ViewPager2打造Banner轮播图

implementation "androidx.viewpager2:viewpager2:1.0.0"

<androidx.viewpager2.widget.ViewPager2
    android:id="@+id/bannerVp"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    />

<style name="BannerStyle">
    <item name="cornerFamily">rounded</item>
    <item name="cornerSize">@dimen/_10dp</item>
</style>

<com.google.android.material.imageview.ShapeableImageView
    android:id="@+id/banner_image"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:scaleType="fitXY"
    app:shapeAppearance="@style/BannerStyle"
/>

val newList = arrayListOf<String>()
newList.add(pic[pic.size-1])

for (item in pic) {
    newList.add(item)
}
newList.add(pic[0])

bannerVp.registerOnPageChangeCallback(object :
    ViewPager2.OnPageChangeCallback() {
    override fun onPageSelected(position: Int) {
        currentPosition = position
    }
    override fun onPageScrollStateChanged(state: Int) {
        //只有在空闲状态，才让自动滚动
        if (state == ViewPager2.SCROLL_STATE_IDLE) {
            if (currentPosition == 0) {
                bannerVp.setCurrentItem(adapter.itemCount - 2, false)
            } else if (currentPosition == adapter.itemCount - 1) {
                bannerVp.setCurrentItem(1, false)
            }
        }
    }
})

bannerVp.postDelayed(mLooper,1000)

private val mLooper = object : Runnable {
    override fun run() {
        bannerVp.currentItem = ++bannerVp.currentItem
        bannerVp.postDelayed(this,1000)
    }
}

override fun onWindowFocusChanged(hasFocus: Boolean) {
    super.onWindowFocusChanged(hasFocus)
    if (hasFocus){
        bannerVp.postDelayed(counter,1000)
    }else{
    //失去焦点时移除
        bannerVp.removeCallbacks(counter)
    }
}

bannerVp.getChildAt(0).setOnTouchListener { _, event ->
    when (event.action) {
        MotionEvent.ACTION_DOWN -> {
           bannerVp.removeCallbacks(mLooper)
        }
        MotionEvent.ACTION_UP -> {
            bannerVp.postDelayed(mLooper,1000)
        }
    }
    return@setOnTouchListener false
}