Every app should provide a smooth and user-friendly login experience, as it is the first point of contact between app and user. To provide easy login in SUSI, auto-suggestion email address is used. With this feature, the user is able to select his email from autocomplete dropdown if he has successfully logged in earlier in the app just by typing first few letters of his email. Thus one need not write the whole email address each and every time for login.
Let’s see how to implement it.
AutoCompleteTextView is the subclass of EditText class, which displays a list of suggestions in a drop down menu from which user can select only one suggestion or value. To use AutoCompleteTextView the dependency of the latest version of design library to the Gradle build file should be added.

dependencies {
compile "com.android.support:design:$support_lib_version"
}

Next, in the susi_android/app/src/main/res/layout/activity_login.xml. The AutoCompleteTextView is wrapped inside TextInputLayout to provide an input field for email to the user.

<android.support.design.widget.TextInputLayout
android:id="@+id/email"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:errorEnabled="true">
<AutoCompleteTextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/email"
android:id="@+id/email_input"
android:textColor="@color/edit_text_login_screen"
android:inputType="textEmailAddress"
android:textColorHint="@color/edit_text_login_screen" />
<android.support.design.widget.TextInputLayout/>

href=”https://github.com/fossasia/susi_android/blob/development/app/src/main/java/org/fossasia/susi/ai/activities/LoginActivity.java”>susi_android/app/src/main/java/org/fossasia/susi/ai/activities/LoginActivity.java following import statements is added to import the collections.

import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;

The following code binds the AutoCompleteTextView using ButterKnife.

@BindView(R.id.email_input)
AutoCompleteTextView autoCompleteEmail;

To store every successfully logged in email id, use Preference Manager in login response.

...
if (response.isSuccessful() && response.body() != null) {
Toast.makeText(LoginActivity.this, response.body().getMessage(), Toast.LENGTH_SHORT).show();
// Save email for autocompletion
savedEmails.add(email.getEditText().getText().toString());
PrefManager.putStringSet(Constant.SAVED_EMAIL,savedEmails);
}
...

Here Constant.SAVED_EMAIL is a string defined in Constants.java as

public static final String SAVED_EMAIL="saved_email";

Next to specify the list of suggestions emails to be displayed the array adapter class is used. The setAdapter method is used to set the adapter of the autoCompleteTextView.

private Set savedEmails = new HashSet<>();
if (PrefManager.getStringSet(Constant.SAVED_EMAIL) != null) {
savedEmails.addAll(PrefManager.getStringSet(Constant.SAVED_EMAIL));
autoCompleteEmail.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, new ArrayList<>(savedEmails)));
}

Then just test it with first logging in and after that every time you log in, just type first few letters and see the email suggestions. So, next time when you make an app with login interface do include AutoCompleteview for hassle-free login.