android - XmlPullParser 处理多维重复元素

Question

我试图从我的 XML 中获取顶级元素的列表(包含重复的子元素)

示例 XML

<feed>
   <folder name="subfolder1">
       <file name="subfile1" />
       <file name="subfile2" />
       <folder name="subsubfolder1">
            <file name="subsubfile1" />
            <file name="subsubfile2" />
        </folder>
   </folder>
   <folder name="subfolder2">
       <file name="subfile1" />
       <file name="subfile2" />
       <folder name="subsubfolder1">
            <file name="subsubfile1" />
            <file name="subsubfile2" />
        </folder>
   </folder>
   <file name="file1"/>
</feed>

我正在尝试获取顶级元素的所有名称的列表，例如

.subfolder1
.subfolder2

这是我的 FeedReader....

private List<Entry> readFeed(XmlPullParser parser) throws XmlPullParserException, IOException {
        List<Entry> entries = new ArrayList<Entry>();

        Log.v("ab", "reed feed started");

        parser.require(XmlPullParser.START_TAG, ns, "feed");
        while (parser.next() != XmlPullParser.END_TAG) {

            if (parser.getEventType() != XmlPullParser.START_TAG) {
                continue;
            }
            String sectionName = parser.getName();

            if(sectionName.equals("folder")) {
                readFolder(parser);
            } 
        }

        return entries;
    }

private void readFolder (XmlPullParser parser) throws XmlPullParserException, IOException  {
        parser.require(XmlPullParser.START_TAG, ns, "folder");
        Log.v("ab", parser.getAttributeValue(null, "name"));
        parser.require(XmlPullParser.END_TAG, ns, "folder");
    }

这是我的 LogCat....

09-02 13:40:22.537  31736-31753/? V/ab reed feed started
09-02 13:40:22.537  31736-31753/? V/ab﹕ subfolder1

任何人都可以帮助解释为什么在找到文件夹元素的第一个实例后停止吗？

Answer 1

看起来你的最后一个 parser.require 行有问题:

parser.require(XmlPullParser.END_TAG, ns, "folder");

From the documentation,您在这里所做的是检查是否满足这些条件，如果不满足，则抛出异常。因此，您当前位于刚刚阅读的“文件夹”开始标记处，并且正在检查您是否位于“文件夹”结束标记处。由于您不在“文件夹”结束标记处，因此 parser.require 将抛出异常。

如果您删除该行，它应该让您的 while 循环继续运行，直到下一个文件夹开始标记。

编辑:这是一个完整的解决方案

我们需要一直进行到文档结尾，而不仅仅是直到任何 END_TAG，所以我将您的 while 循环修改为 while (parser.next() != XmlPullParser.END_DOCUMENT)，然后添加了一些readFolder 方法调用后的额外代码。如果我理解正确，您只是在名为“子文件夹”的文件夹之后并跳过“子子文件夹”。所以我已经包含了一个应该跳过那些的循环。我还删除了 parser.require 行，因为我个人认为没有必要，但这只是一种方法。

private List<Entry> readFeed(XmlPullParser parser) throws XmlPullParserException, IOException {
    List<Entry> entries = new ArrayList<Entry>();

    Log.v("ab", "reed feed started");

    while (parser.next() != XmlPullParser.END_DOCUMENT) {

        if (parser.getEventType() != XmlPullParser.START_TAG) {
            continue;
        }
        String sectionName = parser.getName();

        if(sectionName.equals("folder")) {
            readFolder(parser);

            //these booleans will be used to help us skip the subfolders
            boolean finishedTopLevelElement = false;
            boolean unwantedSubFolderFound = false;

            //this will loop until we are at a "folder" tag and have 
            //confirmed we have finished with the top level folder
            while (!(("folder".equals(parser.getName())) && finishedTopLevelElement)){
                parser.next();

                //we only care about 'folder' tags, for anything else
                //we keep looping
                if ("folder".equals(parser.getName())){

                    if (parser.getEventType() == XmlPullParser.START_TAG){

                        //if we hit a folder start tag, we're at a sub-folder
                        unwantedSubFolderFound = true;

                    } else if (parser.getEventType() == XmlPullParser.END_TAG && !unwantedSubFolderFound){

                        //if we hit a 'folder' end tag and we've not got an unwanted subfolder then
                        //we're done, it's the end tag of the top-level folder
                        finishedTopLevelElement = true;
                        unwantedSubFolderFound = false;

                    } else {

                        //if it's a folder end tag and we HAVE previously found an unwanted sub folder start tag
                        //then we've successfully skipped that sub-folder and can keep looking
                        unwantedSubFolderFound = false;
                    }
                }


            }
        } 
    }

    return entries;
}

private void readFolder (XmlPullParser parser) throws XmlPullParserException, IOException  {
    Log.v("ab", parser.getAttributeValue(null, "name"));
}