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Android HttpURLConnection GET 请求

从前面的章节中我们学习到，Android 提供了 HttpURLConnection 来处理 HTTP 请求操作，这章节我们就使用它来完成一个简单的 HTTP GET 请求吧

Android HttpURLConnection GET 请求

我们要请求的网址是 https://www.twle.cn/dy/text/getpost?lang=Android

创建一个空的 Android 项目 cn.twle.android.HttpGet

修改 activity_main.xml 添加布局

<?xml version="1.0" encoding="utf-8" ?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/ms_url"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入你要获取的网址"
        android:text="https://www.twle.cn/dy/text/getpost?lang=Android" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_get"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="加载" />

        <Button
            android:id="@+id/btn_source"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="源码" />

        <Button
            android:id="@+id/btn_headers"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:hint="响应头" />

    </LinearLayout>

    <ScrollView
        android:id="@+id/ms_scroll"
        android:padding="16dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone">

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

    <WebView
        android:id="@+id/ms_webview"
        android:padding="16dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

然后在 MainActivity.java 目录下创建 WebHelper.java

package cn.twle.android.httpget;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;
import java.util.Map;

public class WebHelper {

    // 获取网页的 html 源代码

    public static String getHtml(String path) throws Exception {

        URL url = new URL(path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(5000);
        conn.setRequestMethod("GET");

        if (conn.getResponseCode() == 200)
        {
            InputStream in = conn.getInputStream();

            BufferedInputStream bis = new BufferedInputStream(in);
            ByteArrayOutputStream buf = new ByteArrayOutputStream();
            int result = bis.read();
            while(result != -1) {
                buf.write((byte) result);
                result = bis.read();
            }

            return buf.toString("UTF-8");
        }

        return null;
    }

    // 获取 HTTP 的请求头和响应头

    public static String getHeaders(String path) throws Exception {

        URL url = new URL(path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(5000);
        conn.setRequestMethod("GET");

        StringBuilder sb = new StringBuilder();
        Map<String,List<String>> headers;

        headers = conn.getHeaderFields();

        for (Map.Entry<String,List<String>> entry : headers.entrySet()) {

            String key = entry.getKey();

            if ( key != null ) {
                sb.append(key + ":");
            }

            for (String s : entry.getValue()) {
                sb.append(s + " ");
            }
            sb.append("\n");
        }

        return sb.toString();

    }
}

修改 AndroidManifest.xml 加上网络权限

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

最后修改 MainActivity.java 完善各种逻辑

package cn.twle.android.httpget;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.webkit.WebView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ScrollView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView ms_data_content;
    private Button btn_get,btn_source,btn_headers;
    private EditText ms_url;
    private WebView ms_webview;
    private ScrollView ms_scroll;
    private String detail = "";
    private boolean flag = false;

    // 用于刷新界面
    private Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
                case 0x001:
                    hideAllWidget();
                    ms_scroll.setVisibility(View.VISIBLE);
                    ms_data_content.setText(detail);
                    Toast.makeText(MainActivity.this, "响应头加载完毕", Toast.LENGTH_SHORT).show();
                    break;

                case 0x002:
                    hideAllWidget();
                    ms_scroll.setVisibility(View.VISIBLE);
                    ms_data_content.setText(detail);
                    Toast.makeText(MainActivity.this, "HTML代码加载完毕", Toast.LENGTH_SHORT).show();
                    break;
                case 0x003:
                    hideAllWidget();
                    ms_webview.setVisibility(View.VISIBLE);

                    Bundle bd = (Bundle)msg.getData();
                    ms_webview.loadUrl(bd.getString("url"));
                    Toast.makeText(MainActivity.this, "网页加载完毕", Toast.LENGTH_SHORT).show();
                    break;
                default:
                    break;
            }
        }

        ;
    };

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

    private void bindViews() {

        btn_get =  (Button) findViewById(R.id.btn_get);
        btn_source = (Button) findViewById(R.id.btn_source);
        btn_headers = (Button) findViewById(R.id.btn_headers);

        ms_url = (EditText) findViewById(R.id.ms_url);

        ms_data_content = (TextView) findViewById(R.id.ms_data_content);
        ms_webview = (WebView) findViewById(R.id.ms_webview);
        ms_scroll = (ScrollView) findViewById(R.id.ms_scroll);

        btn_headers.setOnClickListener(this);
        btn_get.setOnClickListener(this);
        btn_source.setOnClickListener(this);

    }

    // 定义一个隐藏所有控件的方法:
    private void hideAllWidget() {
        ms_scroll.setVisibility(View.GONE);
        ms_webview.setVisibility(View.GONE);
    }

    @Override
    public void onClick(View view) {

        Bundle bd = new Bundle();
        bd.putString("url",ms_url.getText().toString());

        Message msg = new Message();
        msg.setData(bd);

        switch (view.getId()) {
            case R.id.btn_headers:
                new Thread() {
                    public void run() {
                        try {

                            detail = WebHelper.getHeaders(ms_url.getText().toString());
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        handler.sendEmptyMessage(0x001);
                    };
                }.start();
                break;

            case R.id.btn_source:
                new Thread() {
                    public void run() {
                        try {

                            detail = WebHelper.getHtml(ms_url.getText().toString());
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        handler.sendEmptyMessage(0x002);
                    };
                }.start();
                break;
            case R.id.btn_get:
                    msg.what = 0x003;
                break;
        }

        handler.sendMessage(msg);
    }
}

我们使用 Handler 完成异步更新 UI
使用 WebView 加载网络，嗯，这个还没学到，后面我们会详解

注意: Android 不允许在非 UI 线程中进行 UI 操作

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Android HttpURLConnection GET 请求

Android HttpURLConnection GET 请求

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