問題：
ViewPager 巢狀多個Fragment，但是每個Fragment高度不一致，導致高度比較小的Fragment底部留有大片空白區域。
解決方法：
參考文章 關於ViewPager高度自適應（隨著pager頁的高度改變Viewpager的高度）
ViewPager 常用重寫類：
1.viewpager巢狀在scrollview中，為了解決viewpager和scorllview的衝突，重寫的類

public class CustomViewPager extends ViewPager {  

    public CustomViewPager(Context context) {  
        super
 
(context);  
    }  

    public CustomViewPager(Context context, AttributeSet attrs) {  
        super(context, attrs);  
    }  

    @Override  
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  

        int height = 0;  
        for (int i = 0; i < getChildCount(); i++) {  
            View child = getChildAt(i);  
            child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0
 
, MeasureSpec.UNSPECIFIED));  
            int h = child.getMeasuredHeight();  
            if (h > height)  
                height = h;  
        }  

        heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);  

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);  
    }  
}  
 

2.為了解決上述空白問題，首先定義一個CustomViewPager類，繼承自ViewPager，重寫onMeasure方法，重新計算高度

public class CustomViewPager extends ViewPager
{
    private int current;
    private int height = 0;
    /**
     * 儲存position與對於的View
     */
    private HashMap<Integer, View> mChildrenViews = new LinkedHashMap<Integer, View>();

    private boolean scrollble = true;

    public CustomViewPager(Context context)
    {
        super(context);
    }

    public CustomViewPager(Context context, AttributeSet attrs)
    {
        super(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        if (mChildrenViews.size() > current) {
            View child = mChildrenViews.get(current);
            child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
            height = child.getMeasuredHeight();
        }

        heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    public void resetHeight(int current) {
        this.current = current;
        if (mChildrenViews.size() > current) {

            LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) getLayoutParams();
            if (layoutParams == null) {
                layoutParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, height);
            } else {
                layoutParams.height = height;
            }
            setLayoutParams(layoutParams);
        }
    }
    /**
     * 儲存position與對於的View
     */
    public void setObjectForPosition(View view, int position)
    {
        mChildrenViews.put(position, view);
    }


    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (!scrollble) {
            return true;
        }
        return super.onTouchEvent(ev);
    }


    public boolean isScrollble() {
        return scrollble;
    }

    public void setScrollble(boolean scrollble) {
        this.scrollble = scrollble;
    }
}

使用方法：
首先在Fragment裡呼叫setObjectForPosition方法，存放view和他對應的position：

   private int fragmentID=0;

    private  View rootView=null;

    public XXXXXFragment(CustomViewPager vp,int fragmentID)
    {
        this.vp = vp;
        this.fragmentID =fragmentID;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        rootView = inflater.inflate(R.layout.fragment_chart_bp, container, false);
        ButterKnife.bind(this, rootView);

        vp.setObjectForPosition(rootView,fragmentID);
        return rootView;
    }

如果從服務端獲取資料，得到資料後，重新繪製Fragment，比如顯示線形圖，或者顯示資料為空的提示之類的，需要在繪製之後，重新呼叫
vp.setObjectForPosition(rootView,fragmentID);

在設定ViewPager時，如果繪製有延遲，需要延遲呼叫viewPager.resetHeight(position);

  private LinkedHashMap<String, Fragment> titleFragmentMap = new LinkedHashMap<>();
    private Fragment fragment1, fragment2, fragment3;


         fragment1 = new XXXXXFragment(viewPager,0);
        fragment2 = new XXXXXFragment(viewPager,1);
        fragment3 = new XXXXXFragment(viewPager,2);

        titleFragmentMap.put("日", fragment1);
        titleFragmentMap.put("周", fragment2);
        titleFragmentMap.put("月", fragment3);

        pagerAdapter = new MyFragmentPageAdapter(getChildFragmentManager(), titleFragmentMap);
        viewPager.setAdapter(pagerAdapter);

        viewPager.setOffscreenPageLimit(3);
        viewPager.setCurrentItem(1);

        viewPager.addOnPageChangeListener(this);

        tabLayout.setupWithViewPager(viewPager);
        tabLayout.post(new Runnable()
        {
            @Override
            public void run()
            {
                TabLayoutUtil.setUpIndicatorWidth(getContext(), tabLayout, 20, 20);
                viewPager.resetHeight(1);
            }
        });

 @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
    {
    }

    @Override
    public void onPageSelected(int position)
    {
        viewPager.resetHeight(position);

        setInitLineChart();
    }

    @Override
    public void onPageScrollStateChanged(int state)
    {

    }