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解析XML XmlPullParser android[英] Parsing XML XmlPullParser android

 

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问题描述

我在 android 中使用 xmlpullparser 来解析一个如下所示的 xml 文档:

<top>
  <category>
    <name></name>
    <desc></desc>
    <songs>
      <song>
        <clip></clip>
        <thumb></thumb>
      </song>
      <song>
        <clip></clip>
        <thumb></thumb>
      </song>
    </songs>
  </category>
</top>

我试过这个:

while (eventType != XmlPullParser.END_DOCUMENT && !done){
                String name = null;
                switch (eventType){
                    case XmlPullParser.START_DOCUMENT:
                        categoriesSong = new ArrayList<TopMousika>();
                        break;
                    case XmlPullParser.START_TAG:
                        name = parser.getName();
                        if (name.equalsIgnoreCase(CATEGORY)){
                            currentCategory = new TopMousika();
                            currentCategory.setId(parser.getAttributeValue(0));
                            currentCategory.setId(parser.getAttributeValue(1));
                        } else if (currentCategory != null){
                            if (name.equalsIgnoreCase(NAME)){
                                currentCategory.setName(parser.nextText());
                            } else if (name.equalsIgnoreCase(DESCRIPTION)){
                                currentCategory.setDescription(parser.nextText());
                            } else if (name.equalsIgnoreCase(THUMBNAIL)){
                                currentCategory.setThumbnail(parser.nextText());
                            } else if (name.equalsIgnoreCase(SONGS)){
                                songs = new ArrayList<SongMousika>();
                                if(name.equalsIgnoreCase(SONG)){
                                    currentSong = new SongMousika();
                                    currentSong.setId(parser.getAttributeValue(0));
                                    Log.d("TEST", "OK");
                                    songs.add(currentSong);
                                } else if (name.equalsIgnoreCase(TITLE)){
                                    Log.d("TEST", "OK2");
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(SINGER)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(THUMBNAIL)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(PUBLICATION_DATE)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(CLIP)){
                                    currentSong.setTitle(parser.nextText());
                                }
                                currentCategory.setSongs(songs);
                            }
                        }
                        break;
                    case XmlPullParser.END_TAG:
                        name = parser.getName();
                        if (name.equalsIgnoreCase(CATEGORY) && 
currentCategory != null){
                            currentCategory.setSongs(songs);
                            categoriesSong.add(currentCategory);
                        } else if (name.equalsIgnoreCase(TOP)){
                            done = true;
                        }
                        break;
                }
                eventType = parser.next();
            }

但我无法检索我的歌曲列表.

有人可以帮我吗?

推荐答案

你似乎期待 name 在检查之间神奇地改变:

if (name.equalsIgnoreCase(SONGS)) {
    songs = new ArrayList<SongMousika>();
    if(name.equalsIgnoreCase(SONG)) {

SONG 和 SONGS会怎样?您需要不断提取 XML 并对循环中的每个元素名称做出不同的反应.因此，在对 START_TAG 事件作出反应时，您可能会有一堆没有任何嵌套的 if/else if 语句.(顺便说一下，很可能值得将其处理到一个单独的方法中.)

编辑:好的，所以你需要让循环的每次迭代只对一个标签做出反应.因此，您对开始标记的处理类似于:

case XmlPullParser.START_TAG:
    name = parser.getName();
    if (name.equalsIgnoreCase(CATEGORY)){
        currentCategory = new TopMousika();
        currentCategory.setId(parser.getAttributeValue(0));
        currentCategory.setId(parser.getAttributeValue(1));
    } else if (currentCategory != null) {
        if (name.equalsIgnoreCase(NAME)){
            currentCategory.setName(parser.nextText());
        } else if (name.equalsIgnoreCase(DESCRIPTION)){
            currentCategory.setDescription(parser.nextText());
        } else if (name.equalsIgnoreCase(THUMBNAIL)){
            currentCategory.setThumbnail(parser.nextText());
        } else if (name.equalsIgnoreCase(SONGS)){
            songs = new ArrayList<SongMousika>();
        } else if (songs != null) {
            if(name.equalsIgnoreCase(SONG)) {
                currentSong = new SongMousika();
                currentSong.setId(parser.getAttributeValue(0));
                Log.d("TEST", "OK");
                songs.add(currentSong);
            } else if (currentSong != null) {
                 else if (name.equalsIgnoreCase(TITLE)) {
                    Log.d("TEST", "OK2");
                    currentSong.setTitle(parser.nextText());
                } else if (name.equalsIgnoreCase(SINGER)){
                    currentSong.setSinger(parser.nextText());
                } else if (name.equalsIgnoreCase(THUMBNAIL))
                    // etc
                }
            }
        }

请注意，在通过那里的任何路径中，我们从不检查 name 是否具有多个值 - 我们说:

  • 我们是否要开设一个新类别?
    • 如果是，请创建并记住它 - 然后继续下一次迭代.
    • 如果没有(如果我们有一个类别)，我们是否要开始一个新的歌曲列表?
    • 如果是，请创建并记住它 - 然后继续下一次迭代.
    • 如果没有(如果我们有歌曲列表)，我们是否要开始一首新歌?
      • 如果是，请创建并记住它 - 然后继续下一次迭代.
      • 如果没有(如果我们有一首歌)...
      • 我们在读标题吗?如果是这样，请阅读文本并进行设置，然后继续.
      • 我们在读歌手吗?如果是这样，请阅读文本并进行设置，然后继续.
      • 我们正在阅读缩略图吗?如果是这样，请阅读文本并进行设置，然后继续.
      • 等

