Android实现雪花特效自定义view
一、前言
这个冬天，老家一直没有下雨， 正好圣诞节，就想着制作一个下雪的特效。
圣诞祝福：平安夜，舞翩阡。雪花飘，飞满天。心与心，永相伴。
圣诞节是传统的宗教节日，对于基 督徒，那是庆祝耶稣的诞生，纪念耶稣和发扬基督精神。现在整个西方社会都在过圣诞节，像许多宗教节日一样，它已经越来越民俗化了。
尽管如此，圣诞节依然倍受尊重。人们在圣诞快乐中怀有对耶稣的敬仰，欢乐的节庆里含有庄严肃穆的神念。欢度圣诞佳节的人都不拒绝耶稣的教诲，要仁爱、善良、诚实、忍耐、感恩……在信神的国度，不是基 督徒的人们，也都知道人应该感恩，心存谢意。对需要帮助的人给予关爱；对他人的帮助给予感谢。这是西方社会价值观的一部份，而不是说圣诞夜就只是一家坐在壁炉前，共进有火鸡或烤鹅的圣诞大餐或是冬季里开的一个最热闹的大派对。
二、创意名
Android实现雪花特效自定义view
三、效果展示
四、实现步骤
1.创建一个view，里面加载雪花类的集合，有一个死循环线程，一直执行动画
public class myRunnable implements Runnable {
@Override
public void run() {
while (true){
Canvas canvas =null;
try {
synchronized (holder){
canvas = holder.lockCanvas();
//清除画布
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
for (Snowflake snowflake :list){
snowflake.draw(canvas);
snowflake.update();
}
}
}catch (Exception e){
e.printStackTrace();
}finally {
if (canvas!=null){
holder.unlockCanvasAndPost(canvas);
}
}
}
}
}
这样的话，可以让所有的雪花图片动起来
2.创建雪花类，其实就是一个bitmap，然后设置不同尺寸和动画
这步相对来说简单一些，其实就是将bitmap绘制到画布上面
public void reset(){
size = randomizer.randomInt(sizeMinInPx, sizeMaxInPx, true);
if (image!=null){
if (bitmap==null){
bitmap = Bitmap.createScaledBitmap(image, size, size, false);
}
}
float speed = (float)(size - sizeMinInPx) / (sizeMaxInPx - sizeMinInPx) * (speedMax - speedMin) + speedMin;
double angle = Math.toRadians(randomizer.randomDouble(angleMax) * randomizer.randomSignum());
speedX = speed* Math.sin(angle);
speedY = speed* Math.cos(angle);
alpha = randomizer.randomInt(alphaMin, alphaMax, false);
paint.setAlpha(alpha);
positionX = randomizer.randomDouble(parentWidth);
this.positionY=randomizer.randomDouble(parentHeight);
if (!alreadyFalling){
this.positionY = this.positionY-parentHeight-size;
}
}
3.界面展示
实现manifest加载视图即可
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000"
tools:context="com.marvin.snowfall_master.MainActivity">
<com.itbird.SnowfallView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/sf_snow"
app:snowflakesNum="200"
app:snowflakeAlphaMin="150"
app:snowflakeAlphaMax="255"
app:snowflakeAngleMax="5"
app:snowflakeSizeMin="2dp"
app:snowflakeSizeMax="40dp"
app:snowflakeSpeedMin="2"
app:snowflakeSpeedMax="10"
app:snowflakesFadingEnabled="true"
app:snowflakesAlreadyFalling="false"
app:snowflakeImage="@mipmap/snowflake"
/>
</android.support.constraint.ConstraintLayout>
五、编码实现
界面类SnowfallView
public class SnowfallView extends SurfaceView implements SurfaceHolder.Callback {
private int DEFAULT_SNOWFLAKES_NUM = 200;
private int DEFAULT_SNOWFLAKE_ALPHA_MIN = 150;
private int DEFAULT_SNOWFLAKE_ALPHA_MAX = 250;
private int DEFAULT_SNOWFLAKE_ANGLE_MAX = 10;
private int DEFAULT_SNOWFLAKE_SIZE_MIN_IN_DP = 2;
private int DEFAULT_SNOWFLAKE_SIZE_MAX_IN_DP = 8;
private int DEFAULT_SNOWFLAKE_SPEED_MIN = 2;
private int DEFAULT_SNOWFLAKE_SPEED_MAX = 8;
private boolean DEFAULT_SNOWFLAKES_FADING_ENABLED = false;
private boolean DEFAULT_SNOWFLAKES_ALREADY_FALLING = false;
private int snowflakesNum;
private Bitmap snowflakeImage;
private int snowflakeAlphaMin;
private int snowflakeAlphaMax;
private int snowflakeAngleMax;
private int snowflakeSizeMinInPx;
private int snowflakeSizeMaxInPx;
private int snowflakeSpeedMin;
private int snowflakeSpeedMax;
private boolean snowflakesFadingEnabled;
private boolean snowflakesAlreadyFalling;
//雪花类集合
private ArrayList<Snowflake> list =new ArrayList<>();
private SnowfallView.myRunnable myRunnable = new myRunnable();
private Thread myThread;
