Android实现雷达View效果的示例代码

样式效果

还是先来看效果：

这是一个仿雷达扫描的效果，是之前在做地图sdk接入时就想实现的效果，但之前由于赶着毕业设计，就没有亲手去实现，不过现在自己撸一个发现还是挺简单的。

这里主要分享一下我的做法。

目录

主体轮廓的实现（雷达的结构）

动画的实现（雷达扫描的效果）

目标点的加入（图片/点）

主体轮廓实现

不难分析得出，这个View主要由外部的一个圆，中间的锚点圆以及扇形旋转区域组成。而且每个部分理应由不同的Paint去绘制，以方便去定制各部分的样式。

外部圆以及锚点圆的绘制较为简单，主要的点还是要对整个View的宽高进行一定的限制，例如宽高必须相等且在某种模式下，取小的那个值来限定整个RadarView的最大值。那么该如何去控制呢？

onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int)

  由于我们继承自View，在onMeasure方法中，我们可以根据两个参数来获取Mode，并且根据Mode来指定宽/高对应的值，再通过setMeasuredDimension去指定控件主体的宽高即可。

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec)
 val vWidth = measureDimension(widthMeasureSpec)
 val vHeight = measureDimension(heightMeasureSpec)
 val size = min(vWidth, vHeight)

 setMeasuredDimension(size, size)
}

private fun measureDimension(spec: Int) = when (MeasureSpec.getMode(spec)) {
 MeasureSpec.EXACTLY -> {
 // exactly number or match_parent
 MeasureSpec.getSize(spec)
 }
 MeasureSpec.AT_MOST -> {
 // wrap_content
 min(mDefaultSize, MeasureSpec.getSize(spec))
 }
 else -> {
 mDefaultSize
 }
}

测量工作完成了，我们自然可以去绘制了。为了不让中间的小圆看起来那么突兀（偏大或偏小），这里设置了一个scaleFactor的缩放因子，使其能根据外圆的尺寸来进行缩放。

override fun onDraw(canvas: Canvas?) {
 super.onDraw(canvas)
 // draw outside circle (background)
 canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2, measuredWidth.toFloat() / 2, mOutlinePaint)
 if (mBorderWidth > 0F && mOutlinePaint.shader == null) {
  drawBorder(canvas)
 }

 // mOutlineRect = Rect(0, 0, measuredWidth, measuredHeight)
 canvas?.drawArc(mOutlineRect.toRectF(), mStartAngle, mSweepAngle, true, mSweepPaint)

 // draw center circle
 // scaleFactor = 30F
 canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2, measuredWidth.toFloat() / 2 / mScaleFactor, mPaint)
}

private fun drawBorder(canvas: Canvas?) {
 Log.i("RadarView", "drawBorder")
 mOutlinePaint.style = Paint.Style.STROKE
 mOutlinePaint.color = mBorderColor
 mOutlinePaint.strokeWidth = mBorderWidth
 canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2,
  (measuredWidth.toFloat() - mBorderWidth) / 2, mOutlinePaint)
 // 还原
 mOutlinePaint.style = Paint.Style.FILL_AND_STROKE
 mOutlinePaint.color = mBackgroundColor
}

绘制了基准圆以后，要实现雷达扫描时那种渐变的效果，我们可以通过SweepGradient来操作。通过指定中心点，渐变颜色，以及颜色的分布，来定制扫描渐变的样式，默认的即时开头时gif展示的那种。由于这里是从第一象限开始旋转，因此将旋转的起点通过matrix逆时针旋转90度，从而达到由浅入深的效果。

private fun setShader(size: Int) {
 val shader = SweepGradient(size.toFloat() / 2, size.toFloat() / 2,
  mScanColors?: mDefaultScanColors, // 可通过setScanColors()来定制颜色
  floatArrayOf(0F, 0.5F, 1F)) // 这里默认走平均分布
 val matrix = Matrix()
 // 逆时针旋转90度
 matrix.setRotate(-90F, size.toFloat() / 2, size.toFloat() / 2)
 shader.setLocalMatrix(matrix)
 mSweepPaint.shader = shader
}

