설정 (Preferences)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:weightSum="1"
        android:gravity="center">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Username:"/>

        <EditText
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/textInput1"
            android:layout_weight="0.38" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:gravity="center">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Password:"/>

        <EditText
            android:layout_width="137dp"
            android:layout_height="wrap_content"
            android:inputType="textPassword"
            android:id="@+id/textInput2"
            />
    </LinearLayout>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Login"
        android:id="@+id/button1"/>
</LinearLayout>

public class MainActivity extends AppCompatActivity {

*   public static final String PREFERENCES_GROUP = "LoginInfo";
    public static final String PREFERENCES_ATTR1 = "Username";
    ... 생략 ...
    SharedPreferences setting;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // SharedPreferences 객체 얻기
*       setting = getSharedPreferences(PREFERENCES_GROUP, MODE_PRIVATE);
        // setting = getPreferences(MODE_PRIVATE);

        final EditText textInput1 = (EditText) findViewById(R.id.textInput1);
        ... 생략 ...

*       textInput1.setText(retrieveName());
        ... 생략 ...

        Button btn = (Button) findViewById(R.id.button1);
        btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                String name = textInput1.getText().toString();

*               saveName(name);
                
                ... 생략 ...
            }
        });
    }

    private String retrieveName() {
        String nameText = "";
        // SharedPreferences 객체에서 PREFERENCES_ATTR1 이름으로 저장된 값을 얻기
 *      if (setting.contains(PREFERENCES_ATTR1)) {
 *          nameText = setting.getString(PREFERENCES_ATTR1, "");
        }
        return nameText;
    }

    private void saveName(String text) {
        // SharedPreferences 객체에 PREFERENCES_ATTR1 이름으로 text 문자열 값을 저장하기
*       SharedPreferences.Editor editor = setting.edit();
*       editor.putString(PREFERENCES_ATTR1, text);
*       editor.commit();
    }
    ... 생략 ...
}