前言：
这个效果实现的原作者是国外一位大神。我在其基础上测试，以及在代码上加了不少注释，以及局部修改。后面我有根据漫天飞舞雪花，实现下雨天场景的效果。原作者项目还是android studio版本的。我改成eclipse android 版本。
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
<span style="font-size:14px;">package com.ex</span>ample.snowflake.view;
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];
}
}
3、效果图
在这里我说一下为什么是没有gif效果图，android手机录制屏幕太太麻烦了，还要转为gif。以前我是用腾讯应用宝截图做成gif效果图。但是这次效果不好我就直接截图了。
需要看动画效果，下载我demo。或者去中文翻译那片文章也有效果图。
还有各位有什么推荐工具，关于android 机器录制gif工具或者软件。
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。
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