addHeaderView()异常 —— setAdapter has already been called

解决ListView添加头部视图异常

最新推荐文章于 2020-06-18 17:16:49 发布

转载最新推荐文章于 2020-06-18 17:16:49 发布 · 528 阅读

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本文探讨了在Android应用开发中，ListView组件在不同API版本下addHeaderView()方法的调用顺序问题，特别是在Android 4.3及以下版本中出现的java.lang.IllegalStateException异常。通过对比API-17与API-18的源码差异，提供了详细的解决方案。

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.youkuaiyun.com/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();  
        }  
}