使用Http协议请求网络

声明:笔者参考《第一行代码》一书！
在Android中，发送Http网络请求的方式一般有2种，HttpURLConnection和HttpClient。
下面先使用前者，代码如下：
先来看一下布局文件:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context="com.yu.httpurlconnection.MainActivity">    <Button  android:layout_width="match_parent" android:layout_height="wrap_content" android:text="发送HTTP请求" android:id="@+id/send" android:layout_gravity="center_horizontal" />    <ScrollView  android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/scrollView" >        <TextView  android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/textview"/>    </ScrollView></LinearLayout>

核心代码如下(HttpURLConnection):

public class MainActivity extends AppCompatActivity {    private Button mSend;    private TextView mTextView;    Handler handler  = new Handler(){        @Override        public void handleMessage(Message msg) {       if(msg.what==1){         String text  = (String) msg.obj;           mTextView.setText(text);       }            super.handleMessage(msg);        }    };    private HttpURLConnection connection;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mTextView= (TextView) findViewById(R.id.textview);        mSend= (Button) findViewById(R.id.send);        mSend.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                sendHttp();            }        });    }    private void sendHttp() {    //请求网络比较耗时，所以放在子线程中        new Thread(new Runnable() {            @Override            public void run() {                try {                   URL uri =  new URL("https://www.baidu.com/");                    connection = (HttpURLConnection) uri.openConnection();                    connection.setRequestMethod("GET");                    connection.setConnectTimeout(5000);                    connection.setReadTimeout(5000);                    InputStream inputStream = connection.getInputStream();                    StringBuilder sb   = new StringBuilder();                    BufferedReader reader   = new BufferedReader(new InputStreamReader(inputStream));                  String line;                    while((line=reader.readLine())!=null){                        sb.append(line);                    }                   Message  message = new Message();                    message.obj   =  sb.toString();                    message.what  = 1;                    handler.sendMessage(message);                } catch (Exception e) {                    e.printStackTrace();                }finally {                    if(connection!=null){                  connection.disconnect();                    }                }            }        }).start();    }}

下面用HttpClient：
PS:HttpClient好像被谷歌弃用了，所以想要使用它的话，导入jar包

public class MainActivity extends AppCompatActivity {    private Button mSend;    private TextView mTextView;    Handler handler  = new Handler(){        @Override        public void handleMessage(Message msg) {            if(msg.what==2){                String text  = (String) msg.obj;                mTextView.setText(text);            }            super.handleMessage(msg);        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mTextView= (TextView) findViewById(R.id.textview);        mSend= (Button) findViewById(R.id.send);        mSend.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                sendHttp();            }        });    }    private void sendHttp() {        new Thread(new Runnable() {            @Override            public void run() {                try {  HttpClient  mHttpClient  =  new DefaultHttpClient(); HttpGet mHttpGet =new HttpGet("https://www.baidu.com/");  HttpResponse response = mHttpClient.execute(mHttpGet);                    if(response.getStatusLine().getStatusCode()==200){                        HttpEntity httpEntity = response.getEntity();                        String result = EntityUtils.toString(httpEntity，"utf-8");                       Message message  = new Message();                        message.obj =  result;                        message.what=2;                        handler.sendMessage(message);                    }                } catch (Exception e) {                    e.printStackTrace();                }finally {                    if(connection!=null){                  connection.disconnect();                    }                }            }        }).start();    }}

运行效果:

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