Android加阴影 -（一键无脑引入，无兼容问题）

老规矩，无图言 × ，先上图

好像看不清，换个颜色再来一张吧，再加宽点

这颜色好丑哈哈哈哈哈哈，这是从黑到白色，你们用的时候一定要用有透明度的色值啊哈哈哈

接下来上代码！

	/**
	* 示例用法 这里涉及到的一个 dip2px 方法就是把 8dp 转成对应的像素值而已
	*/
    public static View setViewBoundShadow(View view) {
        int shadowSize = dip2px(view.getContext(), 8);
        int startColor = Color.parseColor("#001795FF");
        int endColor = Color.parseColor("#1A1795FF");
        return setViewBoundShadow(view, shadowSize, startColor, endColor);
    }

    /**
     * @param view       需要设置阴影的 view
     * @param shadowSize 阴影宽度
     * @param startColor 贴近 view 一侧的色值
     * @param endColor   远离 view 一侧的色值
     * @return 失败 null ； 成功则返回阴影 所属的 parentView，可通过设置 visibility 控制是否显示
     * @author lzd
     * 为 view 设置阴影
     * #Note 使用此方法后 viewTree的父容器 的 ClipChildren 属性会置true
     * 这里可能会导致某些父布局里的元素超出容器，后期需要优化
     */
    public static View setViewBoundShadow(View view, int shadowSize, int startColor, int endColor) {
        if (view == null || shadowSize < 0) {
            return null;
        }

        ViewGroup parentView = new ConstraintLayout(view.getContext());
        if (view instanceof ViewGroup) {
            parentView.setLayoutParams(new ConstraintLayout.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
            ((ViewGroup) view).addView(parentView);
        } else {
            parentView.setLayoutParams(new ConstraintLayout.LayoutParams(
                    ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        }
        setViewFamilyClipChildren(parentView, false);

        class childValue {
            int width;
            int height;
            int horPos;
            int verPos;
            GradientDrawable.Orientation orientation;

            public childValue(int width, int height, int horPos, int verPos, GradientDrawable.Orientation orientation) {
                this.width = width;
                this.height = height;
                this.horPos = horPos;
                this.verPos = verPos;
                this.orientation = orientation;
            }
        }

        childValue[] childValues = new childValue[]{
                new childValue(shadowSize, ViewGroup.LayoutParams.MATCH_PARENT, 1, 0
                        , GradientDrawable.Orientation.RIGHT_LEFT),
                new childValue(shadowSize, ViewGroup.LayoutParams.MATCH_PARENT, -1, 0
                        , GradientDrawable.Orientation.LEFT_RIGHT),
                new childValue(ViewGroup.LayoutParams.MATCH_PARENT, shadowSize, 0, -1
                        , GradientDrawable.Orientation.TOP_BOTTOM),
                new childValue(ViewGroup.LayoutParams.MATCH_PARENT, shadowSize, 0, 1
                        , GradientDrawable.Orientation.BOTTOM_TOP),
                new childValue(shadowSize, shadowSize, 1, 1, null),
                new childValue(shadowSize, shadowSize, -1, 1, null),
                new childValue(shadowSize, shadowSize, -1, -1, null),
                new childValue(shadowSize, shadowSize, 1, -1, null),
        };

        for (childValue childValue : childValues) {
            ConstraintLayout.LayoutParams childParams
                    = new ConstraintLayout.LayoutParams(childValue.width, childValue.height);
            View child = new View(view.getContext());
            // 位置
            if (childValue.horPos == 1) {
                childParams.startToEnd = ConstraintLayout.LayoutParams.PARENT_ID;
            } else if (childValue.horPos == -1) {
                childParams.endToStart = ConstraintLayout.LayoutParams.PARENT_ID;
            }

            if (childValue.verPos == 1) {
                childParams.topToBottom = ConstraintLayout.LayoutParams.PARENT_ID;
            } else if (childValue.verPos == -1) {
                childParams.bottomToTop = ConstraintLayout.LayoutParams.PARENT_ID;
            }

            // 背景图
            GradientDrawable childBg = new GradientDrawable();
            if (childValue.orientation != null) {
                childBg.setColors(new int[]{startColor, endColor});
                childBg.setOrientation(childValue.orientation);
            } else {
                childBg.setColors(new int[]{endColor, startColor});
                childBg.setGradientRadius(shadowSize);
                childBg.setGradientCenter(Math.max(0, -childValue.horPos)
                        , Math.max(0, -childValue.verPos));
                childBg.setGradientType(GradientDrawable.RADIAL_GRADIENT);
                childBg.setCornerRadii(new float[]{
                        childValue.horPos + childValue.verPos == -2 ? shadowSize : 0,
                        childValue.horPos + childValue.verPos == -2 ? shadowSize : 0,
                        childValue.horPos == 1 && childValue.verPos == -1 ? shadowSize : 0,
                        childValue.horPos == 1 && childValue.verPos == -1 ? shadowSize : 0,
                        childValue.horPos + childValue.verPos == 2 ? shadowSize : 0,
                        childValue.horPos + childValue.verPos == 2 ? shadowSize : 0,
                        childValue.horPos == -1 && childValue.verPos == 1 ? shadowSize : 0,
                        childValue.horPos == -1 && childValue.verPos == 1 ? shadowSize : 0
                });
            }

            child.setBackground(childBg);
            child.setLayoutParams(childParams);

            parentView.addView(child);
        }
        parentView.getViewTreeObserver().addOnGlobalLayoutListener(() -> {
            setViewFamilyClipChildren(parentView, false);
        });
        return parentView;
    }

    public static void setViewFamilyClipChildren(ViewGroup view, boolean clipChildren) {
        if (view == null) {
            return;
        }
        view.setClipChildren(clipChildren);
        ViewParent rooter = view.getParent();
        while (rooter instanceof ViewGroup) {
            ((ViewGroup) rooter).setClipChildren(false);
            rooter = rooter.getParent();
        }
    }

导致就这样吧，好累了上了一天班，关于注释里提到的 “可能会导致某些父布局里的元素超出容器” 的问题，如果各位有什么解决方案的话，请务必留言交流！！！