GridLayoutManager ItemDecoration 左右边距小，中间平均分配

GridLayoutManager ItemDecoration 左右边距小，中间平均分配

GridLayoutDivideFragment类：

package com.example.androidkotlindemo2.gridlayout

import android.content.Context
import android.os.Bundle
import android.util.DisplayMetrics
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.view.WindowManager
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.GridLayoutManager
import com.example.androidkotlindemo2.R
import com.example.androidkotlindemo2.databinding.GridlayoutDivideMainBinding
import com.example.androidkotlindemo2.utils.LogUtils

/**
 * Author : wn
 * Email : maoning20080809@163.com
 * Date : 2024/9/8 15:13
 * Description : GridLayoutManager ItemDecoration 左右边距小，中间平均分配
 */
class GridLayoutDivideFragment : Fragment(){


    private lateinit var binding : GridlayoutDivideMainBinding

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = GridlayoutDivideMainBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)


        var datas = getData()
        var adapter = GridLayoutAdapter(datas)
        binding.gridlayoutRecyclerView.let {
            it.layoutManager = GridLayoutManager(requireActivity(), 3)
            var gridItemDecoration = GridItemDecoration(getHorizontalSpace(), 30)
            it.addItemDecoration(gridItemDecoration)
            it.adapter = adapter
        }
    }

    /**
     * 获取水平方向的空白
     */
    private fun getHorizontalSpace() : Int{
        //每个item的宽度
        var dp60 = resources.getDimensionPixelSize(R.dimen.dp_60)
        //RecyclerView左右间距的宽度
        var dp12 = resources.getDimensionPixelSize(R.dimen.dp_12)
        var screenWidth = getScreenWidth(requireActivity())
        //除以2是3个item，2个空白间距
        var horizontalSpace = (screenWidth - 3 * dp60 - 2 * dp12) / 2
        LogUtils.i("AAA", "getHorizontalSpace ${screenWidth} , ${dp60} , ${horizontalSpace}")
        return horizontalSpace
    }

    fun getScreenWidth(context: Context): Int {
        val windowManager = context.getSystemService(Context.WINDOW_SERVICE) as WindowManager
        val metrics = DisplayMetrics()
        windowManager.defaultDisplay.getMetrics(metrics)
        LogUtils.i("AAA", "getScreenWidth ${metrics.density} ${metrics.widthPixels} , ${metrics.heightPixels} , ${metrics.densityDpi} , ${metrics.scaledDensity}")
        return metrics.widthPixels
    }

    private fun getData() : MutableList<GridLayoutBean>{

        var urls = arrayListOf<String>(
            "https://img.duoziwang.com/2016/09/02/16135043775.jpg",
            "https://img.woyaogexing.com/2016/03/18/c4df209cad1840bb%21200x200.jpg",
            "http://img.duoziwang.com/2016/11/21/13565441404.jpg",
            "http://img.duoziwang.com/2016/11/29/220134634.jpg",
            "https://tupian.qqw21.com/article/UploadPic/2018-3/20183817105179447.jpg",
            "http://img.duoziwang.com/2021/01/1618554889818120.jpg",
        )
        var datas = mutableListOf<GridLayoutBean>()
        for(i in 0 until urls.size){
            var gridLayoutBean = GridLayoutBean()
            gridLayoutBean.id = i
            gridLayoutBean.name = "测试${i}"
            gridLayoutBean.url = urls[i]
            datas.add(gridLayoutBean)
        }
        return datas
    }


}

GridLayoutAdapter类：

package com.example.androidkotlindemo2.gridlayout

import android.widget.ImageView
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.chad.library.adapter.base.BaseQuickAdapter
import com.chad.library.adapter.base.viewholder.BaseViewHolder
import com.example.androidkotlindemo2.MyApp
import com.example.androidkotlindemo2.R
import com.example.androidkotlindemo2.utils.LogUtils

/**
 * Author : wn
 * Email : maoning20080809@163.com
 * Date : 2024/9/8 15:17
 * Description :
 */
class GridLayoutAdapter(list : MutableList<GridLayoutBean>)
    : BaseQuickAdapter<GridLayoutBean , BaseViewHolder>(R.layout.gridlayout_divide_item, list)  {

    override fun convert(holder: BaseViewHolder, item: GridLayoutBean) {

        holder.setText(R.id.grid_layout_item_name, item.name)
        LogUtils.i("AAA", "position : ${holder.layoutPosition}, ${item.name} ,${item.url}")
        holder.getView<ImageView>(R.id.grid_layout_item_img).let{
            Glide.with(MyApp.myApp).load(item.url).placeholder(R.mipmap.ic_launcher).error(R.mipmap.ic_launcher).into(it)
        }

    }
}

GridItemDecoration类：

package com.example.androidkotlindemo2.gridlayout

import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.androidkotlindemo2.utils.LogUtils

/**
 * Author : wn
 * Email : maoning20080809@163.com
 * Date : 2024/9/8 15:56
 * Description :
 */
class GridItemDecoration(horizontal: Int, vertical: Int): RecyclerView.ItemDecoration() {
    private val spaceHorizontal by lazy { horizontal }
    private val spaceVertical by lazy { vertical }
    private var spanCount = -1

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        if (parent.layoutManager is GridLayoutManager) {
            if (spanCount == -1) {
                spanCount =
                    (parent.layoutManager as GridLayoutManager).spanCount
            }
            val position = parent.getChildAdapterPosition(view)
            /* 绘制垂直边距 */
            if (position >= spanCount) { //第一行之外绘制垂直边距
                outRect.top = spaceVertical
            }
            /* 绘制水平边距 */
            val pInLine: Int = position % spanCount // 行内位置
            if (pInLine == 0) {
                outRect.left = 0
            } else {
                outRect.left = (pInLine * 1f * spaceHorizontal / spanCount).toInt()
            }
            outRect.right = ((spanCount - pInLine - 1) * 1f * spaceHorizontal / spanCount).toInt()
        } else {
            LogUtils.e("GridItemDecoration", "layoutManager isn't GridLayoutManager")
        }
    }
}

GridLayoutBean类：

package com.example.androidkotlindemo2.gridlayout

/**
 * Author : wn
 * Email : maoning20080809@163.com
 * Date : 2024/9/8 15:18
 * Description :
 */
class GridLayoutBean {

    var id :Int = 0

    var name : String = ""

    var url : String = ""

}

gridlayout_divide_main.xml布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textColor="@color/red"
        android:textSize="30sp"
        android:layout_marginBottom="30dp"
        android:text="九宫格平分"/>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/gridlayout_recycler_view"
        android:layout_marginHorizontal="12dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

gridlayout_divide_item.xml布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="60dp"
    android:layout_height="wrap_content"
    android:orientation="vertical">


    <TextView
        android:id="@+id/grid_layout_item_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textColor="@color/red"
        android:textSize="22sp"
        android:text="测试1"/>

    <ImageView
        android:id="@+id/grid_layout_item_img"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@mipmap/ic_launcher"/>

</LinearLayout>