android执行网络操作

本篇我们会介绍连接到网络中涉及的基本任务，监测的网络连接（包括连接更改），并给予用户控制应用程序的网络使用情况。还介绍了如何解析和使用XML数据。

这个类包含一个示例应用程序来说明如何执行常见的网络操作。您可以下载示例（在右边），并用它作为自己的应用程序源代码的可重用代码。本章的重点有三：

1.连接到网络

2.管理网络的使用

3.解析XML数据

一、连接到网络

在mainfest中声明权限，代码如下：

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

选择http客户端

大多数联网的Android应用程序使用HTTP来发送和接收数据。Android包括两个HTTP客户:HttpURLConnection HttpClient和Apache。都支持HTTPS,流媒体上传和下载,可配置的超时,IPv6,和连接池。我们建议使用HttpURLConnection目标应用程序。

检查网络连接

在你的应用程序尝试连接到网络,它应该检查是否一个网络连接可用使用getActiveNetworkInfo()和一个()。记住,这个装置可能范围的一个网络,或用户可能已经禁用wi - fi和移动数据访问。

    Java代码 
   
 public void myClickHandler(View view) {  
     ...  
     ConnectivityManager connMgr = (ConnectivityManager)   
         getSystemService(Context.CONNECTIVITY_SERVICE);  
     NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();  
     if (networkInfo != null && networkInfo.isConnected()) {  
         // fetch data  
     } else {  
         // display error  
     }  
     ...  
 }  

在单独线程中执行网络操作

网络操作可以包括不可预测的延迟。为了防止这种导致一个糟糕的用户体验,总是执行网络操作在一个单独的线程。

    Java代码 
   
 public class HttpExampleActivity extends Activity {  
     private static final String DEBUG_TAG = "HttpExample";  
     private EditText urlText;  
     private TextView textView;  
       
     @Override  
     public void onCreate(Bundle savedInstanceState) {  
         super.onCreate(savedInstanceState);  
         setContentView(R.layout.main);     
         urlText = (EditText) findViewById(R.id.myUrl);  
         textView = (TextView) findViewById(R.id.myText);  
     }  
 // When user clicks button, calls AsyncTask.  
     // Before attempting to fetch the URL, makes sure that there is a network connection.  
     public void myClickHandler(View view) {  
         // Gets the URL from the UI's text field.  
         String stringUrl = urlText.getText().toString();  
         ConnectivityManager connMgr = (ConnectivityManager)   
             getSystemService(Context.CONNECTIVITY_SERVICE);  
         NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();  
         if (networkInfo != null && networkInfo.isConnected()) {  
             new DownloadWebpageText().execute(stringUrl);  
         } else {  
             textView.setText("No network connection available.");  
         }  
     }  
 // Uses AsyncTask to create a task away from the main UI thread. This task takes a   
      // URL string and uses it to create an HttpUrlConnection. Once the connection  
      // has been established, the AsyncTask downloads the contents of the webpage as  
      // an InputStream. Finally, the InputStream is converted into a string, which is  
      // displayed in the UI by the AsyncTask's onPostExecute method.  
      private class DownloadWebpageText extends AsyncTask {  
         @Override  
         protected String doInBackground(String... urls) {  
                 
             // params comes from the execute() call: params[0] is the url.  
             try {  
                 return downloadUrl(urls[0]);  
             } catch (IOException e) {  
                 return "Unable to retrieve web page. URL may be invalid.";  
             }  
         }  
         // onPostExecute displays the results of the AsyncTask.  
         @Override  
         protected void onPostExecute(String result) {  
             textView.setText(result);  
        }  
     }  
     ...  
 }  

连接和下载数据

在你的线程执行您的网络交易,你可以使用HttpURLConnection来执行一个GET和下载数据。在您调用connect(),你可以得到一个InputStream的数据通过调用getInputStream()。

    Java代码 
   
 // Given a URL, establishes an HttpUrlConnection and retrieves  
 // the web page content as a InputStream, which it returns as  
 // a string.  
 private String downloadUrl(String myurl) throws IOException {  
     InputStream is = null;  
     // Only display the first 500 characters of the retrieved  
     // web page content.  
     int len = 500;  
           
     try {  
         URL url = new URL(myurl);  
         HttpURLConnection conn = (HttpURLConnection) url.openConnection();  
         conn.setReadTimeout(10000 /* milliseconds */);  
         conn.setConnectTimeout(15000 /* milliseconds */);  
         conn.setRequestMethod("GET");  
         conn.setDoInput(true);  
         // Starts the query  
         conn.connect();  
         int response = conn.getResponseCode();  
         Log.d(DEBUG_TAG, "The response is: " + response);  
         is = conn.getInputStream();  
 // Convert the InputStream into a string  
         String contentAsString = readIt(is, len);  
         return contentAsString;  
           
