LoginActivity.java

package com.daifan.activity;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.KeyEvent;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import android.widget.TextView;

import com.actionbarsherlock.app.SherlockActivity;
import com.daifan.R;
import com.daifan.Singleton;
import com.daifan.domain.User;
import com.daifan.service.UserService;

/**
 * Activity which displays a login screen to the user, offering registration as
 * well.        setTheme(R.style.Theme_Sherlock_Light);
 super.onCreate(savedInstanceState);

 setContentView(R.layout.activity_login);

 // Set up the login form.
 mEmailView = (EditText) findViewById(R.id.email);
 mPasswordView = (EditText) findViewById(R.id.password);
 mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) {
if (id == R.id.login || id == EditorInfo.IME_NULL) {
attemptLogin();
return true;
}
return false;
}
});

 mLoginFormView = findViewById(R.id.login_form);
 mLoginStatusView = findViewById(R.id.login_status);
 mLoginStatusMessageView = (TextView) findViewById(R.id.login_status_message);

 findViewById(R.id.sign_in_button).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
attemptLogin();
}
});

 // Link to Register Screen
 findViewById(R.id.btnLinkToRegister).setOnClickListener(new View.OnClickListener() {

 public void onClick(View view) {
 Intent i = new Intent(getApplicationContext(),
 RegisterActivity.class);
 startActivity(i);
 finish();
 }
 });

 */
public class LoginActivity extends SherlockActivity {
    /**
     * Keep track of the login task to ensure we can cancel it if requested.
     */
    private UserLoginTask mAuthTask = null;

    // Values for email and password at the time of the login attempt.
    private String mEmail;
    private String mPassword;

    // UI references.
    private EditText mEmailView;
    private EditText mPasswordView;
    private View mLoginFormView;
    private View mLoginStatusView;
    private TextView mLoginStatusMessageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        setTheme(R.style.Theme_Sherlock_Light);
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_login);

        // Set up the login form.
        mEmailView = (EditText) findViewById(R.id.email);
        mPasswordView = (EditText) findViewById(R.id.password);
        mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) {
                if (id == R.id.login || id == EditorInfo.IME_NULL) {
                    attemptLogin();
                    return true;
                }
                return false;
            }
        });

        mLoginFormView = findViewById(R.id.login_form);
        mLoginStatusView = findViewById(R.id.login_status);
        mLoginStatusMessageView = (TextView) findViewById(R.id.login_status_message);

        findViewById(R.id.sign_in_button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                attemptLogin();
            }
        });

        // Link to Register Screen
        findViewById(R.id.btnLinkToRegister).setOnClickListener(new View.OnClickListener() {

            public void onClick(View view) {
                Intent i = new Intent(getApplicationContext(),
                        RegisterActivity.class);
                startActivity(i);
                finish();
            }
        });
    }

    /**
     * Attempts to sign in or register the account specified by the login form.
     * If there are form errors (invalid email, missing fields, etc.), the
     * errors are presented and no actual login attempt is made.
     */
    public void attemptLogin() {
        if (mAuthTask != null) {
            return;
        }

        // Reset errors.
        mEmailView.setError(null);
        mPasswordView.setError(null);

        // Store values at the time of the login attempt.
        mEmail = mEmailView.getText().toString();
        mPassword = mPasswordView.getText().toString();

        boolean cancel = false;
        View focusView = null;

        // Check for a valid password.
        if (TextUtils.isEmpty(mPassword)) {
            mPasswordView.setError(getString(R.string.error_field_required));
            focusView = mPasswordView;
            cancel = true;
        }

        // Check for a valid email address.
        if (TextUtils.isEmpty(mEmail)) {
            mEmailView.setError(getString(R.string.error_field_required));
            focusView = mEmailView;
            cancel = true;
        } else if (!mEmail.contains("@")) {
            mEmailView.setError(getString(R.string.error_invalid_email));
            focusView = mEmailView;
            cancel = true;
        }

        if (cancel) {
            // There was an error; don't attempt login and focus the first
            // form field with an error.
            focusView.requestFocus();
        } else {
            // Show a progress spinner, and kick off a background task to
            // perform the user login attempt.
            mLoginStatusMessageView.setText(R.string.login_progress_signing_in);
            showProgress(true);
            mAuthTask = new UserLoginTask();
            mAuthTask.execute((Void) null);
        }
    }

    /**
     * Shows the progress UI and hides the login form.
     */
    @SuppressWarnings("ConstantConditions")
    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
    private void showProgress(final boolean show) {
        // On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
        // for very easy animations. If available, use these APIs to fade-in
        // the progress spinner.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
            int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);

            mLoginStatusView.setVisibility(View.VISIBLE);
            mLoginStatusView.animate()
                    .setDuration(shortAnimTime)
                    .alpha(show ? 1 : 0)
                    .setListener(new AnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(Animator animation) {
                            mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
                        }
                    });

            mLoginFormView.setVisibility(View.VISIBLE);
            mLoginFormView.animate()
                    .setDuration(shortAnimTime)
                    .alpha(show ? 0 : 1)
                    .setListener(new AnimatorListenerAdapter() {
                        @Override
                        public void onAnimationEnd(Animator animation) {
                            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
                        }
                    });
        } else {
            // The ViewPropertyAnimator APIs are not available, so simply show
            // and hide the relevant UI components.
            mLoginStatusView.setVisibility(show ? View.VISIBLE : View.GONE);
            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
        }
    }

    /**
     * Represents an asynchronous login/registration task used to authenticate
     * the user.
     */
    public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
        @Override
        protected Boolean doInBackground(Void... params) {
            UserService userService = new UserService(getApplicationContext());
            User logU = userService.login(mEmail, mPassword);
            if (logU != null) {
                Singleton.getInstance().setCurrUser(logU);
                return true;
            } else
                return false;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            if (success) {
                Intent postList = new Intent(getApplicationContext(), PostListActivity.class);
                postList.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(postList);
                finish();
            } else {
                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }

        @Override
        protected void onCancelled() {
            mAuthTask = null;
            showProgress(false);
        }
    }
}