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CSAS Android Workshop

This is a continuation of the iBookmark activity started as part of our Android workshop. Please check that page for a project description and for the first two parts of the project.

• Part 3: We have enabled adding a new bookmark as a seperate activity and we made sure that the CAB was working out to implement deleting bookmarks. Editing still does not work yet. Also improved the web viewser. Check here for the printed source code or click here for the complete project file.

  Homework: Implement the "edit" feature to edit an existing bookmark and update it in the list. As a hint, here is what I did (but you are welcome to find your own solution):

• added an "update(Bookmark item)" method to the Bookmark class that updates itself with info from the input bookmark 'item'
• added a method "findFirstSelectedIndex" to the BookmarkAdapter class that returns the index of the first selected bookmark item, or -1 if none are selected (if mutliple items are selected, the lowest selected index is returned)
• implemented the "editSelectedItem" method that was already available as a place holder. It retrieves the (lowest) currently selected bookmark item, if possible, and puts the title, url, *and index* of that selected item into an intent via the "putExtra" methods. Then I start the familiar "BookmarkItemEdit" activity (with "startActivityForResult" and the intent with the extra data)
• add a field 'selectedIndex' to the BookmarkItemEdit class that defaults to -1
• get the title, url, and index from the intent. If the activity was called from the 'addItem', then these values will be blank and in particular the selectedIndex field remains at -1. If the activity was called from editSelectedItem, though, then selectIndex will be non-negative and indicates which item is to be updated.
• When the "Okay" button of the BookmarkItemEdit activity is clicked, I put the url and title into new intent, as well as the current value of selectedIndex. Then I call on "setResult" and finally on "finish()" to close the activity.
• Since I called the new activity with "startActivityForResult", the method "onActivityResult(int requestCode, int resultCode, Intent intent)" of the parent activity BookmarkActivity will be called when the second activity finishes. I can extract the title and url from the intent, as usual. Then, if the selectedIndex value is -1, I create a new bookmark and add it to the list, or if that value is non-negative I will update the Bookmark element corresponding to selectedIndex with the values of the new bookmark item. Then, of course, I call "saveData" and if necessary "data.notifyDataChanged" so that whatever changes I made will become visible.

• To try out the new features, you can "side-load" my compiled app, but you can't see the final code that includes the "edit" feature: After all, it is a homework question! Side-loading is easy: on your device (which must be running Android 4 or higher to be compatible with iBookmark), turn on the "Unknown sources" settings. You will find that in "Settings" (on your device), then "Security". After that, use a web browser on your device to click on this "apk" file iBookmark2.apk here. It will be downloaded to your device. You can go to the notification bar and tap on the downloaded file. Everything should be a "go" now and the new app will get installed. Make sure to test the app thoroughly to see if you find anything that does not work properly.

• Part 4: In our last portion we want to define some settings for our app. For a detailed explanation, check the Android Guide on Settings. In short:

  •  create an XML file named (usually) preferences.xml in the /res/xml folder

  • define various preferences using tags like "CheckBoxPreference", "EditTextPreference", "ListPreference", or simple "Preference" etc. (you can group them via "PreferenceCategory"). Each entry must have a unique "key" and a "title" as well as additional options specific to the type of preference you are defining.

  • create either a "PreferenceActivity" (if programming prior to Android 3.) or a "SettingsFragment" (if programming for Android 3.0 or later) embedded in a "SettingsActivity" (don't forget to add that activity to your manifest file) and inflate the preferences via "addPreferencesFromResource(R.xml.preferences)"

  • you could attach an "OnPreferenceClickListener" to a preference so that it could act like a 'button' when clicked to perform some action (such as resetting all variables to their default values)

  • you should call "PreferenceManager.setDefaultValues(this, R.xml.preferences, false)" to initialize the preferences from their default values (if the last parameter is set to "true", the preferences are supposed to be reset even if the user has already changed them)

  • finally, to access the preferences from anywhere in your project, use "SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this)" to get access to the prefs object, and then for example
    prefs.getBoolean("key", true));

• To download the complete source code for our Bookmark app including editing and preferences, get this ZIP file iBookmark2_plus.zip and integrate it into Eclipse (or cut-and-paste).
  
  Homework: What the above project file iBookmark2_plus does not yet contain, is to implement the preferences for changing the font size of the bookmark title and address - guess what, that will be your homework and will conclude our iBookmark project. The completed project will be posted after the next class.

• Here is the final version,of iBookmark, such as it is,- check it out if necessary to see how to work with different types of Preferences.