Mercury-IM/app/src/main/java/org/olomono/messenger/view/LoginActivity.java

package org.olomono.messenger.view;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.inputmethod.EditorInfo;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import org.jxmpp.jid.EntityBareJid;
import org.jxmpp.jid.impl.JidCreate;
import org.olomono.messenger.R;

/**
 * A login screen that offers login via email/password.
 */
public class LoginActivity extends AppCompatActivity implements TextView.OnEditorActionListener {

    // UI references.
    private AutoCompleteTextView mJidView;
    private EditText mPasswordView;
    private View mProgressView;
    private View mLoginFormView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        // Set up the login form.
        mJidView = findViewById(R.id.jid);
        mPasswordView = findViewById(R.id.password);

        mJidView.setOnEditorActionListener(this);
        mPasswordView.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView textView, int id, KeyEvent keyEvent) {
                if (id == EditorInfo.IME_ACTION_DONE || id == EditorInfo.IME_NULL) {
                    loginDetailsEntered();
                    return true;
                }
                return false;
            }
        });

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

        mLoginFormView = findViewById(R.id.login_form);
        mProgressView = findViewById(R.id.login_progress);
    }

    private void loginDetailsEntered() {
        String jidInput = mJidView.getText().toString();
        if (jidInput.isEmpty()) {
            mJidView.setError(getResources().getString(R.string.error_field_required));
        }

        EntityBareJid jid = asValidJidOrNull(jidInput);
        if (jid == null) {
            mJidView.setError(getResources().getString(R.string.error_invalid_jid));
        }

        String password = mPasswordView.getText().toString();
        if (!isPasswordValid(password)) {
            mPasswordView.setError(getResources().getString(R.string.error_invalid_password));
        }
    }

    /**
     * Try to parse the input string into a {@link EntityBareJid} and return it.
     * Return null on failure.
     * @param input input string
     * @return valid jid or null
     */
    private EntityBareJid asValidJidOrNull(String input) {
        return JidCreate.entityBareFromOrNull(input);
    }

    private boolean isPasswordValid(String password) {
        return !password.isEmpty();
    }

    @Override
    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
        switch (v.getId()) {
            case R.id.jid:
                if (actionId == EditorInfo.IME_ACTION_NEXT) {
                    mPasswordView.requestFocus();
                    return true;
                }
                break;

            case R.id.password:
                if (actionId == EditorInfo.IME_ACTION_DONE || actionId == EditorInfo.IME_NULL) {
                    loginDetailsEntered();
                    return true;
                }
        }
        return false;
    }
}