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这篇文章将为大家详细讲解有关自定义View系列之kotlin绘制手势设置温度控件的示例分析，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。
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引言
最近公司接了一个车联网的项目，主要是新能源汽车的一些控制功能，其中涉及到一个是温度的调节功能，产品的意思是做一个手势滑动调节温度,大概意思我是明白的。就是要手势调节呗，没办法，谁让我是搬砖的呢，人为刀俎,我为鱼肉，只有搞了；
最后搞出来的效果大概如下，不过还没确定，
思路
在这里我先说下自己的实现思路，这个控件的难点主要是手势控制，其他的都很简单，没有什么好说的，控制的一些具体的数值我是写死的，没有做自定义拓展，主要是闲麻烦，如果有需要可以自己的实现；
具体的实现步奏
首先绘制圆盘，刻度，阴影（需要关闭硬件加速），文字
然后根据划过的角度绘制进度条
最后根绝touch事件重新绘制，并设置数据回调
代码实现
1，绘制前的准备
首先kotlin提供了init方法，我们需要在这个方法里面初始化我们需要的画笔和一些数据
注：这里涉及到阴影的绘制，所以必须关闭硬件加速
init {
//关闭硬件加速
setLayerType(View.LAYER_TYPE_SOFTWARE, null)
mInCirclePaint.color = Color.WHITE
mInCirclePaint.strokeWidth = 1f
mInCirclePaint.style = Paint.Style.FILL
mInCirclePaint.setShadowLayer(25f, 0f, 0f, Color.GRAY)
mGrayLinePaint.color = Color.parseColor("#00EEEE")
mGrayLinePaint.strokeWidth = dp2px(1f).toFloat()
mGrayLinePaint.style = Paint.Style.STROKE
mGrayLinePaint.setShadowLayer(15f, 0f, 0f, Color.GRAY)
mTempTextPaint.textSize = sp2px(32f).toFloat()
mTempTextPaint.style = Paint.Style.FILL
mTempTextPaint.color = Color.parseColor("#7CCD7C")
mTempTextPaint.textAlign = Paint.Align.CENTER
mTempTextPaint.isFakeBoldText = true
mTempTextPaint.setShadowLayer(5f, 0f, 0f, Color.GRAY)
mTextPaint.textSize = sp2px(18f).toFloat()
mTextPaint.style = Paint.Style.FILL
mTextPaint.color = Color.parseColor("#aaaaaa")
mTextPaint.textAlign = Paint.Align.CENTER
// mTextPaint.setShadowLayer(5f, 0f, 0f, Color.GRAY)
mLineProgressPaint.style = Paint.Style.STROKE
mLineProgressPaint.strokeWidth = dp2px(10f).toFloat()
mLineProgressPaint.color = Color.parseColor("#7CCD7C")
// mLineProgressPaint.setShadowLayer(5f, 0f, 0f, Color.GRAY)
mProgressCirclePaint.style = Paint.Style.FILL
// mProgressCirclePaint.setShadowLayer(15f, 0f, 0f, Color.GRAY)
mProgressPaint.style = Paint.Style.FILL
mProgressPaint.color = Color.parseColor("#436EEE")
mProgressPaint.strokeCap = Paint.Cap.ROUND
// mProgressPaint.setShadowLayer(5f, 0f, 0f, Color.GRAY)
mPaintTriangle.style = Paint.Style.FILL
mPaintTriangle.color = Color.parseColor("#436EEE")
}然后我们需要重写onMeasure()方法，因为这个控件必须是正方形的，所以我们必须保证宽和高一致；
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
val width = View.MeasureSpec.getSize(widthMeasureSpec)
val height = View.MeasureSpec.getSize(heightMeasureSpec)
val imageSize = if (width < height) width else height
setMeasuredDimension(imageSize, imageSize)
}再之后我们需要知道一些具体的宽高值，从而设置半径的大小，一般是在onSizeChanged()方法里面拿到
override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
super.onSizeChanged(w, h, oldw, oldh)
mHeight = Math.min(h, w)
mWidth = height
dialRadius = (width / 2 - dp2px(10f))
arcRadius = dialRadius / 2
mBgRectf = RectF(-dialRadius * 1f / 2 - dp2px(5f), -dialRadius * 1f / 2 - dp2px(5f), dialRadius * 1f / 2 + dp2px(5f), dialRadius * 1f / 2 + dp2px(5f))
}2，绘制
接下来就开始绘制视图了，绘制之前需要把视图的原心移动到中心位置
canvas.translate(mWidth * 1f / 2, mHeight * 1f / 2);
接着就开始绘制，首先我们绘制最外边源的线，这里绘制180根线，其中30根长线
private var beginAngle = 0f
private val drawLine = { canvas: Canvas ->
beginAngle = 0f
canvas.save()
for (i in 0..180) {
canvas.save()
canvas.rotate(beginAngle)
mGrayLinePaint.setARGB(180, (0.7 * i * 2).toInt(), ((255 - 0.7 * i * 2).toInt()), ((255 - 0.7 * i * 2).toInt()))
if (beginAngle % 12 == 0f) {
canvas.drawLine(dialRadius * 7f / 9 - dp2px(5f), 0f, dialRadius * 8f / 9, 0f, mGrayLinePaint)
} else {
canvas.drawLine(dialRadius * 7f / 9, 0f, dialRadius * 8f / 9, 0f, mGrayLinePaint)
}
beginAngle += 2f
canvas.restore()
}
canvas.restore()
}效果如下
接着开始绘制中心的文字，如果如下
private val drawText = { canvas: Canvas ->
val baseLineY = Math.abs(mTempTextPaint.ascent() + mTempTextPaint.descent()) / 2