     // Makes sure that the InputStream is closed after the app is  
     // finished using it.  
     } finally {  
         if (is != null) {  
             is.close();  
         }   
     }  
 }  

getResponseCode()返回连接的状态码。这是一种有用的方式获得一些额外的信息的连接。一个200的状态代码表示成功。

转换InputStream到String

    Java代码 
   
 // Reads an InputStream and converts it to a String.  
 public String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {  
     Reader reader = null;  
     reader = new InputStreamReader(stream, "UTF-8");          
     char[] buffer = new char[len];  
     reader.read(buffer);  
     return new String(buffer);  
 }  

二、管理网络

检查设备的网络连接

一个设备可以有各种类型的网络连接。这节课的重点是使用wi - fi或手机或网络连接，这个代码片段测试网络连接wi - fi和移动。它确定这些网络接口是可用的或连接的(即网络连接是否存在,如果可以建立套接字和传递数据)

    Java代码 
   
 private static final String DEBUG_TAG = "NetworkStatusExample";  
 ...        
 ConnectivityManager connMgr = (ConnectivityManager)   
         getSystemService(Context.CONNECTIVITY_SERVICE);  
 NetworkInfo networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);   
 boolean isWifiConn = networkInfo.isConnected();  
 networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);  
 boolean isMobileConn = networkInfo.isConnected();  
 Log.d(DEBUG_TAG, "Wifi connected: " + isWifiConn);  
 Log.d(DEBUG_TAG, "Mobile connected: " + isMobileConn);  

管理网络的使用

您可以实现一个首选项活动,让用户明确控制应用程序的使用网络资源。例如: 1.你可能允许用户上传的视频只有当设备被连接到wi - fi网络。2.你可能会同步(或没有)根据特定标准如网络可用性、时间间隔,等等。

编写一个应用程序,支持网络访问和管理网络的使用,你的清单必须有正确的权限和意图过滤器。

在样例应用程序中,这个规定了SettingsActivity,将显示一个UI让用户知道何时可以进行下载操作。

    Xml代码 
   
 <?xml version="1.0" encoding="utf-8"?>  
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"  
     package="com.example.android.networkusage"  
     ...>  
 <uses-sdk android:minSdkVersion="4"   
            android:targetSdkVersion="14" />  
           
     <uses-permission android:name="android.permission.INTERNET" />  
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />  
 <application  
         ...>  
         ...  
         <activity android:label="SettingsActivity" android:name=".SettingsActivity">  
              <intent-filter>  
                 <action android:name="android.intent.action.MANAGE_NETWORK_USAGE" />  
                 <category android:name="android.intent.category.DEFAULT" />  
           </intent-filter>  
         </activity>  
     </application>  
 </manifest>  

    Java代码 
   
 public class SettingsActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener {  
       
     @Override  
     protected void onCreate(Bundle savedInstanceState) {  
         super.onCreate(savedInstanceState);  
           
         // Loads the XML preferences file  
         addPreferencesFromResource(R.xml.preferences);  
     }  
     
     @Override  
     protected void onResume() {  
         super.onResume();  
 // Registers a listener whenever a key changes              
         getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);  
     }  
     
     @Override  
     protected void onPause() {  
         super.onPause();  
 // Unregisters the listener set in onResume().  
        // It's best practice to unregister listeners when your app isn't using them to cut down on   
        // unnecessary system overhead. You do this in onPause().              
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);      
     }  
     
     // When the user changes the preferences selection,   
     // onSharedPreferenceChanged() restarts the main activity as a new  
     // task. Sets the the refreshDisplay flag to "true" to indicate that   
     // the main activity should update its display.  
     // The main activity queries the PreferenceManager to get the latest settings.  
       
