This document provides an overview of how to create homescreen widgets for Android. It discusses key reasons for building widgets like providing at-a-glance information or controlling apps. It then outlines the major steps to develop a widget, including creating an AppWidgetProvider class that extends BroadcastReceiver, declaring metadata in AppWidgetProviderInfo, designing an XML layout, and updating the manifest. Code examples are provided for tasks like updating the widget remotely using RemoteViews.

1. Homescreen Widgets
Demystified
Pearl Chen
@androidsNsheep
AndroidTO // Oct 26, 2010

2. Hi, I'm a web developer...
So many ways to create
an Android application…
but none of them
create homescreen widgets!

3. ...and I ♥ homescreen widgets
Examples
default Donut homescreen
default Froyo homescreen

4. ...and I ♥ homescreen widgets
Examples
Gmail Unread Count
HTC SenseUI email widget

5. ...and I ♥ homescreen widgets
Examples
Music Players
Settings controls

6. Key reasons to build a widget
• At-a-glance information
– unread messages, calendar items, to do lists
• Control apps that run in the background
– Music player
• Toggle settings
– settings that affect other applications such as GPS or wifi
– Consider how the Google Voice widget can toggle between “Use for all calls”,
“Do not use for calls”, “International calls only”, and “Ask for every call”. You
might want to toggle this setting before opening the Dailer app
• “Smart” shortcuts
– Reduce something that would normally take at least 2 steps into 1
– If it simply opens another application, keep it as a regular application shortcut

7. (Another) key reason to build a widget
Keep users engaged with your app!
out of sight == out of mind 
Hey!
Don’t forget about me!

8. Designing Widgets
Widget Design Best Practices UI Guidelines
developer.android.com/guide/practices/ui_guidelines/widget_design.html

9. Designing Widgets
Lighter color theme
in Cupcake and Donut
Darker color theme
in Éclair and Froyo

10. Coding Widgets
App Widgets Framework Guide
developer.android.com/guide/topics/appwidgets/index.html

11. 1. Download
2. Import into Eclipse
as an ‘Existing Project’
3. Run
Sample Widget Code
code.google.com/p/androidto-basicwidget/

12. Overview of Widget Development
1) Create a new Android project in Eclipse
without an Activity class
2) Declare AppWidgetProviderInfo object
3) Create xml layout file for widget view
4) Extend the AppWidgetProvider class
5) Update AndroidManifest.xml

13. Overview of Widget Development
1) Create a new Android project in Eclipse
without an Activity class

14. Create a new Android project
Widgets not available in
Android 1.1
No need for an Activity
unless there’s going to be
a standalone application

15. Overview of Widget Development
2) Declare AppWidgetProviderInfo object

16. AppWidgetProviderInfo
1. Create an xml folder
in the res folder.
2. In the xml folder,
create a new
Android XML File

17. AppWidgetProviderInfo
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
android:minWidth="294dp"
android:minHeight="72dp"
android:updatePeriodMillis=“30000"
android:initialLayout="@layout/widget">
</appwidget-provider>
(number of cells * 74) - 2
Following this formula, you should use 72 dp for a height of one cell, 294 dp and for a width of four cells.
(number of cells * 74) - 2

18. Overview of Widget Development
3) Create xml layout file for widget view

19. XML Layout File
1. There’s already a main.xml file in the
res/layout folder so just reuse that.

20. XML Layout File
2. I renamed it to widget.xml so it was more descriptive.
3. Added a background and padding to the container.
4. And gave the TextView an id of current_time.

21. XML Layout File
5. And let’s also add a refresh button as a ImageButton
with and id of refresh.

22. If a widget is not an Activity, what is it?
An Activity could simply be
described as an UI screen.

23. If a widget is not an Activity, what is it?
An Activity could simply be
described as an UI screen.
It contains View widgets such
as LinearLayout, TextView,
and Button typically marked
up in a layout xml file.

24. If a widget is not an Activity, what is it?
An Activity could simply be
described as an UI screen.
It contains View widgets such
as LinearLayout, TextView,
and Button typically marked
up in a layout xml file.
e.g.
Button btn =
(Button) findViewById(R.id.my_button);
btn.setText(“Submit”);

25. If a widget is not an Activity, what is it?
Widgets also contain View
widgets such as LinearLayout,
TextView, and Button (but
there are limitations to what
Views you can use).

26. If a widget is not an Activity, what is it?
Button btn =
(Button) findViewById(R.id.my_button);
btn.setText(“Submit”);

27. If a widget is not an Activity, what is it?
RemoteViews
RemoteViews remoteView =
new RemoteViews(
context.getPackageName(),
R.layout.widget
);
remoteView.setTextViewText(
R.id.my_button,
“Submit”
);

28. If a widget is not an Activity, what is it?
The application component that
supplies the UI for a widget is a
BroadcastReceiver
RemoteViews

29. Overview of Widget Development
4) Extend the AppWidgetProvider class

30. AppWidgetProvider
public class BasicWidgetProvider extends AppWidgetProvider {
@Override
public void onUpdate(
Context context,
AppWidgetManager appWidgetManager,
int[] appWidgetIds)
{
super.onUpdate(
context,
appWidgetManager,
appWidgetIds
);
//do some stuff every updatePeroidMillis!
}
}

31. AppWidgetProvider
void onUpdate( Context context,
AppWidgetManager appWidgetManager,
int[] appWidgetIds )
void onEnabled( Context context )
void onDeleted( Context context,
int[] appWidgetIds )
void onDisabled( Context context )
void onReceive( Context context,
Intent intent )

32. AppWidgetProvider
final int N = appWidgetIds.length;
for (int i=0; i<N; i++) {
int appWidgetId = appWidgetIds[i];
setAlarm(context, appWidgetId, 30000);
}

33. AppWidgetProvider

34. AppWidgetProvider

35. Overview of Widget Development
5) Update AndroidManifest.xml

36. AndroidManifest.xml

37. THANK YOU!
Pearl Chen
@androidsNsheep