安卓Kotlin dp转px px转dp

工具类如下

class ToolsBox(w: WeakReference<Any>) {
    
    
    private val zis = (w as WeakReference<Activity>).get()
    
    fun dp2px(dp:Int):Int?{
    
    
        return zis?.resources?.displayMetrics?.density?.let {
    
     (dp * it + 0.5).toInt()}
    }
    fun px2dp(px:Int):Int?{
    
    
        return zis?.resources?.displayMetrics?.density?.let {
    
     (px.toDouble() / it + 0.5).toInt()}
    }
    private fun root(a:Double, b:Double, c:Double):List<Double>?{
    
    
        val d = b*b - 4.0 * a * c
        if(d < 0) return null
        val sd = sqrt(d)
        val x1 = (-b + sd)/(2.0 * a)
        val x2 = (-b - sd)/(2.0 * a)
        return listOf(x1, x2)
    }
    fun calcWidthFromDp(marginLeftDp:Int, widthDp:Int):List<Int>{
    
    
        val margin = marginLeftDp.toDouble()
        val marginPx = dp2px(marginLeftDp)?:16
        val root = root(margin, widthDp.toDouble(), -((px2dp(zis?.resources?.displayMetrics?.widthPixels?:1080))?:400).toDouble())
        val numPerRow = root?.let {
    
     (it[0]+0.5).toInt()}?:3
        val w = ((zis?.resources?.displayMetrics?.widthPixels?:1080)-marginPx*(numPerRow+1))/numPerRow
        val totalWidth = ((zis?.resources?.displayMetrics?.widthPixels?:1080)-marginPx)/numPerRow
        return listOf(numPerRow, w, totalWidth)
    }
}

使用方法

val t =  ToolsBox(WeakReference(this))
val px = t.dp2px(1)
val dp = t.px2dp(px)

另外calcWidthFromDp函数还可以根据想设定的dp宽度自动计算与之最相近的能够容纳整数个控件的px宽度。