HttpURLConnection 用法

浏览数：57 / 时间：2015年06月09日

Android的网络通信的方式有两种：

Socket
HTTP

而其中，HTTP又包括两种编程方式：

HttpURLConnection
HttpClient

这篇文章介绍的就是，HttpURLConnection

首先，当然是创建HttpURLConnection的对象

URL url = new URL("www.baidu.com");  
HttpURLConnection connection=(HttpURLConnection)url.openConnection();  

第二步是设置，其中最重要的就是 GET or POST？（GET是从服务器读取数据，POST是提交数据给服务器）

connection.setRequestMethod("GET");

connection.setConnectTimeout(8000);//连接超时

connection.setReadTimeout(8000);//读取超时

接着，就可以从connection中获取数据了

InputStream in = connection.getInputStream();

最后需要关闭连接

connection.disconnect();

例子

要访问网络，所以需要在清单文件里添加权限：

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

MainActivity.java

public class MainActivity extends Activity implements OnClickListener {
 
    private Button sendRequest;
    private TextView responseText;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        sendRequest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response);
        sendRequest.setOnClickListener(this);
    }
 
    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if (v.getId() == R.id.send_request) {
            sendRequestWithHttpURLConnection();
        }
    }
 
    private void sendRequestWithHttpURLConnection() {
        new Thread(new Runnable() {
 
            @Override
            public void run() {
                // TODO Auto-generated method stub
                HttpURLConnection connection = null;
                try {
                    URL url = new URL("www.baidu.com");
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    connection.setRequestMethod("GET");
                    String line = null;
                    StringBuilder response = new StringBuilder();
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(
                            new InputStreamReader(in));
                    while ((line = reader.readLine()) != null) {
                        response.append(line);
                        Log.e("MainActivity", line);
                    }
                    responseText.setText(response.toString());
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (connection != null)
                        connection.disconnect();
                }
            }
        }).start();
    }
}

上面代码的逻辑很简单，就是：点击“发送”按钮，从百度首页获取数据，并显示在文本框里。

但这里有两个问题需要注意：

写网址，也就是URL时，需要加上协议名，也就是"http://"
上面的代码如果真的运行，文本框里是不会显示任何内容的，因为子线程中无法对 UI 进行操作

第一个问题容易解决，加上http://就行了。

而第二个问题，解决的办法是：创建一个Message对象，使用Handler把它发送出去，在Handler的方法里来处理这条Message。

修改后的代码

 
public class MainActivity extends Activity implements OnClickListener {
 
    private Button sendRequest;
    private TextView responseText;
 
    public static final int SHOW_RESPONSE = 0;
    private Handler handler = new Handler(){
        public void handleMessage(Message msg){
            switch (msg.what) {
            case SHOW_RESPONSE:
                String response = (String)msg.obj;
                responseText.setText(response);
                break;
 
            default:
                break;
            }
        }
    };
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        sendRequest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response);
        sendRequest.setOnClickListener(this);
    }
 
    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if (v.getId() == R.id.send_request) {
            sendRequestWithHttpURLConnection();
        }
    }
 
    private void sendRequestWithHttpURLConnection() {
        new Thread(new Runnable() {
 
            @Override
            public void run() {
                // TODO Auto-generated method stub
                HttpURLConnection connection = null;
                try {
                    URL url = new URL("http://www.baidu.com");
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    connection.setRequestMethod("GET");
                    String line = null;
                    StringBuilder response = new StringBuilder();
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(
                            new InputStreamReader(in));
                    while ((line = reader.readLine()) != null) {
                        response.append(line);
                        Log.e("MainActivity", line);
                    }
                    Message message = new Message();
                    message.what = SHOW_RESPONSE;
                    message.obj = response.toString();
                    handler.sendMessage(message);
                    
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (connection != null)
                        connection.disconnect();
                }
            }
        }).start();
    }
}