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问题描述

i'm using xmlpullparser in android to parse an xml document that looks like : 

<top>
  <category>
    <name></name>
    <desc></desc>
    <songs>
      <song>
        <clip></clip>
        <thumb></thumb>
      </song>
      <song>
        <clip></clip>
        <thumb></thumb>
      </song>
    </songs>
  </category>
</top>

I tried this : 

while (eventType != XmlPullParser.END_DOCUMENT && !done){
                String name = null;
                switch (eventType){
                    case XmlPullParser.START_DOCUMENT:
                        categoriesSong = new ArrayList<TopMousika>();
                        break;
                    case XmlPullParser.START_TAG:
                        name = parser.getName();
                        if (name.equalsIgnoreCase(CATEGORY)){
                            currentCategory = new TopMousika();
                            currentCategory.setId(parser.getAttributeValue(0));
                            currentCategory.setId(parser.getAttributeValue(1));
                        } else if (currentCategory != null){
                            if (name.equalsIgnoreCase(NAME)){
                                currentCategory.setName(parser.nextText());
                            } else if (name.equalsIgnoreCase(DESCRIPTION)){
                                currentCategory.setDescription(parser.nextText());
                            } else if (name.equalsIgnoreCase(THUMBNAIL)){
                                currentCategory.setThumbnail(parser.nextText());
                            } else if (name.equalsIgnoreCase(SONGS)){
                                songs = new ArrayList<SongMousika>();
                                if(name.equalsIgnoreCase(SONG)){
                                    currentSong = new SongMousika();
                                    currentSong.setId(parser.getAttributeValue(0));
                                    Log.d("TEST", "OK");
                                    songs.add(currentSong);
                                } else if (name.equalsIgnoreCase(TITLE)){
                                    Log.d("TEST", "OK2");
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(SINGER)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(THUMBNAIL)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(PUBLICATION_DATE)){
                                    currentSong.setTitle(parser.nextText());
                                } else if (name.equalsIgnoreCase(CLIP)){
                                    currentSong.setTitle(parser.nextText());
                                }
                                currentCategory.setSongs(songs);
                            }
                        }
                        break;
                    case XmlPullParser.END_TAG:
                        name = parser.getName();
                        if (name.equalsIgnoreCase(CATEGORY) && 
currentCategory != null){
                            currentCategory.setSongs(songs);
                            categoriesSong.add(currentCategory);
                        } else if (name.equalsIgnoreCase(TOP)){
                            done = true;
                        }
                        break;
                }
                eventType = parser.next();
            }

but I can not retrieve my Songs List.

can any one help me please ?

推荐答案

You seem to be expecting name to change magically between checks:

if (name.equalsIgnoreCase(SONGS)) {
    songs = new ArrayList<SongMousika>();
    if(name.equalsIgnoreCase(SONG)) {

How is it going to be SONG and SONGS? You need to keep pulling XML and react to each element name differently in the loop. So you'll probably have a bunch of if/else if statements without any nesting when reacting to a START_TAG event. (It's very likely to be worth pulling the handling of that into a separate method, by the way.)

EDIT: Okay, so you need to make each iteration of the loop just react to one tag. So your handling for a start tag would be something like:

case XmlPullParser.START_TAG:
    name = parser.getName();
    if (name.equalsIgnoreCase(CATEGORY)){
        currentCategory = new TopMousika();
        currentCategory.setId(parser.getAttributeValue(0));
        currentCategory.setId(parser.getAttributeValue(1));
    } else if (currentCategory != null) {
        if (name.equalsIgnoreCase(NAME)){
            currentCategory.setName(parser.nextText());
        } else if (name.equalsIgnoreCase(DESCRIPTION)){
            currentCategory.setDescription(parser.nextText());
        } else if (name.equalsIgnoreCase(THUMBNAIL)){
            currentCategory.setThumbnail(parser.nextText());
        } else if (name.equalsIgnoreCase(SONGS)){
            songs = new ArrayList<SongMousika>();
        } else if (songs != null) {
            if(name.equalsIgnoreCase(SONG)) {
                currentSong = new SongMousika();
                currentSong.setId(parser.getAttributeValue(0));
                Log.d("TEST", "OK");
                songs.add(currentSong);
            } else if (currentSong != null) {
                 else if (name.equalsIgnoreCase(TITLE)) {
                    Log.d("TEST", "OK2");
                    currentSong.setTitle(parser.nextText());
                } else if (name.equalsIgnoreCase(SINGER)){
                    currentSong.setSinger(parser.nextText());
                } else if (name.equalsIgnoreCase(THUMBNAIL))
                    // etc
                }
            }
        }

Note how in any path through there we never check for name having multiple values - we say:

  • Are we starting a new category?
    • If so, create it and remember it - then continue with the next iteration.
    • If not (and if we've got a category), are we starting a new song list?
    • If so, create it and remember it - then continue with the next iteration.
    • If not (and if we've got a song list), are we starting a new song?
      • If so, create it and remember it - then continue with the next iteration.
      • If not (and if we've got a song)...
      • Are we reading the title? If so, read the text and set it, then continue.
      • Are we reading the singer? If so, read the text and set it, then continue.
      • Are we reading the thumbnail? If so, read the text and set it, then continue.
      • etc
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