Saturday, 15 December 2012

Absolute Layout

AbsoluteLayout is based on the simple idea of placing each control at an absolute position.  You specify the exact x and y coordinates on the screen for each control.  This is not recommended for most UI development (in fact AbsoluteLayout is currently deprecated) since absolutely positioning every element on the screen makes an inflexible UI that is much more difficult to maintain.  Consider what happens if a control needs to be added to the UI. You would have to change the position of every single element that is shifted by the new control.
Here is a sample Layout XML using AbsoluteLayout.


    

Android to Sql server Connection

Android cannot directly connect to the database server. Instead we will use HttpUtils to connect to a simple ASP.NET script that will issue the query and return the result as a JSON string

Steps to connect android application to sql server :
1. Create an asp.net script which connects to our sql server database and return the result as a JSON format.
Ex. Create a “LoginApp” website application, In this the Default.aspx file is as,
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Web.Script.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;
using System.Web.Services;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
String nm = Request.QueryString["name"];
String pwd = Request.QueryString["password"];
String query = "select * from UserLogin where name='" + nm + "' and password='" + pwd+"'";
SqlConnection con = new SqlConnection(getConnection());
SqlCommand cmd = new SqlCommand(query, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
string str=makejsonoftable(dt);
Response.Write(str);
}
private string getConnection()
{
string connStr =
System.Configuration.ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
return connStr;
}
string makejsonoftable(DataTable table)
{
StringBuilder sb = new StringBuilder();
foreach (DataRow dr in table.Rows)
{
if (sb.Length != 0)
sb.Append(",");
sb.Append("{");
StringBuilder sb2 = new StringBuilder();
foreach (DataColumn col in table.Columns)
{
string fieldname = col.ColumnName;
string fieldvalue = dr[fieldname].ToString();
if (sb2.Length != 0)
sb2.Append(",");
sb2.Append(string.Format("{0}:\"{1}\"", fieldname, fieldvalue));
}
sb.Append(sb2.ToString());
sb.Append("}");
}
sb.Insert(0, "[");
sb.Append("]");
return sb.ToString();
}
}

2. Create Android application “LoginApplication” as,
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.content.Intent;
import android.net.ParseException;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class LoginApplicationActivity extends Activity
{
JSONArray jArray;
String result = null;
InputStream is = null;
StringBuilder sb=null;
public static final String LOG_TAG="HI..";
EditText un,pw;
TextView error;
Button ok;
int flag=0;
public static String name;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
un=(EditText)findViewById(R.id.et_un);
pw=(EditText)findViewById(R.id.et_pw);
ok=(Button)findViewById(R.id.btn_login);
error=(TextView)findViewById(R.id.tv_error);

ok.setOnClickListener(new View.OnClickListener()
{
public void onClick(final View v)
{
// create a new thread for httppost request
new Thread()
{
public void run()
{
ArrayList nameValuePairs = new ArrayList ();
//http post
try
{
String nm=un.getText().toString();
String pwd=pw.getText().toString();
HttpClient httpclient = new DefaultHttpClient();
//provide the values to asp.net script through query string
String qs="http://192.168.2.22/LoginApp/Default.aspx?name="+nm+"&password="+pwd;
HttpPost httppost = new HttpPost(qs);
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);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
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());
}

try
{
jArray = new JSONArray(result);
JSONObject json_data=null;
for(int i=0;i<jArray.length();i++)
{
flag=1;
json_data = jArray.getJSONObject(i);
name=json_data.getString("name");
String pwd=json_data.getString("password");
// get values from database and show on logcat view
//for invalid user, the values are null
Log.v(LOG_TAG,"name :"+name);
Log.v(LOG_TAG,"password :"+pwd);
}
if(flag==0)
{
//create new thread derived from “runOnUiThread” class to connect with View
// bcz simple Thread class can’t access View
LoginApplicationActivity.this.runOnUiThread(new Runnable()
{
public void run() {
error.setText("Invalid User...");
//Toast.makeText(LoginApplicationActivity.this, "Invalid
Login",Toast.LENGTH_LONG).show();
}
});
}
else{
Log.v("LOG-TAG","valid");
LoginApplicationActivity.this.runOnUiThread(new Runnable() {
public void run() {
error.setText("Login successful....");
// Toast.makeText(LoginApplicationActivity.this, "Login Successful",
Toast.LENGTH_LONG).show();
//for valid user, start another activity “ULogin” which says ‘hello’ to user..
Intent myIntent = new Intent(v.getContext(), Ulogin.class);
startActivityForResult(myIntent, 0);
}
});
}
}
catch(JSONException e1){
Toast.makeText(getBaseContext(), "No food Found" ,Toast.LENGTH_LONG).show();
} catch (ParseException e1) {
e1.printStackTrace();
}
}
}.start();
}
});
}



3. .Create a new activity named “Ulogin”,which starts when user is loged in ,
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class Ulogin extends Activity
{
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
Button back = (Button)findViewById(R.id.btn_back);
TextView msg=(TextView) findViewById(R.id.tv_show);
msg.setText("Hello, " + LoginApplicationActivity.name);
back.setOnClickListener(new View.OnClickListener()
{
public void onClick(View view)
{
Intent myIntent = new Intent(view.getContext(),
LoginApplicationActivity.class);
startActivityForResult(myIntent, 0);
}
});
}
}


4. Gives Internet access permission in AndroidManifest.xml file as,

Also add new activity in AndroidManifest.xml file in category ,