NSC AD 340 5210 - Week 4

1. Week 4 Lecture Intents, Multiple Activities Menus, Dialogs & Shared Preferences
2. What are we building this week? How to create, and navigate to, additional Activities? 02 Project Demo Using Multiple Activities 01 How to use SharedPreferences to store simple data? Saving Data With SharedPreferences 04 Displaying Menus & Dialogs How to add menus and display dialogs for user interaction? 03
3. Project Demo What are we building this week?
5. Week 4 Project Updates • Create a ForecastDetailsActivity • Pass clicked forecast data to ForecastDetailsActivity and dislpay it • Create a menu with a single item to control our temp display units • Show an AlertDialog when settings item is clicked to select display setting • Update UI formatting based on selected setting
6. Using Multiple Activities How to create, and navigate to, additional Activities?
7. How do we navigate to a new screen?
8. • Create a new Activity class • Declare the new Activity in our AndroidManifest.xml • Navigate to the new Activity using an Intent How do we navigate to a new screen?
9. Create a new Activity class class NewActivity : Activity { ... } NewActivity.kt
10. Declare new Activity in AndroidManifest.xml <manifest … > <activity android:name=”.NewActivity”/> </manifest> AndroidManifest.xml
11. Navigate to new Activity using an Intent enterButton.setOnClickHandler { val intent = Intent(this, NewActivity::class.java) startActivity(intent) } MainActivity.kt
12. What is an Intent?
13. • Communicates to the system that some action should be carried out • Start an Activity, send message to a BroadcastReciver, send a tweet or an email, make a phone call • Primarily includes an ACTION and DATA What is an Intent?
14. • ACTION_VIEW -> content://contacts/people/1 • ACTION_DIAL -> content://contacts/people/1 • ACTION_SEND -> EXTRA_EMAIL, EXTRA_SUBJECT What is an Intent?
15. Implicit vs Explicit Intents Choosing a generic actions vs specifying a specific app component
16. • Implicit intents describe an action like ACTION_SEND for sending an email ◦ Implicit intents can be handled by an component in the system registered to handle that intent type • Explicit intents describe a specific app component to interact with ◦ Can open a specific Activity using an explicit intent Implicit vs Explicit Intents
17. Intent Filters <!-- Intent filter for launcher Activity --> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> AndroidManifest.xml
18. Intent Filters <!-- Intent filter for possible email app --> <intent-filter> <action android:name="android.intent.action.VIEW"/> <action android:name="android.intent.action.SENDTO"/> <data android:scheme="mailto"/> </intent-filter> AndroidManifest.xml
19. Passing Data With Intents // Pass student ID and student name with Intent so it can be used // by NewActivity when it’s started // val intent = Intent(this, NewActivity::class.java) intent.putExtra("key_id", “student616”) intent.putExtra("key_name", “Peter Parker”) startActivity(intent) MainActivity.kt
20. Displaying Menus & Dialogs How to add menus and display dialogs for user interaction?
21. How can we display a menu?
22. • Define a menu resource • Add individual menu items to the menu • Add text & icons to each menu item • Respond to item clicks How To Display A Menu?
23. Create A Menu Resource <?xml version="1.0" encoding="utf-8"?> <menu xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/tempDisplaySetting" android:title="Display Units" /> </menu> res/menu/settings_menu.xml
24. Create A Menu Resource override fun onCreateOptionsMenu(menu: Menu?): Boolean { val inflater: MenuInflater = menuInflater inflater.inflate(R.menu.settings_menu, menu) return true } MainActivity.kt
25. Create A Menu Resource override fun onOptionsItemSelected(item: MenuItem): Boolean { return when (item.itemId) { R.id.tempDisplaySetting -> { // Respond to item click true } else -> super.onOptionsItemSelected(item) } } MainActivity.kt
26. How to display a dialog?
27. • Create and show an AlertDialog • Use AlertDialog.Builder to customize the dialog • Update title, message, and buttons • Respond to button clicks and dialog dismissal How To Display A Dialog?
28. Show An AlertDialog // Build/customize the dialog val dialogBuilder = AlertDialog.Builder(this) .setTitle("Choose Display Units") .setMessage("Choose which temperature unit to display") .setPositiveButton("F°") { _, _ -> } .setNeutralButton("C°") { _,_ -> } // Show the dialog dialogBuilder.show() MainActivity.kt
29. Saving Data With SharedPreferences How to use SharedPreferences to save simple data?
30. How to store persistent data in our app?
31. • Database • Files • SharedPreferences How To Store Persistent Data?
32. Database • Store large, complex data sets • Supports complex queries, paging, reactive updates • Go to option for caching network data
33. Files • Images, vides, maps, books, audio, etc • Can be used for custom storage of other data types like settings or network responses
34. SharedPreferences • Default solution for saving simple data • Works off of key/value pairs • Great for simple, local users settings • Saved to disk under the hood
35. Working With SharedPreferences val preferences = context.getSharedPreferences("settings", Context.MODE_PRIVATE) // Save a key/value pair to SharedPreferences preferences.edit().putString("key_temp_display", setting.name).commit() // Retrieve a key/value pair from SharedPreferences val settingValue = preferences.getString("key_temp_display", default) MainActivity.kt
36. Demo
37. Check Canvas For Additional Resources & Assignments