HttpURLConnection 用法

Android的网络通信的方式有两种：

1. Socket
2. HTTP

而其中，HTTP又包括两种编程方式：

1. HttpURLConnection
2. 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：

1. 写网址，也就是URL时，需要加上协议名，也就是"http://"
2. 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();

    }

}

 

如果在本机上开了Tomcat服务器，那么URL里的内容就可以是http://192.168.0.100:8080 

 

这样，点击按钮后，就能在文本框里显示本机里的这个URL的内容了。