Android Ui Fragments Ch 7

Front 1

Example of UI flexibility

Back 1

ability to compose/recompose an activity's view at runtime depending on what is required.

e.g., two activities can be next to each other on a tablet, but on a phone it makes more sense for user to swipe from one activity to the second

Front 2

Can you swap an activity's entire view without destroying it or pass a view from one activity to another at runtime?

Back 2

No. Activity's are tightly bound to their views. They are not built for this flexibility. Use fragments

Front 3

Fragment

Back 3

controller object that an activity can deputize to perform tasks

Front 4

UI fragment

Back 4

fragment that is managing all or part of the UI. Has a view of its own that is inflated from a layout file

Front 5

If you are using UI fragments, how do you set up the activity's view?

Back 5

set it up to contain spots where the fragments will be placed.

since the activity is technically staying the same throughout its lifetime, no laws of android are violated

Front 6

hosting (in terms of activity and UI fragment)

Back 6

activity is providing a spot in its view hierarchy where the fragment can place its view. fragment views must be within an activity's view in order to appear

Front 7

How do you manage backwards compatibility for fragments?

Back 7

support library that takes care of most of it is automatically included in project. To be double certain, modify the base code to extend FragmentActivity instead of Activity

Front 8

What's a good default superclass to use when creating a new class?

Back 8

java.lang.Object

Front 9

declare a variable to store a unique identifier and then generate a random unique identifier

Back 9

UUID mID;

mID = UUID.randomUUID();

Front 10

What does UUID stand for?

Back 10

universal unique identifier

Front 11

two general things an activity must do in order to host a UI fragment

Back 11

- define a spot in its layout for the fragment's view

- manage the lifecycle of the fragment instance

Front 12

two approaches to hosting a UI fragment in an activity

Back 12

1. Layout fragment

2. Add fragment to code

Front 13

Pros and cons of adding fragment to activity's layout

Back 13

simple

inflexible. this hard-wires the fragment to the view, so you can't swap it out during the activity's lifecycle

Front 14

pros and cons of adding fragment to activity's code

Back 14

more complex

lets you change the view at runtime

Front 15

3 basic steps to create a UI fragment

Back 15

1. compose an interface by defining widgets in a layout file

2. create the class and set its view to the layout you defined

3. wire up the widgets from the layout inflated in the code

Front 16

utf-8

Back 16

unicode transformation format

Front 17

xml mandates that you reference things using a....

Back 17

namespace

Front 18

superclass when you're creating a new class for a fragment

Back 18

android.support.v4.app.Fragment

this one ensures it will import the right support libraries for backwards compatibility

Front 19

dp

Back 19

density independent pixel

Front 20

How do you create a container to host a layout fragment?

Back 20

Create a view group within the activity's layout file. You'll create a separate xml file for the fragment, but it will ultimately be placed in this spot

Front 21

What methods do you need to override in your fragment class?

Back 21

public void onCreate(Bundle savedInstanceState);

public View onCreate(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState);

Front 22

Why is Fragment.onCreate(...) public when Activity.onCreate(...) is protected?

Back 22

Fragment's lifecycle methods must be public so Activity can manage them

Front 23

What does NOT happen in Fragment.onCreate that is significant?

Back 23

You don't inflate the view.

Instead, inflate the view in public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState)

Front 24

What do you do in Fragment.onCreateView(...)?

Back 24

View v = inflater.inflate(R.layout.fragment_crime, parent, false); //false means we won't add the inflated view to the parent. Instead, we're going to do it in the activity's code

//insert code to wire up widgets here!

return v;

Front 25

What's the difference between getting references for a fragment vs. in an activity?

Back 25

For a fragment, you do it on onCreateView and must use v.findViewById instead of just findViewById

Front 26

What does FragmentManager do?

Back 26

manages fragments and adds their views to the activity's hierarchy

Front 27

What are the general steps to add a fragment to an activity in code?

Back 27

1. Get the FragmentManager

2. Give it a fragment to manage

Front 28

Syntax to get the FragmentManager

Back 28

FragmentManager fm = getSupportFragmentManager();

Front 29

Once you have the FragmentManager, how do you give it a fragment to manage?

Back 29

Fragment fragment = fragMngr.findFragmentById(R.id.fragmentContainer);

if (fragment == null)

fragment = new CrimeFragment();

fm.beginTransaction().add(R.id.fragmentContainer, fragment).commit();

Front 30

what are fragment transactions used for?

Back 30

add/remove/detach/replace fragments in the fragment list

FragmentManager.beginTransaction() returns an instance of FragmentTransaction, and then you can take action on the fragments in the list (it tells them apart by the container view)

Front 31

What methods are called when you add the fragment to the FragmentManager?

Back 31

onAttach(Activity)

onCreate(Bundle)

onCreateView(...)

Afterward, Activity.onCreated(Bunde) is called, along with Activity.onStart() and Activity.onResume()

Front 32

Once the fragment's state is caught up to the activity's state, what does the FragmentManager do?

Back 32

calls corresponding lifecycle methods around the same time the OS receives it. No guarantee of fragment or activity receiving it first

Front 33

Should you start a program and then add fragments later on?

Back 33

No, much harder to add fragments later. Plan to have them right away