Android笔记（二十三）HttpClient

一、HttpClient用法

1. HttpClient是接口，因此无法创建它的实例，通常情况下都会创
   建一个 DefaultHttpClient 的实例
2. 创建一个 HttpGet 对象，传入目标的网络地址
3. 调用 HttpClient 的 execute()方法
4. 返回一个 HttpResponse 对象
5. 取出服务器返回的状态码，如果等于 200 就说明请求和响应成功
6. 调用 getEntity()方法获取到一个 HttpEntity 实例

7. EntityUtils.toString()将 HttpEntity 转换成字符串

   二、具体实例
   1.建立布局

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

    <Button  android:id="@+id/send_request" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Send Request" />

    <ScrollView  android:layout_width="match_parent" android:layout_height="match_parent" >

        <TextView  android:id="@+id/response" android:layout_width="match_parent" android:layout_height="wrap_content" />
    </ScrollView>

</LinearLayout>

2.添加权限
3.MainActivity

public class MainActivity extends ActionBarActivity implements OnClickListener {

    public static final int SHOW_RESPONSE = 0;
    private Button button;
    private TextView responseText;
    private Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            // TODO Auto-generated method stub
            super.handleMessage(msg);
            switch (msg.what) {
            case SHOW_RESPONSE:
                String response = (String) msg.obj;
                responseText.setText(response);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.send_request) {
            sendRequestWithHttpClient();
        }
    }

    private void sendRequestWithHttpClient() {
        new Thread(new Runnable() {

            @Override
            public void run() {
                try {
                    HttpClient httpClient = new DefaultHttpClient();
                    HttpGet httpGet = new HttpGet("http://www.baidu.com");
                    HttpResponse httpResponse = httpClient.execute(httpGet);
                    if (httpResponse.getStatusLine().getStatusCode() == 200) {
                        HttpEntity entity = httpResponse.getEntity();
                        String response = EntityUtils.toString(entity, "utf-8");
                        Message msg = Message.obtain();
                        msg.what = SHOW_RESPONSE;
                        msg.obj = response;
                        handler.sendMessage(msg);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}