android实现漫天雪花&下雨效果

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前言：

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英文原文地址：https://blog.stylingandroid.com/snowfall/
中文翻译地址：http://www.open-open.com/lib/view/open1452263908573.html
国外大神实现效果youtube视频地址：https://www.youtube.com/watch?v=pk66ZziTfOw
中文翻译是open开发者经验库一位作者翻译，翻译的很好。在那篇文章也能看到实现的最原始的效果。
实现漫天飞舞的雪花下载地址：http://download.csdn.net/detail/qq_16064871/9420804
实现下雨天效果的下载地址：http://download.csdn.net/detail/qq_16064871/9420808
1、漫天飞舞的雪花主要代码
SnowView

import android.content.Context;  
import android.graphics.Canvas;  
import android.graphics.Color;  
import android.graphics.Paint;  
import android.util.AttributeSet;  
import android.view.View;  

/** * 雪花视图, DELAY时间重绘, 绘制NUM_SNOWFLAKES个雪花 */  
public class SnowView extends View {  

    private static final int NUM_SNOWFLAKES = 150; // 雪花数量 
    private static final int DELAY = 5; // 延迟 
    private SnowFlake[] mSnowFlakes; // 雪花 

    public SnowView(Context context) {  
        super(context);  
    }  

    public SnowView(Context context, AttributeSet attrs) {  
        super(context, attrs);  
    }  

    public SnowView(Context context, AttributeSet attrs, int defStyleAttr) {  
        super(context, attrs, defStyleAttr);  
    }  

    @Override   
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {  
        super.onSizeChanged(w, h, oldw, oldh);  
        if (w != oldw || h != oldh) {  
            initSnow(w, h);  
        }  
    }  

    private void initSnow(int width, int height) {  
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); // 抗锯齿 
        paint.setColor(Color.WHITE); // 白色雪花 
        paint.setStyle(Paint.Style.FILL); // 填充; 
        mSnowFlakes = new SnowFlake[NUM_SNOWFLAKES];  
        //mSnowFlakes所有的雪花都生成放到这里面 
        for (int i = 0; i < NUM_SNOWFLAKES; ++i) {  
            mSnowFlakes[i] = SnowFlake.create(width, height, paint);  
        }  
    }  

    @Override   
    protected void onDraw(Canvas canvas) {  
        super.onDraw(canvas);  
        //for返回SnowFlake 
        for (SnowFlake s : mSnowFlakes) {  
            //然后进行绘制 
            s.draw(canvas);  
        }  
        // 隔一段时间重绘一次, 动画效果 
        getHandler().postDelayed(runnable, DELAY);  
    }  

    // 重绘线程 
    private Runnable runnable = new Runnable() {  
        @Override  
        public void run() {  
            //自动刷新 
            invalidate();  
        }  
    };  
}  

SnowFlake

package com.example.snowflake.view;  

import com.example.snowflake.RandomGenerator;  

import android.graphics.Canvas;  
import android.graphics.Paint;  
import android.graphics.Point;  

/** * 雪花的类, 移动, 移出屏幕会重新设置位置. */  
public class SnowFlake {  
    // 雪花的角度 
    private static final float ANGE_RANGE = 0.1f; // 角度范围 
    private static final float HALF_ANGLE_RANGE = ANGE_RANGE / 2f; // 一般的角度 
    private static final float HALF_PI = (float) Math.PI / 2f; // 半PI 
    private static final float ANGLE_SEED = 25f; // 角度随机种子 
    private static final float ANGLE_DIVISOR = 10000f;  
    // 雪花的移动速度 
    private static final float INCREMENT_LOWER = 2f;  
    private static final float INCREMENT_UPPER = 4f;  

