Android : Android onBackPressed avoid exit

When the user press the back button on his device I want to move to the previous Activity but not to go back to the Home.

For example, if the user has opened some Activities, the back stack is supposed to be:

• Activity_A


• Activity_B


• Activity_C [ Currently displayed ]

When the user presses the Back button, it's supposed to get:

• Activity_A


• Activity_B [ Currently displayed ]

And the, if he presses the button once again:

• Activity_A [ Currently displayed ]

Then I want to disable this button to avoid to go back to the Home screen.

Is that possible ?

So far, I'm using this method, but I've read that it won't be supported on Android L:

protected int getActivitiesStackSize()
{
    ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
    List<ActivityManager.RunningTaskInfo> taskList = am.getRunningTasks(1);
    return taskList.get(0).numActivities; 
}

@Override
public void onBackPressed()
{
    // Pop activity
    if (getActivitiesStackSize() != 1) super.onBackPressed();
}