private SurfaceHolder holder;
public SnowfallView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context,attrs);
}
private void init(Context context, AttributeSet attributeSet) {
TypedArray typedArray = context.obtainStyledAttributes(attributeSet, R.styleable.SnowfallView);
snowflakesNum = typedArray.getInt(R.styleable.SnowfallView_snowflakesNum, DEFAULT_SNOWFLAKES_NUM);
snowflakeImage = drawable2Bitmap(typedArray.getDrawable(R.styleable.SnowfallView_snowflakeImage));
snowflakeAlphaMin = typedArray.getInt(R.styleable.SnowfallView_snowflakeAlphaMin, DEFAULT_SNOWFLAKE_ALPHA_MIN);
snowflakeAlphaMax = typedArray.getInt(R.styleable.SnowfallView_snowflakeAlphaMax, DEFAULT_SNOWFLAKE_ALPHA_MAX);
snowflakeAngleMax = typedArray.getInt(R.styleable.SnowfallView_snowflakeAngleMax, DEFAULT_SNOWFLAKE_ANGLE_MAX);
snowflakeSizeMinInPx = typedArray.getDimensionPixelSize(R.styleable.SnowfallView_snowflakeSizeMin, dp2Px(DEFAULT_SNOWFLAKE_SIZE_MIN_IN_DP));
snowflakeSizeMaxInPx = typedArray.getDimensionPixelSize(R.styleable.SnowfallView_snowflakeSizeMax, dp2Px(DEFAULT_SNOWFLAKE_SIZE_MAX_IN_DP));
snowflakeSpeedMin = typedArray.getInt(R.styleable.SnowfallView_snowflakeSpeedMin, DEFAULT_SNOWFLAKE_SPEED_MIN);
snowflakeSpeedMax = typedArray.getInt(R.styleable.SnowfallView_snowflakeSpeedMax, DEFAULT_SNOWFLAKE_SPEED_MAX);
snowflakesFadingEnabled = typedArray.getBoolean(R.styleable.SnowfallView_snowflakesFadingEnabled, DEFAULT_SNOWFLAKES_FADING_ENABLED);
snowflakesAlreadyFalling = typedArray.getBoolean(R.styleable.SnowfallView_snowflakesAlreadyFalling, DEFAULT_SNOWFLAKES_ALREADY_FALLING);
typedArray.recycle();
holder = this.getHolder();
holder.addCallback(this);
//设置背景为透明
setZOrderOnTop(true);
holder.setFormat(PixelFormat.TRANSPARENT);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//获取雪花集合
for (int i=0;i<snowflakesNum;i++){
list.add(new Snowflake(w, h, snowflakeImage, snowflakeAlphaMin, snowflakeAlphaMax
, snowflakeAngleMax, snowflakeSizeMinInPx, snowflakeSizeMaxInPx, snowflakeSpeedMin, snowflakeSpeedMax
, snowflakesFadingEnabled, snowflakesAlreadyFalling));
}
}
@Override
protected void onVisibilityChanged(@NonNull View changedView, int visibility) {
super.onVisibilityChanged(changedView, visibility);
if (changedView==this&&visibility==GONE){
//初始化雪花类
try {
for (Snowflake snowflake :list){
snowflake.reset();
}
}catch (Exception e){
e.printStackTrace();
}
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (isInEditMode()){
return;
}
}
/**
* dp转px
* @param dp
* @return
*/
private int dp2Px(int dp){
return (int) (dp*getResources().getDisplayMetrics().density);
}
/**
* drawble转Bitmap
* @param drawable
* @return
*/
private Bitmap drawable2Bitmap(Drawable drawable){
Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0,0,drawable.getIntrinsicWidth(),drawable.getIntrinsicHeight());
drawable.draw(canvas);
return bitmap;
}
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
if (myThread==null){
myThread = new Thread(myRunnable);
}
if(!myThread.isAlive()){
myThread.start();
}
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
if (myThread!=null){
myThread.interrupt();
}
}
public class myRunnable implements Runnable {
@Override
public void run() {
while (true){
Canvas canvas =null;
try {
synchronized (holder){
canvas = holder.lockCanvas();
//清除画布
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
for (Snowflake snowflake :list){
