Android安卓动态墙纸编程

安卓从2.1开始支持动态墙纸编程，英文名字叫live wallpaper 。自己编写的动态壁纸必须从WallpaperService类派生，并且在重载其方法onCreateEngine里实现自己的动态效果。其代码如下，SimpleWallpaperEngine是我们基于Engine类派生的类：

public Engine onCreateEngine() {

       return new SimpleWallpaperEngine();

}

上面retun返回的代码就是我们用Engine类的派生类创建的对象，其实现过程使用surfaceview更新。所以要学习动态墙纸编程，最好是已经熟练的掌握了surfaceview使用技巧。在Engine类里，有很多方法，我们需要重载以下三个方法，

1．创建壁纸

public void onCreate(SurfaceHoldersurfaceHolder){...}

2．释放壁纸

public void onDestroy(){...}

3．VisibilityChanged是用来设置当前动态壁纸可见时显示动画。当其不可见时，壁纸会停止运行，不显示动画，代码如下：

@Override
		public void onVisibilityChanged(boolean visible) {
			canDraw = visible;
			if (visible) {
				drawDroid(); // 自己的绘屏函数
			} else {
				handler.removeCallbacks(drawRequest); // 不可见时，移除回调
			}
		}

drawDroid是我写的一个简单的根据随机数画线的函数，代码如下：

		private void drawDroid() {
			final SurfaceHolder holder = getSurfaceHolder();
			Canvas canvas = null;
			try {
				canvas = holder.lockCanvas();
				if (canvas != null) {
					paint.setColor(Color.BLUE);
					paint.setStrokeWidth(10);
					paint.setStyle(Style.STROKE);
					nx = (int) (rand.nextFloat() * virtualWidth);
					ny = (int) (rand.nextFloat() * virtualHeight);
					m_path.lineTo(nx, ny);
					canvas.drawPath(m_path, paint);
				}
			} finally {
				if (canvas != null) {
					holder.unlockCanvasAndPost(canvas);
				}
			}
			handler.removeCallbacks(drawRequest);
			if (canDraw) {
				handler.postDelayed(drawRequest, 33);
			}
		}

由于动画是使用surfacewive实现的，所以我们也要重载surfacewive的方法：

1．  建立

onSurfaceCreated

2．  释放

onSurfaceDestroyed

3．  大小变化，横竖屏操作，与用户交互时修改

onSurfaceChanged

如果需要添加用户交互，需要重载

public voidonTouchEvent(MotionEvent event)

surfacewive使用线程更新屏幕，我们可以使用Runnable接口创建一个线程，把我们的绘画函数放进去，并把他添加到窗口handler回调里，代码如下：

private final Runnable drawRequest = new Runnable() {
			@Override
			public void run() {
				try {
					Thread.sleep(1000);
					drawDroid();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		};

完整的代码如下“：

package com.androidbook.simplelivewallpaper;

import java.util.Random;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Paint.Style;
import android.os.Handler;
import android.service.wallpaper.WallpaperService;
import android.view.MotionEvent;
import android.view.SurfaceHolder;

public class SimpleDroidWallpaper extends WallpaperService {
	// private static final String DEBUG_TAG = "SimpleDroidWallpaper";
	private final Handler handler = new Handler();

	@Override
	public Engine onCreateEngine() {
		return new SimpleWallpaperEngine();
	}

	class SimpleWallpaperEngine extends WallpaperService.Engine {

		boolean canDraw = true;
		private int virtualHeight;
		private int virtualWidth;
		Paint paint = new Paint();
		Path m_path = new Path();
		volatile int ox = 0, oy = 0, nx = 100, ny = 200;
		final Random rand = new Random();

		private final Runnable drawRequest = new Runnable() {
			@Override
			public void run() {
				try {
					Thread.sleep(1000);
					drawDroid();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		};

		public SimpleWallpaperEngine() {
			m_path.lineTo(ox, oy);
		}

		@Override
		public void onCreate(SurfaceHolder surfaceHolder) {
			super.onCreate(surfaceHolder);
			// When touch is enable, all MotionEvents are passed, even those
			// handled by other widgets
			setTouchEventsEnabled(true);
			virtualHeight = getDesiredMinimumHeight();
			virtualWidth = getDesiredMinimumWidth();
		}

