瞭解RecyclerView的分割線

在這裏插入圖片描述

效果

效果圖

實現思路

  • 核心方法
    繪製分割線的核心方法onDraw();
    定位分割線位置(也可以說是與其他組件之間的空隙)方法getItemOffsets()

  • 計算
    每條分割線的長度都是根據每一個ItemVIew的長度計算,位置同樣根據ItemView的位置來確定,詳細的計算在drawTop()drawLeft()drawRight()drawBottom()、四個方法中!

靈魂圖解

靈魂的畫師

完整代碼

/**
 * 萬能分割線
 * <p>
 * 橫向列表分割線 {@link #HORIZONTAL_DIV}
 * 縱向列表分割線 {@link #VERTICAL_DIV}
 * 表格列表分割線 {@link #GRID_DIV}
 * </P>
 */
public class ItemDecorationPowerful extends RecyclerView.ItemDecoration {
    private static final String TAG = "ItemDecorationPowerful";
    //橫向佈局分割線
    public static final int HORIZONTAL_DIV = 0;
    //縱向佈局分割線
    public static final int VERTICAL_DIV = 1;
    //表格佈局分割線
    public static final int GRID_DIV = 2;
    private int mOrientation;
    private int mDividerWidth = 0;
    private Paint mPaint;

    /**
     * 默認縱向布分割線
     */
    public ItemDecorationPowerful() {
        this(VERTICAL_DIV);
    }

    /**
     * @param orientation 方向類型
     */
    public ItemDecorationPowerful(int orientation) {
        this(orientation, Color.parseColor("#808080"), 2);
    }

    /**
     * @param orientation 方向類型
     * @param color       分割線顏色
     * @param divWidth    分割線寬度
     */
    public ItemDecorationPowerful(int orientation, int color, int divWidth) {
        this.setOrientation(orientation);
        mDividerWidth = divWidth;
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setColor(color);
        mPaint.setStyle(Paint.Style.FILL);
    }


    @Override
    public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        switch (mOrientation) {
            case HORIZONTAL_DIV:
                //橫向佈局分割線
                drawHorizontal(c, parent);
                break;
            case VERTICAL_DIV:
                //縱向佈局分割線
                drawVertical(c, parent);
                break;
            case GRID_DIV:
                //表格格局分割線
                drawGrid(c, parent);
                break;
            default:
                //縱向佈局分割線
                drawVertical(c, parent);
                break;
        }
    }


    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        int itemPosition = parent.getChildAdapterPosition(view);
        RecyclerView.Adapter mAdapter = parent.getAdapter();
        if (mAdapter != null) {
            int mChildCount = mAdapter.getItemCount();
            switch (mOrientation) {
                case HORIZONTAL_DIV:
                    /**
                     * 橫向佈局分割線
                     * <p>
                     *     如果是第一個Item,則不需要分割線
                     * </p>
                     */
                    if (itemPosition != 0) {
                        outRect.set(mDividerWidth, 0, 0, 0);
                    }
                    break;
                case VERTICAL_DIV:
                    /**
                     * 縱向佈局分割線
                     * <p>
                     *     如果是第一個Item,則不需要分割線
                     * </p>
                     */
                    if (itemPosition != 0) {
                        outRect.set(0, mDividerWidth, 0, 0);
                    }
                    break;
                case GRID_DIV:
                    /**
                     * 表格格局分割線
                     * <p>
                     *      1:當是第一個Item的時候,四周全部需要分割線
                     *      2:當是第一行Item的時候,需要額外添加頂部的分割線
                     *      3:當是第一列Item的時候,需要額外添加左側的分割線
                     *      4:默認情況全部添加底部和右側的分割線
                     * </p>
                     */
                    RecyclerView.LayoutManager mLayoutManager = parent.getLayoutManager();
                    if (mLayoutManager instanceof GridLayoutManager) {
                        GridLayoutManager mGridLayoutManager = (GridLayoutManager) mLayoutManager;
                        int mSpanCount = mGridLayoutManager.getSpanCount();
                        if (itemPosition == 0) {//1
                            outRect.set(mDividerWidth, mDividerWidth, mDividerWidth, mDividerWidth);
                        } else if ((itemPosition + 1) <= mSpanCount) {//2
                            outRect.set(0, mDividerWidth, mDividerWidth, mDividerWidth);
                        } else if (((itemPosition + mSpanCount) % mSpanCount) == 0) {//3
                            outRect.set(mDividerWidth, 0, mDividerWidth, mDividerWidth);
                        } else {//4
                            outRect.set(0, 0, mDividerWidth, mDividerWidth);
                        }
                    }
                    break;
                default:
                    //縱向佈局分割線
                    if (itemPosition != (mChildCount - 1)) {
                        outRect.set(0, 0, 0, mDividerWidth);
                    }
                    break;
            }
        }
    }

    /**
     * 繪製橫向列表分割線
     *
     * @param c      繪製容器
     * @param parent RecyclerView
     */
    private void drawHorizontal(Canvas c, RecyclerView parent) {
        int mChildCount = parent.getChildCount();
        for (int i = 0; i < mChildCount; i++) {
            View mChild = parent.getChildAt(i);
            drawLeft(c, mChild, parent);
        }
    }

