[Notes] android 爬取网页

使用HttpURLConnection来进行http连接。
首先打开AndroidManifests.xml，加入user permission：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.check_house">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

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

</manifest>

然后参考代码：

public class MainActivity extends AppCompatActivity {

    private TextView textView;

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

        findViewById(R.id.send_request).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                send();
            }
        });

        textView = (TextView) findViewById(R.id.response_data);
    }

    private void send() {
        //开启线程，发送请求
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                BufferedReader reader = null;
                try {
                    URL url = new URL("http://www.163.com");
                    connection = (HttpURLConnection) url.openConnection();
                    //设置请求方法
                    connection.setRequestMethod("GET");
                    //设置连接超时时间（毫秒）
                    connection.setConnectTimeout(5000);
                    //设置读取超时时间（毫秒）
                    connection.setReadTimeout(5000);

                    //返回输入流
                    InputStream in = connection.getInputStream();

                    //读取输入流
                    reader = new BufferedReader(new InputStreamReader(in));
                    StringBuilder result = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null) {
                        result.append(line);
                    }
                    show(result.toString());
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (ProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if (reader != null) {
                        try {
                            reader.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                    if (connection != null) {//关闭连接
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }

    /**
     * 展示
     *
     * @param result
     */
    private void show(final String result) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                textView.setText(result);
            }
        });
    }
}