addHeaderView()异常 —— setAdapter has already been called

本博文为转载，由于找不到第一作者所以只能留下我转自的地址：
http://blog.csdn.net/shaoyezhangliwei/article/details/50385912

异常提示：java.lang.IllegalStateException: Cannot add header view to list – setAdapter has already been called.
产生原因：addHeaderView()调用在setAdapter()之后，并且该代码运行在Android4.3之前的系统版本。Android SDK与API Level对应表

我们来看看（Android4.3）API-18 和 （Android4.2）API-17的Listview代码片段：

API-18

public void addHeaderView(View v, Object data, boolean isSelectable) { final FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = data; info.isSelectable = isSelectable; mHeaderViewInfos.add(info); // Wrap the adapter if it wasn't already wrapped. if (mAdapter != null) { if (!(mAdapter instanceof HeaderViewListAdapter)) { mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter); } // In the case of re-adding a header view, or adding one later on, // we need to notify the observer. if (mDataSetObserver != null) { mDataSetObserver.onChanged(); } } }

API-17

public void addHeaderView(View v, Object data, boolean isSelectable) { if (mAdapter != null && ! (mAdapter instanceof HeaderViewListAdapter)) { throw new IllegalStateException( "Cannot add header view to list -- setAdapter has already been called."); } FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = data; info.isSelectable = isSelectable; mHeaderViewInfos.add(info); // in the case of re-adding a header view, or adding one later on, // we need to notify the observer if (mAdapter != null && mDataSetObserver != null) { mDataSetObserver.onChanged(); } }

在API-17中，假如adapter不为空，则会直接抛出异常，而在API-18中则做了相关的优化。

建议

木有建设性的提议，只能提醒大家，目前市面上主流的Android系统还是Android4.3以下版本，所以在使用addHeaderView()要注意这一点。

转载于:https://www.cnblogs.com/codenoodles/p/6421165.html

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