCompleteTextView. It isn’t hard at all, i just had to extend AutoCompleteTextView and override the methods.

4) CustomAutoCompleteView which extends AutoCompletetextView

public class CustomAutoCompleteView extends AutoCompleteTextView {
	
	public CustomAutoCompleteView(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
	}

	public CustomAutoCompleteView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
	}

	public CustomAutoCompleteView(Context context, AttributeSet attrs,
			int defStyle) {
		super(context, attrs, defStyle);
		// TODO Auto-generated constructor stub
	}
	
	@Override
	protected void performFiltering(final CharSequence text, final int keyCode) {
		String filterText = "";
		super.performFiltering(filterText, keyCode);
	}
    /**
    * After a selection, capture the new value and append to the existing
    * text
    */
    @Override
    protected void replaceText(final CharSequence text) {
    	super.replaceText(text);
    }

}

How to remove the filter on an ArrayAdapter used in an AutoCompleteTextView? I had to override performFiltering() method. In this method i am telling AutoCompletetextView to not filter any suggestions, just show all suggestions. I searched on google for this topic but i didn’t find any good solution, maybe i didn’t searched it properly. Whatever, i just wrote a stupid trick to remove any filter, actually instead of technically removing filter i am adding a filter which does a job to show all suggestions :D. I defined a filter which filters all suggestion based on “” yeah a blank string :D. But this works like a charm. Just try it.

So now your are getting results suggestion from database dynamically to AutoCompleteTextView.

But But But But But ok enough, In above code way of fetching data from database to AutoCompletetextView just sucks. Never never ever call a http PHP call in UI Thread. I did a lot of testing with this code. When i was getting small number of results from Database(live database not local) it was working fine but when i was getting large number of results say more than 150 and it was taking a bit of time which caused my UI to be non-responsive and thus famous FORCE CLOSE occured. So never call it from UI thread because u don’t know how much time it will take to complete whole http connection. So always call it in separate thread that i will discuss in Part II of this subject. yes i’l be posting new better version of same problem.

Gracias

While working on submitting and retrieving global game high scores from a remote database like mysql i learned few things. During start experiment i decided to use PHP to connect to mysql database. What i was trying to do is that i wanted to call php, then php would make a database connection and make a sql query and retrieve the result, then php would encode that result into JSON format and i would decode this JSON at my android program and display the results. I haven’t done much PHP before(never actually setup PHP server before :D). So i came to know this xampp server, so i installed/setup the xampp server(its a php apache server and it comes with mysql also). I am not telling how to setup xampp and create a databse and tables as you can find it in their wiki.

I create a php file, which makes a database connection and makes a query and encodes a result. As i told before i am not familiar to PHP so i wrote this code looking here and there by googling it :D. Code looks like this:


Well code is not that hard to understand. You are making a mysql connection by providing credentials. Then you select a databse. Then you execute a query and result is assigned to $q. Next what i seen is that result is in ArrayCollection type (i saw it in xampp console) so i think we are converting it into Array while iterating through collection(I am not quite sure so if u know then please share). Then You are just encoding the result into JSON.

Now lets see how we will decode the JSON at our android program. Code looks like this:

void parseJSON()
    {
    	
    	String result = "";
    	String x = "";
    	InputStream is=null;
    	//http post
    	try{
    			ArrayList nameValuePairs = new ArrayList();
    	        HttpClient httpclient = new DefaultHttpClient();
    	        HttpPost httppost = new HttpPost("http://localhost/game_php_testing/android_database.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());
    	}
    	//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 catch(JSONException e){ Log.e(“log_tag”, “Error parsing data “+e.toString()); } }

I faced two problems/exception while connecting to php. PHP was connecting to mysql perfectly as when i run in browser it printed results so there was some issues on my above code which i’l address here and this is common problems which will be faced by every newcomer to android like me :D. Before that i’l just explain my php file and localhost path setup. When i installed xampp, in xampp folder there must be folder called htDocs so i have to make a project folder here inside htDocs and inside this project folder will be my php. So my php path would look like this “/htDocs/game_php_testing/android_database.php” So when i will make a call to php via “http://localhost/game_php_testing/android_database.php”

Now i will address the two problems that i faced.
First,

java.net.socketexception -permission denied

yes whenever i was trying to call my php i was getting this exception. How did i solved it ??? Well i just provided a permission to internet access at AndroidManifest.xml file. You have to put this permission above tag


Now second Problem, this one is very important.

java.net.ConnectException -Connection Refused.

Well what i found is that when u call localhost android thinks that u r calling to android emulator itself not the localhost machine. So localhost/127.0.0.1 wouldn’t work. So i found the solution to that: instead of localhost use 10.0.2.2, code will be like this:

HttpPost httppost = new HttpPost("http://10.0.2.2/game_php_testing/android_database.php");

Well problem solved :D. Now i decode the json that i got from php. I am printing the result on LOG. Please see that when i am calling “json_data.getString(“Player_name”)“, Player_name is a column/attribute in my database table and its type is varchar so i used getString() on it.

I hope this post helped you as you may also faced similar problem at first time.

Gracias.