自定义ItemDecoration实现线性列表的分割线

此自定义ItemDecoration采用Builder模式，可根据需求设置上下左右分割线的是否显示、颜色、和分割线的高度。

/**
 * @ClassName: LinearItemDecoration
 * @Description: 线性Recyclerview分割线
 * @Author: CHN_Liao
 * @CreateDate: 2020-11-02 16:59
 */
public class LinearItemDecoration extends RecyclerView.ItemDecoration {
    private Context mContext;

    //顶部是否增加分割线
    private boolean isDividerTop = false;
    //左边是否增加分割线
    private boolean isDividerLeft = false;
    //右边是否增加分割线
    private boolean isDividerRight = false;
    //底部是否增加分割线,默认为true
    private boolean isDividerBottom = true;

    //顶部分割线颜色;
    private int dividerTopColor;
    //左边分割线颜色;
    private int dividerLeftColor;
    //右边分割线颜色;
    private int dividerRightColor;
    //底部分割线颜色;
    private int dividerBottomColor;

    //分割线画笔
    private Paint dividerPaint;
    //分割线高度
    private int dividerHeight = 4;

    public LinearItemDecoration(Context context) {
        mContext = context;
        dividerPaint = new Paint();

        //默认分割线颜色
        dividerTopColor = dividerLeftColor = dividerRightColor = dividerBottomColor = Color.GRAY;
    }

    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        outRect.bottom = isDividerBottom ? dividerHeight : 0;
        outRect.left = isDividerLeft ? dividerHeight : 0;
        outRect.right = isDividerRight ? dividerHeight : 0;
        outRect.top = isDividerTop ? dividerHeight : 0;
    }

    @Override
    public void onDraw(@NonNull Canvas canvas, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        super.onDraw(canvas, parent, state);
        int childCount = parent.getChildCount();
        //绘制头部分割线颜色
        drawTop(canvas, parent, childCount);
        //绘制左边分割线颜色
        drawLeft(canvas, parent, childCount);
        //绘制右边分割线颜色
        drawRight(canvas, parent, childCount);
        //绘制底部分割线颜色
        drawBottom(canvas, parent, childCount);
    }

    private void drawTop(@NonNull Canvas canvas, @NonNull RecyclerView parent, int childCount) {
        if (!isDividerTop) return;
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();

        for (int i = 0; i < childCount; i++) {
            View view = parent.getChildAt(i);
            float top = view.getTop() - dividerHeight;
            float bottom = view.getTop();
            dividerPaint.setColor(dividerTopColor);
            canvas.drawRect(left, top, right, bottom, dividerPaint);
        }

    }

    private void drawLeft(@NonNull Canvas canvas, @NonNull RecyclerView parent, int childCount) {
        if (!isDividerLeft) return;

        int left = parent.getPaddingLeft();
        int right = parent.getPaddingLeft() + dividerHeight;

        dividerPaint.setColor(dividerLeftColor);

        for (int i = 0; i < childCount; i++) {
            View view = parent.getChildAt(i);
            float top = view.getTop();
            float bottom = view.getBottom();
            canvas.drawRect(left, top, right, bottom, dividerPaint);
        }

    }

    private void drawRight(@NonNull Canvas canvas, @NonNull RecyclerView parent, int childCount) {
        if (!isDividerRight) return;

        int left = parent.getRight() - parent.getPaddingRight() - dividerHeight;
        int right = parent.getRight() - parent.getPaddingRight();

        dividerPaint.setColor(dividerRightColor);

        for (int i = 0; i < childCount; i++) {
            View view = parent.getChildAt(i);
            float top = view.getTop();
            float bottom = view.getBottom();
            canvas.drawRect(left, top, right, bottom, dividerPaint);
        }
    }

    private void drawBottom(@NonNull Canvas canvas, @NonNull RecyclerView parent, int childCount) {
        if (!isDividerBottom) return;

        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();

        dividerPaint.setColor(dividerBottomColor);

        for (int i = 0; i < childCount - 1; i++) {
            View view = parent.getChildAt(i);
            float top = view.getBottom();
            float bottom = view.getBottom() + dividerHeight;
            canvas.drawRect(left, top, right, bottom, dividerPaint);
        }
    }

    public static class Builder {
        private Context context;
        private LinearItemDecoration itemDecoration;

        public Builder(Context context) {
            this.context = context;
            itemDecoration = new LinearItemDecoration(context);
        }

        //设置是否显示各个分割线，默认显示底部分割线
        public Builder showDividers(boolean top, boolean left, boolean right, boolean bottom) {
            itemDecoration.isDividerTop = top;
            itemDecoration.isDividerLeft = left;
            itemDecoration.isDividerRight = right;
            itemDecoration.isDividerBottom = bottom;
            return this;
        }

        //分割线高度(dp)
        public Builder dividerHeight(int dividerHeight) {
            itemDecoration.dividerHeight = dp2px(dividerHeight);
            return this;
        }

        private int dp2px(float dpValue) {
            final float scale = context.getResources().getDisplayMetrics().density;
            return (int) (dpValue * scale + 0.5f);
        }

        //统一分割线颜色
        public Builder dividerColor(@ColorRes int color) {
            int c = context.getResources().getColor(color);
            itemDecoration.dividerTopColor = c;
            itemDecoration.dividerLeftColor = c;
            itemDecoration.dividerRightColor = c;
            itemDecoration.dividerBottomColor = c;

            return this;
        }

        //设置各个分割线颜色
        public Builder dividerColors(@ColorRes int topColor,@ColorRes int leftColor,@ColorRes int rightColor,@ColorRes int bottomColor) {
            itemDecoration.dividerTopColor = context.getResources().getColor(topColor);
            itemDecoration.dividerLeftColor = context.getResources().getColor(leftColor);
            itemDecoration.dividerRightColor = context.getResources().getColor(rightColor);
            itemDecoration.dividerBottomColor = context.getResources().getColor(bottomColor);

            return this;
        }

        public LinearItemDecoration build() {
            return itemDecoration;
        }
    }
}

快速实现及效果如下：

LinearItemDecoration itemDecoration = new LinearItemDecoration.Builder(this).build();

recyclerView.addItemDecoration(itemDecoration);

效果0.png

其他配置代码实现及效果如下：

LinearItemDecoration itemDecoration = new LinearItemDecoration.Builder(this)
//                .dividerColor(R.color.green)//统一分割线颜色
                .dividerColors(R.color.green,R.color.blue,R.color.colorAccent,R.color.colorPrimaryDark)//设置各个分割线的颜色
                .showDividers(true,true,true,true)//设置各个分割线是否显示,默认只显示底部分割线
                .dividerHeight(4)//设置分割线高度(单位:dp)
                .build();

recyclerView.addItemDecoration(itemDecoration);

效果1.png