homescreen widgets demystified pearl chen @androidsnsheep androidto // oct 26, 2010

Homescreen Widgets

DemystifiedPearl Chen

@androidsNsheep

AndroidTO // Oct 26, 2010

Hi, I'm a web developer...

So many ways to create an Android application…

but none of them create homescreen widgets!

...and I ♥ homescreen widgets

Examples

default Donut homescreendefault Froyo homescreen

...and I ♥ homescreen widgets

Examples

Gmail Unread Count 

HTC SenseUI email widget

...and I ♥ homescreen widgets

Examples

Music Players 

Settings controls

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

(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!

Designing Widgets

Widget Design Best Practices UI Guidelinesdeveloper.android.com/guide/practices/ui_guidelines/widget_design.html

Designing Widgets

Lighter color themein Cupcake and Donut  Darker color theme

in Éclair and Froyo 

Coding Widgets

App Widgets Framework Guidedeveloper.android.com/guide/topics/appwidgets/index.html

1. Download

2. Import into Eclipse as an ‘Existing Project’

3. Run

Sample Widget Code

code.google.com/p/androidto-basicwidget/

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

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

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

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

AppWidgetProviderInfo

1. Create an xml folder in the res folder.

2. In the xml folder, create a new Android XML File

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>

Because the Home screen's layout orientation (and thus, the cell sizes) can change, as a rule of thumb, you should assume the worst-case cell size of 74 pixels for the height and width of a cell. However, you must subtract 2 from the final dimension to account for any integer rounding errors that occur in the pixel count. To find your minimum width and height in density-independent pixels (dp), use this formula:(number of cells * 74) - 2Following 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

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

XML Layout File

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

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.

XML Layout File

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

If a widget is not an Activity, what is it?

An Activity could simply be described as an UI screen.

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.

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”);

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).

If a widget is not an Activity, what is it?

Button btn = (Button) findViewById(R.id.my_button);btn.setText(“Submit”);

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”);

If a widget is not an Activity, what is it?

The application component that supplies the UI for a widget is a BroadcastReceiver

RemoteViews

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

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!

}}

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 )

AppWidgetProvider

public void onUpdate( Context context, AppWidgetManager AppWidgetManager, int[] appWidgetIds) {

/* update each widget that belongs to this provider individually by setting an alarm because we're setting an alarm, onUpdate is really only called when a new widget is added, or the phone restarts */

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

AppWidgetProvider

public static void setAlarm(Context context, int appWidgetId, int updateRate) {

// To prevent any ANR timeouts, // we perform the update in an intent service

PendingIntent pendingIntent = createUpdatePendingIntent(context,REFRESH,appWidgetId);

AlarmManager alarms = (AlarmManager)

context.getSystemService(Context.ALARM_SERVICE);

//and then have the alarm wake up the system to do updates alarms.setRepeating(AlarmManager.ELAPSED_REALTIME,

SystemClock.elapsedRealtime(), updateRate, pendingIntent);

}

AppWidgetProvider

public static class UpdateService extends IntentService {

@Override public void onHandleIntent(Intent intent) { ComponentName widget =

new ComponentName( this, BasicWidgetProvider.class );

AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this); appWidgetManager.updateAppWidget(widget, buildUpdate(this, intent)); }

private RemoteViews buildUpdate(Context context, Intent intent) { RemoteViews views =

new RemoteViews( context.getPackageName(), R.layout.widget ); //update the UI here… return views; }

}

context.startService(new Intent(context, UpdateService.class));

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

AndroidManifest.xml

<receiver android:name="BasicWidgetProvider" >

<intent-filter> <action android:name="android.appwidget.action.APPWIDGET_UPDATE" /> <action android:name="android.appwidget.action.APPWIDGET_ENABLED" /> <action android:name="android.appwidget.action.APPWIDGET_DISABLED" /> <action android:name="android.appwidget.action.APPWIDGET_DELETED" /> </intent-filter>

<meta-data android:name="android.appwidget.provider" android:resource="@xml/basic_provider_info" /></receiver>

<service android:name=".BasicWidgetProvider$UpdateService" />

THANK YOU!

Pearl Chen @androidsNsheep