Android_TabLayout使用问题

TabLayout在设置TabLayout.addTab()不显示的问题

TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("Tab"));


     /**
       * The one-stop shop for setting up this {@link TabLayout} with a {@link ViewPager}.
       *
       * <p>This method will link the given ViewPager and this TabLayout together so that any
       * changes in one are automatically reflected in the other. This includes adapter changes,
       * scroll state changes, and clicks. The tabs displayed in this layout will be populated
       * from the ViewPager adapter's page titles.</p>
       *
       * <p>After this method is called, you will not need this method again unless you want
       * to change the linked ViewPager.</p>
       *
       * <p>If the given ViewPager is non-null, it needs to already have a
       * {@link PagerAdapter} set.</p>
       *
       * @param viewPager The ViewPager to link, or {@code null} to clear any previous link.
       */

  public void setupWithViewPager(@Nullable final ViewPager viewPager) {
      if (mViewPager != null && mPageChangeListener != null) {
          // If we've already been setup with a ViewPager, remove us from it
          mViewPager.removeOnPageChangeListener(mPageChangeListener);
      }

    if (viewPager != null) {
        final PagerAdapter adapter = viewPager.getAdapter();
        if (adapter == null) {
            throw new IllegalArgumentException("ViewPager does not have a PagerAdapter set");
        }

        mViewPager = viewPager;

        // Add our custom OnPageChangeListener to the ViewPager
        if (mPageChangeListener == null) {
            mPageChangeListener = new TabLayoutOnPageChangeListener(this);
        }
        mPageChangeListener.reset();
        viewPager.addOnPageChangeListener(mPageChangeListener);

        // Now we'll add a tab selected listener to set ViewPager's current item
        setOnTabSelectedListener(new ViewPagerOnTabSelectedListener(viewPager));

        // Now we'll populate ourselves from the pager adapter
        setPagerAdapter(adapter, true);
    } else {
        // We've been given a null ViewPager so we need to clear out the internal state,
        // listeners and observers
        mViewPager = null;
        setOnTabSelectedListener(null);
        setPagerAdapter(null, true);
    }
}

---

private void setPagerAdapter(@Nullable final PagerAdapter adapter, final boolean addObserver) {
        if (mPagerAdapter != null && mPagerAdapterObserver != null) {
            // If we already have a PagerAdapter, unregister our observer
            mPagerAdapter.unregisterDataSetObserver(mPagerAdapterObserver);
        }

        mPagerAdapter = adapter;

        if (addObserver && adapter != null) {
            // Register our observer on the new adapter
            if (mPagerAdapterObserver == null) {
                mPagerAdapterObserver = new PagerAdapterObserver();
            }
            adapter.registerDataSetObserver(mPagerAdapterObserver);
        }

        // Finally make sure we reflect the new adapter
        populateFromPagerAdapter();
    }

---

private void populateFromPagerAdapter() {
        removeAllTabs();

    if (mPagerAdapter != null) {
        final int adapterCount = mPagerAdapter.getCount();
        for (int i = 0; i < adapterCount; i++) {
            addTab(newTab().setText(mPagerAdapter.getPageTitle(i)), false);
        }

        // Make sure we reflect the currently set ViewPager item
        if (mViewPager != null && adapterCount > 0) {
            final int curItem = mViewPager.getCurrentItem();
            if (curItem != getSelectedTabPosition() && curItem < getTabCount()) {
                selectTab(getTabAt(curItem));
            }
        }
    } else {
        removeAllTabs();
    }
}


不显示的问题在于 removeAllTabs()方法，修改设置tabLayout.setupWithViewPager(viewPager)，TabLayout绑定ViewPager  
与addTab的执行顺序。