addHeaderView()异常 —— setAdapter has already been called
【摘要】
异常提示：java.lang.IllegalStateException: Cannot add header view to list -- setAdapter has already been called.
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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。
文章来源: wukong.blog.csdn.net，作者：再见孙悟空_，版权归原作者所有，如需转载，请联系作者。
原文链接：wukong.blog.csdn.net/article/details/50385912
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