ViewPager2 无限循环 自动播放(修改切换动画,切换速度

实现原因:

ViewPager2虽然修改了vp的一些弊端,比如 ViewPager2的切换时间以及切换的动画,且ViewPager2被final 修饰不能被继承.所以就试着修改一下切换的动画 以及切换的时间以此记录

实现难点:
A:自动播放
B:无限播放
C:切换动画

1:自动播放 Timer Handler 定时切换页面

    Timer  timer = Timer()       
    var timerTask = object : TimerTask() {
        override fun run() {
            runOnUiThread {
              // 切换 页面以及处理 切换的速度
                MyPagerHelper.setCurrentItem(binding!!.vpBg, count++, 300)
            }
        }
    }
    timer.schedule(timerTask, 500, 2000)      

2:切换速度以及切换时长

  import android.animation.Animator;
  import android.animation.ValueAnimator;
  import android.view.animation.AccelerateDecelerateInterpolator;

  import androidx.viewpager2.widget.ViewPager2;

/**
 * @author wkq
 * @date 2021年08月17日 15:07
 * @des
 */

public class MyPagerHelper {
/**
 * 保存前一个animatedValue
 */
private static int previousValue;

/**
 * 设置当前Item
 * @param pager    viewpager2
 * @param item     下一个跳转的item
 * @param duration scroll时长
 */
public static void setCurrentItem(final ViewPager2 pager, int item, long duration) {
    previousValue = 0;
    int currentItem = pager.getCurrentItem();
    int pagePxWidth = pager.getWidth();
    int pxToDrag = pagePxWidth * (item - currentItem);
    final ValueAnimator animator = ValueAnimator.ofInt(0, pxToDrag);
    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            int currentValue = (int) animation.getAnimatedValue();
            float currentPxToDrag = (float) (currentValue - previousValue);
            pager.fakeDragBy(-currentPxToDrag);
            previousValue = currentValue;
        }
    });
    animator.addListener(new Animator.AnimatorListener() {
        @Override
        public void onAnimationStart(Animator animation) {
            pager.beginFakeDrag();
        }

        @Override
        public void onAnimationEnd(Animator animation) {
            pager.endFakeDrag();
        }

        @Override
        public void onAnimationCancel(Animator animation) { }

        @Override
        public void onAnimationRepeat(Animator animation) { }
    });
    animator.setInterpolator(new AccelerateDecelerateInterpolator());
    animator.setDuration(duration);
    animator.start();
}

}

3:切换动画

    //设置切换动画
private fun transformer(
) {
    //设置多个果冻动画 CompositePageTransformer
    val compositePageTransformer = CompositePageTransformer()
    // 叠加 渐变
    compositePageTransformer.addTransformer(ViewPagerOverlay())
    //偏移
    //        compositePageTransformer.addTransformer(MarginPageTransformer(100))
    binding!!.vpBg.setPageTransformer(compositePageTransformer)

}

PageTransformer:ViewPager2 的切换动画

import android.view.View
import androidx.viewpager2.widget.ViewPager2
import kotlin.math.abs
private const val MIN_SCALE = 1f

class ViewPagerOverlay : ViewPager2.PageTransformer {

override fun transformPage(view: View, position: Float) {
    val pageWidth = view.width

    when {
        position < -1 -> { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.alpha = 0f
        }
        position <= 0 -> { // [-1,0]
            // Use the default slide transition when moving to the left page
            view.alpha = 1F
            view.translationX = 0f
            view.scaleX = 1f
            view.scaleY = 1f
        }
        position <= 1 -> { // (0,1]
            // Fade the page out.
            view.alpha = 1 - position

            // Counteract the default slide transition
            view.translationX = pageWidth * -position

            // Scale the page down (between MIN_SCALE and 1)
            val scaleFactor: Float = (MIN_SCALE
                    + (1 - MIN_SCALE) * (1 - abs(position)))
            view.scaleX = scaleFactor
            view.scaleY = scaleFactor
        }
        else -> { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.alpha = 0f
        }
    }
}

}

4: 无限播放 Int.MAX_VALUE 方案

class ZrBgAdapter(mContext: Context) : KtAdapter<String>(mContext) {

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
    var viewDatabinding= DataBindingUtil.inflate<ItemZrBgBinding>(LayoutInflater.from(mContext), R.layout.item_zr_bg,parent,false)

    var viewHolder= DataBindingViewHolder(viewDatabinding.root)
    viewHolder.binding=viewDatabinding
    return viewHolder
}

override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {

    var viewHolder=holder as DataBindingViewHolder
    var binding=viewHolder.binding as ItemZrBgBinding
    Glide.with(mContext).load(getItem(position%3)).into(binding.iv)

}

override fun getItemCount(): Int {
    return Int.MAX_VALUE
}

}

项目地址: https://gitee.com/wkqoschina/ZrDemo/tree/Timer