pull 方式解析xml文件

关于xml的解析，网上提供了许多的解析方式；sax和pull和dom的各有优缺点；

但常用的还是pull这里我就自己理解的pull来解释；pull是基于事件触发的可以认为是流形式的；姑且认为读到一个tag或一串字符都会停顿；

1，数据结构类：

public class Book {
	private int id;
	private String name;
	private float price;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public float getPrice() {
		return price;
	}

	public void setPrice(float price) {
		this.price = price;
	}

	@Override
	public String toString() {
		return "id:" + id + ",name:" + name + ",price:" + price;
	}
}

public class PullBookParser  {

	private String TAG = "PullBookParser";
	private Context context = null;

	public PullBookParser(Context context) {
		// TODO Auto-generated constructor stub
		this.context = context;
	}
	
	public List<Book> readXml(InputStream is) throws XmlPullParserException,IOException {
		List<Book> books = null;
		Book book = null;

		XmlResourceParser parser = context.getResources().getXml(R.xml.books);

		// XmlPullParser parser = Xml.newPullParser(); //
		// 由android.util.Xml创建一个XmlPullParser实例
		// parser.setInput(is,"UTF-8"); // 设置输入流 并指明编码方式
		int eventType = parser.getEventType();
		while (eventType != XmlResourceParser.END_DOCUMENT) {//这里体现了pull的流形式，事件主要为eventtype
			switch (eventType) {
			case XmlResourceParser.START_DOCUMENT:
				books = new ArrayList<Book>();
				break;

			case XmlResourceParser.START_TAG:
				String name = parser.getName();
				if (name.equalsIgnoreCase("book")) {
					book = new Book();
					int id = Integer.parseInt(parser.getAttributeValue(null,"id"));
					book.setId(id);
				} else if (null != book) {
					if (name.equalsIgnoreCase("name")) {
						book.setName(parser.nextText());
					} else if (name.equalsIgnoreCase("price")) {
						float price = Float.parseFloat(parser.nextText());
						book.setPrice(price);
					}
				}
				break;
			case XmlPullParser.END_TAG:// 结束元素事件
				if (parser.getName().equalsIgnoreCase("book") && book != null) {
					books.add(book);
					book = null;
				}

				break;
			default:
				break;
			}
			eventType = parser.next();
		}
		return books;
	}

	@Override
	public String serialize(List<Book> books) throws Exception {
		// XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
		// XmlSerializer serializer = factory.newSerializer();

		Log.i(TAG,"laskdjf:" + books.toString());
		XmlSerializer serializer = Xml.newSerializer(); // 由android.util.Xml创建一个XmlSerializer实例
		StringWriter writer = new StringWriter();
		serializer.setOutput(writer); // 设置输出方向为writer
		serializer.startDocument("UTF-8",true);
		serializer.startTag("","books");
		for (Book book : books) {//流形式页在这里体现
			serializer.startTag("","book");
			serializer.attribute("","id",book.getId() + "");

			serializer.startTag("","name");
			serializer.text(book.getName());
			serializer.endTag("","name");

			serializer.startTag("","price");
			serializer.text(book.getPrice() + "");
			serializer.endTag("","price");

			serializer.endTag("","book");
		}
		serializer.endTag("","books");
		serializer.endDocument();

		return writer.toString();
	}

	public void writeFile(String xml) {
		try {
			Log.i(TAG,xml);
			File file = new File("books.xml");
			if (file.exists()) {
				file.delete();
			}
//			FileOutputStream fos = new FileOutputStream(file);
			FileOutputStream fos = context.openFileOutput("books.xml",Context.MODE_PRIVATE);
			fos.write(xml.getBytes("UTF-8"));
			fos.close();
		} catch (Exception e) {
			Log.e(TAG,e.getMessage());
		}
	}
}

public class MainActivity extends Activity {
	private Button readButton = null;
	private Button writeButton = null;

	private String TAG = "MainActivity";
	PullBookParser parser = null;
	List<Book> books = null;
	private Context context = this;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		readButton = (Button) findViewById(R.id.read);
		writeButton = (Button) findViewById(R.id.write);

		readButton.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				try {
					parser = new PullBookParser(context);
					books = parser.readXml(null);
					for (Book book : books) {
						Log.i(TAG,book.toString());
					}
				} catch (Exception e) {
					// Log.e(TAG,e.getMessage());
					e.printStackTrace();
				}
			}
		});

		writeButton.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {

				String xml = null;
				try {
					xml = parser.serialize(books);
					parser.writeFile(xml);
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} // 序列化

			}
		});

	}

}

4，主布局文件activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/read"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="读取xml" />

    <Button
        android:id="@+id/write"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="写入xml" />

    <Button
        android:id="@+id/update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="更新xml" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>  
<books>  
    <book id="1001">  
        <name>Thinking In Java</name>  
        <price>80.00</price>  
    </book>  
    <book id="1002">  
        <name>Core Java</name>  
        <price>90.00</price>  
    </book>  
    <book id="1003">  
        <name>Hello,Andriod</name>  
        <price>100.00</price>  
    </book>  
</books>  

（编辑：李大同）

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