简易Banner 通用指示器封装

项目中需要使用到轮播图，为了方便，使用了Banner第三方库，但banner的轮播指示器太死，不符合项目要求，于是自己封装了一个方便的指示器，下面是使用效果：

QQ图片20200111195135.jpg QQ图片20200111195146.jpg

下面看一下怎么调用的

        IndicatorView indicator = new IndicatorView.Builder()
                .setContext(_mActivity)
                //指示器数量
                .setIndicatorCount(indicatorCount)
                //初始选择第几个
                .setSelectPosition(0)
                //被选中后的样式
                .setSelectColor(selectDrawble)
                //未选中的样式
                .setNormalColor(normalDrawble)
                //未选中的透明度 0 ~ 1
                .setNormalAlpha(0.6f)
                .builder();

只需要将需要的样式传进去就可以了，会自行根据banner的数量生成指示器。
生成后将指示器添加到自己的ViewGroup中就可以了，可以放在任何位置

FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.WRAP_CONTENT, FrameLayout.LayoutParams.WRAP_CONTENT);
        layoutParams.gravity = Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL;
        indicator.setLayoutParams(layoutParams);
       //将指示器添加到想要放置的位置
        viewGroup.addView(indicator);

之后在Viewpage的监听中改变选择的指示器：

//改变指示器选中项
indicatorView.changeIndicator(i);

只是简单的使用，没做复杂的动画，需要做动画的可以将指示器的Imageview替换成自定义View实现自己想要的动画，下面贴一下代码：

public class IndicatorView extends LinearLayoutCompat {
    private Context context;

    private Drawable selectColor;
    private Drawable normalColor;
    private float alpha;

    public IndicatorView(Context context) {
        super(context);
        this.context = context;
    }

    public IndicatorView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.context = context;
    }

    public IndicatorView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        this.context = context;
    }

    public IndicatorView initView(int indicatorCount,int selectPosition,Drawable selectDrawble,Drawable normalDrawble,float alpha){
        this.selectColor = selectDrawble;
        this.normalColor = normalDrawble;
        this.alpha = alpha;
        for (int i=0;i<indicatorCount;i++){
            AppCompatImageView ivIndicator = new AppCompatImageView(context);
            LinearLayoutCompat.LayoutParams lp = new LinearLayoutCompat.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
            lp.leftMargin = i == 0 ? 0 : SizeUtils.dp2px(6);
            ivIndicator.setLayoutParams(lp);
            ivIndicator.setBackgroundDrawable(i == selectPosition ? selectDrawble : normalDrawble);
            ivIndicator.setAlpha(i == selectPosition ? 1 : alpha);
            addView(ivIndicator);
        }
        return this;
    }

    public void changeIndicator(int position){
        int count = getChildCount();
        for (int i=0;i<count;i++){
            AppCompatImageView ivIndecator  = (AppCompatImageView) getChildAt(i);
            ivIndecator.setBackgroundDrawable(normalColor);
            ivIndecator.setAlpha(alpha);
        }
        AppCompatImageView ivIndecator  = (AppCompatImageView) getChildAt(position);
        ivIndecator.setBackgroundDrawable(selectColor);
        ivIndecator.setAlpha(1.0f);
    }

    public static class Builder{
        private Context context;
        private int position;
        private int indicatorCount;
        private Drawable selectColor;
        private Drawable normalColor;
        private float alpha;

        public Builder setContext(Context context){
            this.context = context;
            return this;
        }

        public Builder setSelectPosition(int position){
            this.position = position;
            return this;
        }

        public Builder setIndicatorCount(int indicatorCount){
            this.indicatorCount = indicatorCount;
            return this;
        }

        public Builder setSelectColor(Drawable selectColor){
            this.selectColor = selectColor;
            return this;
        }

        public Builder setNormalColor(Drawable normalColor){
            this.normalColor = normalColor;
            return this;
        }

        public Builder setNormalAlpha(float alpha){
            this.alpha = alpha;
            return this;
        }

        public IndicatorView builder(){
            return  new IndicatorView(context).initView(indicatorCount,position,selectColor,normalColor,alpha);
        }
    }
}