这里完成了测量与绘制的工作，那么我们在布局里引用以后，就会看到这样的效果：

这时，由于我们之前在测量的时候，将宽高最小值作为绘制的基准大小给予了RadarView，因此measuredWidth和measuredHeight是相等的，但是由于在布局中指定了match_parent属性，那么实际的控件宽高还是和父布局一致（在这里即占满屏幕宽高，由于宽比高小，所以看到绘制的图形会偏向上方；如果设置了高比宽小，那么绘制的图形就会位于左侧）。一般的雷达控件应该都是居中显示的，所以我在这里也重写了onLayout方法，来实现居中的效果。

override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
 // 设置默认居中
 var l = left
 var r = right
 var t = top
 var b = bottom
 when {
  width > height -> {
   // 宽度比高度大 那么要设置默认居中就得把left往右移 right往左移
   l = (width - measuredWidth) / 2
   r = width - l
   layout(l, t, r, b)
  }
  height > width -> {
   // 高度比宽度大 那么要设置默认居中就得把top往下移 bottom往上移
   t = (height - measuredHeight) / 2
   b = height - t
   layout(l, t, r, b)
  }
  else -> super.onLayout(changed, left, top, right, bottom)
 }
}

动画的实现

完成了绘制，接下来就是思考该如何让他动起来了。由绘制的代码不难想到，我这里考虑的是通过mStartAngle的变化来控制绘制的角度旋转，而ValueAnimator则正好能获取到每次更新时value的值，因此这里我选用了这个方案。

fun start() {
 Log.i("RadarView", "animation start")
 mIsAnimating = true
 mAnimator.duration = 2000
 mAnimator.repeatCount = ValueAnimator.INFINITE
 mAnimator.addUpdateListener {
  val angle = it.animatedValue as Float
  mStartAngle = angle

//  Log.i("RadarView", "mStartAngle = $mStartAngle and curValue = ${it.animatedValue}")
  postInvalidate()
 }
 mAnimator.start()
}

坑

这里就需要注意一个点，就是canvas在绘制时，后绘制的会覆盖在前绘制的图像上，所以需要注意绘制的顺序。当然，这里也可以把mOutlineRect的宽高设置为measuredWidth - mBorderWidth，那么就能保证绘制填充角度时，不会把边界覆盖。

至此，动画的效果便完成了。

目标点的加入

首先，前两点已经能满足大多的雷达扫描需求了。这里这个添加目标点（target）纯粹是我自己想加入的功能，因为觉得可以结合地图sdk的MapView来共同使用，目前也只是开发阶段，扩展性可能考虑得还不是特别充足，也还没应用到具体项目中。但是，总觉得自己想的功能也该试着去实践一下~

这里主要运用的圆的计算公式：

由于Android的坐标系的原点是在左上角，y轴过顶点向下延伸。由我们的绘制可知，此绘制图像在坐标系中的位置大概如下图所示：

那么，对应的公式就为：

要注意的是，这里r的计算会根据图/点的设置来动态计算，具体例子通过代码来进行分析。

// 随机落点
fun addTarget(size: Int, type: TYPE = TYPE.RANDOM) {
 val list = ArrayList<PointF>()
 val r = measuredWidth.toFloat() / 2
 val innerRect = Rect((r - r / mScaleFactor).toInt(), (r - r / mScaleFactor).toInt(),
  (r + r / mScaleFactor).toInt(), (r + r / mScaleFactor).toInt())
 // 圆的中心点
 val circle = PointF(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2)
 while (list.size < size) {
  val ranX = Random.nextDouble(0.0, r * 2.0).toFloat()
  val ranY = Random.nextDouble(0.0, r * 2.0).toFloat()
  val ranPointF = PointF(ranX, ranY)
  if (innerRect.contains(ranPointF.toPoint())) {
   continue
  }
  // 圆公式
  if (!mNeedBitmap &&
   (ranX - circle.x).pow(2) + (ranY - circle.y).pow(2) <
    (r - mTargetRadius - mBorderWidth).toDouble().pow(2.0)) {
   // 普通点
   addTargetFromType(type, list, ranX, ranY, r, ranPointF)
  } else if (mNeedBitmap &&
   (ranX - circle.x).pow(2) + (ranY - circle.y).pow(2) <
    (r - mBorderWidth - max(mBitmap.width, mBitmap.height) / 2).toDouble().pow(2)) {
   // 图
   addTargetFromType(type, list, ranX, ranY, r, ranPointF)
  } else {
   continue
  }
 }
 mTargetList = list
 for (target in list) {
  Log.i("RadarView", "target = [${target.x}, ${target.y}]")
 }
 invalidate()
}

可以看到，当target为普通点时，r的计算还要减去targetRadius，即目标点的半径，同时还要减去边界的宽度，如图所示：

当target为图时，由于宽高不定，故除了边界外，还要减去大的边，那么r的计算则为：

同时为了避免图片的尺寸过大，这里同样采取了一个默认值与一个缩放因子，从而保证图的完整性以及避免过大而引起的视觉丑化。

关于落点的位置，目前采取的是随机落点，如果应用到地图扫点的话，可以通过地图sdk内的距离计算工具再与RadarView的坐标做一个比例转换，从而达到雷达内显示该点具体方位。

