https://homeostasis.scs.carleton.ca/wiki/index.php?action=history&feed=atom&title=Mobile_App_Development_2021W_Lecture_21 2026-04-24T00:40:10Z Revision history for this page on the wiki MediaWiki 1.42.1 https://homeostasis.scs.carleton.ca/wiki/index.php?title=Mobile_App_Development_2021W_Lecture_21&diff=23118&oldid=prev 2021-03-31T18:36:37Z

<p>Created page with &quot;==Video== Video from the lecture given on March 31, 2021 [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/lectures/comp1601-2021w-lec21-20210331.m4v is now available]. =...&quot;</p> <p><b>New page</b></p><div>==Video==<br /> <br /> Video from the lecture given on March 31, 2021 [https://homeostasis.scs.carleton.ca/~soma/mad-2021w/lectures/comp1601-2021w-lec21-20210331.m4v is now available].<br /> <br /> ==Notes==<br /> <br /> &lt;pre&gt;<br /> Lecture 21<br /> ----------<br /> * Assignment 3 solutions<br /> * app manifest<br /> * Intents<br /> - explicit<br /> - implicit<br /> * drawable shapes<br /> * touch events<br /> <br /> Tutorial 9 and A4 will come out this week, probably tomorrow.<br /> <br /> Tutorial 10 will be optional and on iOS storyboard<br /> - can substitute for a tutorial that you missed<br /> - won&#039;t be on the final exam<br /> <br /> Application manifest<br /> - tells Android how to run the app<br /> - this is where you define activities<br /> - really, classes that are associated with layouts<br /> - and also define intents your app will respond to<br /> - such as launching the app<br /> <br /> Intents are the basic inter-process communication mechanism on android<br /> - think of them as messages that can be sent between programs, including a program to itself<br /> - used to launch activities<br /> <br /> (By the way, intents are built on mechanisms that are not<br /> Linux-native, rely on modifications to the Linux kernel that were only upstreamed relatively recently)<br /> <br /> idea is to do fast message passing with minimal amount of memory copying<br /> - copying memory is slow<br /> - example, zero-copy networking<br /> <br /> If you want to start a new class with a new screen, standard way is to use an intent<br /> - and your new class will have to set things up just<br /> as we did in MainActivity, including specifying the layout<br /> - be sure to add the activity to the application manifest<br /> <br /> Launching your own class as a new activity is an &quot;explicit&quot; intent<br /> - you specified what code should run (i.e., the class)<br /> <br /> But in many contexts, you don&#039;t know what code to run<br /> - you want a service provided by another application<br /> <br /> Implicit intents let you make requests when you don&#039;t know what application will handle the request.<br /> - simple example: open web page in a browser<br /> - when you specify a default browser in android, you<br /> are specifying what browser will handle intents such as<br /> ACTION_VIEW<br /> <br /> You have to be careful when defining intents, especially implicit intents<br /> - can be called by arbitrary apps<br /> - so, you may need to do access control<br /> - can be a big security hole, depending on how they are used<br /> <br /> If you care about security or privacy at all as a developer, you need to pay attention to android intents and the permissions associated with them<br /> <br /> Drawable shapes<br /> - in iOS SwiftUI, we&#039;d just say Circle, Rectangle etc<br /> and we&#039;d get shapes<br /> - in Android, it is a bit more complicated<br /> - with a canvas, we can do these things programmatically<br /> much like a canvas in a web page<br /> - but in a regular view, you need to specify<br /> drawings using drawable shapes and paths normally<br /> specified in XML<br /> - you can display using an ImageView (just like a jpeg)<br /> <br /> Touch events in Android are a lot more complicated than in SwiftUI<br /> - we&#039;re not going to achieve parity with iOS in this class,<br /> that will have to wait until 2601<br /> <br /> <br /> Regarding grading<br /> - assignments, tutorials, and participation can<br /> only improve your grade relative to the midterm and final<br /> &lt;/pre&gt;</div>

Soma