     @Override  
     public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {      
         // Sets refreshDisplay to true so that when the user returns to the main  
         // activity, the display refreshes to reflect the new settings.  
         NetworkActivity.refreshDisplay = true;  
     }  
 }  

响应网络变动

如果有一个匹配发生在设置和设备的网络连接(例如,如果设置为“wi - fi”和设备有一个wi - fi连接)之间,应用程序下载提继续并刷新显示

    Java代码 
   
 public class NetworkActivity extends Activity {  
     public static final String WIFI = "Wi-Fi";  
     public static final String ANY = "Any";  
     private static final String URL = "http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest";  
      
     // Whether there is a Wi-Fi connection.  
     private static boolean wifiConnected = false;   
     // Whether there is a mobile connection.  
     private static boolean mobileConnected = false;  
     // Whether the display should be refreshed.  
     public static boolean refreshDisplay = true;  
       
     // The user's current network preference setting.  
     public static String sPref = null;  
       
     // The BroadcastReceiver that tracks network connectivity changes.  
     private NetworkReceiver receiver = new NetworkReceiver();  
       
     @Override  
     public void onCreate(Bundle savedInstanceState) {  
         super.onCreate(savedInstanceState);  
           
         // Registers BroadcastReceiver to track network connection changes.  
         IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);  
         receiver = new NetworkReceiver();  
         this.registerReceiver(receiver, filter);  
     }  
       
     @Override   
     public void onDestroy() {  
         super.onDestroy();  
         // Unregisters BroadcastReceiver when app is destroyed.  
         if (receiver != null) {  
             this.unregisterReceiver(receiver);  
         }  
     }  
       
     // Refreshes the display if the network connection and the  
     // pref settings allow it.  
       
     @Override  
     public void onStart () {  
         super.onStart();    
           
         // Gets the user's network preference settings  
         SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);  
           
         // Retrieves a string value for the preferences. The second parameter  
         // is the default value to use if a preference value is not found.  
         sPref = sharedPrefs.getString("listPref", "Wi-Fi");  
 updateConnectedFlags();   
          
         if(refreshDisplay){  
             loadPage();      
         }  
     }  
       
     // Checks the network connection and sets the wifiConnected and mobileConnected  
     // variables accordingly.   
     public void updateConnectedFlags() {  
         ConnectivityManager connMgr = (ConnectivityManager)   
                 getSystemService(Context.CONNECTIVITY_SERVICE);  
           
         NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();  
         if (activeInfo != null && activeInfo.isConnected()) {  
             wifiConnected = activeInfo.getType() == ConnectivityManager.TYPE_WIFI;  
             mobileConnected = activeInfo.getType() == ConnectivityManager.TYPE_MOBILE;  
         } else {  
             wifiConnected = false;  
             mobileConnected = false;  
         }    
     }  
         
     // Uses AsyncTask subclass to download the XML feed from stackoverflow.com.  
     public void loadPage() {  
         if (((sPref.equals(ANY)) && (wifiConnected || mobileConnected))  
                 || ((sPref.equals(WIFI)) && (wifiConnected))) {  
             // AsyncTask subclass  
             new DownloadXmlTask().execute(URL);  
         } else {  
             showErrorPage();  
         }  
     }  
 ...  
       
 }  

检测网络连接变化

    Java代码 
   
 public class NetworkReceiver extends BroadcastReceiver {     
         
 @Override  
 public void onReceive(Context context, Intent intent) {  
     ConnectivityManager conn =  (ConnectivityManager)  
         context.getSystemService(Context.CONNECTIVITY_SERVICE);  
     NetworkInfo networkInfo = conn.getActiveNetworkInfo();  
          
     // Checks the user prefs and the network connection. Based on the result, decides whether  
     // to refresh the display or keep the current display.  
     // If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection.  
     if (WIFI.equals(sPref) && networkInfo != null && networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {  
         // If device has its Wi-Fi connection, sets refreshDisplay  
         // to true. This causes the display to be refreshed when the user  
         // returns to the app.  
         refreshDisplay = true;  
         Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show();  
 // If the setting is ANY network and there is a network connection  
     // (which by process of elimination would be mobile), sets refreshDisplay to true.  
     } else if (ANY.equals(sPref) && networkInfo != null) {  
         refreshDisplay = true;  
                    
     // Otherwise, the app can't download content--either because there is no network  
     // connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there   
     // is no Wi-Fi connection.  
     // Sets refreshDisplay to false.  
     } else {  
         refreshDisplay = false;  
         Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show();  
     }  
 }  