    // 雪花的大小 
    private static final float FLAKE_SIZE_LOWER = 7f;  
    private static final float FLAKE_SIZE_UPPER = 20f;  

    private final RandomGenerator mRandom; // 随机控制器 
    private final Point mPosition; // 雪花位置 
    private float mAngle; // 角度 
    private final float mIncrement; // 雪花的速度 
    private final float mFlakeSize; // 雪花的大小 
    private final Paint mPaint; // 画笔 

    private SnowFlake(RandomGenerator random, Point position, float angle, float increment, float flakeSize, Paint paint) {  
        mRandom = random;  
        mPosition = position;  
        mIncrement = increment;  
        mFlakeSize = flakeSize;  
        mPaint = paint;  
        mAngle = angle;  
    }  

    public static SnowFlake create(int width, int height, Paint paint) {  
        RandomGenerator random = new RandomGenerator();  
        int x = random.getRandom(width);  
        int y = random.getRandom(height);  
        Point position = new Point(x, y);  
        float angle = random.getRandom(ANGLE_SEED) / ANGLE_SEED * ANGE_RANGE + HALF_PI - HALF_ANGLE_RANGE;  
        float increment = random.getRandom(INCREMENT_LOWER, INCREMENT_UPPER);  
        float flakeSize = random.getRandom(FLAKE_SIZE_LOWER, FLAKE_SIZE_UPPER);  
        return new SnowFlake(random, position, angle, increment, flakeSize, paint);  
    }  

    // 绘制雪花 
    public void draw(Canvas canvas) {  
        int width = canvas.getWidth();  
        int height = canvas.getHeight();  
        move(width, height);  
        canvas.drawCircle(mPosition.x, mPosition.y, mFlakeSize, mPaint);  
    }  

    // 移动雪花 
    private void move(int width, int height) {  
        //x水平方向，那么需要晃动，主要设置这个值就可以，现在取消晃动了 
        //如果 mPosition.x不加上后面那个值，就不会晃动了 
        double x = mPosition.x + (mIncrement * Math.cos(mAngle));  
        //y是竖直方向，就是下落 
        double y = mPosition.y + (mIncrement * Math.sin(mAngle));  

        mAngle += mRandom.getRandom(-ANGLE_SEED, ANGLE_SEED) / ANGLE_DIVISOR;  
        //这个是设置雪花位置，如果在很短时间内刷新一次，就是连起来的动画效果 
        mPosition.set((int) x, (int) y);  

        // 移除屏幕, 重新开始 
        if (!isInside(width, height)) {  
            // 重置雪花 
            reset(width);  
        }  
    }  

    // 判断是否在其中 
    private boolean isInside(int width, int height) {  
        int x = mPosition.x;  
        int y = mPosition.y;  
        return x > mFlakeSize -5 && x + mFlakeSize <= width && y >= -mFlakeSize - 1 && y - mFlakeSize < height;  
    }  

    // 重置雪花 
    private void reset(int width) {  
        mPosition.x = mRandom.getRandom(width);  
        mPosition.y = (int) (-mFlakeSize - 1); // 最上面 
        mAngle = mRandom.getRandom(ANGLE_SEED) / ANGLE_SEED * ANGE_RANGE + HALF_PI - HALF_ANGLE_RANGE;  
    }  
}  

2、实现下雨天效果代码
RainView

package com.example.raindrop.view;  

import com.example.raindrop.R;  

import android.content.Context;  
import android.graphics.Canvas;  
import android.graphics.Paint;  
import android.util.AttributeSet;  
import android.view.View;  

/** * 雨滴视图, DELAY时间重绘, 绘制NUM_SNOWFLAKES个雨滴 */  
public class RainView extends View {  

    private static final int NUM_SNOWFLAKES = 150; // 雨滴数量 
    private static final int DELAY = 5; // 延迟 
    private RainFlake[] mSnowFlakes; // 雨滴 

    public RainView(Context context) {  
        super(context);  
    }  

    public RainView(Context context, AttributeSet attrs) {  
        super(context, attrs);  
    }  

    public RainView(Context context, AttributeSet attrs, int defStyleAttr) {  
        super(context, attrs, defStyleAttr);  
    }  

    @Override   
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {  
        super.onSizeChanged(w, h, oldw, oldh);  
        if (w != oldw || h != oldh) {  
            initSnow(w, h);  
        }  
    }  

    private void initSnow(int width, int height) {  
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); // 抗锯齿 
        paint.setColor(getResources().getColor(R.color.colorWater)); // 雨滴的颜色 
        paint.setStyle(Paint.Style.FILL); // 填充; 
        mSnowFlakes = new RainFlake[NUM_SNOWFLAKES];  
        //mSnowFlakes所有的雨滴都生成放到这里面 
        for (int i = 0; i < NUM_SNOWFLAKES; ++i) {  
            mSnowFlakes[i] = RainFlake.create(width, height, paint);  
        }  
    }  