snowflake.draw(canvas);
snowflake.update();
}
}
}catch (Exception e){
e.printStackTrace();
}finally {
if (canvas!=null){
holder.unlockCanvasAndPost(canvas);
}
}
}
}
}
}
雪花类Snowflake
public class Snowflake {
private int parentWidth;
private int parentHeight;
private int alphaMin;
private int alphaMax;
private int angleMax;
private int sizeMinInPx;
private int sizeMaxInPx;
private int speedMin;
private int speedMax;
private Bitmap image;
private boolean fadingEnabled;
private boolean alreadyFalling;
private int size = 0 ;
private int alpha = 255;
private Bitmap bitmap = null;
private double speedX= 0.0;
private double speedY = 0.0;
private double positionX = 0.0;
private double positionY = 0.0;
private final Randomizer randomizer;
private Paint paint;
public Snowflake(int parentWidth, int parentHeight, Bitmap image
,int alphaMin,int alphaMax,int angleMax,int sizeMinInPx,int sizeMaxInPx,
int speedMin,int speedMax,boolean fadingEnabled,boolean alreadyFalling ){
this.parentWidth = parentWidth;
this.parentHeight = parentHeight;
this.alphaMin = alphaMin;
this.alphaMax = alphaMax;
this.angleMax = angleMax;
this.sizeMinInPx = sizeMinInPx;
this.sizeMaxInPx = sizeMaxInPx;
this.speedMin = speedMin;
this.speedMax = speedMax;
this.image = image;
this.fadingEnabled=fadingEnabled;
this.alreadyFalling=alreadyFalling;
randomizer = new Randomizer();
initPaint();
reset();
}
/**
* 初始化画笔
*/
private void initPaint() {
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.rgb(255,255,255));
paint.setStyle(Paint.Style.FILL);
}
public void reset(double positionY){
size = randomizer.randomInt(sizeMinInPx, sizeMaxInPx, true);
if (image!=null){
if (bitmap==null){
bitmap = Bitmap.createScaledBitmap(image, size, size, false);
}
}
float speed = (float)(size - sizeMinInPx) / (sizeMaxInPx - sizeMinInPx) * (speedMax - speedMin) + speedMin;
double angle = Math.toRadians(randomizer.randomDouble(alphaMax) * randomizer.randomSignum());
if (angle<-1||angle>1){
angle = 0;
}
speedX = speed* Math.sin(angle);
speedY = speed* Math.cos(angle);
alpha = randomizer.randomInt(alphaMin, alphaMax, false);
paint.setAlpha(alpha);
positionX = randomizer.randomDouble(parentWidth);
this.positionY = positionY;
}
public void reset(){
size = randomizer.randomInt(sizeMinInPx, sizeMaxInPx, true);
if (image!=null){
if (bitmap==null){
bitmap = Bitmap.createScaledBitmap(image, size, size, false);
}
}
float speed = (float)(size - sizeMinInPx) / (sizeMaxInPx - sizeMinInPx) * (speedMax - speedMin) + speedMin;
double angle = Math.toRadians(randomizer.randomDouble(angleMax) * randomizer.randomSignum());
speedX = speed* Math.sin(angle);
speedY = speed* Math.cos(angle);
alpha = randomizer.randomInt(alphaMin, alphaMax, false);
paint.setAlpha(alpha);
positionX = randomizer.randomDouble(parentWidth);
this.positionY=randomizer.randomDouble(parentHeight);
if (!alreadyFalling){
this.positionY = this.positionY-parentHeight-size;
}
}
public void update(){
positionX = positionX+speedX;
positionY = positionY+speedY;
if (positionY>parentHeight){
positionY = -(double)size;
reset(positionY);
}
if (fadingEnabled){
paint.setAlpha((int) (alpha * ((float) (parentHeight - positionY) / parentHeight)));
}
}
public void draw(Canvas canvas){
if (bitmap!=null){
canvas.drawBitmap(bitmap,(float)positionX,(float)positionY,paint);
}else {
canvas.drawCircle((float)positionX,(float)positionY,(float)size,paint);
}
}
}