Utilisez SurfaceView pour obtenir des effets d'animation de pluie et de neige

package com.xiasuhuei321.gank_kotlin.customview.weather

import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.PointF
import com.xiasuhuei321.gank_kotlin.context
import com.xiasuhuei321.gank_kotlin.extension.getScreenWidth
import java.util.*

/**
 * Created by xiasuhuei321 on 2017/9/5.
 * author:luo
 * e-mail:xiasuhuei321@163.com
 *
 * desc: All shape's parent class.It describes a shape will have
 * what feature.It's draw flows are:
 * 1.Outside the class init some value such as the start and the
 * end point.
 * 2.Invoke draw(Canvas) method, in this method, there are still
 * two flows:
 * 1) Get random value to init paint, this will affect the shape
 * draw style.
 * 2) When the shape is not used, invoke init method, and when it
 * is not used invoke drawWhenInUse(Canvas) method. It should be
 * override by user and to implement draw itself.
 *
 */
abstract class WeatherShape(val start: PointF, val end: PointF) {
 open var TAG = "WeatherShape"

 /**
  * 是否是正在被使用的状态
  */
 var isInUse = false

 /**
  * 是否是随机刷新的Shape
  */
 var isRandom = false

 /**
  * 下落的速度，特指垂直方向，子类可以实现自己水平方向的速度
  */
 var speed = 0.05f

 /**
  * shape的宽度
  */
 var width = 5f

 var shapeAlpha = 100

 var paint = Paint().apply {
  strokeWidth = width
  isAntiAlias = true
  alpha = alpha
 }

 // 总共下落的时间
 var lastTime = 0L
 // 原始x坐标位置
 var originX = 0f

 /**
  * 根据自己的规则计算加速度，如果是匀速直接 return 0
  */
 abstract fun getAcceleration(): Float

 /**
  * 绘制自身，这里在Shape是非使用的时候进行一些初始化操作
  */
 open fun draw(canvas: Canvas) {
  if (!isInUse) {
   lastTime += randomPre()
   initStyle()
   isInUse = true
  } else {
   drawWhenInUse(canvas)
  }
 }

 /**
  * Shape在使用的时候调用此方法
  */
 abstract fun drawWhenInUse(canvas: Canvas)

 /**
  * 初始化Shape风格
  */
 open fun initStyle() {
  val random = Random()
  // 获取随机透明度
  shapeAlpha = random.nextInt(155) + 50
  // 获得起点x偏移
  val translateX = random.nextInt(10).toFloat() + 5
  if (!isRandom) {
   start.x = translateX + originX
   end.x = translateX + originX
  } else {
   // 如果是随机Shape，将x坐标随机范围扩大到整个屏幕的宽度
   val randomWidth = random.nextInt(context.getScreenWidth())
   start.x = randomWidth.toFloat()
   end.x = randomWidth.toFloat()
  }
  speed = randomSpeed(random)
  // 初始化length的工作留给之后对应的子类去实现
  // 初始化color也留给子类去实现
  paint.apply {
   alpha = shapeAlpha
   strokeWidth = width
   isAntiAlias = true
  }
  // 如果有什么想要做的，刚好可以在追加上完成，就使用这个函数
  wtc(random)
 }

 /**
  * Empty body, this will be invoke in initStyle
  * method.If current initStyle method can satisfy your need
  * but you still add something, by override this method
  * will be a good idea to solve the problem.
  */
 open fun wtc(random:Random): Unit {

 }

 abstract fun randomSpeed(random: Random): Float

 /**
  * 获取一个随机的提前量，让shape在竖屏上有一个初始的偏移
  */
 open fun randomPre(): Long {
  val random = Random()
  val pre = random.nextInt(1000).toLong()
  return pre
 }
}

package com.xiasuhuei321.gank_kotlin.customview.weather

import android.graphics.*
import com.xiasuhuei321.gank_kotlin.context
import com.xiasuhuei321.gank_kotlin.extension.getScreenHeight
import java.util.*

/**
 * Created by xiasuhuei321 on 2017/9/5.
 * author:luo
 * e-mail:xiasuhuei321@163.com
 */
class Snow(start: PointF, end: PointF) : WeatherShape(start, end) {

 /**
  * 圆心，用户可以改变这个值
  */
 var center = calcCenter()

 /**
  * 半径
  */
 var radius = 10f

 override fun getAcceleration(): Float {
  return 0f
 }

 override fun drawWhenInUse(canvas: Canvas) {
  // 通过圆心与半径确定圆的位置及大小
  val distance = speed * lastTime
  center.y += distance
  start.y += distance
  end.y += distance
  lastTime += 16
  canvas.drawCircle(center.x, center.y, radius, paint)
  if (end.y > context.getScreenHeight()) clear()
 }

 fun calcCenter(): PointF {
  val center = PointF(0f, 0f)
  center.x = (start.x + end.x) / 2f
  center.y = (start.y + end.y) / 2f
  return center
 }

 override fun randomSpeed(random: Random): Float {
  // 获取随机速度0.005 ~ 0.01
  return (random.nextInt(5) + 5) / 1000f
 }

 override fun wtc(random: Random) {
  // 设置颜色渐变
  val shader = RadialGradient(center.x, center.y, radius,
    Color.parseColor("#FFFFFF"), Color.parseColor("#D1D1D1"),
    Shader.TileMode.CLAMP)
  // 外部设置的起始点其实并不对，先计算出半径
  radius = random.nextInt(10) + 15f
  // 根据半径计算start end
  end.x = start.x + radius
  end.y = start.y + radius
  // 计算圆心
  calcCenter()

  paint.apply {
   setShader(shader)
  }
 }

 fun clear() {
  isInUse = false
  lastTime = 0
  start.y = -radius * 2
  end.y = 0f

  center = calcCenter()
 }
}

package com.xiasuhuei321.gank_kotlin.customview.weather

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.PixelFormat
import android.graphics.PorterDuff
import android.util.AttributeSet
import android.view.SurfaceHolder
import android.view.SurfaceView
import com.xiasuhuei321.gank_kotlin.extension.LogUtil
import java.lang.Exception

