Android 漂浮动画，下雪动画效果

因工作需要最近在研究了动画，先看下效果：

1.先得了解下canvas.drawBitmap(mBitmap, mSrcRect, mDestRect, mBitPaint);

在绘制图片时，使用，参数分别，图片bitmap,绘制bitmap自己的区域，绘制bitmap在手机上显示位置区域，画笔；

mSrcRect，mDestRect都是Rect(int left, int top, int right, int bottom) 的对象；
2.思路

a.漂浮的图片，可能是小球，星星，雪花之类的，根据需求，选若干个不同小图片，先称之他们漂浮的星星；

b.根据效果，漂浮图片设置其实有关数据，像坐标，大小，透明度，移动速度进水，移动方向等；

c.然后初始化以上数据，生成批量小球，进行绘制；

d.开设个线程或handle造成定时器，来不断刷新，同时修改漂浮星星属性，

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3.代码

a.定义一个继承View的类，初始化画笔，所需若干星星，设置不同速度

private void initPaint() {
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
// 防抖动
paint.setDither(true);
// 开启图像过滤
paint.setFilterBitmap(true);
}

/**
* 设置动画目标,三张大小不同，样式不一，为了美观
* init bitmap info
*/
private void initBitmapInfo() {
mStarOne = ((BitmapDrawable) mResources.getDrawable(R.drawable.star2)).getBitmap();
mStarOneWidth = mStarOne.getWidth();
mStarOneHeight = mStarOne.getHeight();
mStarTwo = ((BitmapDrawable) mResources.getDrawable(R.drawable.star1)).getBitmap();
mStarTwoWidth = mStarTwo.getWidth();
mStarTwoHeight = mStarTwo.getHeight();
mStarThree = ((BitmapDrawable) mResources.getDrawable(R.drawable.star3)).getBitmap();
mStarThreeWidth = mStarThree.getWidth();
mStarThreeHeight = mStarThree.getHeight();
}

//定义三种不同快慢的漂浮速度
private void initData(Context context) {
mResources = getResources();
DisplayMetrics dm = context.getApplicationContext().getResources().getDisplayMetrics();
mTotalWidth = dm.widthPixels;
mTotalHeight = dm.heightPixels;
Log.i(TAG, "mTotalWidth=" + mTotalWidth + "--1--mTotalHeight=" + mTotalHeight);
//设置三个不同大小的速度值
mFloatTransLowSpeed = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 0.5f,
mResources.getDisplayMetrics());
mFloatTransMidSpeed = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 0.75f,
mResources.getDisplayMetrics());
mFloatTransFastSpeed = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 1f,
mResources.getDisplayMetrics());
}

b.初始化星星，因为在构造方法里把一些基本数据初始化结束后，接着会进行测量，我把初始化星星方法放在
onMeasure方法了

/**
* 初始化星星信息
*/
private void initStarInfo() {
StarInfo starInfo = null;
Random random = new Random();
for (int i = 0; i < mFloatCount; i++) {
// 获取星星大小比例
float starSize = getStarSize(0.4f, 0.8f);
//小球的坐标
float[] starLocation = STAR_LOCATION[i];
starInfo = new StarInfo();
// 初始化星星大小
starInfo.sizePercent = starSize;
// 初始化漂浮速度
int randomSpeed = random.nextInt(3);
switch (randomSpeed) {
case 0:
starInfo.speed = mFloatTransLowSpeed;
break;
case 1:
starInfo.speed = mFloatTransMidSpeed;
break;
case 2:
starInfo.speed = mFloatTransFastSpeed;
break;
default:
starInfo.speed = mFloatTransMidSpeed;
break;
}
// 初始化星星透明度
starInfo.alpha = getStarSize(0.3f, 0.8f);
// 初始化星星位置
starInfo.xLocation = (int) (starLocation[0] * mTotalWidth);
starInfo.yLocation = (int) (starLocation[1] * mTotalHeight);
Log.i(TAG, "xLocation = " + starInfo.xLocation + "--yLocation = "
+ starInfo.yLocation);
Log.i(TAG, "stoneSize = " + starSize + "---stoneAlpha = "
+ starInfo.alpha);
// 初始化星星位置
starInfo.direction = getStarDirection();
mStarInfos.add(starInfo);
}
}

STAR_LOCATION[]数组的人为的确定星星占手机屏幕大小比例的位置，自己试过随机生成一些数据，但是有时就扎堆了，应该找个手机屏幕上随机不重复生成点坐标的算法，正在思考，有会的，给我说下，学习下

c.设置星星的移动方向，这里只是常态化的左右上下，对角线的方向，自己可以添加其他轨迹方向

/**
* 不同移动轨迹，除过左右上下，也可以定义其他方向，如对角线，曲线之类的
* 初始化星星运行方向
*/
private int getStarDirection() {
int randomInt;
Random random = new Random();
if(floatTyep==100){
randomInt = random.nextInt(3);
}else {
randomInt=floatTyep;
}
int direction = 0;
switch (randomInt) {
case 0:
direction = LEFT;
break;
case 1:
direction = RIGHT;
break;
case 2:
direction = TOP;
break;
case 3:
direction = BOTTOM;
break;
case 4:
direction = FREE_POINT;
break;
default:
break;
}
return direction;
}

