Soma at 19:48, 29 March 2021

2021-03-29T19:48:21Z

← Older revision		Revision as of 19:48, 29 March 2021
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	==Video==		==Video==

	Video from the lecture given on March 29, 2021 ~~may be corrupted~~. ~~If the video is successfully converted it will be posted here~~.		Video from the lecture given on March 29, 2021 [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/lectures/comp1601-2021w-lec20-20210329.m4v is now available]. Note that this recording ends a bit abruptly and early as there were technical issues.

	==Notes==		==Notes==

Soma: Created page with "==Video== Video from the lecture given on March 29, 2021 may be corrupted. If the video is successfully converted it will be posted here. ==Notes==

 Lecture 20 ------..."

2021-03-29T18:27:26Z

Created page with "==Video== Video from the lecture given on March 29, 2021 may be corrupted. If the video is successfully converted it will be posted here. ==Notes== <pre> Lecture 20 ------..."

New page

==Video==

Video from the lecture given on March 29, 2021 may be corrupted. If the video is successfully converted it will be posted here.

==Notes==

<pre>
Lecture 20
----------

* Tutorial 8 is finally posted
- will be finalized this afternoon

* Tutorial 9 will come out by next Monday

* Assignment 4 will be due still on April 12
- will come out this week, hopefully by Wednesday
- will give away answers in class

* No Tutorial 10 (schedule will be updated)

* Final exam on April 23, 2 PM
- same format as the midterm, just 2 hours instead of 80 min

* Solutions for A3 will be posted on Wednesday
- turn in by Tuesday night if you haven't already

Kotlin is a bit funny about numbers
- it does NO automatic conversions
- a number with no decimals is an Int
- a number with decimals is a Double
- but then, how do you write a Float as a constant?
- append with an F

Floats vs Doubles
- floats use 4 bytes, doubles use 8 bytes
- so, doubles allow for much greater precision
- larger exponent and mantissa
- both are binary representations of numbers in
scientific notation

Android intents & activities go together
- intents are messages to an app to do something
- activities are screens that can be displayed in response to intents
- an intent doesn't have to cause a screen to be
displayed, but if you want to display a new screen
(including the first one), it will start with an
intent

- so, to switch screens we generate and receive intents
- also, to call outside apps, we send intents

Intents have two kinds: explicit and implicit
- explicit specifies exactly what to do
- implicit allows the receiver to interpret,
may even be receivable by multiple apps
</pre>

==Code==

Below is the layout created during class. The app was just the default Kotlin hello world (empty activity).

<syntaxhighlight lang="xml" line>
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<TextView
android:id="@+id/valueLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="33dp"
android:layout_marginBottom="215dp"
android:text="Value"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/value" />

<EditText
android:id="@+id/value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="74dp"
android:ems="8"
android:inputType="numberDecimal"
app:layout_constraintBaseline_toBaselineOf="@+id/valueLabel"
app:layout_constraintEnd_toEndOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
</syntaxhighlight>

Mobile App Development 2021W Lecture 20 - Revision history

Soma at 19:48, 29 March 2021

Soma: Created page with "==Video== Video from the lecture given on March 29, 2021 may be corrupted. If the video is successfully converted it will be posted here. ==Notes==
Lecture 20 ------..."