/**
 * Created by xiasuhuei321 on 2017/9/5.
 * author:luo
 * e-mail:xiasuhuei321@163.com
 */
class WeatherView(context: Context, attributeSet: AttributeSet?, defaultStyle: Int) :
  SurfaceView(context, attributeSet, defaultStyle), SurfaceHolder.Callback {
 private val TAG = "WeatherView"

 constructor(context: Context, attributeSet: AttributeSet?) : this(context, attributeSet, 0)

 constructor(context: Context) : this(context, null, 0)

 // 低级并发，Kotlin中支持的不是很好，所以用一下黑科技
 val lock = Object()
 var type = Weather.RAIN
 var weatherShapePool = WeatherShapePool()

 @Volatile var canRun = false
 @Volatile var threadQuit = false

 var thread = Thread {
  while (!threadQuit) {
   if (!canRun) {
    synchronized(lock) {
     try {
      LogUtil.i(TAG, "条件尚不充足，阻塞中...")
      lock.wait()
     } catch (e: Exception) {
     }
    }
   }
   val startTime = System.currentTimeMillis()
   try {
    // 正式开始表演
    val canvas = holder.lockCanvas()
    if (canvas != null) {
     canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR)
     draw(canvas, type, startTime)
    }
    holder.unlockCanvasAndPost(canvas)
    val drawTime = System.currentTimeMillis() - startTime
    // 平均16ms一帧才能有顺畅的感觉
    if (drawTime < 16) {
     Thread.sleep(16 - drawTime)
    }
   } catch (e: Exception) {
//    e.printStackTrace()
   }
  }
 }.apply { name = "WeatherThread" }

 override fun surfaceChanged(holder: SurfaceHolder?, format: Int, width: Int, height: Int) {
  // surface发生了变化
//  canRun = true

 }

 override fun surfaceDestroyed(holder: SurfaceHolder?) {
  // 在这里释放资源
  canRun = false
  LogUtil.i(TAG, "surfaceDestroyed")
 }

 override fun surfaceCreated(holder: SurfaceHolder?) {
  threadQuit = false
  canRun = true
  try {
   // 如果没有执行wait的话，这里notify会抛异常
   synchronized(lock) {
    lock.notify()
   }
  } catch (e: Exception) {
   e.printStackTrace()
  }
 }

 init {
  LogUtil.i(TAG, "init开始")
  holder.addCallback(this)
  holder.setFormat(PixelFormat.RGBA_8888)
//  initData()
  setZOrderOnTop(true)
//  setZOrderMediaOverlay(true)
  thread.start()
 }

 private fun draw(canvas: Canvas, type: Weather, startTime: Long) {
  // type什么的先放一边，先实现一个
  weatherShapePool.drawSnow(canvas)
 }

 enum class Weather {
  RAIN,
  SNOW
 }

 fun onDestroy() {
  threadQuit = true
  canRun = true
  try {
   synchronized(lock) {
    lock.notify()
   }
  } catch (e: Exception) {
  }
 }
}

package com.xiasuhuei321.gank_kotlin.customview.weather

import android.graphics.Canvas
import android.graphics.PointF
import com.xiasuhuei321.gank_kotlin.context
import com.xiasuhuei321.gank_kotlin.extension.getScreenWidth

/**
 * Created by xiasuhuei321 on 2017/9/7.
 * author:luo
 * e-mail:xiasuhuei321@163.com
 */
class WeatherShapePool {
 val constantRain = ArrayList<Rain>()
 val randomRain = ArrayList<Rain>()

 val constantSnow = ArrayList<Snow>()
 val randomSnow = ArrayList<Snow>()

 init {
  // 初始化
  initData()
  initSnow()
 }

 private fun initData() {
  val space = context.getScreenWidth() / 20
  var currentSpace = 0f
  // 将其均匀的分布在屏幕x方向上
  for (i in 0..19) {
   val rain = Rain(PointF(currentSpace, 0f), PointF(currentSpace, 0f))
   rain.originLength = 20f
   rain.originX = currentSpace
   constantRain.add(rain)
   currentSpace += space
  }

  for (j in 0..9) {
   val rain = Rain(PointF(0f, 0f), PointF(0f, 0f))
   rain.isRandom = true
   rain.originLength = 20f
   randomRain.add(rain)
  }
 }

 fun drawRain(canvas: Canvas) {
  for (r in constantRain) {
   r.draw(canvas)
  }
  for (r in randomRain) {
   r.draw(canvas)
  }
 }

 private fun initSnow(){
  val space = context.getScreenWidth() / 20
  var currentSpace = 0f
  // 将其均匀的分布在屏幕x方向上
  for (i in 0..19) {
   val snow = Snow(PointF(currentSpace, 0f), PointF(currentSpace, 0f))
   snow.originX = currentSpace
   snow.radius = 20f
   constantSnow.add(snow)
   currentSpace += space
  }

  for (j in 0..19) {
   val snow = Snow(PointF(0f, 0f), PointF(0f, 0f))
   snow.isRandom = true
   snow.radius = 20f
   randomSnow.add(snow)
  }
 }

 fun drawSnow(canvas: Canvas){
  for(r in constantSnow){
   r.draw(canvas)
  }

  for (r in randomSnow){
   r.draw(canvas)
  }
 }
}