Mobile Application Development (AD-703 (B)) - Unit 3 Short Notes

How unit 3 is examined

This unit covers screen elements (views and widgets), layouts and animation; no past question has been asked on any of them, so learn the definitions and the class names.

User Interface Screen elements

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A View is the basic building block of an Android UI: a rectangular screen area that draws itself and handles user events, and widgets such as TextView, EditText, Button and ImageView are its subclasses.</mark>

Key points.

1. TextView displays text and EditText is its editable form for user input.
2. Button, CheckBox, RadioButton and Spinner take user choices, and each fires a listener such as onClick.
3. ImageView shows pictures, and ListView or RecyclerView shows scrolling lists.
4. Views are declared in XML with attributes like android:id, android:text, layout_width and layout_height, and are fetched in code with findViewById().

Designing User Interfaces with Layouts

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A layout is a ViewGroup, an invisible container that defines how its child views are arranged on the screen.</mark>

Key points.

1. LinearLayout places children in one row or column, set by android:orientation.
2. RelativeLayout positions children relative to each other or to the parent.
3. ConstraintLayout positions views with constraints to siblings and the parent, giving a flat, efficient hierarchy.
4. FrameLayout stacks children on top of each other, and TableLayout arranges them in rows and columns.
5. match_parent fills the parent, wrap_content fits the content, and layout_weight shares leftover space.

Drawing and Working with Animation

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Android animation changes a view's properties such as position, size, rotation or transparency over time, and drawing is done by painting shapes and bitmaps on a Canvas with a Paint object.</mark>

Key points.

1. Frame (drawable) animation plays a sequence of images one after another using AnimationDrawable.
2. Tween (view) animation applies translate, scale, rotate and alpha to a view, defined in XML under res/anim.
3. Property animation with ValueAnimator or ObjectAnimator changes any property of any object.
4. Custom drawing overrides onDraw(Canvas) in a View, using Paint for colour and style.

Last-minute revision

• A View is the basic UI block, and a ViewGroup (layout) is a container of views.
• TextView shows text, EditText takes input, Button fires onClick.
• findViewById() links an XML view to Java code.
• LinearLayout is one row or column, set by orientation.
• ConstraintLayout gives a flat hierarchy using constraints.
• wrap_content fits content, match_parent fills the parent.
• Frame animation plays images, tween animation transforms a view.
• Tween types are translate, scale, rotate and alpha.
• Custom drawing uses Canvas, Paint and onDraw().

Memory hooks

• View is the brick, ViewGroup is the box of bricks.
• Tween types spell STRA: Scale, Translate, Rotate, Alpha.
• Frame animation is a flip-book, tween is a stretch of one picture.

Coverage checklist

• User Interface Screen elements: no past questions.
• Designing User Interfaces with Layouts: no past questions.
• Drawing and Working with Animation: no past questions.