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).

Douglas Farias · Oct 29, 2014

hi @Erel
i have try your sample, but dont work on my moto g, i dont make any change, i open the app , select one image on galery and later i see a toast image set, but dont work dont put my image at background *-*
LiveWallpaperImage.zip

Erel · Oct 30, 2014

Have you selected this app as the current set live wall paper?

Douglas Farias · Oct 30, 2014

aaaaa xD
thx is working

Troberg · Jan 16, 2015

Is it possible to get antialiasing? I have a LWP which draws some curves, and the lines really look jagged.

NeoTechni · Jan 16, 2015

B4X:

Sub ActivateAA(BG As Canvas, AAstate As Boolean ) As Boolean 
	Dim Obj1 As Reflector
	If AntiAliasing Then 
		'Try
			Obj1.Target = BG
			Obj1.Target = Obj1.GetField("paint")
			Obj1.RunMethod2("setAntiAlias", AAstate, "java.lang.boolean")
			Return AAstate
		'Catch
		'End Try
	End If
End Sub
[/code[

Troberg · Jan 16, 2015

I've already tried that, and, while it runs without errors, it doesn't give me any antialiasing either.

It doesn't matter which lwm engine event I run it in, no result whatsoever.

koaunglay · Jan 22, 2015

Hi! All friends! I'm trying with three module(Main, userP, WallpaperService).
This is my code from wallpaper.xml
-----------------

B4X:

<?xml version="1.0" encoding="utf-8"?>
<wallpaper xmlns:android="http://schemas.android.com/apk/res/android"
  android:thumbnail="@drawable/icon" 
  android:settingsActivity="com.aunglw2.userP"
/>

---------------------------
This is my code from manifest editor
-------------------------------------

B4X:

'This code will be applied to the manifest file during compilation.
'You do not need to modify it in most cases.
'See this link for for more information: http://www.b4x.com/forum/showthread.php?p=78136
AddManifestText(
<uses-sdk android:minSdkVersion="4" android:targetSdkVersion="14"/>
<supports-screens android:largeScreens="true"
    android:normalScreens="true"
    android:smallScreens="true"
    android:anyDensity="true"/>)
SetApplicationAttribute(android:icon, "@drawable/icon")
SetApplicationAttribute(android:label, "$LABEL$")
SetApplicationAttribute(android:theme, "@android:style/Theme.Holo")
'End of default text.
AddApplicationText(
<service
android:label="HI!"
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>
)
SetActivityAttribute(userP,android:exported, true)

But when I click settings.. button in preview, my app is not work. It show " Unfortunately, Live Wallpaper Picker has stopped."
How should I do? Help some body! Thanks all....

Erel · Jan 22, 2015

Check the logs to find the error message.

koaunglay · Jan 22, 2015

This is from my log. I think no error. I don't know...
=============
** Service (wallpaperservice) Create **

** Service (wallpaperservice) Start **

** Activity (main) Create, isFirst = true **

** Activity (main) Resume **

** Activity (main) Pause, UserClosed = false **

** Activity (userp) Create, isFirst = true **

Downsampling image due to lack of memory.

Downsampling image due to lack of memory.

** Activity (userp) Resume **

Downsampling image due to lack of memory.

** Activity (userp) Pause, UserClosed = true **

===============Help me please................

NeoTechni · Jan 22, 2015

It really doesn't like how big the image you're using is.

Erel · Jan 23, 2015

Are you testing it in Release mode?

koaunglay · Jun 22, 2015

Erel said:
Are you testing it in Release mode?

Yes. Erel

Erel · Jun 23, 2015

You need to use usb debug mode and check the logs when the app crashes.

Anastasios Michaelides · Jul 7, 2015

Hello can you please help me, I want to add image background instead of color, can you guide me please?

Erel · Jul 8, 2015

Please start a new thread for this question.

Android Tutorial Android Live Wallpaper tutorial

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