开发实时壁纸

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所谓实时壁纸，即动态壁纸，就是手机桌面不再是简单的图片，而是运行中的动画，该动画由程序实时绘制的，所以称为实时壁纸。Android中提供WallpaperService基类来开发实时壁纸，步骤如下：

下面用一个示例来演示，该示例原型来源于疯狂讲义一书，代码如下：

WallpaperService的子类：LiveWallpaper

package com.home.service;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Handler;
import android.service.wallpaper.WallpaperService;
import android.view.MotionEvent;
import android.view.SurfaceHolder;

public class LiveWallpaper extends WallpaperService {
	// 继承WallpaperService必须实现的抽象方法
	@Override
	public Engine onCreateEngine() {
		// 返回自定义的Engine
		return new MyEngine();
	}

	class MyEngine extends Engine {
		private int ScreenWidth;
		private int ScreenHeight;
		// 记录程序界面是否可见
		private boolean mVisible;
		// 记录当前用户事件的发生位置
		private float mTouchX = -1;
		private float mTouchY = -1;
		// 记录当前圆圈的绘制位置
		private float cx = 15;
		private float cy = 15;
		// 定义画笔
		private Paint mPaint = new Paint();
		// 定义一个Handler
		Handler mHandler = new Handler();
		// 定义一个周期性执行的任务
		private final Runnable drawTarget = new Runnable() {

			@Override
			public void run() {
				drawFrame();
			}

		};

		public void onCreate(android.view.SurfaceHolder surfaceHolder) {
			super.onCreate(surfaceHolder);
			// 获得屏幕宽和高
			ScreenWidth = getDesiredMinimumWidth() / 2;
			ScreenHeight = getDesiredMinimumHeight();
			// 初始化画笔
			mPaint.setColor(0xffffffff);
			mPaint.setAntiAlias(true);
			mPaint.setStrokeWidth(2);
			mPaint.setStrokeCap(Paint.Cap.ROUND);
			mPaint.setStyle(Paint.Style.STROKE);
			// 设置处理触摸事件
			setTouchEventsEnabled(true);
		}

		@Override
		public void onDestroy() {
			super.onDestroy();
			// 删除回调
			mHandler.removeCallbacks(drawTarget);
		}

		@Override
		public void onVisibilityChanged(boolean visible) {
			mVisible = visible;
			// 当界面可见时，执行drawFrame()方法
			if (mVisible) {
				// 动态绘制图形
				drawFrame();
			} else {
				// 如果界面不可见，删除回调
				mHandler.removeCallbacks(drawTarget);
			}
		}

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

		// 当屏幕大小改变时调用该方法
		@Override
		public void onSurfaceChanged(SurfaceHolder holder, int format,
				int width, int height) {
			super.onSurfaceChanged(holder, format, width, height);
			drawFrame();
		}

		@Override
		public void onSurfaceDestroyed(SurfaceHolder holder) {
			super.onSurfaceDestroyed(holder);
			mVisible = false;
			mHandler.removeCallbacks(drawTarget);
		}

		@Override
		public void onTouchEvent(MotionEvent event) {
			// 如果检测到滑动操作
			if (event.getAction() == MotionEvent.ACTION_MOVE) {
				mTouchX = event.getX();
				mTouchY = event.getY();
			} else {
				mTouchX = -1;
				mTouchY = -1;
			}
			super.onTouchEvent(event);
		}

		/**
		 * 定义绘制图形的工具方法
		 */
		private void drawFrame() {
			// 获取该壁纸的SurfaceHolder对象
			final SurfaceHolder holder = getSurfaceHolder();
			Canvas c = null;
			try {
				// 对画布加锁
				c = holder.lockCanvas();
				if (c != null) {
					c.save();
					// 绘制背景色
					c.drawColor(0xff000000);
					// 在触碰点绘制圆圈
					drawTouchPoint(c);
					// 绘制圆圈
					c.drawCircle(cx, cy, 80, mPaint);
					c.restore();
				}
			} finally {
				if (c != null) {
					holder.unlockCanvasAndPost(c);
				}
			}
			mHandler.removeCallbacks(drawTarget);
			// 调度下一次重绘
			if (mVisible) {
				cx += 15;
				cy += 20;
				// 如果cx、cy移出屏幕，从左上角重新开始
				if (cx >= ScreenWidth - 80) {
					cx = 15;
				}
				if (cy >= ScreenHeight - 80) {
					cy = 20;
				}
				// 指定0.1秒后重新执行一次drawTarget
				mHandler.postDelayed(drawTarget, 100);
			}
		}

		/**
		 * 在屏幕触碰点绘制圆圈
		 * 
		 * @param canvas
		 */
		private void drawTouchPoint(Canvas canvas) {
			if (mTouchX >= 0 && mTouchY >= 0) {
				canvas.drawCircle(mTouchX, mTouchY, 40, mPaint);
			}
		}
	}
}

配置LiveWallpaper：

        <service
            android:name="com.home.service.LiveWallpaper"
            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/mywallpaperxml"/>
        </service>

mywallpaperxml：

<?xml version="1.0" encoding="utf-8"?>
<wallpaper xmlns:android="http://schemas.android.com/apk/res/android" 
    android:description="@string/wallpaper_des"
    android:thumbnail="@drawable/ic_launcher">
</wallpaper>

权限：

 <!-- 加入设置壁纸权限 -->
    <uses-permission android:name="android.permission.SET_WALLPAPER" />