Android動態壁紙的製作教程

動態壁紙是在Android 2.1新增的一個功能。動態壁紙可以添加到Android的桌面，具有交互式的動畫背景效果。在本教程中，我們將教會你如何去製作一個交互式的動態壁紙。

動態壁紙是一個Android應用程序，包括一個服務(WallpaperService)。該服務必須包括一個引擎(WallpaperService.Engine)。該引擎是連接用戶、桌面、系統之間的橋樑。它也可以繪製桌面壁紙。

首先，必須由內在的Engine類創建一個WallpaperService類。該服務必須在AndroidManifest.xml中聲明爲"android.service.wallpaper.WallpaperService"，這樣它纔會作爲動態壁紙被手機識別。而且還要在服務配置中附加"android.permission.BIND_WALLPAPER"的權限許可： 

01

<service

02	android:name="LiveWallpaperService"

03	android:enabled="true"

04	android:icon="@drawable/icon"

05	android:label="@string/app_name"

06	android:permission="android.permission.BIND_WALLPAPER">

07	<intent-filter android:priority="1" >

08	<action android:name="android.service.wallpaper.WallpaperService" />

09	</intent-filter>

10	<meta-data

11	android:name="android.service.wallpaper"

12	android:resource="@xml/wallpaper" />

13	</service>

創建一個XML文件，放置在應用程序目錄下的/res/xml/中。它用來描述你的動態壁紙。 

1	<?xml version="1.0" encoding="UTF-8"?>

2	<wallpaper

3	xmlns:android="http://schemas.android.com/apk/res/android"

4	android:thumbnail="@drawable/thumbnail"

5	android:description="@string/description"

6	android:settingsActivity="PreferenceActivity"/>

再創建一個xml的屬性文件 attrs.xml ，代碼如下： 

01	<declare-styleable name="Wallpaper">

02	<!-- Component name of an activity that allows the user to modify

03	the current settings for this wallpaper. -->

04	<attr name="settingsActivity" />

05

06	<!-- Reference to a the wallpaper's thumbnail bitmap. -->

07	<attr name="thumbnail" format="reference" />

08

09	<!-- Name of the author of this component, e.g. Google. -->

10	<attr name="author" format="reference" />

11

12	<!-- Short description of the component's purpose or behavior. -->

13	<attr name="description" />

14	</declare-styleable>

動態壁紙的服務代碼如下： 

001	package net.androgames.blog.sample.livewallpaper;

002

003	import android.content.SharedPreferences;

004	import android.service.wallpaper.WallpaperService;

005	import android.view.MotionEvent;

006	import android.view.SurfaceHolder;

007

008

/**

009	* Android Live Wallpaper Archetype

010	* @author antoine vianey

011	* under GPL v3 : http://www.gnu.org/licenses/gpl-3.0.html

012

*/

013	public class LiveWallpaperService extends WallpaperService {

014

015

@Override

016	public Engine onCreateEngine() {

017	return new SampleEngine();

018

}

019

020

@Override

021	public void onCreate() {

022	super.onCreate();

023

}

024

025

@Override

026	public void onDestroy() {

027	super.onDestroy();

028

}

029

030	public class SampleEngine extends Engine {

031

032	private LiveWallpaperPainting painting;

033

034	SampleEngine() {

035	SurfaceHolder holder = getSurfaceHolder();

036	painting = new LiveWallpaperPainting(holder,

037	getApplicationContext());

038

}

039

040

@Override

041	public void onCreate(SurfaceHolder surfaceHolder) {

042	super.onCreate(surfaceHolder);

043	// register listeners and callbacks here

044	setTouchEventsEnabled(true);

045

}

046

047

@Override

048	public void onDestroy() {

049	super.onDestroy();

050	// remove listeners and callbacks here

051	painting.stopPainting();

052

}

053

054

@Override

055	public void onVisibilityChanged(boolean visible) {

056	if (visible) {

057	// register listeners and callbacks here

058	painting.resumePainting();

059

} else {

060	// remove listeners and callbacks here

061	painting.pausePainting();

062

}

063

}

064

065

@Override

066	public void onSurfaceChanged(SurfaceHolder holder, int format,

067	int width, int height) {

068	super.onSurfaceChanged(holder, format, width, height);

069	painting.setSurfaceSize(width, height);

070

}

071

072

@Override

073	public void onSurfaceCreated(SurfaceHolder holder) {

074	super.onSurfaceCreated(holder);

075	// start painting

076	painting.start();

077

}

078

079

@Override

080	public void onSurfaceDestroyed(SurfaceHolder holder) {

081	super.onSurfaceDestroyed(holder);

082	boolean retry = true;

083	painting.stopPainting();

084	while (retry) {

085

try {

086	painting.join();

087	retry = false;

