前言

很多情況我們需要用到ListView的addHeaderView(View v)以及addFooterView(View v)以滿足我們的需求。比如我們專案中的情況：ListView上面需要顯示一個迴圈的廣告輪播圖，我們是使用了自定義的一個控制元件Loopbanner來顯示輪播圖，使用的listview.addHeaderView(loopbanner);來新增到ListView的頭部這樣就可以不用巢狀ScrollView。但是又有一個新的需求，就是假如廣告圖片沒有資料的時候將廣告位隱藏掉。本來我想的挺開心，直接loopbanner.setVisibility(View.GONE);不久可以了嘛，但是試了一下，loopbanner倒是隱藏掉了，但是還是它佔據一定的空間還是保留著，空蕩蕩的一片

找方案

在網上找了一個方法就是先隱藏然後，設定padding，
隱藏時

loopBanner.setVisibility(View.VISIBLE);
this.loopBanner.setPadding(0, -loopBanner.getHeight(), 0, 0)

需要顯示時

 loopBanner.setVisibility(View.GONE);
 this.loopBanner.setPadding(0, 0, 0, 0);

這種方案，確實有了效果，去除了空蕩蕩的一篇片，但是在我們的專案中出了狀況，就是使用者先下拉重新整理幾次，然後上滑，就忽然崩潰，報的錯誤是：

Process
 
: com.test, PID: 20067
    java.lang.NullPointerException: Attempt to invoke virtual method 'com.test.base.adapter.ViewHolder com.test.base.adapter.ViewHolder.setViewGone(int)' on a null object reference

    at com.test.adapter.CPostAdapter.convert(CPostAdapter.java:63)
    at com.test.adapter.CPostAdapter
 
.convert(CPostAdapter.java:33)
    at com.test.base.adapter.UniversalAdapter.getView(UniversalAdapter.java:53)
    at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:220)
    at android.widget.AbsListView.obtainView(AbsListView.java:2346)
    at android.widget.ListView.makeAndAddView(ListView.java:1876)
    at android.widget.ListView.fillDown(ListView.java:702)
    at android.widget.ListView.fillGap(ListView.java:666)
    at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5106)
    at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3463)
    at android.widget.AbsListView.onTouchMove(AbsListView.java:3878)
    at android.widget.AbsListView.onTouchEvent(AbsListView.java:3691)
    at android.view.View.dispatchTouchEvent(View.java:9306)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2548)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2241)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at cn.bingoogolapple.refreshlayout.BGARefreshLayout.dispatchTouchEvent(BGARefreshLayout.java:425)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2554)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2255)
    at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2403)
    at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1737)
    at android.app.Activity.dispatchTouchEvent(Activity.java:2820)
    at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2364)
    at android.view.View.dispatchPointerEvent(View.java:9526)
    at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4255)
    at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4121)
    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3662)
    at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3715)
    at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3681)
    at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3807)
    at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3689)
    at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3864)
    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java

這個錯誤挺奇怪的，holder報空，以前應該從來沒遇到過，我們的baseAdapter也是經多多次檢驗與改良應該沒什麼問題，但是有一點可以確定，就是我改了隱藏headerView之後才出現的這個錯誤的，所以我就又尋找了一個方案

最終方案

就是給LoopBanner外加了一層FrameLayout，使用frameLayout.removeAllViews和addView確定顯示以及不顯示，目前還未遇到holder報空的情況

FrameLayout frameLayout = new FrameLayout(this);
listView.addFooterView(frameLayout);
......
......
//For adding footerView
frameLayout.removeAllViews();
frameLayout.addView(mFooterView);
//For hide FooterView
frameLayout.removeAllViews();