[Android] Intent and Activity
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The document provides an overview of Android programming focusing on intents and activities, explaining how intents represent actions in Android, and how to use them to launch activities. It covers essential concepts such as exporting activities, using extras to pass information, and managing the activity lifecycle with specific method callbacks. Additionally, it discusses launching activities and sub-activities, including handling result codes and data returned from sub-activities.
[Android] Intent and Activity
- 1. Android Programming Lesson 6 Intent and Activity NGUYEN The Linh
- 2. Android Programming Contents 1 Understanding Intents 2 Activity 3 Exercise 6 2
- 3. Android Programming Intent and Activity Understanding Intents 3
- 4. Android Programming Understanding Intents http://blog.nikmesoft.com Verbs URL HTTP 4
- 5. Android Programming Understanding Intents Just as a Web browser knows how to process a verb + URL pair, Android knows how to find activities or other application logic that will handle a given intent. You can use intents to represent actions. At the simplest level, an intent is an action that you can tell Android to invoke. 5
- 7. Android Programming Understanding Intents Notes: android:exported: Whether or not the activity can be launched by components of other applications — "true" if it can be, and "false" if not. The general convention for an action name is <your-package- name>.intent.action.YOUR_ACTION_NAME. 7
- 8. Android Programming Understanding Intents Available Intents in Android http://developer.android.com/guide/appendix/g-app-intents.html A browser application to open a browser window An application to call a telephone number An application to present a phone dialer so the user can enter the numbers and make the call through the UI A mapping application to show the map of the world at a given latitude/longitude coordinate A detailed mapping application that can show Google stree views 8
- 9. Android Programming Event Listeners and Callback Methods Example 6.1 6.2 9
- 10. Android Programming Understanding Intents Using Extra Information An extra can provide more information to the component that receives the intent. This extra information is repre-sented by an Android class called android.os.Bundle. The following two methods on an Intentclass provide access to the extra Bundle: 10
- 11. Android Programming Understanding Intents Using Extra Information (cont.) 11
- 12. Android Programming Understanding Intents Using Extra Information (cont.) 12
- 13. Android Programming Understanding Intents Using Components to Directly Invoke an Activity Android also provides a more direct way to start an activity: you can specify the activity’s ComponentName, which is an abstraction around an object’s package name and class name. 13
- 14. Android Programming Understanding Intents Using Components to Directly Invoke an Activity (cont.) ComponentName wraps a package name and a class name together. For example, the follow-ing code invokes the SubActivity: 14
- 15. Android Programming Understanding Intents Using Components to Directly Invoke an Activity (cont.) You can also use the class name directly without constructing a ComponentName. You should register the activity in the AndroidManifest.xml file like this: • <activity android:name=".SubActivity"> 15
- 16. Android Programming Understanding Intents Using Components to Directly Invoke an Activity (cont.) No intent-filters are necessary for invoking an activity directly through its class name or component name. 16
- 17. Android Programming Intent and Activity Activity 17
- 18. Android Programming Activity Activity Lifecycle Most management of the life cycle is done automatically by the system via the activity stack. The activity class has the following method callbacks to help you manage the app: • onCreate() • onStart() • onResume() • onPause() • onStop() • onRestart() • onDestroy() 18
- 19. Android Programming Activity Activity Lifecycle 19
- 20. Android Programming Activity Saving activity state 20
- 21. Android Programming Activity Launching Activities and Sub-Activities(cont.) Activity A Activity B Activity C 21
- 22. Android Programming Activity Launching Activities and Sub-Activities(cont.) Activity A Activity B 22
- 23. Android Programming Activity Launching Activities and Sub-Activities(cont.) Activity A Activity B finish(); 23
- 24. Android Programming Activity Launching Activities and Sub-Activities(cont.) 24
- 25. Android Programming Activity Launching Activities and Sub-Activities(cont.) The Request Code: The request code that was used to launch the returning sub-Activity A Result Code: The result code set by the sub-Activity to indicate its result. It can be any inte-ger value, but typically will be either Activity.RESULT_OK or Activity.RESULT_CANCELLED. 25
- 26. Android Programming Activity Launching Activities and Sub-Activities(cont.) If the sub-Activity closes abnormally or doesn’t specify a result code before it closes, the result code is Activity.RESULT_CANCELED. Data: An Intent used to bundle any returned data. 26