    /**
     * 繪製縱向列表分割線
     *
     * @param c      繪製容器
     * @param parent RecyclerView
     */
    private void drawVertical(Canvas c, RecyclerView parent) {
        int mChildCount = parent.getChildCount();
        for (int i = 0; i < mChildCount; i++) {
            View mChild = parent.getChildAt(i);
            drawTop(c, mChild, parent);
        }
    }

    /**
     * 繪製表格類型分割線
     *
     * @param c      繪製容器
     * @param parent RecyclerView
     */
    private void drawGrid(Canvas c, RecyclerView parent) {
        int mChildCount = parent.getChildCount();
        for (int i = 0; i < mChildCount; i++) {
            View mChild = parent.getChildAt(i);
            RecyclerView.LayoutManager mLayoutManager = parent.getLayoutManager();
            if (mLayoutManager instanceof GridLayoutManager) {
                GridLayoutManager mGridLayoutManager = (GridLayoutManager) mLayoutManager;
                int mSpanCount = mGridLayoutManager.getSpanCount();
                if (i == 0) {
                    drawTop(c, mChild, parent);
                    drawLeft(c, mChild, parent);
                }
                if ((i + 1) <= mSpanCount) {
                    drawTop(c, mChild, parent);
                }
                if (((i + mSpanCount) % mSpanCount) == 0) {
                    drawLeft(c, mChild, parent);
                }
                drawRight(c, mChild, parent);
                drawBottom(c, mChild, parent);
            }
        }
    }

    /**
     * 繪製右邊分割線
     *
     * @param c            繪製容器
     * @param mChild       對應ItemView
     * @param recyclerView RecyclerView
     */
    private void drawLeft(Canvas c, View mChild, RecyclerView recyclerView) {
        RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();
        int left = mChild.getLeft() - mDividerWidth - mChildLayoutParams.leftMargin;
        int top = mChild.getTop() - mChildLayoutParams.topMargin;
        int right = mChild.getLeft() - mChildLayoutParams.leftMargin;
        int bottom;
        if (isGridLayoutManager(recyclerView)) {
            bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin + mDividerWidth;
        } else {
            bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin;
        }
        c.drawRect(left, top, right, bottom, mPaint);
    }

    /**
     * 繪製頂部分割線
     *
     * @param c            繪製容器
     * @param mChild       對應ItemView
     * @param recyclerView RecyclerView
     */
    private void drawTop(Canvas c, View mChild, RecyclerView recyclerView) {
        RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();
        int left;
        int top = mChild.getTop() - mChildLayoutParams.topMargin - mDividerWidth;
        int right = mChild.getRight() + mChildLayoutParams.rightMargin;
        int bottom = mChild.getTop() - mChildLayoutParams.topMargin;
        if (isGridLayoutManager(recyclerView)) {
            left = mChild.getLeft() - mChildLayoutParams.leftMargin - mDividerWidth;
        } else {
            left = mChild.getLeft() - mChildLayoutParams.leftMargin;
        }
        c.drawRect(left, top, right, bottom, mPaint);
    }

    /**
     * 繪製右邊分割線
     *
     * @param c            繪製容器
     * @param mChild       對應ItemView
     * @param recyclerView RecyclerView
     */
    private void drawRight(Canvas c, View mChild, RecyclerView recyclerView) {
        RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();
        int left = mChild.getRight() + mChildLayoutParams.rightMargin;
        int top;
        int right = left + mDividerWidth;
        int bottom = mChild.getBottom() + mChildLayoutParams.bottomMargin;
        if (isGridLayoutManager(recyclerView)) {
            top = mChild.getTop() - mChildLayoutParams.topMargin - mDividerWidth;
        } else {
            top = mChild.getTop() - mChildLayoutParams.topMargin;
        }
        c.drawRect(left, top, right, bottom, mPaint);
    }

    /**
     * 繪製底部分割線
     *
     * @param c            繪製容器
     * @param mChild       對應ItemView
     * @param recyclerView RecyclerView
     */
    private void drawBottom(Canvas c, View mChild, RecyclerView recyclerView) {
        RecyclerView.LayoutParams mChildLayoutParams = (RecyclerView.LayoutParams) mChild.getLayoutParams();
        int left = mChild.getLeft() - mChildLayoutParams.leftMargin;
        int top = mChild.getBottom() + mChildLayoutParams.bottomMargin;
        int bottom = top + mDividerWidth;
        int right;
        if (isGridLayoutManager(recyclerView)) {
            right = mChild.getRight() + mChildLayoutParams.rightMargin + mDividerWidth;
        } else {
            right = mChild.getRight() + mChildLayoutParams.rightMargin;
        }
        c.drawRect(left, top, right, bottom, mPaint);
    }

    /**
     * 判斷RecyclerView所加載LayoutManager是否爲GridLayoutManager
     *
     * @param recyclerView RecyclerView
     * @return 是GridLayoutManager返回true,否則返回false
     */
    private boolean isGridLayoutManager(RecyclerView recyclerView) {
        RecyclerView.LayoutManager mLayoutManager = recyclerView.getLayoutManager();
        return (mLayoutManager instanceof GridLayoutManager);
    }

    /**
     * 初始化分割線類型
     *
     * @param orientation 分割線類型
     */
    public void setOrientation(int orientation) {
        if (mOrientation != HORIZONTAL_DIV && mOrientation != VERTICAL_DIV && mOrientation != GRID_DIV) {
            throw new IllegalArgumentException("ItemDecorationPowerful:分割線類型設置異常");
        } else {
            this.mOrientation = orientation;
        }
    }
}
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