How to use Http connection , SaxParser and SharedPreferences in Android
The following code helps you to create a login screen and connect with the server using the Http connection.
The login url will give the following xml file as a output.
-----------------------------
< login>
< status> SUCCESS
< message> Login Successful
------------------------------
< login>
< status> ERROR
< message> Login Failed
------------------------------
Here im using the saxparser to retreive the xml output.
Application will navigate the user to the welcome page once he logged in successfully.
Otherwise user will get login failed message.
The username and password will be stored in the SharedPreferences after the successful login.
Application will navigate the user to the main page directly once the user completed the login successfully.
User need not to login each time of application launching.
AndroidManifest.xml
--------------------
< manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="login.sample"
android:versionCode="1"
android:versionName="1.0.0">
< uses-permission android:name="android.permission.INTERNET" />
< application android:icon="@drawable/icon"
android:label="@string/app_name">
< activity android:name=".LoginActivity"
android:label="@string/app_name">
< intent-filter>
< action android:name="android.intent.action.MAIN" />
< category
android:name="android.intent.category.LAUNCHER"/>
< activity android:name=".LoginError"
android:label="@string/app_name"
android:theme="@style/Theme.CustomDialog">
< intent-filter>
< action android:name="android.intent.action.VIEW" />
< category android:name="android.intent.category.DEFAULT" />
< activity android:name=".Welcome"
android:label="@string/app_name">
< intent-filter>
< action android:name="android.intent.action.VIEW" />
< category android:name="android.intent.category.DEFAULT" />
main.xml
---------
< AbsoluteLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >
< Button
android:id="@+id/btn_sign_in"
android:layout_width="100px"
android:layout_height="wrap_content"
android:text="Sign In"
android:layout_x="103px"
android:layout_y="197px"/>
< EditText
android:id="@+id/txt_username"
android:layout_width="250px"
android:layout_height="wrap_content"
android:hint="Username"
android:singleLine="true"
android:textSize="18sp"
android:layout_x="40px"
android:layout_y="32px" />
< EditText
android:id="@+id/txt_password"
android:layout_width="250px"
android:layout_height="wrap_content"
android:hint="Password"
android:singleLine="true"
android:textSize="18sp"
android:password="true"
android:layout_x="40px"
android:layout_y="86px" />
Login Failed message will be displayed in the customized dialog box.
styles.xml
----------
< resources>
< style name="Theme.CustomDialog" parent="android:style/Theme.Dialog">
< item name="android:windowBackground">@drawable/box
box.xml
-------
< shape xmlns:android="http://schemas.android.com/apk/res/android">
< solid android:color="#f0600000" />
< stroke android:width="3dp" color="#ffff8080" />
< corners android:radius="3dp" />
< padding android:left="10dp" android:top="10dp" android:right="10dp"
android:bottom="10dp" />
< /shape>
loginerror.xml
--------------
< AbsoluteLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >
< TextView
android:id="@+id/tv"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"/>
< Button android:id="@+id/btn_ok" android:layout_width="80px"
android:layout_height="wrap_content" android:text="OK"
android:layout_x="83px" android:layout_y="60px" />
welcome.xml
-----------
< LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
< TextView
android:id="@+id/myEditText"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Welcome, You are Successfully logged in"/>
LoginActivity.java
------------------
package login.sample;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
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.apache.http.protocol.HTTP;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class LoginActivity extends Activity {
/** Called when the activity is first created. */
private static final String TAG = "Login";
Button signin;
String loginmessage = null;
Thread t;
private SharedPreferences mPreferences;
ProgressDialog dialog;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mPreferences = getSharedPreferences("CurrentUser", MODE_PRIVATE);
if (!checkLoginInfo()) {
signin = (Button) findViewById(R.id.btn_sign_in);
signin.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
showDialog(0);
t=new Thread() {
public void run() {
tryLogin();
}
};
t.start();
}
});
}
else {
/*Directly opens the Welcome page, if the username and password is already available
in the SharedPreferences*/
Intent intent=new Intent(getApplicationContext(),Welcome.class);
startActivity(intent);
finish();
}
}
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case 0: {
dialog = new ProgressDialog(this);
dialog.setMessage("Please wait while connecting...");
dialog.setIndeterminate(true);
dialog.setCancelable(true);
return dialog;
}
}
return null;
}
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
String loginmsg=(String)msg.obj;
if(loginmsg.equals("SUCCESS")) {
removeDialog(0);
Intent intent=new Intent(getApplicationContext(),Welcome.class);
startActivity(intent);
finish();
}
}
};
public void tryLogin() {
Log.v(TAG, "Trying to Login");
EditText etxt_user = (EditText) findViewById(R.id.txt_username);
EditText etxt_pass = (EditText) findViewById(R.id.txt_password);
String username = etxt_user.getText().toString();
String password = etxt_pass.getText().toString();
DefaultHttpClient client = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://.......");
List nvps = new ArrayList();
nvps.add(new BasicNameValuePair("username", username));
nvps.add(new BasicNameValuePair("password", password));
try {
UrlEncodedFormEntity p_entity = new UrlEncodedFormEntity(nvps,
HTTP.UTF_8);
httppost.setEntity(p_entity);
HttpResponse response = client.execute(httppost);
Log.v(TAG, response.getStatusLine().toString());
HttpEntity responseEntity = response.getEntity();
Log.v(TAG, "Set response to responseEntity");
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
LoginHandler myLoginHandler = new LoginHandler();
xr.setContentHandler(myLoginHandler);
xr.parse(retrieveInputStream(responseEntity));
ParsedLoginDataSet parsedLoginDataSet = myLoginHandler.getParsedLoginData();
if (parsedLoginDataSet.getExtractedString().equals("SUCCESS")) {
// Store the username and password in SharedPreferences after the successful login
SharedPreferences.Editor editor=mPreferences.edit();
editor.putString("UserName", username);
editor.putString("PassWord", password);
editor.commit();
Message myMessage=new Message();
myMessage.obj="SUCCESS";
handler.sendMessage(myMessage);
} else if(parsedLoginDataSet.getExtractedString().equals("ERROR")) {
Intent intent = new Intent(getApplicationContext(), LoginError.class);
intent.putExtra("LoginMessage", parsedLoginDataSet.getMessage());
startActivity(intent);
removeDialog(0);
}
} catch (Exception e)
{
Intent intent = new Intent(getApplicationContext(), LoginError.class);
intent.putExtra("LoginMessage", "Unable to login");
startActivity(intent);
removeDialog(0);
}
}
private InputSource retrieveInputStream(HttpEntity httpEntity) {
InputSource insrc = null;
try {
insrc = new InputSource(httpEntity.getContent());
} catch (Exception e) {
}
return insrc;
}
//Checking whether the username and password has stored already or not
private final boolean checkLoginInfo() {
boolean username_set = mPreferences.contains("UserName");
boolean password_set = mPreferences.contains("PassWord");
if ( username_set || password_set ) {
return true;
}
return false;
}
}
