原理：利用fillType画出和背景色一致的圆角边框
class CornersView(context: Context, attrs: AttributeSet?) : ImageView(context, attrs) {
override fun onDraw(canvas: Canvas) {
super.onDraw(canvas)
canvas.save()
var mPaint = Paint()
mPaint.color = getParentBackGroundColor(parent)
var mPath = Path()
mPath.reset()
// add round rect
mPath.setFillType(Path.FillType.INVERSE_EVEN_ODD)
var radius = dp2px(5f)
var mCorners =floatArrayOf(radius,radius,radius,radius,radius,radius,radius,radius)
mPath.addRoundRect(RectF(0f, 0f, canvas.width.toFloat(), canvas.height.toFloat()), mCorners, Path.Direction.CCW)
canvas.drawPath(mPath, mPaint)
canvas.restore()
}
/**
* 获取父控件颜色
* @param parent
* @return
*/
private fun getParentBackGroundColor(parent: ViewParent?): Int {
if (parent ==null) {
return Color.WHITE
}
if (parentis View) {
val parentView = parentas View
val parentColor = getViewBackGroundColor(parentView)
if (parentColor != Color.TRANSPARENT) {
return parentColor
}else {
getParentBackGroundColor(parentView!!.parent)
}
}
return Color.WHITE
}
/**
* 获取 View 的背景色
* @param view
* @return
*/
private fun getViewBackGroundColor(view: View): Int {
val drawable = view.background
if (drawable !=null) {
try {
val mField = drawable.javaClass.getDeclaredField("mColorState")
mField.isAccessible =true
val mColorState = mField.get(drawable)
val mColorState_class = mColorState.javaClass
val mColorState_field = mColorState_class.getDeclaredField("mUseColor")
mColorState_field.isAccessible =true
val color = mColorState_field.get(mColorState)as Int
if (color != Color.TRANSPARENT) {
return color
}
}catch (e: Exception) {
e.printStackTrace()
}
}
return Color.TRANSPARENT
}
private fun dp2px(dpValue: Float): Float {
val scale =context.resources.displayMetrics.density
return dpValue * scale +0.5f
}
}