Xivanki Share !!: Store and Get an Object in Android Shared Preferences

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Can I store and retrieve an object in Android Shared Preferences? Yes! This tutorial will walk you through a complete tutorial. Source code included! There are times when you need to store a lightweight object in Shared Preferences. I stress lightweight. We are going to use Google's JSON library to do the object serialization/de-serialization.

• Let's create a new project.

Download the latest gson jar from http://code.google.com/p/google-gson/downloads/list. I am using version 1.7. Place the jar somewhere convenient (If I intend to use the jar in several projects, I will place in a folder outside of my project). For this example, I will create a new folder called "lib" inside the project folder. Place the jar you downloaded in "lib" folder. Now we need to add a reference to gson jar.

• Open the project properties. Right click on project name "ObjectsInSharedPreferenceSample" or whatever you called your project and select "Properties"

• Select "Java Build Path" > "Add External JARS..."

• Let's add a custom class that we are going to store and retrieve in the Shared Preferences. Add a new class "MyObject"

• To keep the example simple, lets add just two public properties to our "MyObject" class
• public int myValue;
• public String MyLabel;
• Add two buttons and two EditText. Make sure to add the onClick directive the XML so when the button is pressed our methods are executed.

• Let's write some code. In the MainActivity add the following method. This method will be called when the store button is pressed. It will create an instance of "MyObject" and set the "MyValue" string to what ever you type in the EditText inputEditText. Then it will convert the object to a string using the gson library and store that string in the SharedPreferences.

public void storeButton_Clicked(View v){
     EditText inputEditText = (EditText) findViewById(R.id.inputEditText);
     MyObject obj = new MyObject();
     obj.myValue = 2;
     obj.MyLabel = inputEditText.getText().toString();
     SharedPreferences appSharedPrefs = PreferenceManager
  .getDefaultSharedPreferences(this.getApplicationContext());
  Editor prefsEditor = appSharedPrefs.edit();
  Gson gson = new Gson();
  String json = gson.toJson(obj);
  prefsEditor.putString("MyObject", json);
  prefsEditor.commit();
  Toast.makeText(this, "Object stored in SharedPreferences", Toast.LENGTH_LONG);
    }

• Now let's get the object from shared preferences and display it's properties in the outputEditText. 

public void getButton_Clicked(View v){
     EditText outputEditText = (EditText) findViewById(R.id.outputEditText);
  SharedPreferences appSharedPrefs = PreferenceManager
  .getDefaultSharedPreferences(this.getApplicationContext());
  Gson gson = new Gson();
  String json = appSharedPrefs.getString("MyObject", "");
  MyObject obj = gson.fromJson(json, MyObject.class);
  outputEditText.setText("obj.MyLabel: [" + obj.MyLabel + "] obj.MyValue: [" + obj.myValue + "]");
    }

Run the program. Save an object and retrieve it from SharedPreferences. To keep things as simple as possible I only included required code. There is a lot of code missing that you will want to add like error checking and running off the UI thread. But this will get you started.

Following is the complete source code for your review.