mTempTextPaint.setARGB(180, (0.7 * currentAngle).toInt(), (255 - 0.7 * currentAngle).toInt(), (255 - 0.7 * currentAngle).toInt())
if (temText == 30 || temText == 29) {
mTempTextPaint.setARGB(255, 255, 0, 0)
} else if (temText == 15) {
mTempTextPaint.setARGB(255, 0, 255, 255)
}
canvas.drawText("${temText}°", 0f, baseLineY + dp2px(20f), mTempTextPaint)
canvas.drawText("最大温度设置", 0f, baseLineY - dp2px(20f), mTextPaint)
}
接下来就开始绘制进度条和阴影部分
private val drawPointCircle = { canvas: Canvas ->
canvas.save()
canvas.rotate(rotateAngle + 2)
mProgressPaint.setARGB(255, (0.7 * currentAngle).toInt(), (260 - 0.7 * currentAngle).toInt(), (260 - 0.7 * currentAngle).toInt())
mPaintTriangle.setARGB(255, (0.7 * currentAngle).toInt(), (260 - 0.7 * currentAngle).toInt(), (260 - 0.7 * currentAngle).toInt())
if (temText == 30 || temText == 29) {
mProgressPaint.setARGB(255, 255, 0, 0)
mPaintTriangle.setARGB(255, 255, 0, 0)
} else if (temText == 15) {
mProgressPaint.setARGB(255, 0, 255, 255)
mPaintTriangle.setARGB(255, 0, 255, 255)
}
val path = Path()
path.moveTo(dialRadius * 1f / 2 + dp2px(5f), (-dp2px(10f)).toFloat())
path.lineTo(dialRadius * 1f / 2 + dp2px(5f), dp2px(10f).toFloat())
path.lineTo(dialRadius * 1f / 2 - dp2px(10f), 0f)
path.close()
canvas.drawPath(path, mPaintTriangle)
val point = dialRadius * 1f / 2 + dp2px(5f)
canvas.drawCircle(point, 0f, dp2px(10f).toFloat(), mProgressPaint)
canvas.restore()
}
private val drawProgress = { canvas: Canvas ->
if (rotateAngle > 0) {
mProgressCirclePaint.color = Color.parseColor("#00ffff")
canvas.drawCircle(dialRadius * 1f / 2 + dp2px(5f), 0f, dp2px(5f).toFloat(), mProgressCirclePaint)
}
val colors = intArrayOf(Color.parseColor("#00ffff"), Color.parseColor("#ff0000"))
val mShader = SweepGradient(0f, 0f, colors, null)
mLineProgressPaint.shader = mShader
canvas.drawArc(mBgRectf, 0f, rotateAngle, false, mLineProgressPaint)
}
2，手势
绘制视图结束，现在开始手势的处理，主要就是处理touch事件，我们以圆心为坐标圆点，建立坐标系，求出(targetX, targetY)坐标与x轴的夹角，显现代码如下
private val calcAngle = { targetX: Float, targetY: Float ->
val x = targetX - width / 2
val y = targetY - height / 2
val radian: Double
if (x != 0f) {
val tan = Math.abs(y / x)
if (x > 0) {
if (y >= 0) {
radian = Math.atan(tan.toDouble())
} else {
radian = 2 * Math.PI - Math.atan(tan.toDouble())
}
} else {
if (y >= 0) {
radian = Math.PI - Math.atan(tan.toDouble())
} else {
radian = Math.PI + Math.atan(tan.toDouble())
}
}
} else {
if (y > 0) {
radian = Math.PI / 2
} else {
radian = -Math.PI / 2
}
}
(radian * 180 / Math.PI).toFloat()
}然后在touch事件中进行处理，主要代码如下
override fun onTouchEvent(event: MotionEvent): Boolean {
when (event.action) {
MotionEvent.ACTION_DOWN -> {
isDown = true
downX = event.x
downY = event.y
currentAngle = calcAngle(downX, downY)
}
MotionEvent.ACTION_MOVE -> {
isMove = true
val targetX: Float = event.x
val targetY: Float = event.y
val angle = calcAngle(targetX, targetY)
// 滑过的角度增量
var angleIncreased = angle - currentAngle
if (angleIncreased < -180) {
angleIncreased += 360
} else if (angleIncreased > 180) {
angleIncreased -= 360
}
increaseAngle(angleIncreased)
currentAngle = angle
invalidate()
// 滑过的角度增量
}
MotionEvent.ACTION_CANCEL, MotionEvent.ACTION_UP -> {
if (isDown) {
if (isMove) {
temparetureChangeListner?.invoke(temText)
isMove = false
}
isDown = false
}
}
}
return true
}计算出当前角度对应的温度值
/**
* 增加旋转角度
*/
private val increaseAngle = { angle: Float ->
rotateAngle += angle
if (rotateAngle < 0) {
rotateAngle = 0f
} else if (rotateAngle > 360f) {
rotateAngle = 360f
}
temText = (rotateAngle / 360 * 15).toInt() + 15
}关于“自定义View系列之kotlin绘制手势设置温度控件的示例分析”这篇文章就分享到这里了，希望以上内容可以对大家有一定的帮助，使各位可以学到更多知识，如果觉得文章不错，请把它分享出去让更多的人看到。
