如何简单实现内凹阴影标题栏效果

先上效果图（支持自定义扩展格数，背景和阴影颜色以及圆角大小）ps：暂不支持滑动动画效果，后期会加上。

实现原理（图解）：

自定义了一个layout布局在布局内画框，位置要超出屏幕之外（为了达到效果，投机的一个办法哈哈哈哈），空出底部间隙是为了阴影的展示。

如图的层次结构，我就不解释了这么简单，应该都能看懂哈哈哈哈哈。源码下面附上。

使用的时候直接setmPosition（）就ok了。

源码：

/**
 * 内凹阴影标题栏
 *
 * @author Sago丶
 * @date 2017/11/17
 */

public class ShadowLinearLayout extends LinearLayout {
    private Paint mPaint, mPaint2;
    private RectF mRectF, mRectF2;
    private int mPosition = 2;
    private int mLyoutColumn;//平分几格
    private int mRadius;//圆角
    private int mShadowColor;//阴影颜色
    private int mLayoutBackgroundColor;//布局背景颜色

    public ShadowLinearLayout(Context context) {
        super(context);
        init();
    }

    public ShadowLinearLayout(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ShadowLinearLayout);
        mLyoutColumn = typedArray.getInteger(R.styleable.ShadowLinearLayout_lyout_column, 4);
        mRadius = typedArray.getInteger(R.styleable.ShadowLinearLayout_shadow_radius, 20);
        mShadowColor = typedArray.getColor(R.styleable.ShadowLinearLayout_shadow_color, ContextCompat.getColor(MyApplication.getInstance(), R.color.red_FFF7DEDA));
        mLayoutBackgroundColor = typedArray.getColor(R.styleable.ShadowLinearLayout_layout_background_color, ContextCompat.getColor(MyApplication.getInstance(), R.color.white_FFFFFF));

        typedArray.recycle();
        init();
    }

    public ShadowLinearLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public ShadowLinearLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init();
    }

    void init() {
        setPadding(0, 0, 0, 15);
        setBackgroundColor(Color.WHITE);
        mPaint = new Paint();
        mPaint2 = new Paint();
        //硬件加速
        setLayerType(LAYER_TYPE_SOFTWARE, mPaint);
        setLayerType(LAYER_TYPE_SOFTWARE, mPaint2);
        mPaint.setColor(mLayoutBackgroundColor);
        mPaint2.setColor(mLayoutBackgroundColor);

        // 设定阴影(柔边, X 轴位移, Y 轴位移, 阴影颜色)
        mPaint.setShadowLayer(10, 5, 5, mShadowColor);
        mPaint2.setShadowLayer(10, -5, 5, mShadowColor);

        mPaint.setAntiAlias(true);//锯齿不显示
        mPaint2.setAntiAlias(true);//锯齿不显示

        mRectF = new RectF();//左边RectF对象
        mRectF2 = new RectF();//右边RectF对象

    }

    public void setmPosition(int mPosition) {
        this.mPosition = mPosition;
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        mRectF.top = 0 - mRadius;  //上边
        mRectF.left = 0 - mRadius;//左边
        mRectF.bottom = this.getMeasuredHeight() - 15;//下边
        mRectF.right = this.getMeasuredWidth() / mLyoutColumn * (mPosition - 1);//右边

        mRectF2.top = 0 - mRadius;  //上边
        mRectF2.bottom = this.getMeasuredHeight() - 15; //下边
        mRectF2.right = this.getMeasuredWidth() + 15;//右边
        mRectF2.left = this.getMeasuredWidth() / mLyoutColumn * (mPosition);//左边


        if (mPosition != 1) {
            //左边
            canvas.drawRoundRect(mRectF, mRadius, mRadius, mPaint);        //绘制圆角矩形
        }
        if (mPosition != mLyoutColumn) {
            //右边
            canvas.drawRoundRect(mRectF2, mRadius, mRadius, mPaint2);        //绘制圆角矩形
        }
        super.onDraw(canvas);
    }
}

自定义样式代码：

<resources>
    <declare-styleable name="ShadowLinearLayout">
        <attr name="lyout_column" format="integer" />
        <attr name="shadow_radius" format="integer" />
        <attr name="layout_background_color" format="color" />
        <attr name="shadow_color" format="color" />
    </declare-styleable>
</resources>

好了，整体实现就是这样，很简单的原理希望对大家有帮助，各位大佬不喜勿喷，有不妥之处还请指点。