1. Intents 1 CS440

2. Intents  Message passing mechanism  Most common uses:  starting an Activity (open an email, contact, etc.)  starting an Activity for a result (scan a barcode, take a picture to attach to an email, etc.) CS440 2

3. Intents  Explicit Intent i = new Intent(this, ActivityTwo.class); i.putExtra("Value1", "This value one for ActivityTwo "); i.putExtra("Value2", "This value two ActivityTwo");  Implicit Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.vogella.com")); startActivity(i); CS440 3

4. Example: Share Intent  Sender Intent intent = new Intent(Intent.ACTION_SEND); intent.setType("text/plain"); intent.putExtra(android.content.Intent.EXTRA_TEXT, "News for you!"); startActivity(intent);  Receiver Bundle extras = getIntent().getExtras(); if (extras == null) { return; } // Get data via the key String value1 = extras.getString(Intent.EXTRA_TEXT); if (value1 != null) { // Do something with the data } CS440 4

5. Calling Sub-Activities for result data  If you need some information from the called Activity use the startActivityForResult() method. public void onClick(View view) { Intent i = new Intent(this, ActivityTwo.class); i.putExtra("Value1", "This value one for ActivityTwo "); i.putExtra("Value2", "This value two ActivityTwo"); // Set the request code to any code you like, you can identify the // callback via this code startActivityForResult(i, REQUEST_CODE); } CS440 5

6. Calling Sub-Activities for result data  If you use the startActivityForResult() method then the started Activity is called a Sub-Activity.  If the Sub-Activity is finished it can send data back to its caller via Intent. This is done in the finish() method. @Override public void finish() { // Prepare data intent Intent data = new Intent(); data.putExtra("returnKey1", "Swinging on a star. "); data.putExtra("returnKey2", "You could be better then you are. "); // Activity finished ok, return the data setResult(RESULT_OK, data); super.finish(); } CS440 6

7. Calling Sub-Activities for result data  Once the Sub-Activity finished, the onActivityResult() method in the calling Activity will be called. @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (resultCode == RESULT_OK && requestCode == REQUEST_CODE) { if (data.hasExtra("returnKey1")) { Toast.makeText(this, data.getExtras().getString("returnKey1"), Toast.LENGTH_SHORT).show(); } CS440 7

8. Intents  Intents use action strings and URIs:  Action Strings Example: ACTION_VIEW content://contacts/people/1 -- Display information about the person whose identifier is "1“ ACTION_VIEW ACTION_DIAL content://contacts/people/1 -- Display the phone dialer with the person filled in. ACTION_DIAL ACTION_DIAL tel:123 -- Display the phone dialer with the given number filled in. ACTION_DIAL  URI Example: Search Google Maps: geo:0,0?q=query Show contacts: content://contacts/people Show a URL: http://www.google.com CS440 8

9. Intent Fun  Create a new Project: IntentFun  Create an intent that has data one of the following URIs:  http://www.google.com http://www.google.com  content://contacts/people  geo:0,0?q=query  Do not forget to start an Activity for this intent! CS440 9

10. Intent Fun  Create an intent that takes a picture:  Use: "android.media.action.IMAGE_CAPTURE“ as an argument in the intent  Start an activity that is based on the result of the intent  Do not forget: you need to override the onActivityResult method… why? CS440 10

11. Intent Fun  Create a Toast with text “lalala”:  What is a Toast class?  Make the text appear on your screen  Check the open intents registry:  http://www.openintents.org/en/intentstable http://www.openintents.org/en/intentstable CS440 11

12. References  http://www.damonkohler.com/2009/02/android- recipes.html http://www.damonkohler.com/2009/02/android- recipes.html  http://developer.android.com http://developer.android.com CS440 12