关于落点的分布，目前提供了5种类型：分别是全象限随机、第一象限、第二象限、第三象限与第四象限随机。

Github

若须直接调用，可移步至 https://github.com/CarsonWoo/RadarView

完整代码

class RadarView : View {

 enum class TYPE { RANDOM, FIRST, SECOND, THIRD, FOURTH }

 private val mPaint by lazy { Paint(Paint.ANTI_ALIAS_FLAG) }

 private val mSweepPaint by lazy { Paint(Paint.ANTI_ALIAS_FLAG) }

 private val mOutlinePaint by lazy { Paint(Paint.ANTI_ALIAS_FLAG) }

 private val mTargetPaint by lazy { Paint(Paint.ANTI_ALIAS_FLAG) }

 private val mDefaultSize = 120// px

 // limit the size of bitmap
 private var mBitmapMaxSize = 0F

 private var mBitmapWHRatio = 0F

 private val mScaleFactor = 30F

 private var mStartAngle = 0F
 private val mSweepAngle = -60F

 private var mScanColors: IntArray? = null

 private val mDefaultScanColors = intArrayOf(Color.parseColor("#0F7F7F7F"),
  Color.parseColor("#7F7F7F7F"),
  Color.parseColor("#857F7F7F"))

 private val mDefaultBackgroundColor = Color.WHITE

 private var mBackgroundColor: Int = mDefaultBackgroundColor

 private var mBorderColor: Int = Color.BLACK

 private var mBorderWidth = 0F

 private var mTargetColor: Int = Color.RED

 private var mTargetRadius = 10F

 private lateinit var mOutlineRect: Rect

 private val mAnimator = ValueAnimator.ofFloat(0F, 360F)

 private var mTargetList: ArrayList<PointF>? = null

 private var mIsAnimating = false

 private var mNeedBitmap = false

 private var mBitmap = BitmapFactory.decodeResource(resources, R.mipmap.ic_launcher)

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

 constructor(context: Context, attributeSet: AttributeSet?) : super(context, attributeSet)

 init {
  mPaint.color = Color.GRAY
  mPaint.strokeWidth = 10F
  mPaint.style = Paint.Style.FILL_AND_STROKE
  mPaint.strokeJoin = Paint.Join.ROUND
  mPaint.strokeCap = Paint.Cap.ROUND

  mSweepPaint.style = Paint.Style.FILL

  mOutlinePaint.style = Paint.Style.FILL_AND_STROKE
  mOutlinePaint.color = mBackgroundColor

  mTargetPaint.style = Paint.Style.FILL
  mTargetPaint.color = mTargetColor
  mTargetPaint.strokeWidth = 10F
 }

 override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec)
  val vWidth = measureDimension(widthMeasureSpec)
  val vHeight = measureDimension(heightMeasureSpec)
  val size = min(vWidth, vHeight)

  setShader(size)

  setMeasuredDimension(size, size)

  setParamUpdate()
 }

 override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
  // 设置默认居中
  var l = left
  var r = right
  var t = top
  var b = bottom
  when {
   width > height -> {
    // 宽度比高度大 那么要设置默认居中就得把left往右移 right往左移
    l = (width - measuredWidth) / 2
    r = width - l
    layout(l, t, r, b)
   }
   height > width -> {
    // 高度比宽度大 那么要设置默认居中就得把top往下移 bottom往上移
    t = (height - measuredHeight) / 2
    b = height - t
    layout(l, t, r, b)
   }
   else -> super.onLayout(changed, left, top, right, bottom)
  }
 }

 private fun setShader(size: Int) {
  val shader = SweepGradient(size.toFloat() / 2, size.toFloat() / 2,
   mScanColors?: mDefaultScanColors,
   floatArrayOf(0F, 0.5F, 1F))
  val matrix = Matrix()
  matrix.setRotate(-90F, size.toFloat() / 2, size.toFloat() / 2)
  shader.setLocalMatrix(matrix)
  mSweepPaint.shader = shader
 }

 fun setScanColors(colors: IntArray) {
  this.mScanColors = colors
  setShader(measuredWidth)
  invalidate()
 }

 fun setRadarColor(@ColorInt color: Int) {
  this.mBackgroundColor = color
  this.mOutlinePaint.color = color
  invalidate()
 }

 fun setRadarColor(colorString: String) {
  if (!colorString.startsWith("#") || colorString.length != 7 || colorString.length != 9) {
   Log.e("RadarView", "colorString parse error, please check your enter param")
   return
  }
  val color = Color.parseColor(colorString)
  setRadarColor(color)
 }

