动态壁纸LiveWallPaper（字母雨及移动文字到屏幕边缘时会反弹）

上面的字母是从上面掉下来的，那个文字是另外的，会一直移动，碰到屏幕边缘时会几何反弹。。

下落的字母只有一个y速度，移动的字符串有一个x速度和一个Y速度。

下面是代码：

1、继承WallPaper的类

package com.wu.wallpaper;

import java.util.ArrayList;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Typeface;
import android.os.Handler;
import android.service.wallpaper.WallpaperService;
import android.util.Log;
import android.view.SurfaceHolder;

public class MyWallpaper extends WallpaperService implements Contants{

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

	class MyEngine extends Engine {
		private ArrayList<Word> list;
		private Paint mPaint;
		private SurfaceHolder holder;
		private int width;
		private int height;
		Word word;
		int num = 0;
		private int mTextSpeedX = 5;//文字的x速度
		private int mTextSpeedY = 2;//文字的y速度
		private int mTextX = TEXT_X;
		private int mTextY = TEXT_Y;
		private int mTextWidth;
		private int mTextHeight;
		Handler mHandler = new Handler();

		private final Runnable ra = new Runnable() {

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

		private void initList() {
			list = new ArrayList<Word>();

			for (int i = 0; i < WORD_NUMBER; i++) {
				addListItem();
			}
		}

		@Override
		public void onCreate(SurfaceHolder surfaceHolder) {
			super.onCreate(surfaceHolder);
			//设置text的字体
			Typeface mTypeface = Typeface.createFromAsset(getAssets(), "fanta.ttf");
			mPaint = new Paint();
			mPaint.setTypeface(mTypeface);
			mTextWidth = (int) mPaint.measureText(TEXT);
			width = getDesiredMinimumWidth()/2;
			height = getDesiredMinimumHeight();
			Log.i("test", "textWidth = " + mTextWidth + "   width = " + width);
			//mPaint.setShadowLayer(30, 0, 0, WORD_COLOR);
			holder = getSurfaceHolder();
			
			initList();
		}

		@Override
		public void onDestroy() {
			mHandler.removeCallbacks(ra);
			super.onDestroy();
		}

		@Override
		public void onVisibilityChanged(boolean visible) {
			if (visible) {
				draw();
			} else {
				mHandler.removeCallbacks(ra);
			}
		}

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

		private void draw() {
			num = 0;
			//锁定画布
			Canvas canvas = holder.lockCanvas();
			if (canvas != null) {
				//清空画布
				mPaint.setColor(BACKGROUND_COLOR);
				canvas.drawRect(0, 0, 1024, 600, mPaint);
				mPaint.setColor(WORD_COLOR);
				mPaint.setTextSize(WORD_SIZE);
				//画从上面掉下的字母
				for (int i = 0; i < list.size(); i++) {
					word = list.get(i);
					canvas.drawText(word.getText(), word.getxOffset(), word
							.getCurrentY(), mPaint);
				}
				//画一直移动的文字
				mPaint.setTextSize(TEXT_SIZE);
				mTextWidth = (int) mPaint.measureText(TEXT);
				mTextHeight = (int) mPaint.getFontSpacing();
				mTextX += mTextSpeedX;
				mTextY += mTextSpeedY;
				if (mTextX+mTextWidth > width || mTextX < 0) {
					mTextSpeedX = -mTextSpeedX;
				}
				
				if (mTextY > height || mTextY < mTextHeight) {
					mTextSpeedY = -mTextSpeedY;
				}
				
				canvas.drawText(TEXT, mTextX, mTextY, mPaint);
				//解锁画布
				holder.unlockCanvasAndPost(canvas);
			}
			//移除回调
			mHandler.removeCallbacks(ra);
			//调整字母的位置
			for (int i = 0; i < list.size(); i++) {
				word = list.get(i);
				int currentY = word.getCurrentY() + word.getSpeed();
				if (currentY > height) {
					//如果有字母出了屏幕，则删除
					list.remove(i);
					num++;
					continue;
				}

				word.setCurrentY(currentY);
			}

			//如果有字母被删除了，则随机添加新的字母
			for (int i = 0; i < num; i++) {
				addListItem();
			}

			//WORD_TIME_UPDATE时间后将线程加入线程队列，即执行线程
			mHandler.postDelayed(ra, WORD_TIME_UPDATE);
		}
		
		private void addListItem() {
			while (!addWord(new Word(width, height)));
		}

		private boolean addWord(Word word) {
			if (list == null) {
				return false;
			}

			//防止两个太近
			for (int i = 0; i < list.size(); i++) {
				if (Math.abs(word.getxOffset() - list.get(i).getxOffset()) < 20) {
					return false;
				}
			}

			list.add(word);
			return true;
		}
	}
}

2、定义了常量的接口

package com.wu.wallpaper;

import android.graphics.Color;

public interface Contants {
	static final String[] WORD = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
								  "a", "b", "C", "d", "e", "f", "g", "h", "i", "j", 
								  "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", 
								  "u", "v", "w", "x", "y", "z", "A", "B", "C", "D", 
								  "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", 
								  "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", 
								  "Y", "Z"};
	//字母的大小
	static final int WORD_SIZE = 30;
	//字母的颜色
	static final int WORD_COLOR = Color.GREEN;
	//背景颜色
	static final int BACKGROUND_COLOR = Color.BLACK;
	//字母的个数,不能太大
	static final int WORD_NUMBER = 8;
	//刷新的时间间隔ms
	static final int WORD_TIME_UPDATE = 10;
	//滚动的字符串
	static final String TEXT = "吴述军";//
	//字符串的起始X、y速度
	static final int TEXT_SPEED_X = 5;
	static final int TEXT_SPEED_Y = 2;
	//字符串的初始显示位置
	static final int TEXT_X = 700;
	static final int TEXT_Y = 300;
	//字符串的字体大小
	static final int TEXT_SIZE = 40;
}

3、xml文件夹下的配置文件

<?xml version="1.0" encoding="utf-8"?>
<wallpaper xmlns:android="http://schemas.android.com/apk/res/android"/>

4、manifest文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.wu.wallpaper"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="10" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <!-- 配置实时壁纸Service -->
		<service android:label="@string/app_name"
			android:name=".MyWallpaper"
			android:permission="android.permission.BIND_WALLPAPER">
			<!-- 为实时壁纸配置intent-filter -->
			<intent-filter>
				<action	android:name="android.service.wallpaper.WallpaperService" />
			</intent-filter>
			<!-- 为实时壁纸配置meta-data -->
			<meta-data android:name="android.service.wallpaper"
				android:resource="@xml/livewallpaper" />
		</service>
    </application>

</manifest>

要图中的效果，还有一个ttf字体文件