teaching machines

CS 491 Lecture 5a – Intents

September 18, 2012 by Chris Johnson. Filed under cs491 mobile, fall 2012, lectures.

Before class

A

Before next class:

• Watch http://youtu.be/2ip2LA3hoR8.
• Read the Intent resolution section of http://developer.android.com/guide/components/intents-filters.html.

Making your own web browser:

1. Widgets: WebView, EditText, Button
2. LinearLayouts and weight again
3. Callback for button clicks
4. INTERNET permission
5. Handling URL views with an intent-filter* (research better ways)
6. Getting intent data back out in onCreate()

B

Before next class:

• Watch http://youtu.be/-r6-mhFVVDc,
• Read http://developer.android.com/guide/components/intents-filters.html until Intent Resolution.

Making a budgeter:

1. A main activity with a button
2. Implicit intents for the web and phone
3. A second activity to get category name and projected amount
4. Using an Intent to spawn an Activity
5. Using an Intent to spawn an Activity for a result
6. Communicating data back to caller via an Intent

In class

You’re pushing out a new social media site called In3. It lets members tell stories with three photos, kind of like a three-panel comic strip. Your task is to create an app that allows the user to create a three panel story with the device’s camera. Consider the following as your develop your app:

• The camera can be conjured with the action MediaStore.ACTION_IMAGE_CAPTURE. In the words of the entire Internet, the Android emulator camera is “flaky.” See your instructor to test on a real device.
• Does the camera require anything in the manifest?
• For a layout, put three ImageButtons side-by-side. When the user clicks on one, take that button’s picture.
• Before the pictures are taken, you can use @android:drawable/ic_menu_camera as the ImageButton’s source attribute.
• The camera activity returns the path where the photo was stored as its intent’s data. You can load it into a bitmap with:

  InputStream stream = getContentResolver().openInputStream(data.getData());
  Bitmap bitmap = BitmapFactory.decodeStream(stream);
  stream.close();

• The bitmap will be very big. Shrink it down so all three ImageButtons continue to fit on the screen.
• You can hook up your company’s website to your native app through an intent-filter and a special URL. Have your app respond to intents to view this address: http://www.in3.com/take. (URLs are broken up into scheme://host/path when matching the data of an intent-filter.) When the user visits that link in a browser, it should pop up your app instead. Neat.