三、解析xml

上传和解析XML数据是很常见的任务,网络连接应用程序。这一课解释了如何解析XML文档并使用他们的数据

选择转换器

我们建议XmlPullParser,这是一种高效且可维护的方式来解析XML在Android里。

分析需求

    Xml代码 
   
 <?xml version="1.0" encoding="utf-8"?>   
 <feed xmlns="http://www.w3.org/2005/Atom" xmlns:creativeCommons="http://backend.userland.com/creativeCommonsRssModule" ...">       
 <title type="text">newest questions tagged android - Stack Overflow</title>  
 ...  
     <entry>  
     ...  
     </entry>  
     <entry>  
         <id>http://stackoverflow.com/q/9439999</id>  
         <re:rank scheme="http://stackoverflow.com">0</re:rank>  
         <title type="text">Where is my data file?</title>  
         <category scheme="http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest/tags" term="android"/>  
         <category scheme="http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest/tags" term="file"/>  
         <author>  
             <name>cliff2310</name>  
             <uri>http://stackoverflow.com/users/1128925</uri>  
         </author>  
         <link rel="alternate" href="http://stackoverflow.com/questions/9439999/where-is-my-data-file" />  
         <published>2012-02-25T00:30:54Z</published>  
         <updated>2012-02-25T00:30:54Z</updated>  
         <summary type="html">  
             <p>I have an Application that requires a data file...</p>  
 </summary>  
     </entry>  
     <entry>  
     ...  
     </entry>  
 ...  
 </feed>  

实例化转化器

    Java代码 
   
 public class StackOverflowXmlParser {  
     // We don't use namespaces  
     private static final String ns = null;  
      
     public List 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 readFeed(parser);  
         } finally {  
             in.close();  
         }  
     }  
  ...   
 }  
 读取xml  
 private List readFeed(XmlPullParser parser) throws XmlPullParserException, IOException {  
     List entries = new ArrayList();  
 parser.require(XmlPullParser.START_TAG, ns, "feed");  
     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("entry")) {  
             entries.add(readEntry(parser));  
         } else {  
             skip(parser);  
         }  
     }    
     return entries;  
 }  

下面这个代码片段展示了如何解析器解析条目、标题、链接和总结：

    Java代码 
   
 public static class Entry {  
     public final String title;  
     public final String link;  
     public final String summary;  
 private Entry(String title, String summary, String link) {  
         this.title = title;  
         this.summary = summary;  
         this.link = link;  
     }  
 }  
     
 // Parses the contents of an entry. If it encounters a title, summary, or link tag, hands them off  
 // to their respective "read" methods for processing. Otherwise, skips the tag.  
 private Entry readEntry(XmlPullParser parser) throws XmlPullParserException, IOException {  
     parser.require(XmlPullParser.START_TAG, ns, "entry");  
     String title = null;  
     String summary = null;  
     String link = null;  
     while (parser.next() != XmlPullParser.END_TAG) {  
         if (parser.getEventType() != XmlPullParser.START_TAG) {  
             continue;  
         }  
         String name = parser.getName();  
         if (name.equals("title")) {  
             title = readTitle(parser);  
         } else if (name.equals("summary")) {  
             summary = readSummary(parser);  
         } else if (name.equals("link")) {  
             link = readLink(parser);  
         } else {  
             skip(parser);  
         }  
     }  
     return new Entry(title, summary, link);  
 }  
 // Processes title tags in the feed.  
 private String readTitle(XmlPullParser parser) throws IOException, XmlPullParserException {  
     parser.require(XmlPullParser.START_TAG, ns, "title");  
     String title = readText(parser);  
     parser.require(XmlPullParser.END_TAG, ns, "title");  
     return title;  
 }  
     
 // Processes link tags in the feed.  
 private String readLink(XmlPullParser parser) throws IOException, XmlPullParserException {  
     String link = "";  
     parser.require(XmlPullParser.START_TAG, ns, "link");  
     String tag = parser.getName();  
     String relType = parser.getAttributeValue(null, "rel");    
     if (tag.equals("link")) {  
         if (relType.equals("alternate")){  
             link = parser.getAttributeValue(null, "href");  
             parser.nextTag();  
         }   
     }  
     parser.require(XmlPullParser.END_TAG, ns, "link");  
     return link;  
 }  
 // Processes summary tags in the feed.  
 private String readSummary(XmlPullParser parser) throws IOException, XmlPullParserException {  
     parser.require(XmlPullParser.START_TAG, ns, "summary");  
     String summary = readText(parser);  
     parser.require(XmlPullParser.END_TAG, ns, "summary");  
     return summary;  
 }  
 // 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;  
 }  
   ...  
 }  

跳过无用的标签

    Java代码 
   
 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;  
         }  
     }  
  }  

使用xml数据

    Java代码 
   
 public class NetworkActivity extends Activity {  
     public static final String WIFI = "Wi-Fi";  
     public static final String ANY = "Any";  
     private static final String URL = "http://stackoverflow.com/feeds/tag?tagnames=android&sort=newest";  
      
     // Whether there is a Wi-Fi connection.  
     private static boolean wifiConnected = false;   
     // Whether there is a mobile connection.  
     private static boolean mobileConnected = false;  
     // Whether the display should be refreshed.  
     public static boolean refreshDisplay = true;   
     public static String sPref = null;  
 ...  
         
