Android 創建與解析XML（四）――詳解Pull方式

2019-12-12 04:28:33

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1、Pull概述

Android系統中和創建XML相關的包為org.xmlpull.v1，在這個包中不僅提供了用于創建XML的 XmlSerializer，還提供了用來解析XML的Pull方式解析器 XmlPullParser

XmlSerializer沒有像XmlPullParser那樣提取XML事件，而是把它們推出到數據流OutputStream或Writer中。

XmlSerializer提供了很直觀的API，即使用startDocument開始文檔，endDocument結束文檔，startTag開始元素，endTag結束元素，text添加文本等。

Pull方式創建XML，應用了標準xml構造器 org.xmlpull.v1.XmlSerializer來創建 XML ，org.xmlpull.v1.XmlPullParser來解析XML，需要導入以下內容

org.xmlpull.v1

org.xmlpull.v1.XmlPullParser;
org.xmlpull.v1.XmlPullParserException;
org.xmlpull.v1.XmlPullParserFactory;
org.xmlpull.v1.XmlSerializer;

Pull 創建和解析 XML 的效果圖：

2、Pull 創建 XML

pull方式，創建xml是通過 XmlSerializer 類實現

首先，通過XmlSerializer得到創建xml的實例 xmlSerializer

接著，通過 xmlSerializer 設置輸出 xmlSerializer.setOutput，xmlSerializer.startDocument("utf-8", null)設置xml屬性等

然后，通過 xmlSerializer 創建 startDocument、startTag、text、endTag、endDocument等

 /** Pull方式，創建 XML */   public String pullXMLCreate(){     StringWriter xmlWriter = new StringWriter();      Person []persons = new Person[3];    // 創建節點Person對象     persons[0] = new Person(1, "sunboy_2050", "http://blogcsdnnet/sunboy_2050");     persons[1] = new Person(2, "baidu", "http://wwwbaiducom");     persons[2] = new Person(3, "google", "http://wwwgooglecom");          try { //     // 方式一：使用Android提供的實用工具類androidutilXml //     XmlSerializer xmlSerializer = XmlnewSerializer();                 // 方式二：使用工廠類XmlPullParserFactory的方式       XmlPullParserFactory factory = XmlPullParserFactorynewInstance();       XmlSerializer xmlSerializer = factorynewSerializer();              xmlSerializersetOutput(xmlWriter);       // 保存創建的xml              xmlSerializersetFeature("http://xmlpullorg/v1/doc/featureshtml#indent-output", true); //     xmlSerializersetProperty("http://xmlpullorg/v1/doc/propertieshtml#serializer-indentation", " ");     // 設置屬性 //     xmlSerializersetProperty("http://xmlpullorg/v1/doc/propertieshtml#serializer-line-separator", "/n");       xmlSerializerstartDocument("utf-8", null);   // <?xml version='0' encoding='UTF-8' standalone='yes' ?>               xmlSerializerstartTag("", "root");       xmlSerializerattribute("", "author", "homer");       xmlSerializerattribute("", "date", "2012-04-28");              int personsLen = personslength;       for(int i=0; i<personsLen; i++) {         xmlSerializerstartTag("", "person");    // 創建person節點                  xmlSerializerstartTag("", "id");         xmlSerializertext(persons[i]getId()+"");         xmlSerializerendTag("", "id");          xmlSerializerstartTag("", "name");         xmlSerializertext(persons[i]getName());         xmlSerializerendTag("", "name");          xmlSerializerstartTag("", "blog");         xmlSerializertext(persons[i]getBlog());         xmlSerializerendTag("", "blog");                  xmlSerializerendTag("", "person");       }              xmlSerializerendTag("", "root");       xmlSerializerendDocument();            } catch (XmlPullParserException e) {    // XmlPullParserFactorynewInstance       eprintStackTrace();     } catch (IllegalArgumentException e) {   // xmlSerializersetOutput       eprintStackTrace();     } catch (IllegalStateException e) {     // xmlSerializersetOutput       eprintStackTrace();     } catch (IOException e) {    // xmlSerializersetOutput       eprintStackTrace();     } catch (Exception e) {       eprintStackTrace();     }          savedXML(fileName, xmlWritertoString());     return xmlWritertoString();   }

運行結果：

3、Pull 解析 XML

pull方式，解析xml是通過 XmlPullParser 類實現

首先，通過XmlPullParser得到解析xml的實例 xpp

接著，通過 xpp設置輸入 xpp.setInput(is, "utf-8")，聲明定義保存xml信息的數據結構（如：Person數組）

然后，通過 xpp 解析 START_DOCUMENT、START_TAG、TEXT、END_TAG、END_DOCUMENT等

 /** Pull方式，解析 XML */   public String pullXMLResolve(){     StringWriter xmlWriter = new StringWriter();          InputStream is = readXML(fileName);     try { //     // 方式一：使用Android提供的實用工具類androidutilXml //     XmlPullParser xpp = XmlnewPullParser();              // 方式二：使用工廠類XmlPullParserFactory的方式       XmlPullParserFactory factory = XmlPullParserFactorynewInstance();       XmlPullParser xpp = factorynewPullParser();              xppsetInput(is, "utf-8");              List<Person> personsList = null;   // 保存xml的person節點       Person person = null;       StringBuffer xmlHeader = null;     // 保存xml頭部       String ele = null;   // Element flag              int eventType = xppgetEventType();       while(XmlPullParserEND_DOCUMENT != eventType) {         switch (eventType) {         case XmlPullParserSTART_DOCUMENT:           personsList = new ArrayList<Person>();    // 初始化persons           xmlHeader = new StringBuffer();       // 初始化xmlHeader           break;                    case XmlPullParserSTART_TAG:           if("root"equals(xppgetName())) {             String attrAuthor = xppgetAttributeValue(0);             String attrDate = xppgetAttributeValue(1);             xmlHeaderappend("root")append("/t/t");             xmlHeaderappend(attrAuthor)append("/t");             xmlHeaderappend(attrDate)append("/n");           } else if("person"equals(xppgetName())) {             person = new Person();     // 創建person實例           } else if("id"equals(xppgetName())) {             ele = "id";           } else if("name"equals(xppgetName())) {             ele = "name";           } else if("blog"equals(xppgetName())) {             ele = "blog";           } else {             ele = null;           }           break;                    case XmlPullParserTEXT:           if(null != ele) {             if("id"equals(ele)) {               personsetId(IntegerparseInt(xppgetText()));             } else if("name"equals(ele)) {               personsetName(xppgetText());             } else if("blog"equals(ele)) {               personsetBlog(xppgetText());             }           }           break;                    case XmlPullParserEND_TAG:           if("person"equals(xppgetName())){             personsListadd(person);             person = null;           }           ele = null;           break;         }                  eventType = xppnext();   // 下一個事件類型       }              xmlWriterappend(xmlHeader);       int personsLen = personsListsize();       for(int i=0; i<personsLen; i++) {         xmlWriterappend(personsListget(i)toString());       }            } catch (XmlPullParserException e) {    // XmlPullParserFactorynewInstance       eprintStackTrace();     } catch (Exception e) {       eprintStackTrace();     }          return xmlWritertoString();       }

運行結果：