 fun setBorderColor(@ColorInt color: Int) {
  this.mBorderColor = color
  invalidate()
 }

 fun setBorderColor(colorString: String) {
  if (!colorString.startsWith("#") || colorString.length != 7 || colorString.length != 9) {
   Log.e("RadarView", "colorString parse error, please check your enter param")
   return
  }
  val color = Color.parseColor(colorString)
  setBorderColor(color)
 }

 fun setRadarGradientColor(colors: IntArray) {
  val shader = SweepGradient(measuredWidth.toFloat() / 2,
   measuredHeight.toFloat() / 2, colors, null)
  mOutlinePaint.shader = shader
  invalidate()
 }

 fun setBorderWidth(width: Float) {
  this.mBorderWidth = width
  invalidate()
 }

 private fun setParamUpdate() {
  mOutlineRect = Rect(0, 0, measuredWidth, measuredHeight)

  mBitmapMaxSize = measuredWidth.toFloat() / mScaleFactor
 }

 private fun measureDimension(spec: Int) = when (MeasureSpec.getMode(spec)) {
  MeasureSpec.EXACTLY -> {
   // exactly number or match_parent
   MeasureSpec.getSize(spec)
  }
  MeasureSpec.AT_MOST -> {
   // wrap_content
   min(mDefaultSize, MeasureSpec.getSize(spec))
  }
  else -> {
   mDefaultSize
  }
 }

 override fun setBackground(background: Drawable?) {
  // 取消传统背景设置
//  super.setBackground(background)
 }

 override fun onDraw(canvas: Canvas?) {
  super.onDraw(canvas)
  // draw outside circle (background)
  canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2, measuredWidth.toFloat() / 2, mOutlinePaint)
  if (mBorderWidth > 0F && mOutlinePaint.shader == null) {
   drawBorder(canvas)
  }

  canvas?.drawArc(mOutlineRect.toRectF(), mStartAngle, mSweepAngle, true, mSweepPaint)

  if (!mTargetList.isNullOrEmpty() && !mIsAnimating) {
   drawTarget(canvas)
  }

  // draw center circle
  canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2, measuredWidth.toFloat() / 2 / mScaleFactor, mPaint)
 }

 private fun drawBorder(canvas: Canvas?) {
  Log.i("RadarView", "drawBorder")
  mOutlinePaint.style = Paint.Style.STROKE
  mOutlinePaint.color = mBorderColor
  mOutlinePaint.strokeWidth = mBorderWidth
  canvas?.drawCircle(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2,
   (measuredWidth.toFloat() - mBorderWidth) / 2, mOutlinePaint)
  // 还原
  mOutlinePaint.style = Paint.Style.FILL_AND_STROKE
  mOutlinePaint.color = mBackgroundColor
 }

 private fun drawTarget(canvas: Canvas?) {
  mTargetList?.let {
   Log.e("RadarView", "draw target")
   for (target in it) {
    if (mNeedBitmap) {
     canvas?.drawBitmap(mBitmap, target.x - mBitmap.width / 2,
      target.y - mBitmap.height / 2, mTargetPaint)
    } else {
     canvas?.drawCircle(target.x, target.y, mTargetRadius, mTargetPaint)
    }
   }
  }
 }

 fun setBitmapEnabled(enabled: Boolean, drawable: Drawable) {
  // 这里是为了防止界面还未获取到宽高时 会导致onMeasure走不到 那么maxSize就会为0
  post {
   this.mNeedBitmap = enabled
   this.mBitmapWHRatio = drawable.intrinsicWidth.toFloat() / drawable.intrinsicHeight.toFloat()
   mBitmap = if (mBitmapWHRatio >= 1) {
    // 宽比高大
    drawable.toBitmap(
     width = min(mBitmapMaxSize, drawable.intrinsicWidth.toFloat()).toInt(),
     height = (min(mBitmapMaxSize, drawable.intrinsicWidth.toFloat()) / mBitmapWHRatio).toInt(),
     config = Bitmap.Config.ARGB_8888)
   } else {
    // 高比宽大
    drawable.toBitmap(
     height = min(mBitmapMaxSize, drawable.intrinsicHeight.toFloat()).toInt(),
     width = (min(mBitmapMaxSize, drawable.intrinsicHeight.toFloat()) * mBitmapWHRatio).toInt(),
     config = Bitmap.Config.ARGB_8888
    )
   }
  }
 }

