Question

我正在显示仅包含ImageViews的ViewPager。但是，我需要它以循环方式不断发生。对于Ex：... c＆gt; B> A＆gt; B> ç...

Answer 1

只需实现ViewPager.OnPageChangeListener：

YOUR_VIEWPAGER.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
    @Override
    public void onPageSelected(int position) {
      currentPage = position;
    }
    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
      // not needed
    }
    @Override
    public void onPageScrollStateChanged(int state) {
      if (state == ViewPager.SCROLL_STATE_IDLE) {
        int pageCount = pages.size();

        if (currentPage == 0){
          YOUR_VIEWPAGER.setCurrentItem(pageCount-2,false);
        } else if (currentPage == pageCount-1){
          YOUR_VIEWPAGER.setCurrentItem(1,false);
        }
      }
    }
  });

Answer 2

尝试这个。它将得到类似C <-> A <-> B <-> C <-> A

的结果

viewPager?.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
      var currentPage : Int = 0
      var mPreviousPosition : Int = 0
      var mIsEndOfCycle = false
      override fun onPageScrollStateChanged(state: Int) {
        val pageCount = viewPager?.adapter?.count
        if (state == ViewPager.SCROLL_STATE_IDLE) {
          if (mPreviousPosition == currentPage && !mIsEndOfCycle) {
            if (currentPage == 0) {
              pageCount?.minus(1)?.let { viewPager?.setCurrentItem(it, false) };
            } else {
              viewPager?.setCurrentItem(0, false);
            }
            mIsEndOfCycle = true;
          } else {
            mIsEndOfCycle = false;
          }
          mPreviousPosition = currentPage;
        }
      }

      override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {}

      override fun onPageSelected(position: Int) {
        currentPage = position
      }

    })

Answer 3

以下为我做了。我不希望用户从第一页“返回”到最后一页。所以基本上我有三个不同的屏幕，但实际上我在适配器中有四个，像这样：A -> B -> C -> A。当用户点击第二个“A”页面时，寻呼机状态变为空闲，我无缝切换到第一个“A”页。我什至有一个页面指示器，我已经类似地覆盖了它。

val pageChangeCallback = object : ViewPager2.OnPageChangeCallback() {
        override fun onPageScrollStateChanged(state: Int) {
            super.onPageScrollStateChanged(state)

            if (state == ViewPager.SCROLL_STATE_IDLE) {
                if (viewPager.currentItem == NUM_PAGES - 1) {
                    viewPager.setCurrentItem(0, false)
                }
            }
        }
    }

循环ViewPager用于连续滚动

3 个答案: