使用 OnPageChangeListener 同步两个 ViewPager [英] Synchronizing two ViewPagers using OnPageChangeListener

问题描述

我正在尝试同步两个 ViewPager，显然我之前有很多人，我已经做到了:

I'm trying to synchronize two ViewPagers, as apparently have quite a lot of people before me, and I've got as far as this:

private ViewPager mNavPager;

private ViewPager mMainPager;

private final OnPageChangeListener mNavPagerListener = new OnPageChangeListener() {

    private boolean mNavDragging;
    private int mScrollPosition;

    @Override
    public void onPageSelected(int position) {
        mScrollPosition = position;
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        if(mNavDragging)
            mMainPager.scrollTo(positionOffsetPixels, 0);
    }

    @Override
    public void onPageScrollStateChanged(int state) {
        switch(state) {
        case ViewPager.SCROLL_STATE_DRAGGING:
        case ViewPager.SCROLL_STATE_SETTLING:
            mNavDragging = true;
            break;
        case ViewPager.SCROLL_STATE_IDLE:
            mNavDragging = false;
            break;
        }
    }
};

private OnPageChangeListener mMainPagerListener = new OnPageChangeListener() {

    private boolean mMainDragging;
    private int mScrollPosition;

    @Override
    public void onPageSelected(int position) {
        mScrollPosition = position;
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        if(mMainDragging)
            mNavPager.scrollTo(positionOffsetPixels, 0);
    }

    @Override
    public void onPageScrollStateChanged(int state) {
        switch(state) {
        case ViewPager.SCROLL_STATE_DRAGGING:
        case ViewPager.SCROLL_STATE_SETTLING:
            mMainDragging = true;
            break;
        case ViewPager.SCROLL_STATE_IDLE:
            mMainDragging = false;
            break;
        }
    }
};

如果手动滚动其中一个，则另一个使用滚动状态属性从属于它.它可以很好地工作，直到物品到达最终位置；此时，从属寻呼机立即弹回先前选择的项目，就好像没有发生滚动一样.

If either one is scrolled manually, the other is slaved to it using the scroll state property. It works beautifully till the items reach their final position; at this point, the slaved pager flicks instantly back to the previously selected item, as though the scrolling hadn't taken place.

我曾尝试使用各种不同的逻辑约束调用 ViewPager#setCurrentItem(mScrolledPosition)，但这也不起作用，尽管它偶尔会使情况变得更糟.我觉得好像必须有什么可以做的，但我不确定是什么.

I have tried calling ViewPager#setCurrentItem(mScrolledPosition) with a variety of different logic constraints but that doesn't work either, though it does occasionally make it worse. I feel as though there must be something that can be done with that but I'm not sure what.

我怎样才能让从属寻呼机保持在正确的位置?

How can I get the slaved pager to remain in the correct position?

推荐答案

我使用 OnPageChangeListener 以更简单(更简洁)的方式解决了这个问题:

I solved this problem in a much easier (and cleaner) way using the OnPageChangeListener:

mViewPager1.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

      private int mScrollState = ViewPager.SCROLL_STATE_IDLE;

      @Override
      public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels) {
        if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
          return;
        }
        mViewPager2.scrollTo(mViewPager1.getScrollX(), mViewPager2.getScrollY());
      }

      @Override
      public void onPageSelected(final int position) {

      }

      @Override
      public void onPageScrollStateChanged(final int state) {
        mScrollState = state;
        if (state == ViewPager.SCROLL_STATE_IDLE) {
          mViewPager2.setCurrentItem(mViewPager1.getCurrentItem(), false);
        }
      }
});

mViewPager2.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

      private int mScrollState = ViewPager.SCROLL_STATE_IDLE;

      @Override
      public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels) {
        if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
          return;
        }
        mViewPager1.scrollTo(mViewPager2.getScrollX(), mViewPager1.getScrollY());
      }

      @Override
      public void onPageSelected(final int position) {

      }

      @Override
      public void onPageScrollStateChanged(final int state) {
        mScrollState = state;
        if (state == ViewPager.SCROLL_STATE_IDLE) {
          mViewPager1.setCurrentItem(mViewPager2.getCurrentItem(), false);
        }
      }
});

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