Android Tutorial Android Live Wallpaper tutorial

Erel · Nov 15, 2011

Using the new LiveWallpaper library you can now create your own live wallpapers. The user can set live wallpapers by long pressing on the home screen and choosing Wallpapers - Live Wallpapers.

Creating a live wallpaper is not too difficult.

A service is responsible for handling the wallpaper events and drawing the wallpaper.

There can be several instances of the same wallpaper at the same time. For example the user can set your wallpaper as the home screen wallpaper and also see a demo of your wallpaper in the wallpaper preview dialog.

LiveWallpaper library contains two objects: LWManager and LWEngine.
LWManager is responsible for raising the events.
The first parameter of each event is of type LWEngine. LWEngine represents a specific wallpaper instance.
LWEngine includes a Canvas property which is used to draw the wallpaper.
When you finish drawing you must call LWEngine.Refresh or LWEngine.RefreshAll. Otherwise the drawing will not appear.

The following example draws a blue background. Red circles are drawn when the user touches the screen:

B4X:

Sub Process_Globals
   Dim lwm As LWManager
End Sub

Sub Service_Create
   lwm.Initialize("lwm", True)
End Sub

Sub LWM_SizeChanged (Engine As LWEngine)
   Engine.Canvas.DrawColor(Colors.Blue)
   Engine.RefreshAll
End Sub

Sub LWM_Touch (Engine As LWEngine, Action As Int, X As Float, Y As Float)
   Engine.Canvas.DrawCircle(X, Y, 20dip, Colors.Red, True, 0)
   Engine.Rect.Left = X - 20dip
   Engine.Rect.Right = X + 20dip
   Engine.Rect.Top = Y - 20dip
   Engine.Rect.Bottom = Y + 20dip
   Engine.Refresh(Engine.Rect)
End Sub

As there could be several different engines, it is convenient to work with the local engine.
LWEngine includes a Tag property which you can use to store data specific to that engine.

LWManager includes an internal timer that you can use if you need to do animations. The Tick event will only be raised for visible wallpapers. This is important to conserve battery.

For example the following code draws the time on the wallpaper:

B4X:

Sub Process_Globals
   Dim lwm As LWManager
End Sub

Sub Service_Create
   lwm.Initialize("lwm", True)
   lwm.StartTicking(1000) 'tick every second
End Sub

Sub LWM_Tick (Engine As LWEngine)
   Engine.Canvas.DrawColor(Colors.Black) 'Erase the background
   Engine.Canvas.DrawText(DateTime.Time(DateTime.Now), _
      300dip, 100dip, Typeface.DEFAULT_BOLD, 40, Colors.White, "LEFT")
   Engine.RefreshAll
End Sub

Offsets
On most devices the wallpaper virtual size is wider than a single screen. When the user moves to a different screen the offset changes.
You can use the OffsetChanged event to handle those changes.
LWEngine.FullWallpaperWidth / Height return the full size of the wallpaper.
LWEngine.CurrentOffsetX / Y return the current position.
Note that the wallpaper scrolls less than the foreground layer with the icons.

The LiveWallpaperImage demonstrates how to use those properties to display an image over the full wallpaper.

LWManager events

SizeChanged - Raised when the engine is first ready and when the screen size changes (for example when the orientation changes).
VisibilityChanged - Raised when a wallpaper becomes visible or invisible.
Touch - Raised when the user touches the wallpaper.
Tick - The internal timer tick event.
OffsetChanged - Raised when the wallpaper offsets change.
EngineDestroyed - Raised when an engine is destroyed.

Configuration
Live wallpapers require some configuration.
1. You should add the inner service declaration to the manifest editor (Project -> Manifest Editor):

B4X:

AddApplicationText(
<!-- ******** Add the internal service declaration - you can change android:label  ******* -->
<service
        android:label="My Livewallpaper"
        android:name="anywheresoftware.b4a.objects.WallpaperInternalService"
        android:permission="android.permission.BIND_WALLPAPER">
        <intent-filter>
            <action android:name="android.service.wallpaper.WallpaperService" />
        </intent-filter>
        <meta-data android:name="android.service.wallpaper" android:resource="@xml/wallpaper" />
</service>
)

It is also recommended to change minSdkVersion to 7 (at the beginning of the manifest editor code).

2. Add wallpaper.xml to Objects\res\xml folder and set it to be readonly (otherwise it will be deleted during compilation).
You can find this file in both attached examples.

3. Your service must be named WallpaperService. Note that there is an additional service inside the library named anywheresoftware.b4a.objects.WallpaperInternalService. The internal service connects to your service.

Examples
LiveWallpaperImage - The user can select an image from the activity. This image is set as the wallpaper. When the user changes the wallpaper offset the image is updated accordingly.

LiveWallpaperBall - A bouncing smiley. Clicking on the smiley will change its direction.
Before running the examples you need to set Object\res\xml\wallpaper.xml to be readonly. Otherwise it will be deleted.

Note that it is recommended to test live wallpapers in Release mode (the wallpaper will fail in debug mode when the process is started by the OS).

Erel · May 2, 2012

Check the logs and see if it is the same error message about the missing activity. If you don't see it please upload your project.

boten · May 2, 2012

It is the same error (wallpaper.livepicker).
I unmarked the "do not overwrite..." so the manifest file will include reference to the "parm" activity - Yes it is there.

