11.Android-Xml读写

android中写XML时,需要用到XmlSerializer类

解析XML时,则需要用到XmlPullParser类

1.XmlSerializer类介绍

通过Xml.newSerializer()来获取XmlSerializer

XmlSerializer常用方法如下所示:

void setOutput(OutputStream os, String encoding);
//设置要写入的XML的文件位置,以及encoding编码格式
//比如:
 //File file = new File(Environment.getExternalStorageDirectory(), "text.xml"); //xmlSerializer.setOutput(new fileOutputStream(file), "utf-8");

void startDocument(String encoding, Boolean standalone);
//设置文档开头描述,比如:" <?xml version="1.0" encoding="utf-8" standalone="yes"?>"
// standalone:表示该XML是否是独立的,默认为true,如果填为false,则表示该XML被外部文件DTD约束

startTag(String namespace, String name);
//写入开始元素标签

endTag(String namespace, String name);
//写入结束元素标签

attribute(String namespace, String name, String value);
//往元素标签里写属性(name="value"),比如<name id="123">
text(String text);
//往元素里添加内容,比如: <name id="123">张三</name>

示例代码如下:

private void writePersonXml(){

        XmlSerializer serializer = Xml.newSerializer();

        try {
            serializer.setOutput(openFileOutput("persons.xml", MODE_PRIVATE), "utf-8");
            serializer.startDocument("utf-8", true);

            serializer.startTag(null,"persons");

            //创建两个成员
            serializer.startTag(null,"person");
            serializer.attribute(null, "id", "");    //添加编号

            serializer.startTag(null,"姓名");
            serializer.text("张三");
            serializer.endTag(null,"姓名");

            serializer.startTag(null,"age");
            serializer.text("");
            serializer.endTag(null,"age");

            serializer.endTag(null,"person");

            serializer.startTag(null,"person");
            serializer.attribute(null, "id", ""); //添加编号

            serializer.startTag(null,"姓名");
            serializer.text("李四");
            serializer.endTag(null,"姓名");

            serializer.startTag(null,"age");
            serializer.text("");
            serializer.endTag(null,"age");

            serializer.endTag(null,"person");

            serializer.endTag(null,"persons");
            serializer.endDocument();            //结束文档,并将内容写入文件

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

 }

运行后,生成persons.xml:

接下来,我们便通过XmlPullParser来解析persons.xml

2.XmlPullParser介绍

通过Xml. newPullParser()来获取XmlPullParser;

XmlPullParser常用方法如下:

void setInput(InputStream inputStream, String inputEncoding);
//设置要解析的文件以及编码

int getEventType();
//获取当前事件类型,返回的类型有START_DOCUMENT(文档开头)、START_TAG (元素开头)、END_TAG(元素结束)、TEXT (内容)、 END_DOCUMENT(文档结束)

int next();
//获取下个事件类型. 返回的类型和getEventType()一样.

getName();             //获取当前元素名

getTextCharacters();  //获取当前内容(当getEventType ()==TEXT时通过这个来获取元素内容)

nextText();       //获取下个内容(当getEventType ()==START_TAG时通过这个来获取元素内容)

示例代码如下:

   private void parsePersonsXml(){

        XmlPullParser pullParser = Xml.newPullParser();

        try {
            pullParser.setInput(this.openFileInput("persons.xml"), "utf-8");
            String name = null;
            String age = null;
            String id = null;

            int eventType = pullParser.getEventType();

            while(eventType!=pullParser.END_DOCUMENT)
            {
                switch (eventType) {
                case XmlPullParser.START_TAG:

                    if("person".equals( pullParser.getName())){

                        id =  pullParser.getAttributeValue(null, "id");       //获取编号,并初始化内容
                        name =null;
                        age = null;

                    }else if("姓名".equals(pullParser.getName())){

                        name =  pullParser.nextText();    //获取姓名

                    }else if("age".equals(pullParser.getName())){

                        age =  pullParser.nextText();    //获取年龄

                    }
                    break;

                case XmlPullParser.END_TAG:

                    if("person".equals( pullParser.getName())){        

                        System.out.println("person : id="+id+" 姓名="+name+" 年龄="+age); //打印信息

                    }

                    break;
                }

                eventType = pullParser.next();
            }

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 

 }

运行打印: