The document discusses using shared preferences in Android to store data. It explains opening shared preferences in private mode, reading and writing values to shared preferences using methods like getString(), edit(), and putString(). It provides code examples of getting and setting username, password, and a checkbox value from shared preferences. The code shows initializing shared preferences, retrieving values on startup to populate fields, and committing edited values on a button click.

1. Develop on Android
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Lesson : The shared preferences

2. The shared preferences
• In this lesson, you will learn to store some
shared preferences.
• For this, you will use the
SharedPreferences.

3. The shared preferences
• Open the shared preferences « demo » in private mode :
SharedPreferences sharedPreferences = getSharedPreferences ("demo",
Context.MODE_PRIVATE);
• To read the preferences, use the method getString() for strings,
getBoolean() for booleans, etc …
et_username.setText (sharedPreferences.getString("username", ""));
cb_keepSession.setChecked (sharedPreferences.getBoolean ("keepSession", false));

4. The shared preferences
• To write the values in the shared preferences, call the method edit() to enter
in edition mode.
Editor editor = sharedPreferences.edit();
• Then use the methods putString(), putBoolean(), etc … depending on the
type of each information.
editor.putString("username", et_username.getText().toString());
editor.putString("password", et_password.getText().toString());
editor.putBoolean("keepSession", cb_keepSession.isChecked());
• A the end, call the method commit() to validate the data.
editor.commit();

5. Layout main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="5dip"
android:text="Username:" />
<EditText
android:id="@+id/et_username"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:singleLine="true" />

6. Layout main.xml
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="5dip"
android:text="Password:" />
<EditText
android:id="@+id/et_password"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:singleLine="true" />

7. Layout main.xml
<CheckBox
android:id="@+id/cb_keepSession"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Keep session ?" />
<Button
android:id="@+id/submit"
android:text="Submit"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</LinearLayout>

8. File Main.java
public class Main extends Activity {
EditText et_username;
EditText et_password;
CheckBox cb_keepSession;
SharedPreferences sharedPreferences;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
et_username = (EditText)findViewById(R.id.et_username);
et_password = (EditText)findViewById(R.id.et_password);
cb_keepSession = (CheckBox)findViewById(R.id.cb_keepSession);
Button btnSubmit = (Button)findViewById(R.id.submit);

9. File Main.java
btnSubmit.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Editor editor = sharedPreferences.edit();
editor.putString("username", et_username.getText().toString());
editor.putString("password", et_password.getText().toString());
editor.putBoolean("keepSession", cb_keepSession.isChecked());
editor.commit();
finish();
}
});
sharedPreferences = getSharedPreferences ("demo", Context.MODE_PRIVATE);
et_username.setText (sharedPreferences.getString("username", ""));
et_password.setText (sharedPreferences.getString("password", ""));
cb_keepSession.setChecked (sharedPreferences.getBoolean ("keepSession", false));

10. File Main.java
}
public void onResume() {
super.onResume();
}
public void onPause() {
super.onPause();
}
}

11. Test on your mobile
Storage_SharedPreferences

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