android – Adding widgets to a launcher page without bindAppWidgetId()-ThrowExceptions

Exception or error:

I’m trying to turn the stock ICS launcher into a standalone app. I’m nearly there – the only things not working are the search icon and dropping widgets onto the screen, which causes a crash.

The crash is because the stock launcher uses appWidgetManager.bindAppWidgetId(appWidgetId, componentName); to add widgets, which apparently only system apps have permission to do.

So my question is, what is the correct way for a non-system app to add widgets and acheive the same UI experience as the stock ICS launcher?

How to solve:

Timmmm,

Your issue is that you are looking to the wrong object. You can’t really control the AppWidgetManager. Its not your job, its the System’s. What you CAN do is control an AppWidgetHost, it just requires a few semantics. Here are the basics.

EDIT: Extra Background on the Widget Binding Process

The AppWidgetManager is a singleton object that runs when the System is started. This means that every instance of every launcher uses the same AppWidgetManager. What differentiates them is their AppWidgetHost and the RemoteViews they are currently holding. The AppWidgetManager basically keeps a list of all of the active hosts and the widgets they are holding. An AppWidgetHost is not a priveleged object. That is, any activity may have a single host. Thus, an entire application may be nothing but Widgets, if they so choose.

When you instantiate the Host, you must then add Views to it. So, basically it is a list of child Views with no mandatory parental bounds, except what your Activity gives it. First, you ask for an ID (via myHost.allocateAppWidgetId()). Then you use your Pick Widget Activity/Dialog. The Dialog returns the WidgetInfo. The View is retrieved when you ask the Host to create the View (via createView) with the WidgetInfo and the ID you asked for. It then asks the widget for its RemoteView.

Finally, you bind the widget by placing the View in your Activity as a Child. This is done via the addView() method of the ViewGroup that holds all of your Widgets.

The Process in Action (EDITED)

First, you have to make sure you have this in your android manifest:

<uses-permission android:name="android.permission.BIND_APPWIDGET" />

Next, you have to create an AppWidgetHost (I extend my own for my launcher). The key to the Host is to keep a reference to the AppWidgetManager via AppWidgetManager.getInstance();.

AppWidgetHost myHost = new AppWidgetHost(context, SOME_NUMERICAL_CONSTANT_AS_AN_ID);

Now, get your ID:

myHost.allocateAppWidgetId()

The next step is done by whatever method you use to get the widget info. Most times it is returned via an Intent through onActivityResult. Now, all you really have to do is use the appInfo and create the view. The WidgetId is normally provided by the pick widget activity result.

AppWidgetProviderInfo withWidgetInfo 
        = AppWidgetManager.getInstance().getAppWidgetInfo(forWidgetId);
AppWidgetHostView hostView 
        = myWidgetHost.createView(myContext, forWidgetId, withWidgetInfo);
hostView.setAppWidget(forWidgetId, withWidgetInfo);

Now you just bind the View as a child to whatever you want to bind it to.

myViewGroup.addView(hostView);

Of course, you always have to consider where and how to place it, etc. Also, you have to make sure that your AppWidgetHost is listening before you start adding widgets.

myHost.startListening()

To Summarize

The Widget binding process spans many methods and steps, but all occurs through the AppWidgetHost. Because Widgets are coded outside of your namespace you don’t have any control except for where you put them and how you size the View. Since they are ultimately code that runs in your space but outside of your control, the AppWidgetManager acts as a neutral mediator, while the AppWidgetHost serves as the facilitator on your app’s behalf. Once this is understood, your task is simple. The steps above are all the required steps for any custom launcher (including my own).

EDIT: Final Clarification

The ICS Launcher does this as well. The appWidgetManager they use is just a wrapper housing the AppWidgetHost and the calls to the AppWidgetManager. I forget that very little of this is explained on the Android Development Central website.

Hope this helps! Let me know if you need anymore details.

FuzzicalLogic

###

I now know the definitive answer. In Android 4.0, you can’t do it. I ended up making my users pick the widget twice, which sucks, but there is no way around it.

In Android 4.1 they fixed the problem!

SDK apps can now host widgets and don’t have to use the rubbish widget picker API! You can look into the Jellybean Launcher2 source code for details, but basically, when you first try to bind a widget, Android will pop up a dialog box saying “Do you want to allow this app to bind widgets”, and then the user can decide to give it permission or not.

I’m not sure why they went for the modal permission-granting dialog box rather than the all-permissions-on-install model they’ve used for everything else, but whatever, it works!

Now we just have to wait 4 or 5 years until everyone has Android 4.1 or greater!

###

I just found this tutorial on how to add appwidgets to normal apps, which might help: http://coderender.blogspot.com/2012/01/hosting-android-widgets-my.html

This tutorial still uses the “AppWidget Picker” list, so it might not work for you since ICS has the widgets picker inside the app drawer itself.

Still, was worth to mention since tutorials on hosting widgets are very rare šŸ™‚

Cheers,
Yuvi

###

Fuzzical Logic,with your code below,

AppWidgetProviderInfo withWidgetInfo 
        = AppWidgetManager.getInstance().getAppWidgetInfo(forWidgetId);
AppWidgetHostView hostView 
        = myWidgetHost.createView(myContext, forWidgetId, withWidgetInfo);
hostView.setAppWidget(forWidgetId, withWidgetInfo);

if have not the permission of bind_widget,widgethost got nothingļ¼Œcus withwidgetinfo is null,widgethost create nothing.

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