package com.android.app_base.widget;
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import android.graphics.Rect;
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import android.view.View;
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import androidx.annotation.NonNull;
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import androidx.recyclerview.widget.RecyclerView;
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/**
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* RecyclerView 网格item等分间距
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*/
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public class GridSpaceItemDecoration extends RecyclerView.ItemDecoration {
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private int mSpanCount;//横条目数量
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private int mRowSpacing;//行间距
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private int mColumnSpacing;// 列间距
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/**
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* @param spanCount 列数
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* @param rowSpacing 行间距
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* @param columnSpacing 列间距
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*/
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public GridSpaceItemDecoration(int spanCount, int rowSpacing, int columnSpacing) {
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this.mSpanCount = spanCount;
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this.mRowSpacing = rowSpacing;
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this.mColumnSpacing = columnSpacing;
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}
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@Override
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public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
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int position = parent.getChildAdapterPosition(view); // 获取view 在adapter中的位置。
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int column = position % mSpanCount; // view 所在的列
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//列间等间距（列数从0开始）
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//列左边 = 所在列 * 列间距 / 总列数
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//列右边 = 列间距 - 下一列的列左边
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outRect.left = column * mColumnSpacing / mSpanCount;
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outRect.right = mColumnSpacing - (column + 1) * mColumnSpacing / mSpanCount;
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if (mRowSpacing == -1) {
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return;
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}
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// 如果position > 行数，说明不是在第一行，则不指定行高，其他行的上间距为 top=mRowSpacing
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if (position >= mSpanCount) {
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outRect.top = mRowSpacing; // item top
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}
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}
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}
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