    @Override   
    protected void onDraw(Canvas canvas) {  
        super.onDraw(canvas);  
        //for返回SnowFlake 
        for (RainFlake s : mSnowFlakes) {  
            //然后进行绘制 
            s.draw(canvas);  
        }  
        // 隔一段时间重绘一次, 动画效果 
        getHandler().postDelayed(runnable, DELAY);  
    }  

    // 重绘线程 
    private Runnable runnable = new Runnable() {  
        @Override  
        public void run() {  
            //自动刷新 
            invalidate();  
        }  
    };  
}  

RainFlake

package com.example.raindrop.view;  

import com.example.raindrop.RandomGenerator;  

import android.graphics.Canvas;  
import android.graphics.Paint;  

/** * 雨滴的类, 移动, 移出屏幕会重新设置位置. */  
public class RainFlake {  

    // 雨滴的移动速度 
    private static final float INCREMENT_LOWER = 6f;  
    private static final float INCREMENT_UPPER = 8f;  

    // 雨滴的大小 
    private static final float FLAKE_SIZE_LOWER = 2f;  
    private static final float FLAKE_SIZE_UPPER = 5f;  

    private final float mIncrement; // 雨滴的速度 
    private final float mFlakeSize; // 雨滴的大小 
    private final Paint mPaint; // 画笔 

    private Line mLine; // 雨滴 

    private RandomGenerator mRandom;  

    private RainFlake(RandomGenerator random,Line line, float increment, float flakeSize, Paint paint) {  
        mRandom = random;  
        mLine = line;  
        mIncrement = increment;  
        mFlakeSize = flakeSize;  
        mPaint = paint;  
    }  

    //生成雨滴 
    public static RainFlake create(int width, int height, Paint paint) {  
        RandomGenerator random = new RandomGenerator();  
        int [] nline;  
        nline = random.getLine(width, height);  

        Line line = new Line(nline[0], nline[1], nline[2], nline[3]);  
        float increment = random.getRandom(INCREMENT_LOWER, INCREMENT_UPPER);  
        float flakeSize = random.getRandom(FLAKE_SIZE_LOWER, FLAKE_SIZE_UPPER);  
        return new RainFlake(random,line, increment, flakeSize, paint);  
    }  

    // 绘制雨滴 
    public void draw(Canvas canvas) {  
        int width = canvas.getWidth();  
        int height = canvas.getHeight();  
        drawLine(canvas, width, height);  
    }  

    /** * 改成线条，类似于雨滴效果 * @param canvas * @param width * @param height */  
    private void drawLine(Canvas canvas, int width, int height) {  
        //设置线宽 
      mPaint.setStrokeWidth(mFlakeSize);  
        //y是竖直方向，就是下落 
      double y1 = mLine.y1 + (mIncrement * Math.sin(1.5));  
      double y2 = mLine.y2 + (mIncrement * Math.sin(1.5));  

      //这个是设置雨滴位置，如果在很短时间内刷新一次，就是连起来的动画效果 
       mLine.set(mLine.x1,(int) y1,mLine.x2 ,(int) y2);  

        if (!isInsideLine(height)) {  
            resetLine(width,height);  
        }  

        canvas.drawLine(mLine.x1, mLine.y1, mLine.x2, mLine.y2, mPaint);  
    }  

    // 判断是否在其中 
    private boolean isInsideLine(int height) {  
        return mLine.y1 < height && mLine.y2 < height;  
    }  

    // 重置雨滴 
    private void resetLine(int width, int height) {  
        int [] nline;  
        nline = mRandom.getLine(width, height);  
        mLine.x1 = nline[0];  
        mLine.y1 = nline[1];  
        mLine.x2 = nline[2];  
        mLine.y2 = nline[3];  
    }  

}  

• **再次说明以下： 英文原文地址：https://blog.stylingandroid.com/snowfall/
  中文翻译地址：http://www.open-open.com/lib/view/open1452263908573.html
  国外大神实现效果youtube视频地址：https://www.youtube.com/watch?v=pk66ZziTfOw
  中文翻译是open开发者经验库一位作者翻译，翻译的很好。在那篇文章也能看到实现的最原始的效果。**