Widgets

What is an App Widget?

• They are main apps that live on the Home screen
• They are usually an extension of an existing app already installed on your device
• They display uptodate information from the app they belong to.

Creating your first App Widget

To add a Widget to your application, you need to add 3 things:

• First, a MyWidgetProvider class that extends AppWidgetProvider
• WidgetProviderInfo.xml which represents the Widget's metadata
• WidgetLayout.xml that describes the Widget's views

Creating your first App Widget

• Widget communicates with the App using broadcast messages
• The MyWidgetProvider, WidgetProviderInfo.xml and WidgetLayout.xml make the Widget a BroadcastReceiver
• We will need to register it in the Manifest using the type
• Android Studio will help us to create all these files with a few clicks

Creating your first App Widget

• Right click on your app module > New > Widget > App Widget
• Give it a name: MyWidgetProvider and keep the other defaults
• And these files are created: MyWidgetProvider class and my_widget_provider_info.xml
• The receiver type is automatically added to the Manifest
• The Layout is profiled-in with a TextView
• Run your app and you'll see the Widget

Customizing your App Widget

• Widget Layouts are based on RemoteViews because the Widget is treated as a second app that runs on the Home screen
• Not every view type can be added in a Widget Layout
• RemoteViews have special methods other then findViewById. It has methods like setTextViewText(viewId, text) etc.

Customizing your App Widget

• Open up my_widget.xml layout file
• Replace the default TextView by an ImageView and add a drawable to its src
• Open up my_widget_info.xml in the xml folder

<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
	android:initialLayout="@layout/my_widget"
	android:minHeight="40dp"
	android:minWidth="40dp"
	android:previewImage="drawable/launcher_icon"
	android:resizeMode="horizontal|vertical"
	android:updatePeriodMillis="1800000"
	android:widgetCategory="home_screen" />

• The smallest update is 30 min = 1800000 Milliseconds

Customizing your App Widget

• Open up MyWidgetProvider class
• The onUpdate method is called every time a new Widget is created, as well as every update involved which is reset to 30 min
• The user can have a multiple instances of the same widget on the Home Screen
• AppWidgetManager gives access to information about all existing widgets on the Home screen
• If you run this app, you can see that the Widget option is now available
• You can drag it over to your Home screen

Click events

• The way RemoteView handle Click events is different from Normal Views
• RemoteViews can be linked to a PendingIntent and launch once that view is clicked

views.setOnClickPendingIntent(R.id.image.pendingIntent)

What is a pending Intent

• The pending intent is just a wrapper on the intent that allows other applications to have access and run that intent in your application

• To launch our app, we need to create an intent for the MainActivity class and then wrap it with a Pending Intent and then call setOnClickPendingIntent

static void updateAppWidget(Context context, AppWidgetManager appWidgetManager, int appWidgetId) {

        // Construct the RemoteViews object
        RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.recipe_widget_provider);

        // Create an Intent to launch the MainActivity when clicked
        Intent intent = new Intent(context, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);

        views.setOnClickPendingIntent(R.id.widget_cake_image, pendingIntent);

        // Instruct the widget manager to update the widget
        appWidgetManager.updateAppWidget(appWidgetId, views);
    }