		@Override
		public void onDestroy() {
			super.onDestroy();
			handler.removeCallbacks(drawRequest);
		}

		@Override
		public void onVisibilityChanged(boolean visible) {
			canDraw = visible;
			if (visible) {
				drawDroid(); // 自己的绘屏函数
			} else {
				handler.removeCallbacks(drawRequest); // 不可见时，移除回调
			}
		}

		@Override
		public void onOffsetsChanged(float xOffset, float yOffset,
				float xOffsetStep, float yOffsetStep, int xPixelOffset,
				int yPixelOffset) {
			super.onOffsetsChanged(xOffset, yOffset, xOffsetStep, yOffsetStep,
					xPixelOffset, yPixelOffset);
		}

		@Override
		public void onSurfaceCreated(SurfaceHolder holder) {
			super.onSurfaceCreated(holder);
		}

		@Override
		public void onSurfaceChanged(SurfaceHolder holder, int format,
				int width, int height) {
			super.onSurfaceChanged(holder, format, width, height);

			drawDroid();
		}

		@Override
		public void onSurfaceDestroyed(SurfaceHolder holder) {
			super.onSurfaceDestroyed(holder);
			canDraw = false;
			handler.removeCallbacks(drawRequest);
		}

		private void drawDroid() {
			final SurfaceHolder holder = getSurfaceHolder();
			Canvas canvas = null;
			try {
				canvas = holder.lockCanvas();
				if (canvas != null) {
					paint.setColor(Color.BLUE);
					paint.setStrokeWidth(10);
					paint.setStyle(Style.STROKE);
					nx = (int) (rand.nextFloat() * virtualWidth);
					ny = (int) (rand.nextFloat() * virtualHeight);
					m_path.lineTo(nx, ny);
					canvas.drawPath(m_path, paint);
				}
			} finally {
				if (canvas != null) {
					holder.unlockCanvasAndPost(canvas);
				}
			}
			handler.removeCallbacks(drawRequest);
			if (canDraw) {
				handler.postDelayed(drawRequest, 33);
			}
		}

		@Override
		public void onTouchEvent(MotionEvent event) {
			/* 添加触屏效果 */
			super.onTouchEvent(event);
		}
	}
}

完整的XML文件如下：

<?xml version="1.0" encoding="utf-8"?>
<manifest
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.androidbook.simplelivewallpaper"
    android:versionCode="1"
    android:versionName="1.0">
    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name"
        android:debuggable="true">
        <activity
            android:name=".SimpleLiveWallpaperMenuActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action
                    android:name="android.intent.action.MAIN" />
                <category
                    android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service
            android:label="@string/wallpaper_name"
            android:name="SimpleDroidWallpaper"
            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/droid_wallpaper" />
        </service>
    </application>
    <uses-sdk
        android:minSdkVersion="7"
        android:targetSdkVersion="8" />
    <uses-feature
        android:name="android.software.live_wallpaper" />
</manifest>

其实我们这里创建的墙纸不需要Activity类，只是一种服务，是被墙纸管理程序调用的，所以对于eclipse生成的工程，你可以去掉XML中有关Activity窗口的声明，同时资源文件里你也可以去掉layout\main.xml文件和源代码文件夹里的Activit文件。当然，我们的墙纸如果支持自定义设置，那你也是需要Activit，那时你需要定义一个Activit供墙纸设置程序调用，以修改自定义墙纸默认设置。需要注意的是，设置文件需要在我们在/res/文件夹中新建一个名为xml的文件夹，名为livewallpaper.xml，内容为如下：

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

然后把设置的值引入到你自己的墙纸类中调用。墙纸设置类一般会派生于PreferenceActivity，以在作用户操作后保存设置内容！