LoginActivity.java

package za.co.ishlema.blog.examples;
/**
 * This is an example of implementing "remember me" login option using SharedPreferences in Android.
 * @author Ishmael Makitla,
 * 
 * */
public class LoginActivity extends Activity {
  private static final String TAG = LoginActivity.class.getSimpleName();
  public static final String USER_SHAREDPREFERENCE_KEY = "userPrefKey";
  public static final String USER_SHAREDPREFERENCE_VALIDITY_KEY = "valid";
  
  //BY DEFAULT the app should remember the user (auto-login) for at most 5 days - unless if he logs out explicitly.
  public static final long DEFAULT_REMEMBER_UNTIL = (1000*60*60*24*5);
  //shared preferences
  SharedPreferences sharedPreferences;
  Editor sharedPreferencesEditor;    
  CheckBox cbRememberMe;   
  	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		this.requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.login_activity);
				
		//before showing login, check if there is userpreference value set and if it is valid still
		if (sharedPreferences.contains(USER_SHAREDPREFERENCE_KEY)){
			String cachedProfile = sharedPreferences.getString(USER_SHAREDPREFERENCE_KEY, "");
			if(!cachedProfile.trim().isEmpty()){
				Log.d(TAG, "Cached User \n"+cachedProfile);
				//check validity
				long now = (new Date()).getTime();
				long rememberUntil =  sharedPreferences.getLong(USER_SHAREDPREFERENCE_VALIDITY_KEY, 0);
				if(rememberUntil > now){
					Log.d(TAG, "Cached User Still Valid Until "+(new Date(rememberUntil)));
					//Here you could use libraries like Gson to convert the cachedProfile string into a POJO
					//we can show the main activity, and then close the current one so that if the user clicks the back button, does not come back to the login activity
					showMyMainActivity();	
					finish();
				}
				else{
					Log.d(TAG, "Cached User EXPIRED  -was only Valid Until "+(new Date(rememberUntil)));	
					//here the user's cached credentials have expired - we prompt the user to re-authenticate
				}
			}			
		}
						
		cbRememberMe = (CheckBox)findViewById(R.id.chRememberMe);		
		Button loginButton = (Button) findViewById(R.id.loginBtn);
		
		loginButton.setOnClickListener(new View.OnClickListener() {
			public void onClick(View v) {
				try{
					EditText username = (EditText) findViewById(R.id.user_name);
					EditText password = (EditText) findViewById(R.id.pass_word);
				if (username.getText().toString().trim().isEmpty()
						|| password.getText().toString().trim().isEmpty()) {
					if (username.getText().toString().trim().isEmpty()) {
						username.setError("Username cannot be empty");
					}
					if (password.getText().toString().trim().isEmpty()) {
						password.setError("Password cannot be empty");
					}
				} else {
					String u_name = username.getText().toString().trim();
					String p_word = password.getText().toString().trim();
					sendLoginRequest(u_name, p_word);
				}
			}
			catch(Exception e){ Log.e(TAG, "Error while processing Login-Button Click", e);}
				//do stuff
			}
		});				
	}


	/**
	 * Helper method to effect login request
	 * @param username - username of the person trying to login 
	 * @param password - password to authenticate
	 */
	private void sendLoginRequest(final String username, final String password) {
							
		RequestQueue queue = Volley.newRequestQueue(this);

		JSONObject joLoginRequest = new JSONObject();
		try {
				joLoginRequest.put("username", username);
				joLoginRequest.put("password", password);
								
				LoginJsonRequest jsObjRequest = new LoginJsonRequest(
					Request.Method.POST, impulseLoginURL, joLoginRequest,
					new Response.Listener<JSONObject>() {
						@Override
						public void onResponse(JSONObject response) {								
							processLoginSuccessful(response, password);
						}
					}, new Response.ErrorListener() {
						@Override
						public void onErrorResponse(VolleyError error) {
							try {
								Toast.makeText(LoginActivity.this, "Wrong Username or Password. Please Try again", Toast.LENGTH_LONG).show();	
								Log.w(TAG, "There was an error processing the Login Request. Error is "+error);
							} 
							catch (NullPointerException err) {Log.e(TAG, err.getLocalizedMessage(), err);}
						}
				});					
				queue.add(jsObjRequest);
			
		} catch (JSONException e) {
			e.printStackTrace();
		}			
	}
	
	
	/**
	 * Helper method to process the login response from Server
	 * @param results
	 */
	private void processLoginSuccessful(JSONObject loginResponse, String successfulPassword) {
		Log.i(TAG, "Got Login Response: \n"+loginResponse.toString());
		MyUser loggedInUser = MyUser.asMyUser(loginResponse.toString());
		try {
			if (loginResponse != null) {
				loggedInUser.setPassword(successfulPassword);
				if(cbRememberMe.isChecked()){						
				sharedPreferencesEditor.putString(USER_SHAREDPREFERENCE_KEY, loggedInUser.toString());	
				//time for which this login is valid
				ong rememberUntil = (new Date()).getTime() + DEFAULT_REMEMBER_UNTIL;
				sharedPreferencesEditor.putLong(USER_SHAREDPREFERENCE_VALIDITY_KEY, rememberUntil);	
				sharedPreferencesEditor.commit();
			}	
			//now we can proceed to main activity...
			showMyMainActivity();	
			finish();
		} else {
			Toast.makeText(LoginActivity.this, "Problem Processing Login Response from Server. Please try again.",Toast.LENGTH_LONG).show();
		}
		} catch (Exception e) {
			e.printStackTrace();
		}
		finally{
			//just clear the entry fields			
		}
	}
	
}