How do I pass data between Activities in Android application?

I have a scenario where, after logging in through a login page, there will be a sign-out button on each activity.

On clicking sign-out, I will be passing the session id of the signed in user to sign-out. Can anyone guide me on how to keep session id available to all activities?

Any alternative to this case

In your current Activity, create a new Intent:

String value="Hello world";
Intent i = new Intent(CurrentActivity.this, NewActivity.class);    
i.putExtra("key",value);
startActivity(i);

Then in the new Activity, retrieve those values:

Bundle extras = getIntent().getExtras();
if (extras != null) {
    String value = extras.getString("key");
    //The key argument here must match that used in the other activity
}

Use this technique to pass variables from one Activity to the other.

The easiest way to do this would be to pass the session id to the signout activity in the Intent you're using to start the activity:

Intent intent = new Intent(getBaseContext(), SignoutActivity.class);
intent.putExtra("EXTRA_SESSION_ID", sessionId);
startActivity(intent);

Access that intent on next activity:

String sessionId = getIntent().getStringExtra("EXTRA_SESSION_ID");

The docs for Intents has more information (look at the section titled "Extras").

Passing Intent extras is a good approach as Erich noted.

The Application object is another way though, and it is sometimes easier when dealing with the same state across multiple activities (as opposed to having to get/put it everywhere), or objects more complex than primitives and Strings.

You can extend Application, and then set/get whatever you want there and access it from any Activity (in the same application) with getApplication().

Also keep in mind that other approaches you might see, like statics, can be problematic because they can lead to memory leaks. Application helps solve this too.

Source class:

Intent myIntent = new Intent(this, NewActivity.class);
myIntent.putExtra("firstName", "Your First Name Here");
myIntent.putExtra("lastName", "Your Last Name Here");
startActivity(myIntent)

Destination Class (NewActivity class):

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view);

    Intent intent = getIntent();

    String fName = intent.getStringExtra("firstName");
    String lName = intent.getStringExtra("lastName");
}

You just have to send extras while calling your intent.

Like this:

Intent intent = new Intent(getApplicationContext(), SecondActivity.class);
intent.putExtra("Variable name", "Value you want to pass");
startActivity(intent);

Now on the OnCreate method of your SecondActivity you can fetch the extras like this.

If the value you sent was in long:

long value = getIntent().getLongExtra("Variable name which you sent as an extra", defaultValue(you can give it anything));

If the value you sent was a String:

String value = getIntent().getStringExtra("Variable name which you sent as an extra");

If the value you sent was a Boolean:

Boolean value = getIntent().getBooleanExtra("Variable name which you sent as an extra", defaultValue);