d.重复绘制时，修改小球的运动轨迹方向，添加case类型，比如一些正余弦轨迹，在手机上菱形运行，折线轨迹等；

private void resetStarFloat(StarInfo starInfo) {
switch (starInfo.direction) {
case LEFT:
if (starInfo.xLocation < -20) {
starInfo.xLocation = mTotalWidth;
} else {
starInfo.xLocation -= starInfo.speed;
}
break;
case RIGHT:
if (starInfo.xLocation > mTotalWidth+20) {
starInfo.xLocation = 0;
} else {
starInfo.xLocation += starInfo.speed;
}
break;
case TOP:
if (starInfo.yLocation < -20) {
starInfo.yLocation = mTotalHeight;
} else {
starInfo.yLocation -= starInfo.speed;
}
break;
case BOTTOM:
if (starInfo.yLocation > mTotalHeight+30) {
starInfo.yLocation = 0;
} else {
starInfo.yLocation += starInfo.speed;
}
break;
case FREE_POINT:
if (starInfo.yLocation > mTotalHeight+30) {
starInfo.yLocation = 0;
} else {
starInfo.yLocation += starInfo.speed;
}
if (starInfo.xLocation < -20) {
starInfo.xLocation = mTotalWidth;
} else {
starInfo.xLocation -= starInfo.speed;
}
break;
default:
break;
}
}

上面的20,30是随便加的，是为了让星星跑到手机屏幕之外，再重新进入界面，否则直接运动到屏幕边界，重新开始，会闪的一下，效果不好；

e.进行绘制

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < mStarInfos.size(); i++) {
StarInfo starInfo = mStarInfos.get(i);
drawStarDynamic(i, starInfo, canvas, paint);
}
}
private void drawStarDynamic(int count, StarInfo starInfo,
Canvas canvas, Paint paint) {
resetStarFloat(starInfo);
float starAlpha = starInfo.alpha;
int xLocation = starInfo.xLocation;
int yLocation = starInfo.yLocation;
float sizePercent = starInfo.sizePercent;
xLocation = (int) (xLocation / sizePercent);
yLocation = (int) (yLocation / sizePercent);
Bitmap bitmap = null;
Rect srcRect = null;
Rect destRect = new Rect();
mStarOneSrcRect = new Rect(0, 0, mStarOneWidth, mStarOneHeight);
if (count % 3 == 0) {
bitmap = mStarOne;
srcRect = mStarOneSrcRect;
destRect.set(xLocation, yLocation,
xLocation + mStarOneWidth, yLocation
+ mStarOneHeight);
} else if (count % 2 == 0) {
bitmap = mStarThree;
srcRect = mStarThreeSrcRect;
destRect.set(xLocation, yLocation, xLocation
+ mStarThreeWidth, yLocation + mStarThreeHeight);
} else {
bitmap = mStarTwo;
srcRect = mStarTwoSrcRect;
destRect.set(xLocation, yLocation, xLocation
+ mStarTwoWidth, yLocation + mStarTwoHeight);
}
paint.setAlpha((int) (starAlpha * 255));
canvas.save();
canvas.scale(sizePercent, sizePercent);
canvas.drawBitmap(bitmap, srcRect, destRect, paint);
canvas.restore();
}

f.定时重会，实现动的效果

Handler handler=new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if(isRuning){
postInvalidate();
handler.sendMessageDelayed(Message.obtain(),50);
}
}
};

public void startAnimationFloat(){
isRuning=true;
handler.sendMessage(Message.obtain());
}
public void stopAnimationFloat(){
isRuning=false;
}
public void restartAnimationFloat(){
startAnimationFloat();
}

基本就这些，然后在activity布局里使用FloatView，设置不同运动方向轨迹即可；

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_float);
int typeKey = getIntent().getIntExtra("type_key", 0);
FloatView startBtn = (FloatView) findViewById(R.id.float_btn);
startBtn.setFloatType(FloatView.FREE_POINT);
if(typeKey==1){
startBtn.setFloatType(FloatView.DEFAULT_TYPE);
}else if(typeKey==2){
startBtn.setFloatType(FloatView.FREE_POINT);
}else if(typeKey==3){
startBtn.setFloatType(FloatView.TOP);
}else if(typeKey==4){
startBtn.setFloatType(FloatView.BOTTOM);
}else if(typeKey==5){
startBtn.setFloatType(FloatView.LEFT);
}else if(typeKey==6){
startBtn.setFloatType(FloatView.RIGHT);
}
startBtn.startAnimationFloat();
}

以上的部分关键代码和思路学习于http://blog.csdn.net/tianjian4592/article/details/45157787，此人很牛，动画绘制这块文章写的很细，容易理解，建议去看下，自己稍作修改，调通，作为笔记，来实现工作需求；
源码

Android 漂浮动画，下雪动画效果

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