How to use

getAdapter

method

in

androidx.viewpager.widget.ViewPager

@Override public void onPageSelected(int position) {
  if (mViewpager.getAdapter() == null
      || mViewpager.getAdapter().getCount() <= 0) {
    return;
  }
  internalPageSelected(position);
  mLastPosition = position;
}

@Override
protected void onSettingsChanged() {
  // Applying settings from toolbar menu, see BaseExampleActivity
  pager.getAdapter().notifyDataSetChanged();
}

@Override
protected void onSettingsChanged() {
  // Applying settings from toolbar menu, see BaseExampleActivity
  viewPager.getAdapter().notifyDataSetChanged();
}

@Override
protected void onSettingsChanged() {
  // Applying settings from toolbar menu, see BaseExampleActivity
  viewPager.getAdapter().notifyDataSetChanged();
}

@Override
protected void onSettingsChanged() {
  // Applying settings from toolbar menu, see BaseExampleActivity
  pager.getAdapter().notifyDataSetChanged();
}

  @Override
  protected View getViewAt(int imagePos) {
    // We should return image view for a given pager position
    PagerAdapter adapter = (PagerAdapter) pager.getAdapter();
    RecyclePagerAdapter.ViewHolder holder = adapter.getViewHolder(imagePos);
    return holder == null ? null : PagerAdapter.getImageView(holder);
  }
};

  @Override
  public View getViewById(@NonNull Position pos) {
    // We should return image view for a given pager position
    int pagerPos = getPositionById(pos);
    PagerAdapter adapter = (PagerAdapter) pager.getAdapter();
    RecyclePagerAdapter.ViewHolder holder = adapter.getViewHolder(pagerPos);
    return holder == null ? null : PagerAdapter.getImageView(holder);
  }
};

public void setViewPager(@Nullable ViewPager viewPager) {
  mViewpager = viewPager;
  if (mViewpager != null && mViewpager.getAdapter() != null) {
    mLastPosition = -1;
    createIndicators();
    mViewpager.removeOnPageChangeListener(mInternalPageChangeListener);
    mViewpager.addOnPageChangeListener(mInternalPageChangeListener);
    mInternalPageChangeListener.onPageSelected(mViewpager.getCurrentItem());
  }
}

private void populateTabStrip() {
  final PagerAdapter adapter = mViewPager.getAdapter();
  final View.OnClickListener tabClickListener = new TabClickListener();

private void populateTabStrip() {
  final PagerAdapter adapter = mViewPager.getAdapter();
  final View.OnClickListener tabClickListener = new TabClickListener();
  for (int i = 0; i < adapter.getCount(); i++) {
    View tabView = null;
    TextView tabTitleView = null;
    if (mTabViewLayoutId != 0) {
      // If there is a custom tab view layout id set, try and inflate it
      tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip,
          false);
      tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
    }
    if (tabView == null) {
      tabView = createDefaultTabView(getContext());
    }
    if (tabTitleView == null && TextView.class.isInstance(tabView)) {
      tabTitleView = (TextView) tabView;
    }
    tabTitleView.setText(adapter.getPageTitle(i));
    tabView.setOnClickListener(tabClickListener);
    mTabStrip.addView(tabView);
  }
}

private void createIndicators() {
  removeAllViews();
  PagerAdapter adapter = mViewpager.getAdapter();
  int count;
  if (adapter == null || (count = adapter.getCount()) <= 0) {
    return;
  }
  createIndicators(count, mViewpager.getCurrentItem());
}

  @Override public void onChanged() {
    super.onChanged();
    if (mViewpager == null) {
      return;
    }
    PagerAdapter adapter = mViewpager.getAdapter();
    int newCount = adapter != null ? adapter.getCount() : 0;
    int currentCount = getChildCount();
    if (newCount == currentCount) {
      // No change
      return;
    } else if (mLastPosition < newCount) {
      mLastPosition = mViewpager.getCurrentItem();
    } else {
      mLastPosition = -1;
    }
    createIndicators();
  }
};