088	} catch (InterruptedException e) {}

089

}

090

}

091

092

@Override

093	public void onOffsetsChanged(float xOffset, float yOffset,

094	float xStep, float yStep, int xPixels, int yPixels) {

095

}

096

097

@Override

098	public void onTouchEvent(MotionEvent event) {

099	super.onTouchEvent(event);

100	painting.doTouchEvent(event);

101

}

102

103

}

104

105

}

當壁紙的顯示、狀態或大小變化是，會調用Engine的onCreate, onDestroy, onVisibilityChanged,onSurfaceChanged, onSurfaceCreated 和 onSurfaceDestroyed方法。有了這些方法，動態壁紙才能展現出動畫效果。而通過設置setTouchEventsEnabled（true），並且調用onTouchEvent（MotionEvent event）方法，來激活觸摸事件。

我們在繪畫牆紙的時候，也會使用一個單獨的繪畫線程： 

001	package net.androgames.blog.sample.livewallpaper;

002

003	import android.content.Context;

004	import android.graphics.Canvas;

005	import android.view.MotionEvent;

006	import android.view.SurfaceHolder;

007

008

/**

009	* Android Live Wallpaper painting thread Archetype

010	* @author antoine vianey

011	* GPL v3 : http://www.gnu.org/licenses/gpl-3.0.html

012

*/

013	public class LiveWallpaperPainting extends Thread {

014

015	/** Reference to the View and the context */

016	private SurfaceHolder surfaceHolder;

017	private Context context;

018

019	/** State */

020	private boolean wait;

021	private boolean run;

022

023	/** Dimensions */

024	private int width;

025	private int height;

026

027	/** Time tracking */

028	private long previousTime;

029	private long currentTime;

030

031	public LiveWallpaperPainting(SurfaceHolder surfaceHolder,

032	Context context) {

033	// keep a reference of the context and the surface

034	// the context is needed if you want to inflate

035	// some resources from your livewallpaper .apk

036	this.surfaceHolder = surfaceHolder;

037	this.context = context;

038	// don't animate until surface is created and displayed

039	this.wait = true;

040

}

041

042

/**

043	* Pauses the live wallpaper animation

044

*/

045	public void pausePainting() {

046	this.wait = true;

047	synchronized(this) {

048	this.notify();

049

}

050

}

051

052

/**

053	* Resume the live wallpaper animation

054

*/

055	public void resumePainting() {

056	this.wait = false;

057	synchronized(this) {

058	this.notify();

059

}

060

}

061

062

/**

063	* Stop the live wallpaper animation

064

*/

065	public void stopPainting() {

066	this.run = false;

067	synchronized(this) {

068	this.notify();

069

}

070

}

071

072

@Override

073	public void run() {

074	this.run = true;

075	Canvas c = null;

076	while (run) {

077

try {

078	c = this.surfaceHolder.lockCanvas(null);

079	synchronized (this.surfaceHolder) {

080	currentTime = System.currentTimeMillis();

081	updatePhysics();

082	doDraw(c);

083	previousTime = currentTime;

084

}

085	} finally {

086	if (c != null) {

087	this.surfaceHolder.unlockCanvasAndPost(c);

088

}

089

}

090	// pause if no need to animate

091	synchronized (this) {

092	if (wait) {

093

try {

094

wait();

095	} catch (Exception e) {}

096

}

097

}

098

}

099

}

100

101

/**

102	* Invoke when the surface dimension change

103

*/

104	public void setSurfaceSize(int width, int height) {

105	this.width = width;

106	this.height = height;

107	synchronized(this) {

108	this.notify();

109

}

110

}

111

112

/**

113	* Invoke while the screen is touched

114

*/

115	public void doTouchEvent(MotionEvent event) {

116	// handle the event here

117	// if there is something to animate

118	// then wake up

119	this.wait = false;

120	synchronized(this) {

121

notify();

122

}

123

}

124

125

/**

126	* Do the actual drawing stuff

127

*/

128	private void doDraw(Canvas canvas) {}

129

130

/**

131	* Update the animation, sprites or whatever.

132	* If there is nothing to animate set the wait

133	* attribute of the thread to true

134

*/

135	private void updatePhysics() {

136	// if nothing was updated :

137	// this.wait = true;

138

}

139

140

}

如果桌面壁紙是可見狀態下，系統服務通知有新的東西，這個類會優先把它繪製在畫布上。如果沒有動畫了，updatePhysics會通知線程去等待。通常SurfaceView在有兩個畫布交替繪製的時候，會在畫布上繪製上一次......

如果要讓你的動態牆紙有配置功能，只要創建一個PreferenceActivity，並將它在wallpaper.xml文件中聲明。同時讓SharedPreference對象可以找到你的配置選項。

教程就寫到這裏，如果還有什麼不懂，你可以通過Eclipse來瀏覽完整的源代碼：SampleLiveWallpaper。