Android使用HttpClient方法和易错问题

HttpClient为Android开发人员提供了跟简洁的操作Http网络连接的方法，在连接过程中也有两种方式，get和post，先看一下怎样实现的

默认是get方式

//先将參数放入List，再对參数进行URL编码  
List<BasicNameValuePair> params = new LinkedList<BasicNameValuePair>();  
params.add(new BasicNameValuePair("param1", "中国"));  
params.add(new BasicNameValuePair("param2", "value2"));  
//baseUrl             
String baseUrl = "http://www.baidu.com";  
  
//将URL与參数拼接  
HttpGet getMethod = new HttpGet(baseUrl + "?" + param);  
              
HttpClient httpClient = new DefaultHttpClient();  
  
try {  
    HttpResponse response = httpClient.execute(getMethod); //发起GET请求  
  
    Log.i(TAG, "resCode = " + response.getStatusLine().getStatusCode()); //获取响应码  
    Log.i(TAG, "result = " + EntityUtils.toString(response.getEntity(), "utf-8"));//获取server响应内容  
} catch (ClientProtocolException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
} catch (IOException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
}  

post方式

//和GET方式一样，先将參数放入List  
params = new LinkedList<BasicNameValuePair>();  
params.add(new BasicNameValuePair("param1", "Post方法"));  
params.add(new BasicNameValuePair("param2", "第二个參数"));  
              
try {  
    HttpPost postMethod = new HttpPost(baseUrl);  
    postMethod.setEntity(new UrlEncodedFormEntity(params, "utf-8")); //将參数填入POST Entity中  
                  
    HttpResponse response = httpClient.execute(postMethod); //运行POST方法  
    Log.i(TAG, "resCode = " + response.getStatusLine().getStatusCode()); //获取响应码  
    Log.i(TAG, "result = " + EntityUtils.toString(response.getEntity(), "utf-8")); //获取响应内容  
                  
} catch (UnsupportedEncodingException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
} catch (ClientProtocolException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
} catch (IOException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
}  

假设须要在获得网络资源后，去更新UI的一些东西，须要使用异步的方式，否则会错误发生

Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {

            if (msg.what == 0x123) {
                tv.setText(result);
            }
        }

    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv = (TextView) findViewById(R.id.tv);
        result = "";

        final HttpClient httpclient = new DefaultHttpClient();

        new Thread() {
            public void run() {
                HttpGet httpRequest = new HttpGet(
                        "http://www.baidu.com");

                try {
                    HttpResponse httpResponse = httpclient.execute(httpRequest);
                    if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                        // 取得返回的字符串
                        result = EntityUtils.toString(httpResponse.getEntity());
                      
                        //tv.setText(result);//假设在这里来使用会报错
                      Message msg = new Message();
                       msg.what = 0x123;
                       handler.sendMessage(msg);
                    }
                } catch (ClientProtocolException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }.start();
    
    }