下載:
如何請求數(shù)據(jù)網(wǎng)絡淮菠？
網(wǎng)絡通信，發(fā)送請求有兩種方式荤堪，GET和POST合陵；
HttpURLConnection的GET方式獲取網(wǎng)絡數(shù)據(jù)，get方式將參數(shù)放在url后一起傳遞過去澄阳，而且會被看到拥知，一般不太安全，但是get方式只獲取數(shù)據(jù)碎赢，不會更新數(shù)據(jù)低剔。
需要注意哪些點：異步獲取數(shù)據(jù)，否則會閃退肮塞；
如何下載電影襟齿，音樂，游戲（本質）
請求結果如何處理:
怎樣解析xml：xml相對于json比較耗空間枕赵，例如猜欺，對于下面一段代碼來說

<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical">

從Linearlayout開始解析，接著是跟著屬性值拆分烁设，再根據(jù)屬性值再進行拆分替梨，屬性里面等號接下來引號钓试，引號里面就是他的value
常用的數(shù)據(jù)格式json
方便的GSON等來源庫
創(chuàng)建activity_network.xml實現(xiàn)在Text中輸入網(wǎng)址點擊Button獲取數(shù)據(jù)在TextView中顯示出網(wǎng)址:

<EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="請輸入網(wǎng)址"http://hint提示装黑，光標移動上去變灰色
        android:layout_gravity="center_horizontal"/>
<Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="獲取數(shù)據(jù)"
        android:layout_gravity="center_horizontal"/>
<TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="結果"/>

獲取數(shù)據(jù)就相當于下載下來
在network.java文件中:

public class NetworkActivity extends Activity implements View.OnClickListener {
    private EditText mEditText;
    private TextView mTextView;
    private Button mButton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_network);
        findViews();
        setListeners();//點擊事件
    }
    private void setListeners() {
        mButton.setOnClickListener(this);
    }
    private void findViews() {
        mEditText = (EditText) findViewById(R.id.editText);
        mTextView = (TextView) findViewById(R.id.textView);
        mButton = (Button) findViewById(R.id.button);
    }
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                String url = getEditTextUrl();
                // 請求網(wǎng)絡數(shù)據(jù)
                // 1.申請網(wǎng)絡權限
                new RequestNetworkDataTask().execute(url);//拿到url
                break;
        }
    }
//請求數(shù)據(jù)
    private String getEditTextUrl() {
        return mEditText != null ? mEditText.getText().toString() : "";
    }
    private String requestData(String urlString) {
        try {
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setConnectTimeout(30000);//請求網(wǎng)絡超時設置，當網(wǎng)絡出現(xiàn)問題半分鐘之內沒有響應返回超時弓熏；
            connection.setRequestMethod("GET");//
  // GET POST
            connection.connect();//請求連接恋谭；
            int responseCode = connection.getResponseCode();
            String responseMessage = connection.getResponseMessage();
            String result = null;
            if(responseCode == HttpURLConnection.HTTP_OK){
                InputStream inputStream = connection.getInputStream();
                Reader reader = new InputStreamReader(inputStream, "UTF-8");
                char[] buffer = new char[1024];
                reader.read(buffer);
                result = new String(buffer);
            }
 else {
            }
            return result;
        }
 catch (MalformedURLException e) {
            e.printStackTrace();
        }
 catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
    // 異步任務處理
    class RequestNetworkDataTask extends AsyncTask<String,Integer,String>{
        // 在后臺work之前
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // 主線程
            // UI Loading
        }
        @Override
        protected String doInBackground(String[] params) {
            //
            String result = requestData(params[0]);
            return result;
        }
        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            //執(zhí)行完之后在主線程中
            mTextView.setText(result);
        }
        @Override
        protected void onCancelled() {
            super.onCancelled();
        }
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
        }
    }
}

在MainiFest中申請權限：

<uses-permission android:name="android.permission.INTERNET"/>

XML解析有三種方式
SAX：基于事件驅動的解析
一個web標簽中有四個小標簽

<?xml version="1.0" encoding="utf-8"?>
<web>
    <item id="0" url="http://www.baidu.com">百度</item>
    <item id="1" url="http://www.taobao.com">淘寶</item>
    <item id="2" url="http://www.qq.com">騰訊</item>
    <item id="3" url="http://www.geekband.com">極客班</item>
</web>

在MainActivity中寫測試命令：

private void testSAXParse() throws ParserConfigurationException, SAXException, IOException {
    SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
    SAXParser saxParser = saxParserFactory.newSAXParser();
    XMLReader xmlReader = saxParser.getXMLReader();
    SAXParseHandler saxParseHandler = new SAXParseHandler();
    xmlReader.setContentHandler(saxParseHandler);
    InputStream inputStream = getResources().openRawResource(R.raw.test);
    InputSource inputSource = new InputSource(inputStream);
    xmlReader.parse(inputSource);
    saxParseHandler.getXMLList();
    // 簡單寫法
    XMLReader xmlReaderTest = SAXParserFactory.newInstance().newSAXParser().getXMLReader();
    xmlReaderTest.setContentHandler(new SAXParseHandler());
                            // 處理xml文件的
    xmlReaderTest.parse(new InputSource(getResources().openRawResource(R.raw.test)));
  // xml文件
    // pull  xml 里面才能讀到
    XmlResourceParser xmlResourceParser = getResources().getXml(R.xml.test);
    try {
        while (xmlResourceParser.getEventType() != XmlResourceParser.END_DOCUMENT){
           if(xmlResourceParser.getEventType() == XmlResourceParser.START_TAG){
                 String tagName = xmlResourceParser.getName();
                 if(TextUtils.equals(tagName, "item")){
                     String id = xmlResourceParser.getAttributeValue(0);
                 }
           }
        }
    }
 catch (XmlPullParserException e) {
        e.printStackTrace();
    }
    // DOM
}

public class SAXParseHandler extends DefaultHandler {
    public static final String ITEM = "item";
    List<WebURL> mWebURLs;
    WebURL mWebURL;
    int type = 1;
    boolean mIsItem;
    @Override
    public void startDocument() throws SAXException {
        super.startDocument();
        mWebURLs = new ArrayList<>();
    }
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
    }
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        super.startElement(uri, localName, qName, attributes);
        mWebURL = new WebURL();
        if(TextUtils.equals(localName, ITEM)){
            for (int i = 0; i < attributes.getLength(); i++) {
                if(TextUtils.equals(attributes.getLocalName(i), "id")){                                
                 mWebURL.setID(Integer.valueOf(attributes.getValue(i)));
                }
            }
            mIsItem = true;
        }
        mIsItem = false;
    }
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        super.endElement(uri, localName, qName);
        if(TextUtils.equals(localName, ITEM)){
            mWebURLs.add(mWebURL);
        }
    }
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        super.characters(ch, start, length);
        String content = String.valueOf(ch,start,length);
        if(mIsItem){
            mWebURL.setContent(content);
            mIsItem = false;
        }
    }
    public List<WebURL> getXMLList() {
        return mWebURLs;
    }
}

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