Android 101 - Introduction to Android Development
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This document provides an introduction to Android development. It covers topics such as setting up the development environment, understanding the file system structure, using activities and fragments, handling fragmentation across different devices, and some best practices. The document discusses tools like Android Studio, the build system, and debugging tools. It also explains concepts like the activity lifecycle, saving activity state, targeting different versions and configurations, and using support libraries for backwards compatibility.
Android 101 - Introduction to Android Development
- 1. Android 101 Introduction to Android Development Andy Scherzinger Spare-time Android Dev AndyScherzinger 28th Jan. 2016
- 2. Topics • Dev Setup • File System Structure • Activities & Fragments • Handle Fragmentation • The little Things
- 3. Dev Setup Tool Chain Java Language Gradle Build System Android Studio IDE Android Studio icon CC BY 2.5 Google Inc.
- 4. Android Studio Coding Environment & Debugger SDK Manager Gradle Integration Android Device Monitor Android Virtual Device Manager Android Studio icon CC BY 2.5 Google Inc.
- 5. Code to Binary Java Byte Code Java Byte Code Java Source Code Java Source Code Java Compiler Java Compiler Dalvik Byte Code Dex Compiler Java Byte Code Dalvik Byte Code Dalvik VM Android Runtime (ART) Java VM https://github.com/devacademy/android-fundamental-one/blob/master/modules/stack.md
- 6. File System Structure * Grid, List, UI Partials • AndroidManifest.xml your App‘s definition • build.gradle,… your build files • src/java douh! your implementation • src/res – anim custom animations – drawable graphics (pixel, patch9, vector-xml, etc.) – layout XML Layouts for Activities, Fragments, *-Items – menu XML Menu Files – raw any non-specific files – values l18n resources, static (array) data, configurations – xml Preference Screen, Sync Adapter, etc.
- 7. Fragment Orchestration Source: http://developer.android.com/training/basics/fragments/fragment-ui.html Fragments are UI modules orchestrated via Activities Fragment A Fragment B Fragment A Fragment B Activity 1 Activity 1 Activity 2 Intent
- 8. Activities & Fragments – Activity Lifecycle Source: http://developer.android.com/training/basics/activity-lifecycle/starting.html Created Started (visible) Resumed (visible) Paused (part. visible) Stopped (hidden) Destroyed onResume() onStart() onStart() onDestroy() onStop() onPause() onResume() onRestart() Android 1 2 3 • (1) Initialize UI • (2) Checks (e.g. GPS enabled) • (3) Activity running - Woohoo! onCreate()
- 9. Activities & Fragments – Activity State Save Source: http://developer.android.com/training/basics/activity-lifecycle/recreating.html Created Resumed (visible) Destroyed onRestoreInstanceState() onSaveInstanceState() Android 2 3 1 • (1) save your state • (2) / (3) restore the state onCreate() Resumed (visible)
- 10. Fragmentation Resolution & Display Size Android Versions http://opensignal.com/reports/2015/08/android-fragmentation/ - http://developer.android.com/about/dashboards/index.html
- 11. Target Versions and Sizes • src/res – drawable-hdpi-v11 used for Android 11 and up – layout-w600dp-land used in landscape w/ at least 600dp width
- 12. Call Version depending code • src/java if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.HONEYCOMB) { builder.setIconAttribute(android.R.attr.alertDialogIcon); }…
- 13. Backwards Compatibility via Support Lib • Add libs to build.gradle dependencies { compile 'com.android.support:support-v4:23.1.1' compile 'com.android.support:design:23.1.1' compile 'com.android.support:appcompat-v7:23.1.1' }
- 14. …and hack away… • UI: AppCompatButton, Drawer, Material Theme, AppCompatDialog, … • Functionality: e.g. ContextCompat.checkSelfPermission Android M Permission System Implementation Backwards Compatibility via Support Lib
- 15. The (many) little Things…CodeUIMisc • Use Support Lib right from the beginning • Use Activities to manage Fragments • Use Fragments to implement the UI • onCreate is monitored by the Android Runtime and is part of the UI Thread time consuming work needs to be done asynchronously (!) • Style UI via style xml files not via specific view attributes in layout xml files • Define a color palette (colors.xml), same for dimensions (dimens.xml) • Prefix layout files (activity_, fragment_, listItem_, …) • Re-use elements using <include> (and <merge> in the to be included layout file) • compileTarget is your Frenemy, test thoroughly • Don‘t set maxSdkVersion • Be specific about your dependencies (2.2.0 not 2.2.+) • Don‘t use too many libs (65k method limit!) • Launcher icon(s) in mipmap folder when generating separate APKs for diff. densities
- 16. Let‘s check out some code DEMO
- 17. Topics we didn‘t talk about… • Network / Communication • Persistence • Service / AsyncTask / Loader / Event Bus • Permission System • Sensors
- 18. Some links to get you started… • Android Tutorials: – http://developer.android.com/training/index.html – https://www.udacity.com/courses/android • Helpful Github Projects – https://github.com/android10/Android-CleanArchitecture – https://github.com/ribot/android-guidelines – https://github.com/txusballesteros/Android-Clean-Testing – https://github.com/ribot/android-boilerplate • Exemplary Apps on Github to play around – https://github.com/WhisperSystems/Signal-Android – https://github.com/owncloud/android • Icons: – https://materialdesignicons.com/
Editor's Notes
- #6: Dalvik makes use of JIT (just in time) compilation. Thus each time the app is run, the part of the code required for its execution is going to becompiled to machine code at that moment. ART compiles the Dalvik bytecode into a system-dependent binary during install (thus only once).