Android自定义Tab 滑动指示条

最近在项目中有用到Tab，Tab下面有个指示条，一般来说可以使用用官方的TabLayout做，但官方提供的Tab指示器太不灵活，没法做到更换任意图形，，，于是自己尝试弄一下了，
先看一下效果：

20200511203638.gif

再看一下如何使用：

//第一排
        scrollIndicator = findViewById(R.id.scrollIndicatorone);
        llParent = findViewById(R.id.ll_parentone);

        //第二排
        scrollIndicatorTwo = findViewById(R.id.scrollIndicatortwo);
        llParentTwo = findViewById(R.id.ll_parenttwo);

        //第一排
        scrollIndicator
                .setWith(20)
                .setHigh(4)
                .setColor(ContextCompat.getColor(this, R.color.colorAccent))
                .setViewGroup(llParent)
                .setPosition(0);

        //第二排
        scrollIndicatorTwo
                //宽
                .setWith(40)
                //高
                .setHigh(4)
                //圆角
                .setRound(10)
                //颜色
                .setColor(ContextCompat.getColor(this, R.color.colorAccent))
                //文字父容器
                .setViewGroup(llParentTwo)
                //初始显示
                .setPosition(0);

scrollIndicator就是自定义的指示器，使用的时候可以设置宽度，高度，圆角，颜色等，基本满足我这项目的需求，当然，光是这样的话和官方的区别也不大， 但这个最灵活的就是scrollIndicator继承自View，可以在onDraw中任意改变形状，可以变三角形，变水滴， 变五角形，任何形状都是可以绘制的， 而且scrollIndicator和显示的文字是分离的，没有一点耦合，可以随意增删，关联只需调用

                //文字父容器
                .setViewGroup(llParentTwo)

将文字的父容器传进去即可，再加上属性动画，感觉也还可以。。。。
下面帖一下全部代码：

public class ScrollIndicator extends View {
    private Paint paint;
    private int with;
    private int high;
    private int round;
    private RectF rectF;
    private ViewGroup viewGroup;
    private int startWith;
    private int color;
    private int defaulteWith;
    private int defaulteHigh;
    //父容器是否加载完
    private boolean isLoad;

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

    public ScrollIndicator(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public ScrollIndicator(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init(){
        paint = new Paint();
        paint.setStyle(Paint.Style.FILL);
        paint.setStrokeWidth(1);
        paint.setAntiAlias(true);
        paint.setDither(true);
        rectF = new RectF();

        defaulteWith = SizeUtils.dp2px(20);
        defaulteHigh = SizeUtils.dp2px(4);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        paint.setColor(color);
        rectF.set(startWith, 0,startWith + with, high);
        canvas.drawRoundRect(rectF, round, round, paint);
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int withModel = MeasureSpec.getMode(widthMeasureSpec);
        int highModel = MeasureSpec.getMode(widthMeasureSpec);

        int specWith = MeasureSpec.getSize(widthMeasureSpec);
        int specHigh = MeasureSpec.getSize(heightMeasureSpec);

        int currentWith;
        int currentHigh;
        switch (withModel){
            case MeasureSpec.AT_MOST:
                currentWith = defaulteWith;
                break;
            case MeasureSpec.EXACTLY:
            default:
                currentWith = specWith;
                break;
        }

        switch (highModel){
            case MeasureSpec.AT_MOST:
                currentHigh = defaulteHigh;
                break;
            case MeasureSpec.EXACTLY:
            default:
                currentHigh = specHigh;
                break;
        }

        setMeasuredDimension(currentWith, currentHigh);
    }

    public ScrollIndicator setWith(int with){
        this.with = SizeUtils.dp2px(with);
        return this;
    }

    public ScrollIndicator setHigh(int high){
        this.high = SizeUtils.dp2px(high);
        return  this;
    }

    public ScrollIndicator setColor(int color){
        this.color = color;
        return this;
    }

    public ScrollIndicator setRound(int round){
        this.round = SizeUtils.dp2px(round);
        return this;
    }

    public ScrollIndicator setViewGroup(ViewGroup viewGroup){
        this.viewGroup = viewGroup;
        return this;

    }

    public void setPosition(final int position){
        if(isLoad){
            int listCenter = (viewGroup.getChildAt(position).getRight() + viewGroup.getChildAt(position).getLeft())/2;
            int endWith = listCenter - with/2;
            startAnim(startWith,endWith);
            startWith = listCenter - with/2;
        }else{
            viewGroup.postDelayed(new Runnable() {
                @Override
                public void run() {
                    int listCenter = (viewGroup.getChildAt(position).getRight() + viewGroup.getChildAt(position).getLeft())/2;
                    int endWith = listCenter - with/2;
                    startAnim(startWith,endWith);
                    startWith = listCenter - with/2;

                    isLoad = true;
                }
            },100);
        }
    }


    public void startAnim(int startWith, int endwith){
        ValueAnimator valueAnimator = ValueAnimator.ofInt(startWith, endwith);
        valueAnimator.setDuration(100);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                ScrollIndicator.this.startWith = (int) animation.getAnimatedValue();
                postInvalidate();
            }
        });
        valueAnimator.start();
    }
}

完。