Android垂直切换的圆角Banner与垂直指示器相关介绍与应用详解

<com.youth.banner.Banner
    android:id="@+id/banner"
    android:layout_width="300dp"
    android:layout_height="400dp"
    android:layout_marginTop="10dp"
    app:banner_radius="30dp"
    app:banner_round_top_left="true"
    app:banner_round_top_right="true"
    app:banner_orientation="vertical"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
<com.hzf.banner.CircleVerticalIndicator
    android:id="@+id/indicator"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="10dp"
    app:layout_constraintTop_toTopOf="@id/banner"
    app:layout_constraintBottom_toBottomOf="@id/banner"
    app:layout_constraintStart_toEndOf="@id/banner" />

// 要轮播的图片地址
val urls = mutableListOf(
    R.mipmap.img1,
    R.mipmap.img2,
    R.mipmap.img3
)
// 垂直指示器
val indicator = findViewById<CircleVerticalIndicator>(R.id.indicator)
// Banner 基本设置
findViewById<Banner<Int,RoundedBannerAdapter>>(R.id.banner).apply {
    setAdapter(RoundedBannerAdapter(urls)) // 设置图片的适配器
    addBannerLifecycleObserver(this@MainActivity) // 添加生命周期监听
    setIndicator(indicator,false) // 设置指示器，false 表示指示器不放在 Banner 内
    setLoopTime(1500) // 轮播间隔时间
    setIndicatorSpace(20) // 指示器圆圈之间的间隔
    setIndicatorNormalWidth(12) // 未选中状态下，指示器圆圈的直径大小
    setIndicatorSelectedWidth(12) // 选中状态下，指示器圆圈的直径大小
    setIndicatorNormalColor(ContextCompat.getColor(this@MainActivity, R.color.black)) // 未选中状态下，指示器圆圈的颜色
    setIndicatorSelectedColor(ContextCompat.getColor(this@MainActivity, R.color.red)) // 选中状态下，指示器圆圈的颜色
}

class RoundedBannerAdapter(urls: MutableList<Int>) : BannerAdapter<Int, RoundedBannerAdapter.BannerViewHolder>(urls) {
    override fun onCreateHolder(parent: ViewGroup?, viewType: Int): BannerViewHolder {
        val imageView = ImageView(parent!!.context).apply {
            layoutParams = ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT
            )
            scaleType = ImageView.ScaleType.CENTER_CROP
        }
        return BannerViewHolder(imageView)
    }
    override fun onBindView(holder: BannerViewHolder?, data: Int?, position: Int, size: Int) {
        data?.let {
            holder?.imageView?.setImageResource(it)
        }
    }
    class BannerViewHolder(var imageView: ImageView) :
        RecyclerView.ViewHolder(imageView)
}

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec)
    val count = config.indicatorSize
    if (count <= 1) {
        return
    }
    mNormalRadius = config.normalWidth / 2
    mSelectedRadius = config.selectedWidth / 2
    // 考虑当选中和默认的大小不一样的情况
    maxRadius = mSelectedRadius.coerceAtLeast(mNormalRadius)
    // 高度 = 间距 *（总数-1）+ 选中直径 + 默认直径 *（总数-1）
    val height =
        (count - 1) * config.indicatorSpace + config.selectedWidth + config.normalWidth * (count - 1)
    setMeasuredDimension(maxRadius * 2, height)
}

override fun onDraw(canvas: Canvas) {
    super.onDraw(canvas)
    val count = config.indicatorSize
    if (count <= 1) {
        return
    }
    var circleY = 0f
    for (i in 0 until count) {
        // 画笔颜色
        mPaint.color =
            if (config.currentPosition == i) config.selectedColor else config.normalColor
        // 圆的直径
        val circleDiameter =
            if (config.currentPosition == i) config.selectedWidth else config.normalWidth
        // 指示器圆圈半径
        val radius = if (config.currentPosition == i) mSelectedRadius else mNormalRadius
        // 绘制圆
        canvas.drawCircle(maxRadius.toFloat(),circleY + radius , radius.toFloat(), mPaint)
        // 更新最小的 y 值：当前的 y 加上当前圆的直径，加上间距
        circleY += (circleDiameter + config.indicatorSpace).toFloat()
    }
}