 // 随机落点
 fun addTarget(size: Int, type: TYPE = TYPE.RANDOM) {
  val list = ArrayList<PointF>()
  val r = measuredWidth.toFloat() / 2
  val innerRect = Rect((r - r / mScaleFactor).toInt(), (r - r / mScaleFactor).toInt(),
   (r + r / mScaleFactor).toInt(), (r + r / mScaleFactor).toInt())
  // 圆的中心点
  val circle = PointF(measuredWidth.toFloat() / 2, measuredHeight.toFloat() / 2)
  while (list.size < size) {
   val ranX = Random.nextDouble(0.0, r * 2.0).toFloat()
   val ranY = Random.nextDouble(0.0, r * 2.0).toFloat()
   val ranPointF = PointF(ranX, ranY)
   if (innerRect.contains(ranPointF.toPoint())) {
    continue
   }
   // 圆公式
   if (!mNeedBitmap &&
    (ranX - circle.x).pow(2) + (ranY - circle.y).pow(2) <
     (r - mTargetRadius - mBorderWidth).toDouble().pow(2.0)) {
    // 在圆内
    addTargetFromType(type, list, ranX, ranY, r, ranPointF)
   } else if (mNeedBitmap &&
    (ranX - circle.x).pow(2) + (ranY - circle.y).pow(2) <
     (r - mBorderWidth - max(mBitmap.width, mBitmap.height) / 2).toDouble().pow(2)) {
    addTargetFromType(type, list, ranX, ranY, r, ranPointF)
   } else {
    continue
   }
  }
  mTargetList = list
  for (target in list) {
   Log.i("RadarView", "target = [${target.x}, ${target.y}]")
  }
  invalidate()
 }

 private fun addTargetFromType(type: TYPE, list: ArrayList<PointF>, ranX: Float, ranY: Float,
         r: Float, ranPointF: PointF) {
  when (type) {
   TYPE.RANDOM -> {
    list.add(ranPointF)
   }
   TYPE.FOURTH -> {
    if (ranX in r.toDouble()..2 * r.toDouble() && ranY in r.toDouble()..2 * r.toDouble()) {
     list.add(ranPointF)
    }
   }
   TYPE.THIRD -> {
    if (ranX in 0.0..r.toDouble() && ranY in r.toDouble()..2 * r.toDouble()) {
     list.add(ranPointF)
    }
   }
   TYPE.SECOND -> {
    if (ranX in 0.0..r.toDouble() && ranY in 0.0..r.toDouble()) {
     list.add(ranPointF)
    }
   }
   TYPE.FIRST -> {
    if (ranX in r.toDouble()..2 * r.toDouble() && ranY in 0.0..r.toDouble()) {
     list.add(ranPointF)
    }
   }
  }
 }

 fun start() {
  Log.i("RadarView", "animation start")
  mIsAnimating = true
  mAnimator.duration = 2000
  mAnimator.repeatCount = ValueAnimator.INFINITE
  mAnimator.addUpdateListener {
   val angle = it.animatedValue as Float
   mStartAngle = angle

   Log.i("RadarView", "mStartAngle = $mStartAngle and curValue = ${it.animatedValue}")
   postInvalidate()
  }
  mAnimator.start()
 }

 fun start(startVal: Float, endVal: Float) {
  mIsAnimating = true
  mAnimator.setFloatValues(startVal, endVal)
  mAnimator.duration = 2000
  mAnimator.repeatCount = ValueAnimator.INFINITE
  mAnimator.addUpdateListener {
   mStartAngle = it.animatedValue as Float

   Log.i("RadarView", "mStartAngle = $mStartAngle and curValue = ${it.animatedValue}")
   postInvalidate()
  }
  mAnimator.start()
 }

 fun stop() {
  mIsAnimating = false
  if (mAnimator.isRunning) {
   mAnimator.cancel()
   mAnimator.removeAllListeners()
  }
  mStartAngle = 0F
 }

}

调用方式

override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 setContentView(R.layout.activity_main)

 radar_view.setBorderWidth(5F)
 radar_view.setRadarColor(Color.TRANSPARENT)
 radar_view.setBitmapEnabled(true, resources.getDrawable(R.mipmap.ic_launcher_round))
//  radar_view.setScanColors(intArrayOf(Color.RED, Color.LTGRAY, Color.CYAN))
//  radar_view.setRadarGradientColor(intArrayOf(Color.RED, Color.GREEN, Color.BLUE))

 btn_start.setOnClickListener {
  radar_view.start()
//  workThreadAndCallback()
 }

 btn_stop.setOnClickListener {
  radar_view.stop()
  radar_view.addTarget(7)
 }
}

总结

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