kolint版本流式布局FlowLayout

流式布局FlawLayout自定義view

package com.example.lsn_compose.view

import android.annotation.SuppressLint
import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.view.ViewGroup
import androidx.core.view.children
import com.blankj.utilcode.util.ConvertUtils.dp2px
import kotlin.math.max

class FlowLayout(context: Context) : ViewGroup(context) {
    private val mHorizontalSpace = dp2px(16.0F)
    private val mVerticalSpace = dp2px(8.0F)

    private var allLinesViews = mutableListOf<List<View>>()//記錄所有的行，用于layout
    private var lineHeights = mutableListOf<Int>()

    constructor(context: Context, attributes: AttributeSet) : this(context)

    constructor(context: Context, attributes: AttributeSet, defStyleAttr: Int) : this(context)

    private fun clearMeasureParams() {
        allLinesViews.clear()
        lineHeights.clear()
    }

    @SuppressLint("DrawAllocation")
    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        clearMeasureParams()//防止頻繁創建空間而發生OOM
        //本View的寬高
        val width = MeasureSpec.getSize(widthMeasureSpec)
        val height = MeasureSpec.getSize(heightMeasureSpec)

        var lineViews = mutableListOf<View>()//記錄一行中已經添加了的View
        var usedWidth = 0//記錄已經用了的寬度
        var lineHeight = 0//記錄已經用了的行高

        var childNeededParentWidth = 0//所有子view加起來需要父控制元件給的寬度
        var childNeededParentHeight = 0//所有子view加起來父控制元件需要給的高度

        //先度量所有子view的寬高--->view是樹形結構，遞回度量
        for (i: Int in 0 until childCount) {
            //度量子view的寬高
            children.elementAt(i).measure(
                getChildMeasureSpec(
                    widthMeasureSpec,
                    paddingLeft + paddingRight,
                    children.elementAt(i).layoutParams.width
                ),
                getChildMeasureSpec(
                    heightMeasureSpec,
                    paddingTop + paddingBottom,
                    children.elementAt(i).layoutParams.height
                )
            )
            //獲取子view的寬高
            val childMeasuredWidth: Int = children.elementAt(i).measuredWidth
            val childMeasuredHeight: Int = children.elementAt(i).measuredHeight

            //換行
            if (usedWidth + childMeasuredWidth + mHorizontalSpace >= width) {
                allLinesViews.add(lineViews)
                lineHeights.add(lineHeight)

                //寬度取需要父控制元件給的寬度和已經使用的寬度的最大值--->通常情況下，如果沒到邊界，子view所需要父控制元件所給與的寬度就是子view已經使用的寬度
                childNeededParentWidth = max(childNeededParentWidth, usedWidth + mHorizontalSpace)
                //高度就是一直累加
                childNeededParentHeight += lineHeight + mVerticalSpace
                lineViews = mutableListOf()//是否能用clear？
                usedWidth = 0
                lineHeight = 0
            }
            //流式布局是分行布置的，所以要先把每個已經算好的子view添加到每一行中，然后再把每一行添加到所有行中--->兩個list
            lineViews.add(children.elementAt(i))
            //每行的寬高
            usedWidth += childMeasuredWidth + mHorizontalSpace
            lineHeight = max(lineHeight, childMeasuredHeight)

            //處理最后一行
            if (i == childCount - 1) {
                allLinesViews.add(lineViews)
                lineHeights.add(lineHeight)
                childNeededParentWidth = max(childNeededParentWidth, usedWidth + mHorizontalSpace)
                childNeededParentHeight += lineHeight + mVerticalSpace
            }
        }
        //再度量自身的viewGroup寬高---->作為一個vp，他自己也是一個view，它的大小也需要根據父view的大小來一起度量才能決定
        val widthViewMode: Int = MeasureSpec.getMode(widthMeasureSpec)
        val heightViewMode: Int = MeasureSpec.getMode(heightMeasureSpec)
        val realWidth = if (widthViewMode == MeasureSpec.EXACTLY) width else childNeededParentWidth
        val realHeight =
            if (heightViewMode == MeasureSpec.EXACTLY) height else childNeededParentHeight
        //度量自己
        setMeasuredDimension(realWidth, realHeight)
    }

    override fun onLayout(p0: Boolean, p1: Int, p2: Int, p3: Int, p4: Int) {
        //1.先獲得此view的左上坐標
        var currentLeft = paddingLeft
        var currentTop = paddingTop
//        val allLineCount = allLinesViews.size
        //2.取出每一行都進行位置計算
        for (i in allLinesViews.indices) {
            val lineHeight = lineHeights[i]
            //3.取出每一行的每個element進行位置計算
            val lineView = allLinesViews[i]
            for (j in lineView.indices) {
                val view = lineView[j]
                val left = currentLeft
                val top = currentTop
                val right = left + view.measuredWidth
                val bottom = top + view.measuredHeight
                view.layout(left, top, right, bottom)
                //移動坐標，準備行內下一個元素的放置
                currentLeft = right + mHorizontalSpace
            }
            currentTop += lineHeight + mVerticalSpace
            //一行放置完畢，需要重置左邊坐標
            currentLeft = paddingLeft
        }
    }
}