Step 1: Create a new app (module)
- Blank Activity
- Activity Name: MainActivity
- Layout Name: activity_main
Step 2: build the app
If you receive the following error, make sure "Project Structure" has the right SDK version settings.
Failure [INSTALL_FAILED_OLDER_SDK]
Step 3: create basic UI
- TextView "My Important Info:"
- EditText infoEditText
- Button saveButton
Enter some super important stuff (type in text).
Step 4: KILL the app, restart
when you re-open the app the text is gone :(
Step 5: Declare your UI components in MainActivity
public class MainActivity extends ActionBarActivity {
private EditText infoEditText;
private Button saveButton;
Step 6: Wire your UI components in onCreate()
infoEditText = (EditText) findViewById(R.id.infoEditText);
saveButton = (Button) findViewById(R.id.saveButton);
saveButton.setOnClickListener(saveListener);
We will use Log, so define the TAG in MainActivity as class member.
private static final String TAG = MainActivity.class.getSimpleName();
Step 7: Define a name for our key-value
/**
* We will be using this constant as a "key" i.e. name of our key-value pair
*/
static final String PREFERENCE_KEY_INFO = "MY_INFO";
Step 8: Write your Listener
/**
* This listener class can be used for any View e.g. Button
*/
View.OnClickListener saveListener = new View.OnClickListener() {
public void onClick(View v) {
Log.i(TAG, "onClick detected in view " + v.getClass().getSimpleName());
String key = PREFERENCE_KEY_INFO;
String value = infoEditText.getText().toString();
if (value.equals("")) {
Log.w(TAG, "You did not provide any text! Saving anyway.");
}
preferences.save(key, value);
}
};
Step 9: Create SharedPreferencesHelper
package com.chicagoandroid.cit299.userpreferences;
import android.content.Context;
import android.content.SharedPreferences;
import android.util.Log;
/**
* This helper class will abstract the use of Shared Preferences and will make them very reusable.
*/
public class SharedPreferencesHelper {
private SharedPreferences preferences;
private Context parentContext;
private String preferencesName;
private static String TAG;
/**
* This is a constructor that will set up context of the preferences.
* @param context - the calling Activity context.
* @param preferencesName - desired preferences store name.
*/
public SharedPreferencesHelper(Context context, String preferencesName) {
parentContext = context;
preferencesName = preferencesName;
TAG = parentContext.getClass().getSimpleName() + "." + SharedPreferencesHelper.class.getSimpleName();
}
Step 10: add save() to SharedPreferencesHelper
/**
* This method will save User Preferences
*
* @param key - the unique name of the preference
* @param value - the String value to be saved
*/
public void save(String key, String value) {
if (preferences == null) {
preferences = parentContext.getSharedPreferences(preferencesName, Context.MODE_APPEND);
Log.i(TAG, "Creating shared preferences");
}
String message = "saveUserPreferences() for " + preferencesName + " key: " + key + ", value: " + value;
Log.d(TAG, message);
SharedPreferences.Editor editor = preferences.edit();
editor.putString(key, value);
editor.commit();
}
Step 11: add fetch() to SharedPreferencesHelper
/**
* Method used to restore Shared Preference
* @param key
* @param defaultValue`
* @return
*/
public String fetch(String key, String defaultValue) {
if (preferences == null) preferences = parentContext.getSharedPreferences(preferencesName, Context.MODE_APPEND);
String savedText = preferences.getString(key, defaultValue);
Log.i("restoreUserPreferences() for " + preferencesName, " key: " + key + " value: " + savedText);
return savedText;
}
Step 12: Define the rest of Activity class variables
public class MainActivity extends ActionBarActivity {
private EditText infoEditText;
private Button saveButton;
/**
* We will be using this constant as a "key" i.e. name of our key-value pair
*/
static final String PREFERENCE_KEY_INFO = "MY_INFO";
SharedPreferencesHelper preferences;
private static final String MAIN_PREFERENCES = MainActivity.class.getCanonicalName(); private static final String TAG = MainActivity.class.getSimpleName();
Step 13: update onCreate() to fetch any saved preferences
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
preferences = new SharedPreferencesHelper(this, MAIN_PREFERENCES);
setContentView(R.layout.activity_main);
infoEditText = (EditText) findViewById(R.id.infoEditText);
saveButton = (Button) findViewById(R.id.saveButton);
saveButton.setOnClickListener(saveListener);
infoEditText.setText(preferences.fetch(PREFERENCE_KEY_INFO, "my default value"));
}
Step 14: restart and test the app
The first time you open the app the default value should be in the EditText.
Step 15: Implement security
read more:
https://github.com/sveinungkb/encrypted-userprefs/blob/master/src/SecurePreferences.java