@Override
public boolean onKeyDown(int code, KeyEvent event) {
  if (code == KeyEvent.KEYCODE_ENTER || code == KeyEvent.KEYCODE_BUTTON_A ||
      code == KeyEvent.KEYCODE_DPAD_CENTER) {
    ViewPager vp = this.findViewById(R.id.view_pager);
    if (vp.getCurrentItem() == vp.getAdapter().getCount() - 1) {
      onDonePressed(fragments.get(vp.getCurrentItem()));
    } else {
      vp.setCurrentItem(vp.getCurrentItem() + 1);
    }
    return false;
  }
  return super.onKeyDown(code, event);
}

private void applyCurrentPage() {
  final ID id = getAnimator().getRequestedId();
  if (id == null) {
    return;
  }
  if (viewPager.getAdapter() == null || viewPager.getAdapter().getCount() == 0) {
    return;
  }
  final int position = tracker.getPositionById(id);
  if (position == IntoTracker.NO_POSITION) {
    switchToCurrentPage();
    return;
  }
  if (position != viewPager.getCurrentItem()) {
    return;
  }
  final View view = tracker.getViewById(id); // View may be null
  if (view instanceof AnimatorView) {
    getAnimator().setToView(id, (AnimatorView) view);
  } else if (view != null) {
    throw new IllegalArgumentException("View for " + id + " should be AnimatorView");
  }
}

private void switchToCurrentPage() {
  if (viewPager.getAdapter() == null || viewPager.getAdapter().getCount() == 0) {
    return;
  }
  final ID id = getAnimator().getRequestedId();
  final ID currentId = tracker.getIdByPosition(viewPager.getCurrentItem());
  // If user scrolled to new page we should silently switch views
  if (id != null && currentId != null && !id.equals(currentId)) {
    // Saving current state
    AnimatorView toView = getAnimator().getToView();
    ViewPositionAnimator toAnimator = toView == null ? null : toView.getPositionAnimator();
    boolean isLeaving = toAnimator != null && toAnimator.isLeaving();
    float position = toAnimator == null ? 0f : toAnimator.getPosition();
    boolean isAnimating = toAnimator != null && toAnimator.isAnimating();
    // Switching to new page, preventing exit of previous page
    skipExit();
    getAnimator().enter(currentId, false);
    // If exit animation was in place we should continue it
    if (isLeaving && position > 0f) {
      getAnimator().exit(isAnimating);
    }
  }
}

int getPageCount() {
  if (mPager == null)
    return 0;
  final PagerAdapter adapter = mPager.getAdapter();
  if (adapter == null)
    return 0;
  return adapter.getCount();
}

@Override
public void onTabSelected(TabLayout.Tab tab) {
  PageFragmentAdapter adapter = (PageFragmentAdapter) mViewPager.getAdapter();
  //noinspection ConstantConditions
  Fragment fragment = adapter.getCachedFragment(tab.getPosition());
  if (fragment instanceof SelectableFragment) {
    mUiHandler.post(((SelectableFragment) fragment)::onFragmentSelected);
  }
  // Show fab if necessary
  showFab();
}

public void setViewPager(ViewPager viewPager) {
  this.viewPager = viewPager;
  viewPager.addOnPageChangeListener(this);
  setPageCount(viewPager.getAdapter().getCount());
  viewPager.getAdapter().registerDataSetObserver(new DataSetObserver() {
    @Override
    public void onChanged() {
      setPageCount(DynamicPageIndicator.this.viewPager.getAdapter().getCount());
    }
  });
  setCurrentPageImmediate();
}

private void onDetachedFromViewPager(@NonNull ViewPager pager) {
  if (mView instanceof TabStripView)
    ((TabStripView) mView).onDetachedFromViewPager(pager);
  else if (mView instanceof TabStripViewGroup)
    ((TabStripViewGroup) mView).onDetachedFromViewPager(pager);
  pager.removeOnPageChangeListener(this);
  pager.removeOnAdapterChangeListener(this);
  final PagerAdapter adapter = pager.getAdapter();
  if (adapter != null) {
    adapter.unregisterDataSetObserver(this);
  }
}

@Override
public void onPageSelected(int i) {
  setTitle(mViewPager.getAdapter().getPageTitle(i));
  if (mPaymentFlowPagerAdapter.getPageAt(i) == PaymentFlowPagerEnum.SHIPPING_INFO) {
    mPaymentFlowPagerAdapter.hideShippingPage();
  }
}