Android accesses Http protocol network through HttpURLConnection

Android native currently supports two ways to access the http protocol network, the first one is HttpURLConnection, the other is oKHttp, let's introduce 用HttpURLConnectionthe method to access the http protocol

Step 1: Add network access

AndroidManifest.xmlAdd the following permissions in the file

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

http request requires AndroidManifest.xmlthe file applicationand add the following property nodes

android:usesCleartextTraffic="true"

Step 2: Use HttpURLConnection to access the network

First of all we need to get HttpURLConnectionthe instance, HttpURLConnectionthe method of obtaining is as follows

URL url = new URL("http://baidu.com");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

After getting an instance of HttpURLConnection, we can use HttpURLConnectionthe instance to set some HTTP request methods

urlConnection.setRequestMethod("GET");
urlConnection.setConnectTimeout(8000);
urlConnection.setRequestProperty("key","value");

Method name	meaning
setRequestMethod	Request method (common include GET and POST, etc.)
setConnectTimeout	Request timeout
setRequestProperty	The parameters in the request

After the request is sent, we can HttpURLConnectionget the returned data of the request through the instance

InputStream inputStream = urlConnection.getInputStream();// 字节流
Reader reader = new InputStreamReader(inputStream);//字符流
 BufferedReader bufferedReader = new BufferedReader(reader);// 缓存流

Then we can bufferedReaderread data from the cache stream

     StringBuilder result = new StringBuilder();;
     String temp;
     while ((temp = bufferedReader.readLine()) != null) {
         result.append(temp);
     }
     Log.i("MainActivity", result.toString());

Don't forget to close the data stream after reading the data

 			if (reader!=null){
		         try {
	                reader.close();
	            } catch (IOException e) {
	                e.printStackTrace();
	            }
      		}
            if (inputStream!=null){
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bufferedReader!=null){
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null){
                urlConnection.disconnect();
            }

We also need to put in the child thread to access the network request

      new Thread(){
        @Override
             public void run() {
                 super.run();
                 getNetwork();
             }
         }.start();  

Cut the obtained data into the main thread and display it with text

  runOnUiThread(new Runnable() {
     @Override
           public void run() {
               mTextView.setText(result);
           }
       });

Code example

The complete code is as follows

MainActivity.java

package com.lucashu.http;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {
    TextView mTextView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.button);
        mTextView = findViewById(R.id.textView);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              new Thread(){
                  @Override
                  public void run() {
                      super.run();
                      getNetwork();
                  }
              }.start();
            }
        });

    }

    private void getNetwork() {
        InputStream inputStream = null;
        Reader reader = null;
        BufferedReader bufferedReader = null;
        HttpURLConnection urlConnection = null;
        try {
            URL url = new URL("http://baidu.com");
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.setConnectTimeout(8000);
            urlConnection.setRequestProperty("key","value");

            inputStream = urlConnection.getInputStream();// 字节流
            reader = new InputStreamReader(inputStream);//字符流
            bufferedReader = new BufferedReader(reader);// 缓存流

            final StringBuilder result = new StringBuilder();;
            String temp;
            while ((temp = bufferedReader.readLine()) != null) {
                result.append(temp);
            }
            Log.i("MainActivity", result.toString());
             runOnUiThread(new Runnable() {
                 @Override
                 public void run() {
                     mTextView.setText(result);
                 }
             });
            inputStream.close();
            reader.close();
            bufferedReader.close();

        } catch (Exception e) {
            Log.i("MainActivity", e.getMessage());
            e.printStackTrace();
        }finally {
            if (reader!=null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (inputStream!=null){
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bufferedReader!=null){
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null){
                urlConnection.disconnect();
            }
        }
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.lucashu.http">

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

    <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"
        android:usesCleartextTraffic="true">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.323" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="96dp"
        android:text="访问网络数据"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>