Use PreferenceManager in place of SharedPreferences

SharedPreferences is used in android to store data in the form of a key-value pair in an application. But, sometimes we need to store data at many places in the application such as saving the login email or a particular information that remains the same for the entire use of the app. In SUSI.AI android app PrefManager.java class is made that uses the sharedpreferences in android and provides a custom wrapper that is used to store the data in the key-value pair form in the app.

To store data in sharedpreferences through the PreferenceManager class we just need to declare an instance of the PreferenceManager in the location in which we want to save the data. The SUSI.AI Android app opens up the login screen and on just viewing the welcome cards for the first time due to the incorrect implementation of the sharedpreferences, using the Preference Manager we can correctly implement the preferences in welcome activity.

Whenever we install the SUSI.AI Android app, on opening it for the first time we see welcome cards that give a basic overview of the app. So, now after swiping all the cards and on reaching the final card instead of clicking GOT IT to move to the login screen and on pressing the home button we put the app in the background. Now, what happened was when the app showed cards, it was due to the WelcomeActivity.java activity.

In the onCreate() method of this activity we check whether the WelcomeActivity is opened for the first time or not. In this case we make use of the PrefManager.java class.

if (PrefManager.getBoolean(“activity_executed”, false)) {
  Intent intent = new Intent(this, LoginActivity.class);
  startActivity(intent);
  finish();
} else {
  PrefManager.putBoolean(“activity_executed”, true);
}

This piece of code calls the getBoolean(<preferenceKey>,<preferenceDefaultValue>) of the PrefManager.java class and checks the boolean value against the preference key passed in the function.

If it is the first time when this function is called then the default value is accessed against the preference key: “activity_executed”, which is passed as false and no code within the if statement is executed and so the code in the else block is executed which puts the value true as the preference value against the key “activity_executed” and the next line is executed in the sequence after this line. In short, on opening the app for the first time the preference key “activity_executed” has a value of true against it.

When we close the app by destroying it while it is in the WelcomeActivity, the onDestroy() method is called and memory is cleared, but when we open the app again we expect to see the Welcome Cards, but instead we find that we are on the login screen, even though the GOT IT button on the final card was not pressed. This is because when we go through the onCreate() method again the if condition is true this time and it sends the user directly to the Login activity.

To, solve this problem the method that was followed was :

  1. Remove the else condition in the if condition where we check the value stored against the key “activity_executed” key.
  2. In the onCreate() method of the LoginActivity.kt file use the PrefManager class to put a boolean value equal to true against the key : “activity_executed”.So the code added in the LoginActivity.kt file’s onCreate() method was :
PrefManager.putBoolean(“activity_executed”, true)

Also, the else condition was removed in the Welcome activity. Now, with these changes in place unless we click GOT IT on the final card in the welcome activity we won’t be able to go to the Login Activity, and since we won’t be able to go to the final activity the value against the key “activity_executed” will be false. Also, once we move to the login activity we will not be able to see the cards as the if condition described above will be true and the intent will fire the user to the Login Activity forever.

Therefore, using the PrefManager class it became very easy to put values or get values stored in the sharedpreferences in android. The methods are created in the Preference manager for different types corresponding to the different return types present that can be used to store the values allowed by the SharedPreferences in Android.

Using the PrefManager class functions it was made easy in SUSI.AI android app to access the SharedPreferences and using it a flaw in the auth flow and opening of the app was resolved.

 

Resources

  1. How to launch an activity only once for the first time! – Divya Jain:  https://androidwithdivya.wordpress.com/2017/02/14/how-to-launch-an-activity-only-once-for-the-first-time/
  2. Save key-value data : ttps://developer.android.com/training/data-storage/shared-preferences
  3. PrefManager Class: https://github.com/fossasia/susi_android/blob/development/app/src/main/java/org/fossasia/susi/ai/helper/PrefManager.java
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Storing a Data List in Phimpme Android

In Phimpme Android, it is required to store all the available camera parameters like a list of ISO values, available camera resolution etc. so that it can be displayed to the user in the camera settings. In Phimpme, we have stored these list of data in SharedPreferences with some modifications. As we cannot store a list directly in SharedPreference, in this post I will be discussing how we achieved this in Phimpme Android application.

To store the ArrayList you have to create a function that will convert the array into a string by using some symbol.

Step – 1

First, Create a class say TinyDB which contains functions to store an array in sharedPreferences.

public class TinyDB
{
private SharedPreferences preferences;
public TinyDB(Context appContext) {
preferences = PreferenceManager.getDefaultSharedPreferences(appContext);
}
}

Step – 2

Create functions to convert the array into string and store in sharedPreferences.

putListInt() method will convert the string ArrayList to String and store in sharedPreferences.

Similarly, putListString() method will convert the integer ArrayList to string and store in sharedPreferences.

public void putListInt(String key, ArrayList<Integer> intList) {
  if (key == null) return;
  if (intList==null) return;
  Integer[] myIntList = intList.toArray(new Integer[intList.size()]);
  preferences.edit().putString(key, TextUtils.join(“‚‗‚”, myIntList)).apply();
}

  
public void putListString(String key, ArrayList<String> stringList) {
  if (key == null) return;
  if (stringList ==null)return;
  String[] myStringList = stringList.toArray(new String[stringList.size()]);
  preferences.edit().putString(key, TextUtils.join(“‚‗‚”, myStringList)).apply();
}

 

 

Now create the object of TinyDB.class to call the above functions using tinyDb object.

Now our data is saved in sharedPreference to get this data we have to create a getter for the ArrayList.

 

Step-3

Add two functions in TinyDB.class to get the string and integer ArrayList.

public ArrayList<String> getListString(String key) {
        return new ArrayList<String>(Arrays.asList(TextUtils.split(preferences.
=getString(key, “”), “‚‗‚”)));
}



public ArrayList<Integer> getListInt(String key) {
  String[] myList = TextUtils.split(preferences.getString(key, “”), “‚‗‚”);
  ArrayList<String> arrayToList = new ArrayList<String>(Arrays.asList(myList));
  ArrayList<Integer> newList = new ArrayList<Integer>();

  for (String item : arrayToList)
      newList.add(Integer.parseInt(item));

  return newList;
}

Now to get the saved integer and string ArrayList simply call this function by creating an instance of TinyDB.class.

The below screenshot depicts how we have stored the list of camera resolutions in SharedPreference using TinyDB class.

So this is how you can store the entire ArrayList in sharedPreferences. For more detail, you can see the TinyDb.class in our Phimpme project.

Resources:  

https://stackoverflow.com/questions/7057845/save-arraylist-to-sharedpreferences

http://blog.nkdroidsolutions.com/arraylist-in-sharedpreferences/

http://findnerd.com/list/view/Save-ArrayList-of-Object-into-Shared-Preferences-in-Android/510?page=10&ppage=3

https://github.com/fossasia/phimpme-android/blob/development/app/src/main/java/org/fossasia/phimpme/opencamera/Camera/TinyDB.java

 

 

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