     // Uses AsyncTask to download the XML feed from stackoverflow.com.  
     public void loadPage() {    
         
         if((sPref.equals(ANY)) && (wifiConnected || mobileConnected)) {  
             new DownloadXmlTask().execute(URL);  
         }  
         else if ((sPref.equals(WIFI)) && (wifiConnected)) {  
             new DownloadXmlTask().execute(URL);  
         } else {  
             // show error  
         }    
     }  

动态下载xml

    Java代码 
   
 // Implementation of AsyncTask used to download XML feed from stackoverflow.com.  
 private class DownloadXmlTask extends AsyncTask<String, Void, String> {  
     @Override  
     protected String doInBackground(String... urls) {  
         try {  
             return loadXmlFromNetwork(urls[0]);  
         } catch (IOException e) {  
             return getResources().getString(R.string.connection_error);  
         } catch (XmlPullParserException e) {  
             return getResources().getString(R.string.xml_error);  
         }  
     }  
 @Override  
     protected void onPostExecute(String result) {    
         setContentView(R.layout.main);  
         // Displays the HTML string in the UI via a WebView  
         WebView myWebView = (WebView) findViewById(R.id.webview);  
         myWebView.loadData(result, "text/html", null);  
     }  
 }  

加载xml

    Java代码 
   
 // Uploads XML from stackoverflow.com, parses it, and combines it with  
 // HTML markup. Returns HTML string.  
 private String loadXmlFromNetwork(String urlString) throws XmlPullParserException, IOException {  
     InputStream stream = null;  
     // Instantiate the parser  
     StackOverflowXmlParser stackOverflowXmlParser = new StackOverflowXmlParser();  
     List<Entry> entries = null;  
     String title = null;  
     String url = null;  
     String summary = null;  
     Calendar rightNow = Calendar.getInstance();   
     DateFormat formatter = new SimpleDateFormat("MMM dd h:mmaa");  
           
     // Checks whether the user set the preference to include summary text  
     SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);  
     boolean pref = sharedPrefs.getBoolean("summaryPref", false);  
           
     StringBuilder htmlString = new StringBuilder();  
     htmlString.append("<h3>" + getResources().getString(R.string.page_title) + "</h3>");  
     htmlString.append("<em>" + getResources().getString(R.string.updated) + " " +   
             formatter.format(rightNow.getTime()) + "</em>");  
           
     try {  
         stream = downloadUrl(urlString);          
         entries = stackOverflowXmlParser.parse(stream);  
     // Makes sure that the InputStream is closed after the app is  
     // finished using it.  
     } finally {  
         if (stream != null) {  
             stream.close();  
         }   
      }  
       
     // StackOverflowXmlParser returns a List (called "entries") of Entry objects.  
     // Each Entry object represents a single post in the XML feed.  
     // This section processes the entries list to combine each entry with HTML markup.  
     // Each entry is displayed in the UI as a link that optionally includes  
     // a text summary.  
     for (Entry entry : entries) {         
         htmlString.append("<p><a href='");  
         htmlString.append(entry.link);  
         htmlString.append("'>" + entry.title + "</a></p>");  
         // If the user set the preference to include summary text,  
         // adds it to the display.  
         if (pref) {  
             htmlString.append(entry.summary);  
         }  
     }  
     return htmlString.toString();  
 }  
 // Given a string representation of a URL, sets up a connection and gets  
 // an input stream.  
 private InputStream downloadUrl(String urlString) throws IOException {  
     URL url = new URL(urlString);  
     HttpURLConnection conn = (HttpURLConnection) url.openConnection();  
     conn.setReadTimeout(10000 /* milliseconds */);  
     conn.setConnectTimeout(15000 /* milliseconds */);  
     conn.setRequestMethod("GET");  
     conn.setDoInput(true);  
     // Starts the query  
     conn.connect();  
     InputStream stream = conn.getInputStream();        
 }  

上面的片段代码为了帮助大家理解，这里还是老习惯，贴上项目的源代码，本来是有项目截图，运行效果图之类的图的，只是这篇文章太长了，再弄图片，就更占篇幅了，所以就只贴源码了，大家可以自己的运行起来看看，希望能从整体的架构和具体的代码细节上帮助到大家。