Then I marked the "do not overwrite..." and changed it as prescribed in the tutuorial (minsdkversion, service declarayion,...). and compiled & run again.

LWP does work, but pressing the "setting..." button cause the error.
Remember, the error does NOT occur when the settingsActivity is main (in wallpapwer.xml)

note: the zipping removed the readonly from strings.xml and wallpaper.xml)

Erel · May 3, 2012

Actually the error is now different. Next time please check the logs and post the full error message.

You should add android:exported="true" to the parm activity attributes.

boten · May 4, 2012

Finally working OK. Toda.

FJS · Jun 1, 2012

Mading live wallpaper with fluid animations

Good evening Erel,

Please, I would like to know two things:

1-How to created fluid movements with live wallpaper?
I used Engine.Canvas.DrawBitmapRotated(luz, Null, Engine.Rect, Degrees) each 100milisec but it doesnt look fluid...: confused:
there are little jumpings...

2-How to use animation library with live wallpaper?
Could you show us several examples?

Any clue and help will be wellcome

Thank you very much for your help and your support

Best regards

Erel · Jun 3, 2012

1. Can you post your drawing code?

2. You cannot use the Animation library with live wallpapers.

FJS · Jun 3, 2012

Good afternoon Erel,

Regarding the first point, I have just found the problem, I put the variables as int, but it works with variables as double. Right now there is not jumpings!!
But What do you recomend to refresh? I mean, with 80miliseconds is enough?, it seems ok to obtain fluid moment, but I dont know if this way reduce the battery so much

On the other hand, it is a pety, maybe is possible use Open GL to create better applications?

Thank you for your help!!

Erel · Jun 3, 2012

The interval depends on the refresh rate that you want to achieve.

You cannot use OpenGL with live wallpapers.

NeoTechni · Jun 7, 2012

100 ms wouldn't be very fluid. That's only a framerate of 10.

Try 33 ms.

FJS · Jun 8, 2012

A error with the sources of texts and problems with rotating the tablet

Good evening everyone,

I have two questions:

First of all, I think that I have a problem with the sources of the texts...
This is the message:

"Compiling code. 0.02
Using existing AndroidManifest.xml.
(Project - Do Not Overwrite Manifest option is checked)
AndroidManifest-Example.xml file will be created instead.
Generating R file. 0.00
Compiling generated Java code. Error
B4A line: 107
Engine.Canvas.DrawText(sentence, X1,Y1,Typeface.STYLE_BOLD,size,Colors.black,\
javac 1.6.0_26
src\anywheresoftware\b4a\samples\fondovivob\wallpaperservice.java:195: inconvertible types
found : int
required: android.graphics.Typeface
_engine.getCanvas().DrawText(processBA,_sentence,_x1,_y1,(android.graphics.Typeface)(anywheresoftware.b4a.keywords.Common.Typeface.STYLE_BOLD),_size,anywheresoftware.b4a.keywords.Common.Colors.Black,BA.getEnumFromString(android.graphics.Paint.Align.class,"CENTER"));
^
1 error
"
then when I change my tablet from portrait to landscape the tablet says: aplication stops (what is happening?)

And on the other hand, I dont know how to dont allow the picture rotates when I rotate the tablet, and nether How to change the layout when I rotate the tablet

Thank you very much for your help, like always!!

Best regards

Erel · Jun 10, 2012

It should be Typeface.DEFAULT_BOLD instead of STYLE_BOLD.

You should check the logs when the process crashes.

NeoTechni · Jun 10, 2012

How do we use the manifest editor to add the XML?
The first post should be altered to show it

I tried:

AddServiceText(WallpaperService,
android:label="PUTYOURWALLPAPERNAMEHERE"
android:name="anywheresoftware.b4a.objects.WallpaperInternalService"
androidermission="android.permission.BIND_WALLPAPER">
<intent-filter>
<action android:name="android.service.wallpaper.WallpaperService" />
</intent-filter>
<meta-data android:name="android.service.wallpaper" android:resource="@xml/wallpaper" />
)

that worked

FJS · Jun 11, 2012

Thank you very much, it works!

NeoTechni · Jun 11, 2012

FJS said:
Thank you very much, it works!

The manifest code I posted?
Cause it's not actually working for me.

NeoTechni · Jun 11, 2012

Yeah, I used the manifest editor on a known-working livewallpaper and it broke it. I manually edited the xml file myself and it worked again.

Please update the tutorial with directions on how to use the manifest editor

FJS · Jun 11, 2012

Thank you very much, it works!

I have another question... how to save several parameter of a live screen configuration, to use it when the tablet restarts.
I have a problem with the configuration, all work but when I restart my table, the initial configuration appears again but no my last configuration..

Thank you!

NeoTechni · Jun 11, 2012

You need to save your config to a file, like a map or ini file.

FJS · Jun 11, 2012

NeoTechni said:
You need to save your config to a file, like a map or ini file.

Sorry... but how to do that in the code?, for example in the LiveWallpaperImage code, to save the imagen, so I will not need to select the imagen each time I restart the tablet, isnt?

PS: I dont have to much experience with the code...

Thank you!

walterf25 · Jun 21, 2012

Live Wall Paper capability

Hello all is it possible to create a wall paper like this with this library?

If so can you guys maybe help me out, I need to make something like this!

thanks all
Walter

NeoTechni · Jun 21, 2012

Yes. Youd have to figure out how to do those effects though

Android Tutorial Android Live Wallpaper tutorial

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