Attempting to teach the fundamentals of Android (circa Nougat, Android Studio 2.2.3)
This page contains an overview of various concepts of Android exercises are found in subdirectories.
Exercise 1: Installing Android Studio and creating a first app
Exercise 2: Creating Activities, Adding Widgets and Android Studio shortcuts
Exercise 3: Using 3rd Party Libraries
This is a supplement to the larger Application Fundamentals guide provided by Google, also undoubtfully more subjective.
Android Debug Bridge is used to communicate over USB (or wifi) to a device to perform the tasks required to develop in Android.
This is installed and managed by Android Studio but must be enabled on devices and ADB drivers for the device installed, i.e. Samsung ADB drivers
A physical device does not have to be used, the emulator works the same way.
Could have been called a "Form" or "Page". Its worth understanding the Activity lifecycle of Create, Resume, Pause, Destroy.
- Calling Activities from other Activities:
startActivity(new Intent(CurrentActivityClass.this, ActivityToCreateClass.class));
Allow background processing without a UI
-
Services can be killed by the operating system if RAM is needed!
-
Foreground services are safer from being killed by the OS but need to show an icon. Icon can be hidden so its only shown in the pull down.
Allows for a globally accessible Singleton (optional and specified in manifest)
Allow data to be passed around. Used everywhere.
Used everywhere, an activity is a context, as is a service. Always need one, never have it when needed.
Get services directly from an activity.
e.g. Location
locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LOCATION_PROVIDER, currentRate, -1, this);
Equally this could be from any context reference
locationManager = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
- Ordered
- Sticky/Not (deprecated)
- XML defines it
- Activity to show it
- Remember to Commit!
- Permissions - Only list those needed. i.e. is READ_CONTACTS needed!?
Android 6+ you need to check the user has granted permissions!
- If an Activity isn’t in the manifest it will not run! Can register broadcast receivers that fire without the application needing to be running!
For example this will call a AutoStart class that inherits from BroadcastReceiver when the device starts up.
<receiver android:name=".utils.receivers.AutoStarter">
<intent-filter android:priority="100">
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
The R file is a class automatically generated to allow Resource files to be referenced in code.
For example a layout file activity_main.xml is given an ID which can then be referenced by R.layout.activity_main
It can be a pain, clean and rebuild if the resources fail.
See LogCat under Android Monitor in Android Studio
Android Asset Studio - Icon Generator https://romannurik.github.io/AndroidAssetStudio/
Icons https://materialdesignicons.com/
Libraries https://android-arsenal.com/
CommonsGuy Blog https://commonsware.com/blog/