Lecture 2

Question 1

What is a Layout concerned with?

Answer 1

Organising component views in rectangular areas

Question 2

Each rectangular area in a layout may be fixed or scrollable

T or F

Answer 2

T

Question 3

Each rectangular area normally overlaps with another in a layout

T or F

Answer 3

F

Question 4

What are the challenges of Layouts?

Answer 4

Must work on multiple resolutions and orientations without losing functionality

Should look good and be usable (right text size etc.)

Question 5

What is the difference between screen resolution and screen density?

Answer 5

Resolution: Total number of pixels in a display

Density: Number of pixels that fit into an inch

Question 6

What is density independence?

Answer 6

The uniform display of UI elements on screens with different densities

Question 7

How many millimeters per inch on android?

Answer 7

25.4

Question 8

How many points per physical inch on android?

Answer 8

72

Question 9

Are points density independent?

Answer 9

Yes

Question 10

What do dp and sp stand for on android?

Answer 10

Density independent pixels

Scale independent pixels

Question 11

Are dp and sp density independent?

Answer 11

Yes

Question 12

How many dp and sp per physical inch?

Answer 12

160

Question 13

What are density buckets? How many are there and what are they?

Answer 13

Categories of densities for which images must be optimised on android

6 - Low, medium, TV, high, extra high, extra extra high

Question 14

Difference between margin and padding?

Answer 14

Margin on outside

Padding on inside

Question 15

What are fill_parent/match_parent and wrap_content layout properties?

Answer 15

wrap_content wants to be just big enough to enclose its contents

fill_parent and match_parent try to be the same size as the parent

Question 16

What are all layouts a subclass of?

Answer 16

GroupView

Question 17

What is LinearLayout?

Answer 17

all children aligned in a single direction vertically or horizontally

Question 18

What is RelativeLayout?

Answer 18

All child views are displayed in relative positions

Question 19

What is a WebView?

Answer 19

Displays web pages

Question 20

In LinearLayout, what properties does each child view have?

Answer 20

Width and Height - either wrap_content or match_parent, OR specified in px or dp

Gravity - which side of the screen it is attracted to (left, centre, right)

Margin

Question 21

How do you make a vertical layout work in device landscape mode?

Answer 21

Place layout file of the same name in the res/layout_land directory

Swap all heights for widths

Question 22

Why is switching layouts at runtime problematic?

Answer 22

Threads

Question 23

Which thread calls the onCreate of the main activity?

Answer 23

UI thread

Question 24

What is the best way to switch content views?

Answer 24

AsyncTask

Question 25

What two methods do you usually override in AsyncTasks?

Answer 25

doInBackground()

onPostExecute()

Question 26

What method might you override to show progress on progress bars with AsyncTasks?

Answer 26

publishProgress()

Question 27

What does using an AsyncTask guarantee?

Answer 27

All callback calls are synchronized in such a way that:

member fields set in constructor or onPreExecute can be accessed from doInBackground

member fields set in doInBackground can be accessed in onProgressUpdate and onPostExecute

Question 28

How can an AsyncTask be cancelled?

Answer 28

Invoke cancel(boolean)

Question 29

What should you do in doInBackground to ensure tasks can be cancelled?

Answer 29

Check isCancelled() regularly

Question 30

What is the main limit of AsyncTask?

Answer 30

Execution is bound to calling activity so rotating screen stops it