在Android中读写外部XML文件

Question

我想学习在Android中读写XML文件（作为一种数据库）。我似乎找不到相关的信息，所以我猜我不知道该搜索什么术语。

我的目标是将两个editText字段中的用户名和密码写入文件中，然后稍后读取它们（并希望成功验证它们），当我要为应用程序创建登录功能时。

我希望读/写的文件位于服务器上，所以这对我来说有些复杂。

如果有人能帮我找到关于读/写XML文件的教程，我会非常高兴。

谢谢。

- Xantrax

Answer 1

这里是写入XML文件的代码：

final String xmlFile = "userData";
String userNAme = "username";
String password = "password";
try {
    FileOutputStream fos = new  FileOutputStream("userData.xml");
    FileOutputStream fileos= getApplicationContext().openFileOutput(xmlFile, Context.MODE_PRIVATE);
    XmlSerializer xmlSerializer = Xml.newSerializer();              
    StringWriter writer = new StringWriter();
    xmlSerializer.setOutput(writer);
    xmlSerializer.startDocument("UTF-8", true);
    xmlSerializer.startTag(null, "userData");
    xmlSerializer.startTag(null, "userName");
    xmlSerializer.text(username_String_Here);
    xmlSerializer.endTag(null, "userName");
    xmlSerializer.startTag(null,"password");
    xmlSerializer.text(password_String);
    xmlSerializer.endTag(null, "password");             
    xmlSerializer.endTag(null, "userData");
    xmlSerializer.endDocument();
    xmlSerializer.flush();
    String dataWrite = writer.toString();
    fileos.write(dataWrite.getBytes());
    fileos.close();
}
catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
catch (IllegalArgumentException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
catch (IllegalStateException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

要从XML文件中读取数据，请按以下操作：

final String xmlFile = "userData";
ArrayList<String> userData = new ArrayList<String>();
try {
    fis = getApplicationContext().openFileInput(xmlFile);
    isr = new InputStreamReader(fis);
    inputBuffer = new char[fis.available()];
    isr.read(inputBuffer);
    data = new String(inputBuffer);
    isr.close();
    fis.close();
}
catch (FileNotFoundException e3) {
    // TODO Auto-generated catch block
    e3.printStackTrace();
}
catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
XmlPullParserFactory factory = null;
try {
    factory = XmlPullParserFactory.newInstance();
}
catch (XmlPullParserException e2) {
    // TODO Auto-generated catch block
    e2.printStackTrace();
}
factory.setNamespaceAware(true);
XmlPullParser xpp = null;
try {
    xpp = factory.newPullParser();
}
catch (XmlPullParserException e2) {
    // TODO Auto-generated catch block
    e2.printStackTrace();
}
try {
    xpp.setInput(new StringReader(data));
}
catch (XmlPullParserException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}
int eventType = 0;
try {
    eventType = xpp.getEventType();
}
catch (XmlPullParserException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}
while (eventType != XmlPullParser.END_DOCUMENT){
    if (eventType == XmlPullParser.START_DOCUMENT) {
        System.out.println("Start document");
    }
    else if (eventType == XmlPullParser.START_TAG) {
        System.out.println("Start tag "+xpp.getName());
    }
    else if (eventType == XmlPullParser.END_TAG) {
        System.out.println("End tag "+xpp.getName());
    }
    else if(eventType == XmlPullParser.TEXT) {
        userData.add(xpp.getText());
    }
    try {
        eventType = xpp.next();
    }
    catch (XmlPullParserException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
String userName = userData.get(0);
String password = userData.get(1);

- Husam A. Al-ahmadi

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这段代码会创建一个名为userData的XML文件吗？如果不存在，它会在哪里被创建？ - Shaon Hasan

@ShaonHasan 这段代码不起作用。你只需要使用try块中的前两行代码的代替品，如下所示： FileOutputStream fileos = new FileOutputStream (new File("Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + "your_app_name" + "/" + "userData.xml")); - Patrick

Answer 2

要在/storage/sdcard0/your_app_name/中创建新文件，请使用以下方法：

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + "your_app_name" + "/" + xmlFile);
        file.createNewFile();
        FileOutputStream fileos = new FileOutputStream(file);

- Marek Suma

Answer 3

public class SkillsParser implements AssyncXmlReader {

    private String ns = "";
    @Override
    public Object parse(InputStream in) throws XmlPullParserException,
            IOException {
        try {
            XmlPullParser parser = Xml.newPullParser();
            parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
            parser.setInput(in, null);
            parser.nextTag();
            return readSkills(parser);
        } finally {
            in.close();
        }
    }

    private Object readSkills(XmlPullParser parser) throws XmlPullParserException, IOException {
        parser.require(XmlPullParser.START_TAG, ns, "skills");
        List<ESkill> skills = new ArrayList<ESkill>();
        
        while (parser.next() != XmlPullParser.END_TAG) {
            if (parser.getEventType() != XmlPullParser.START_TAG) {
                continue;
            }
            String name = parser.getName();
            // Starts by looking for the entry tag
            if (name.equals("skill")) {
                skills.add(readSkill(parser));
            } else {
                skip(parser);
            }
        }  
        return skills;
    }
    
    private ESkill readSkill(XmlPullParser parser) throws XmlPullParserException, IOException {
        /*
        <skill>
            <name>Software Engineering</name>
        
        </skill>
        */
        String skill_name = "";
        
        while (parser.next() != XmlPullParser.END_TAG) {
            if (parser.getEventType() != XmlPullParser.START_TAG) {
                continue;
            }
            String name = parser.getName();
            if ("name".equals(name)) {
                skill_name = readName(parser);
            } else {
                skip(parser);
            }
        }
        
        return new ESkill().setSkill(skill_name);
    }
    
    // Processes title tags in the feed.
    private String readName(XmlPullParser parser) throws IOException, XmlPullParserException {
        parser.require(XmlPullParser.START_TAG, ns, "name");
        String description = readText(parser);
        parser.require(XmlPullParser.END_TAG, ns, "name");
        return description;
    }
    
    // For the tags title and summary, extracts their text values.
    private String readText(XmlPullParser parser) throws IOException, XmlPullParserException {
        String result = "";
        if (parser.next() == XmlPullParser.TEXT) {
            result = parser.getText();
            parser.nextTag();
        }
        return result;
    }
    
    private void skip(XmlPullParser parser) throws XmlPullParserException, IOException {
        if (parser.getEventType() != XmlPullParser.START_TAG) {
            throw new IllegalStateException();
        }
        int depth = 1;
        while (depth != 0) {
            switch (parser.next()) {
            case XmlPullParser.END_TAG:
                depth--;
                break;
            case XmlPullParser.START_TAG:
                depth++;
                break;
            }
        }
     }
}

- hervinhio

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添加一些关于您所更改的描述 - Abdulla Nilam